Left or right, that is the question: Use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncates)

Left or right, that is the question: Use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncates) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Left or right, that is the question: Use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncates) Masaki Tomonaga, Yuka Uwano-Ito, Toyoshi Saito, Natsuko Sakurai This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-2606167/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Jun, 2023 Read the published version in Animal Cognition → Version 1 posted 7 You are reading this latest preprint version Abstract How do bottlenose dolphins visually perceive the space around them? In particular, what coordinates do they use as a frame of reference for left-right perception? To address this question, we examined the dolphin's responses to various manipulations of the spatial relationship between the dolphin and the trainer by using gestural signs for actions given by the trainer, which have different meanings in the left and right hands. When the dolphins were tested with their backs to the trainer (Experiment 1) or in an inverted position underwater (Experiments 2 and 3), correct responses from the trainer's perspective were maintained for signs related to movement direction instructions. In contrast, reversed responses were frequently observed for signs that required different sounds for the left and right hands. When the movement direction instructions were presented with symmetrical graphic signs such as "×" and "●", accuracy decreased in the inverted posture (Experiment 3). Furthermore, when the signs for sounds were presented from either the left or right side of the dolphin's body, performance was better when the side of the sign movement coincided with the body side on which it was presented than when it was mismatched (Experiment 4). In the final experiment, when one eye was covered with an eyecup, the results showed that, as in the case of body-side presentation, performance was better when the open eye coincided with the side on which the sign movement was presented. These results indicate that dolphins used the egocentric frame for visuospatial cognition. In addition, they showed better performances when the gestural signs were presented to the right eye, suggesting a left-hemispheric advantage in the dolphin's visuospatial cognition. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Cetaceans such as dolphins exhibit a variety of postures underwater and on the surface. Not only do they swim with their body axis horizontally, but their body axis is vertical during deep dives or spy hops (Williams, 2001; Williams et al., 2001, 2002). In addition, when rubbing with other individuals, they sometimes flip their body upside down (Dudzinski & Ribic, 2017; Sakai et al., 2006a, b). How do they perceive and recognize this three-dimensional space during moving freely underwater? It is evident that echolocation plays an essential role in dolphins' navigation (Zapetis & Szesciorka, 2018), but they may also utilize visual cues, especially in shallower waters or within short distances (e.g., positional relationships with other individuals; Connor et al., 2006; Karenina et al., 2010, 2013). The fact that they show rubbing and synchronous breathing with specific individuals more frequently than others would suggest their use of visual cues (Sakai et al., 2006a, 2010). Among various aspects of spatial cognition in bottlenose dolphins, the present study mainly focused on the visual recognition of left-right relationships. In humans, it has been known that the body axis (or perspective) of the self plays an important role in the development of visuospatial cognition (Piaget & Inhelder, 1956; but see Presson & Sommerville, 1985, for further discussion). This is exemplified in the classic "three-mountain" problem. In this task, children are presented with models of three differently shaped mountains arranged spatially and asked what those mountains look like from a different perspective than the children's. Children's responses change developmentally from "egocentric," in which they focus on their own perspective from any position to "decentralized," in which they understand the relationship between different perspectives and visibility (Piaget & Inhelder, 1956). On the other hand, another important task related to spatial cognition is "mental rotation" (Shepard & Metzler, 1971). When observers discriminate or make a same-different judgment of mirror-reversed images (such as p vs. q), accuracy and speed deteriorate as a function of the angle of stimulus presentation. In particular, a linear increase in reaction times as a function of stimulus rotation has been robustly replicated in humans, suggesting that we mentally rotate the representation of these stimuli. Thus, it has been argued that such mental representations are image-like (Farah, 1989; Koslyn, 1995; Shepard, 1978; but see Pylysyn, 2002). Both these two tasks are similar in that they involve manipulations of spatial images. However, there is also a critical difference: they involve different spatial transformations (Presson, 1982; Zacks & Michelon, 2005; Zacks et al., 2000). The three-mountain problem, also known as the "perspective-taking task," requires a mental transformation of the observer's perspective. In contrast, the mental rotation task requires not a perspective transformation but a spatial transformation of objects (within the mental image). And this disparity in spatial transformations constitutes the basis for the variation in task performances and the developmental processes underlying them. (e.g., Huttenlocher & Presson, 1973, 1979). How, then, is visuospatial ability in nonhuman animals? So far, there are very few systematic studies on this topic from the comparative perspective except for the studies on navigation and cognitive maps (Biro et al., 2004; Freas & Cheng, 2022; Poucet, 1993; Wang & Spelke, 2002). Among these few studies, for example, Furuya (1998) conducted a series of experiments on pigeons and showed that they might use the egocentric frame of reference to perform the left-right discrimination task within a relatively small Skinner box. The mental rotation has also been studied in pigeons, monkeys, chimpanzees, sea lions, and dolphins, but the results are mixed (Delius & Hollard, 1995; Fujita & Matsuzawa, 1989; Hassett et al., 2022; Hollard & Delius, 1982; Mauck & Dehnhardt, 1997; Murayama & Tobayama, 1995; Lohman et al., 1988; see also DeLong et al., 2020). Some studies found changes in performance according to the angle of stimulus rotation (Hassett et al., 2022; Mauck & Dehnhardt, 1997; Murayama & Tobayama, 1995), whereas others did not (Fujita & Matsuzawa, 1989; Hollard & Delius, 1982). The present study aimed to examine the visuospatial perception in captive bottlenose dolphins by focusing on gestural signs used for them. Gestural signs used in dolphin training and performance shows vary from aquarium to aquarium. Some signs involve moving both hands at the same time. The other signs use only one hand irrespective of the left or right, but some have different meanings depending on which hand is used. For example, at the Port of Nagoya Public Aquarium, Japan, in response to the sign "Right-Talk" (hereafter, we use double quotation marks to indicate the name of the sign), in which the trainer holds his/her right hand out to the side at the waist and rotates it around the wrist, the dolphins produce a specific sound. On the other hand, they produce a different sound to the same action with the left hand ("Left-Talk", Figure 1). Also, in response to the sign "Right-Bye", in which only the right hand is waved at shoulder height like a bye-bye gesture, the dolphins swim slowly to the left from the trainer's perspective (or to the right from the dolphins' perspective) while flapping their left flippers (the opposite direction for the left hand, "Left-Bye"). Tomonaga et al. (2010) studied the dolphins that had already acquired the responses to these signs to investigate their understanding of human's attentional state. When the trainer turned his/her back to the dolphin during presenting the sign (Figure 2A), the accuracy was significantly worse than when the trainer faced the dolphins. Tomonaga et al. concluded that the trainer's attentional state (e.g., loss of eye contact) did not significantly affect the performance declines observed in their study. Instead, they suggested that the impairments in sign comprehension resulted from the trainer's left-right reversal. Inspired by Tomonaga et al.'s study (2010), the present study further examined left-right discrimination using gestural signs in bottlenose dolphins by manipulating the spatial relationships between dolphins and trainers in various ways. What frames of reference do dolphins use to recognize mirror-image gestural signs, that is, to distinguish between left and right? As spatial frames of reference, Zacks and Michelon (2005) proposed three frames; an egocentric frame, an object-based frame, and an environment-based frame. The egocentric frame locates objects in the external world around one's own body's coordinate system. An egocentric reference frame is one in which objects are located relative to axes defined with respect to the self. This frame corresponds to what Piaget called egocentricity (Piaget & Inhelder, 1956). On the other hand, an object-based frame locates things relative to axes defined with respect to a specific object in the environment, for example, a trainer facing dolphins or a landmark such as an artificial rock in a swimming pool. If the dolphins in Tomonaga et al.'s study could have used the object-based frame, they would have understood the signs according to the body axis of the trainer, but the results were negative. And finally, an environment-based frame locates "things relative to axes defined with respect to a fixed space (Zacks & Michelson, 2005; p.98)", such as major and minor axes of elliptical pools or geographic directions (north, south, east, west). Of the two types of spatial transformations, perspective and object-based transformations, we adopted the object-based transformation in this study. However, unlike in the studies on mental rotation, since it was impossible to apply transformation directly to objects, that is, to physically rotate a real trainer to present signs (cf. Tomonaga & Sakurai, 2014), we manipulated the postures of the dolphins. Our participant dolphins usually faced the trainer in a vertical posture with their heads above the surface (see Figure 1). In Experiment 1, the dolphins stood upright with their dorsal side facing the trainer and responded to various signs (Figure 2B). In this posture, the body axis did not change from the standard (frontal or ventral) posture, but their retinal images rotated 180 degrees. In Experiment 2, the dolphins responded to the signs shown from the underwater exhibit area while keeping their body axis horizontal underwater. They were tested in two postures: upright, with the ventral side facing downward (standard), and inverted, with the dorsal side facing downward (Figure 2C). In the inverted posture, not only were the retinal images inverted, but their bodies also rotated physically. In humans, when the head is tilted or the body is laid at 90 degrees (prone posture) during the mental rotation experiments, the response profile is also shifted in the direction of the axis of the retina (Corballis et al., 1976, 1978). Thus, these two experiments could provide insights into whether the axis on the retinal coordinates or the body axis is dominant for the dolphin's visuospatial cognition. In Experiments 1 and 2, the dolphins had to discriminate left and right of the trainer. In addition, they also had to decide which side they moved in response to "Bye". In the case of "Bye" at Nagoya Port Aquarium and "High-Speed Run (HSR)" (swimming at high speed in the direction in which the trainer extends her arm) at Minamichita Beachland Aquarium, there are non-arbitrary relationships between the directions of the trainer's sign and the dolphins' movement. Therefore, in Experiment 3, we trained the dolphins to swim to the left and right using point-symmetric shapes based on arbitrary relationships, i.e., "×" and "●", instead of the gestural signs for "HSR" (Figure 2D). Using these graphic signs, we examined the effect of postural inversion on their decisions regarding swimming directions. Gestural signs in which only one hand moves can be identified by paying attention to the shape of the sign and which side of the body the movement of the sign is on from the dolphin's perspective. In Experiment 4, the dolphins landed at the poolside, and the trainer presented signs from either the left or right side of them (Figure 2E). For example, if "Right-Talk" (the trainer waves her right hand) is presented in the standard (frontal) position, the hand movement is made on the left side of the body and vice versa from the dolphins' perspective. If the dolphins focus solely on the side of their body where the sign movement takes place, regardless of the trainer's waving hand, then when "Right-Talk" is presented on the right side of their body, they would respond as if "Left-Talk" had been presented (see Figure 6A). The presentation of a sign on one side of the dolphin's body is analogous to presenting a sign to only one eye from the standard frontal position. In the final experiment (Experiment 5), one eye was covered using an eyecup (Figure 2F). It is known that the optic nerve fibers of bottlenose dolphins completely cross at the optic chiasm (Ridgway, 1986; Tarpley & Ridgway, 1994; Thewissen, 2009), suggesting that all information input to the right eye is initially sent to only the left hemisphere. If it is more critical which eye sees a moving sign, rather than whether the sign moves at left or right, then, for example, seeing "Right-Talk" with the right eye would result in "Left-Talk" response (see Figure 6B). In addition, it is also known that primates, including humans, have a left visual field (i.e., right-hemispheric) advantage in visuospatial tasks such as mental rotation and perspective taking (e.g., Corballis, 1997; Corblis et al., 2010; Gunia et al., 2021). On the other hand, it has been reported that dolphins showed a right-eye advantage (left-hemispheric advantage) in visuospatial tasks (Kilian et al., 2000). Experiments 4 and 5 also examined the differences in responses to signs presented on either side of the body and to either the left or right eye. General Methods Participants and setting. The present study was conducted at the two aquariums. At the Port of Nagoya Public Aquarium (PNPA) in Nagoya City, Aichi, Japan, four adult male bottlenose dolphins ( Tursiops truncates ), Eagle, Peace, Quick, and Tino, participated (Experiments 1, 2, 4, and 5). They were all wild-born and approximately 11–14 years old at the beginning of the present study. They usually received four 15-minute sessions of husbandry, performance, and cognitive training tasks (Tomonaga et al., 2010, 2014, 2015). There were six pools for dolphins varied in size at PNPA, and the dolphin participants were kept in one of these pools according to the breeding management plans. Experimental sessions were conducted in one of these pools in coordination with other public programs of the aquarium. At the Minamichita Beachland Aquarium (MCBA), Mihama Town, Aichi, Japan, two adult female bottlenose dolphins, Neri and Thihra, participated in Experiment 3. They were also wild-born and approximately ten years old at the beginning of the present study. According to the breeding management plans, they lived in a pool in the dolphin exhibit area (approximately 13m in diameter x 3m in depth). They also participated in daily 15-min public programs. The experiment was also conducted in this pool. We did not conduct any food deprivations during the present study in both aquariums. General Procedures Detailed procedures for each experiment are described in the Methods section of each experiment. This section describes the procedures common to all experiments. Two trainers typically conducted experimental sessions except for Experiment 2 (three trainers). The first trainer presented signs to the dolphin, and the second trainer instructed the first trainer which sign to present and recorded the dolphin's responses. The first trainer initially had the dolphin maintain a waiting posture for the sign. If the waiting posture was not standard, the sign for that posture was presented first. When the dolphin's posture became stable, the first trainer presented the sign instructed by the second trainer. Both trainers simultaneously and independently judged whether the dolphin responded correctly to the sign. The experimental sessions were recorded by a video camera, and if the two trainers' judgments differed, the video recordings were checked, and then corrected responses were coded. The dolphin's responses were judged from the trainer's perspective. If the dolphin's response was correct, a whistle was sounded, followed by a food reward (fish pieces) according to the reinforcement schedule set for each experiment. Several trainers conducted the experiments, but the trainer's role was fixed within a session. Experimental sessions consisting of several trials were conducted once to several times per day. Data Analysis As noted above, the dolphin's responses were coded in real-time. To check for reliability, the first author also coded responses based on video recordings for about two sessions per individual in each experiment (approximately 13% of the available video recordings). The resulting agreement rate was 99% for the entire study. Due to the small number of dolphins participating in each experiment, all statistical analyses were performed individually. Binomial tests were performed on the results for each experimental condition where the chance probability was set at 0.5. Chi-square tests were also performed to compare two conditions, such as the control and experimental conditions. We did not apply Yates' corrections to the chi-square test statistics even though the contingency tables had small cell frequencies (e.g., Camilli & Hopkins, 1978). In addition, Mantel-Haenszel and Breslow-Day tests were performed for the data of stratified 2x2 tables (Experiments 4 and 5). The results of the statistical tests for each experiment are indicated by asterisks in each graph and summarized in Table S2. The datasets for each experiment are attached as Supplementary Material. Experiment 1 In Experiment 1, the dolphins were presented with signs in an upright posture with their backs toward the trainer (dorsal posture, right of Figure 2B). In this posture, there was no change in the body axis relative to the standard upright (ventral) posture (both were vertical) but the dolphins looked up at the trainer from the dorsal direction, and the retinal image rotated 180 degrees. Methods Experiment 1 was conducted at PNPA. The three dolphins, Eagle, Peace, and Quick participated in this experiment. Eleven different signs were used in this experiment (see Supplementary Video 1). Four of the 11 signs were used for test trials: the left and right "Bye" and the left and right "Talk" (see Figure 1). The experiment began with the test in the standard ventral posture, followed by preliminary training in the dorsal posture without test trials, and then the test in the dorsal posture. The number of sessions conducted in each condition differed for each dolphin: the ventral posture test (left of Figure 2A) was conducted for a minimum of three sessions (11 trials per session), the dorsal posture pretraining was conducted for at least three sessions (15 trials), and the dorsal posture test (15 trials) was conducted for at least eight sessions, respectively. The number of sessions in each condition is summarized in Table S1. In this experiment, food rewards were given for correct responses on each trial. During the dorsal posture training and testing, the dolphins responded in the dorsal posture for three consecutive trials, receiving a food reward for each correct response. After every three trials, they were returned to the standard posture, provided with an additional food reward, and then re-positioned in the dorsal posture to continue the experiment. Correct responses in the dorsal posture were judged from the trainer's perspective. Results and Discussion Baseline-trial performances were very high for all individuals, 98.7% on average for the ventral posture testing, 99.3% for the dorsal posture training, and 95.9% for the dorsal posture testing. Figure 3 shows the results of the test trials separately for the two signs. Error responses were categorized into Reversed responses, in which the left-right correspondence was reversed (from the trainer's perspective), and Others (responses to other signs or no response). Asterisks at the bottom of each column indicate the results of binomial tests. Those at the top between the ventral and dorsal postures indicate the results of chi-square tests conducted between conditions. Regarding "Bye", all dolphins but Eagle showed perfect performances from the trainer's perspective, even in the dorsal posture. For example, if the trainer showed "Right-Bye" with his/her right hand to the dolphins in the dorsal posture, they swam slowly to the left from the trainer's perspective, flapping their right flipper. Eagle showed error responses in all trials of "Bye", but most of them were responses to "Talk" or returning to the ventral (standard) posture. All dolphins showed very high performances on "Talk" in the ventral posture, but in the dorsal posture, they predominantly showed error responses (Eagle, χ 2 (1) = 16.00, p < 0.001; Peace, χ 2 (1) = 14.32, p < 0.001; Quick, χ 2 (1) = 14.00, p < 0.001). In addition, for Peace and Quick, most error responses were left-right reversed "Talk" responses. For Eagle, the responses to "Left-Talk" were more frequent in the "Right-Talk" trials, whereas he often produced different sounds from neither "Left-Talk" nor "Right-Talk" responses in the "Left-Talk" trials. For Peace and Quick, when responding to "Talk" in the dorsal posture, they frequently showed left-right reversed responses from the trainer's perspective. These results suggest that the trainer's signs were seen as reversed from the dolphins' perspective. On the other hand, for "Bye", correct responses were maintained from the trainer's perspective, suggesting that the dolphins might have used a different strategy to recognize "Bye". In contrast to "Talk", "Bye" required a directional response, i.e., swimming in the opposite direction of the trainer's waving hand. This correspondence is not arbitrary, making it difficult to distinguish whether the dolphins judged the swimming direction based on the reversed correspondence to the movement of the sign or their body axis. As for Eagle, he showed more other responses to the test signs than left-right reversed responses in the dorsal posture. However, it is clear that the dorsal posture itself, which was not the standard posture, had little disturbing effects on his performance because his responses during the baseline trials in the dorsal posture (93.1%) were as high as the other dolphins (97.6%). Instead, these results might suggest that the dorsal posture altered retinal images of "Talk" and "Bye", resulting in disrupted left-right discrimination. Experiment 2 In Experiment 2, the dolphins responded to signs presented from the underground exhibit area or observation window by maintaining a posture with their body axis horizontal underwater. The dolphins were tested in a standard upright posture with the dorsal side facing upward (left of Figure 2C) and an inverted posture with the ventral side facing upward (right of Figure 2C). In the inverted posture, the retinal image rotated 180 degrees around the body axis, and the body was also inverted against the gravity axis. Methods Experiment 2 was also conducted at PNPA, and Peace and Quick participated. The experiment was conducted in the pools with a glass wall on the underwater exhibit area or observation windows. This experiment was conducted with three trainers: the first and second trainers stood near the exhibit area (or window), and the third trainer stood poolside above the water, communicating with each other via walkie-talkies. Each trial began with the third trainer at the poolside holding the dolphins upright. On instruction from the first trainer standing in front of the exhibit area, the third trainer showed the sign to the dolphins to go to the underwater exhibit area. A suction cup was placed on the glass surface from the trainer's side, and the dolphins waited for signs in a standard upright posture in front of this suction cup (Figure 2C). The first trainer presented the sign in the upright posture condition, while in the inverted posture condition, the dolphins were initially rotated 180 degrees by the sign of the first trainer, and then the test sign was presented. Immediately after the response to the sign, the first trainer sounded a whistle regardless of whether the response was correct or incorrect. The dolphins kept the waiting posture at the suction cup again until the next sign was presented. Four trials were conducted successively, and the dolphins were instructed to return to the water surface. The third trainer gave food rewards to the dolphins that came to the surface (regardless of accuracy in each trial). The same posture was maintained within this four-trial block, and the upright and inverted postures were alternated between blocks. The second trainer provided instructions on signs to be presented to the first trainer and recorded the dolphins' behavior. In Experiment 2, eight different signs were used, including the test signs. The experiment was first conducted where no test signs were presented in the inverted posture (pretest), followed by the main test in which the test signs were presented both in the upright and inverted postures. The pretest consisted of 16 sessions, and the main test consisted of 28. Each session consisted of 16 trials (i.e., four blocks). Since Peace did not complete one main test session, he was given one additional session (see Table S1). Results and Discussion In the pretest, both dolphins showed high accuracy in upright and inverted postures (96.9% on average). However, Quick had difficulty making "Left-Talk" sounds underwater, with an accuracy of 12.5%. They also showed accurate baseline-trial performance on the main test (98.8%). The results of the test trials during the main test are shown in Figure 4. Both dolphins responded correctly to "Bye" in the inverted posture significantly better than the chance level (binominal testes, p s < 0.01), but the accuracies were significantly lower than in the upright position (Peace, χ 2 (1) = 7.54, p = 0.006; Quick, χ 2 (1) = 4.46, p = 0.035). For "Talk," Quick performed poorly on "Left-Talk" in the main test (0% correct in both upright and inverted postures; see the "Talk"/Up bar in Figure 4). However, even under these constraints, both dolphins performed significantly worse in the inverted posture than in the upright posture (Peace, χ 2 (1) = 25.34, p < 0.001; Quick, χ 2 (1) = 11.65, p < 0.001), and the majority of error responses were left-right reversed responses (except for Quick's responses to "Left-Talk"). In the inverted posture of this experiment, the trainer appeared to rotate 180 degrees from the dolphin's perspective. Thus, the dolphins had to discriminate 180-degree rotated mirror-image figures in the test trials, as in the mental rotation experiments, which is difficult even for humans. This object-based transformation might have affected the discrimination between "Left-Bye" and "Right-Bye". For "Talk", the left-right reversed responses were frequently observed in the inverted posture as in Experiment 1. These results suggest that the trainer's vertical direction (upright or inverted) was not so important in discriminating between "Left-Talk" and "Right-Talk". Alternatively, a critical cue for the discrimination might be whether the sign movement occurred on the left or right side with respect to the dolphins' body axis. Experiment 3 In Experiments 1 and 2, in contrast to "Talk", the dolphins showed more "correct" responses to "Bye" from the trainer's perspective. These results suggest that the dolphins might have matched their moving direction simply to the opposite side of the sign movement presented by the trainer. In Experiment 3, we presented point-symmetric geometric forms such as "×" and "●" instead of gestural signs to investigate the effects of postures on dolphins' responses to these signs. Using these graphic signs, we could examine whether the dolphins decided their left-right movements in terms of egocentric or object-based coordinates (for example, the trainer or landmarks in the pool). Methods We conducted Experiment 3 at MCBA, where two dolphins, Neri and Thihra, received two different tests. The experiments were conducted with two trainers in a pool with an underwater exhibit area (Figure 2D). The first trainer presented signs and recorded the dolphin's behavior at the exhibit area. The second trainer at the poolside above the water surface sent the dolphin underwater and gave food rewards for every correct response. These trainers communicated with each other using walkie-talkies. As mentioned earlier, a sign called "HSR", where the dolphins swim at high speed in the direction in which the trainer extends her arm horizontally was being used at MCBA. In this experiment, we replaced "HSR" with geometric forms; cross (×) for "Left-HSR" and filled circle (●) for "Right-HSR". Each shape was colored black and approximately 40 cm in size. For the control condition, filled square (◾) was also replaced with the non-directional sign "Yes" (the trainer shook his/her head up and down, and the dolphins also shook their heads up and down in response). The training for matching between the shapes and responses was incorporated into routine husbandry training and performance-show training. In both tests, postural conditions varied randomly between sessions. The first test was conducted with five signs, including "×" and "●". Gestural signs of "HSR" and "◾" were not used in the first test. Each session consisted of 5 trials, and 24 sessions for each postural condition were conducted. The second test was conducted with eight signs, including gestural left and right "HSRs" and "◾". This second test was done to examine the possibility that the worse performances in the inverted posture of the first test were due to a deterioration of shape discrimination and worse responses to gestural "HSR" in the inverted posture. Due to a breeding program, only Thihra participated in this test. Each session consisted of 6 trials, and 48 sessions for each postural condition were conducted. Results and Discussion The training for matching between the graphic signs and responses took approximately a month. Figure 5 shows the results of the test sessions. In the first test, the dolphins performed very accurately during the baseline trials (99.3% on average). The average percentage of correct responses to "×" and "●" in the upright posture was 76.0%, not a perfect response, but significantly better than the chance level (binomial tests: p s < 0.001; see Figure 5 and Table S2). In contrast, in the inverted posture, accuracies from the trainer's perspective were significantly lower for both dolphins (Neri, χ 2 (1) = 5.44, p = 0.020; Thihra, χ 2 (1) = 8.71, p = 0.003). They showed a strong response bias toward either the left or right direction (Neri toward the left and Thihra toward the right). In the second test, the inverted posture did not disrupt Thihra's performances on "HSR" and "◾". In contrast, she responded to "×" and "●" significantly worse in the inverted than upright posture, as in the first test (χ 2 (1) = 17.42, p < 0.001). Interestingly, when "×" or "●" was presented in the inverted posture, Thihra often returned to the standard upright posture and swam to either the left or right (in this case, these responses were coded as incorrect even though the direction corresponded to the sign). Such responses were observed in 45.7% (16/35) of the incorrect responses. Furthermore, these responses were observed significantly more frequently on the test trials with "×" and "●" than on the baseline trials and the test trials with "◾" in the inverted posture (33.3% vs. 1.7%, χ 2 (1) = 62.07, p <0.001). In contrast to the previous experiments, the dolphins did not consistently show "correct" or left-right reversed responses in the inverted posture. Instead, they showed strong directional biases or "inappropriate" responses to the graphic signs, suggesting that the correspondence of movement to the left and right was disrupted under the testing condition. If the dolphins used the egocentric frame as the basis for the motion directions, then the inverted posture should have caused left-right reversed responses. On the other hand, if the reference frame was based on the trainer's position (i.e., object-based frame), they should have swum in the "correct" directions from the trainer's perspective, even in the inverted posture. The results of the present experiment did not fit either of these criteria, suggesting that these two reference frames might have influenced each other. Some studies suggest that even in human children, these two perspectives interactively affected performances during the three-mountain problem and related tasks (Emerson, 1931; Suzuki et al., 1991). The interactions between egocentric and object-based frames of reference will need to be further investigated with more dolphins in the future. In the second test, Thihra frequently swam to either side after returning to the standard upright posture when "×" or "●" was presented in the inverted posture. In this experiment, such behavior was treated as "incorrect" because the experimenter could not adequately control her behavior, but it might be a kind of adaptive behavior for her. Since she had difficulty judging the direction of swimming in the inverted posture, she might have returned "spontaneously" to the upright posture and judged the direction again. It has been reported that human children older than six years also spontaneously physically rotate stimuli and maps and tilt their heads during mental rotation and map reading tasks (Armitage et al., 2020; Armitage & Redshaw, 2021; cf. Tcaci Popescu & Wexler, 2012). Such behavior is often called cognitive offloading (Risko & Gilbert, 2016). Cognitive offloading is defined as "the use of physical action to alter the information processing requirements of a task so as to reduce cognitive demand" (Risko & Gilbert, 2016, p. 676). Thihra's behavior in this experiment could also be considered cognitive offloading. Experiment 4 In Experiments 1 and 2, the responses to "Talk" were reversed in the dorsal and inverted postures. From these results, we suggested that the left-right reversal of retinal images may have influenced the responses to "Talk". However, if these results were further examined together with those of "Bye", it would be suggested that a critical cue had been whether the "movement" of the trainer's sign was presented on the left or right side of the dolphin's body axis. In Experiment 4, to explore this possibility, the dolphins landed at the poolside, and the trainer him/herself moved to either the left or right side of the dolphin's body and presented the signs from there (Figure 2E). Methods Experiment 4 was conducted at PNPA, and Eagle, Peace, and Quick participated. Experimental sessions were conducted in pools with a large poolside or shallow area where the dolphins could land. In each trial, the first trainer presented the sign to the dolphins to land at the poolside. Then, the trainer presented the sign kneeling in front of the dolphins or on their left or right side (near the dolphin's eye; right of Figure 2E). When the response to the sign was correct, the first trainer blew the whistle immediately. After three consecutive trials with the landing position, the dolphins were returned to the pool and given food rewards regardless of whether the responses were correct or incorrect. The dolphins returned to the landing site again for the following three consecutive trials. In this experiment, only "Talk" was used as the test signs, and six different signs were used, including the test signs. The experiment began with baseline training, where the first trainer always presented the signs in front of the dolphin. Each session consisted of 12 trials, and the dolphins received four (for Eagle and Peace) or eight sessions (for Quick) of this training. After the baseline training, they received eight pretest sessions (5 trials per session) in which the signs were presented not only in front but also from the left and right sides of the body. The dolphins then completed 2–4 sessions (30–48 trials) of re-training before the main test. The main test consisted of 15 trials per session and 32 sessions individually. The position of the first trainer randomly changed from trial to trial in the pretest and main test. Results and Discussion The dolphins showed 96.9%, 93.3%, and 98.2% correct responses on average for baseline training, pretest, and re-training before the main test, respectively. Figure 7 shows the mean accuracy for each position in the main test, separately for baseline and test trials. When the signs were presented from the front, the overall accuracy was 97.7% on average. The dolphins performed better for the signs from the right side than the left, except for the baseline trials in Quick. However, this difference was significant only for Eagle (Mantel-Haenszel test: χ 2 (1) = 5.68, p = 0.017). We conducted a more detailed analysis of the test trials. As shown in Figure 6A, when the trainer placed in front of the dolphins and presented "Right-Talk", the trainer's hand moved at the left side of the dolphins' body and vice versa. On the other hand, if, for example, the trainer placed on the left side and presented "Talk", the hand movement was presented from the left side of the body whether it was "Left-Talk" or "Right-Talk". In the case of "Right-Talk", the trainer's hand moved at the left side of the body as in the front condition (congruent), while in the case of "Left-Talk", the hand moved at the opposite side (left side) of the body from the front condition (incongruent). Based on these congruency relationships between sign movement and presentation side, the test trials were classified into two types, congruent and incongruent. Figure 8 summarizes the results of these analyses. Except for the left side in Peace, the dolphins performed better on the congruent trials than the incongruent trials, and all the incorrect responses were left-right reversed responses. These differences were significant except for the right side in Eagle (Eagle, left, χ 2 (1) = 24.00, p < 0.001; Peace, left, χ 2 (1) = 12.68, p < 0.001, right, χ 2 (1) = 24.00, p < 0.001; Quick, left, χ 2 (1) = 19.33, p < 0.001, right, χ 2 (1) = 8.00, p = 0.005). Furthermore, when the results for the left and right sides were combined and then analyzed, the accuracy was significantly higher for the congruent trials than incongruent trials for Eagle and Quick (Mantel-Haenszel test: Eagle, χ 2 (1) = 20.68, p < 0.001; Quick, χ 2 (1) = 22.55, p < 0.001). We further examined whether there was a difference in the accuracy of test trials between the left and right sides based on congruency. As a result, we found significant differences for Eagle and Peace, but only Eagle showed better performance on the right side than on the left side (Breslow-Day test: χ 2 (1) = 4.69, p = 0.030). These results indicate that mirror-image discrimination of the signs was easier on the right body side than the left side for Eagle. The results of this experiment suggest that in recognizing mirror-image signs like "Talk", the dolphins might pay more attention to which side of the body the sign's movement occurred rather than discriminating mirror-image patterns of the sign's shape. This conclusion is consistent with the previous experiments. However, given that the dolphins did recognize the baseline signs presented from the side of the body, it is evident that they did not recognize gestural signs only by movement. Therefore, it would be suggested that the dolphins recognized static shapes of "Talk" but did not properly pay attention to which hand was used. They might have understood the "meaning" of the signs based solely on movement information. Previous studies showed that dolphins could understand gestural signs even when they were presented with only the movements using point-light displays (Herman et al., 1990). The present results suggest that the role of static shape information of the signs also needs to be examined in more detail. In this experiment, the dolphins showed better performance from the right side of the body compared to the left side. Although this difference was significant only for Eagle, none of the dolphins exhibited an opposite pattern (i.e., better performance from the left side; see Figures 7 and 8). As mentioned in the introduction, since the optic nerves cross completely at the optic chiasm (Ridgway, 1986), the sign presentation from the side implies prioritized information input to the eye on that side (and thus initially to the opposite cerebral hemisphere). Several studies have suggested the right-eye (left-hemispheric) advantage in shape discrimination and visuospatial abilities in bottlenose dolphins (Delfour & Marten, 2006; Kilian et al., 2000, 2005; von Fersen et al., 2000). The present results indicate that the right-eye advantage in visuospatial cognition in bottlenose dolphins needs further investigation. Experiment 5 Although the results of Experiment 4 suggested a right-eye advantage in the discrimination of signs and mirror-image patterns, these were not so robust. The weak evidence may be due to the influence of sign presentation from unusual positions. Furthermore, the information input from the opposite eye might not have been completely blocked, even though the signs were presented from the side of the body. Therefore, in the final experiment, we addressed this issue by testing the dolphins facing the trainer in the standard upright posture but with one eye covered with an eyecup (Figure 2F). Methods This experiment was conducted at PNPA, and the two dolphins, Peace and Tino, participated. Tino participated in this study for the first time but has participated in several cognitive experiments (Tomonaga et al., 2010, 2014, 2015). A silicone suction cup was used as an eyecup to cover one eye (Figure 2F). The eyecup was connected to a PVC ring (30 cm in diameter) with a string, which was hooked onto the dolphin's rostrum during the experiment. This was done to prevent the dolphin from accidentally swallowing the eyecups when detached from the body. Three experimental conditions were prepared: one in which both eyes were open and the other two in which only one of the eyes was open. In the single-eye condition, one eye was covered with an eyecup, and a dummy eyecup was placed in a position that did not interfere with the forward visual field of the other eye (right of Figure 2F). In both-eyes condition, two dummy eyecups were also placed near the eyes (see left of Figure 2F). These dummy cups were used to eliminate the possibility that wearing the eyecup itself could affect performance. This experiment was conducted with two trainers. The trainer always presented the signs to the dolphin in the normal upright posture (Figure 2F). The experiment was conducted with ten different signs, including four test signs; one session consisted of 12 trials, and the eyecup conditions were randomly changed across sessions. The first trainer initially held the dolphin upright and then presented the signs. After the three consecutive trials (trial blocks), food rewards were given to the dolphin regardless of whether the responses were correct or incorrect. The second trainer gave instructions for the signs to the first trainer and recorded the dolphin's responses. Sixteen sessions were conducted for each eyecup condition, totaling 48 sessions. As in Experiment 4, we defined congruency based on the sides of the sign movement and the open eye (Figure 6B). For example, in the right-eye-only condition, "Left-Talk" and "Left-Bye" were congruent because the sign movement of these signs occurred on the right side of the body, whereas "Right-Talk" and "Right-Eye" were incongruent because the sign movement occurred on the left side of the body. Results and Discussion Figure 9 shows the performance on baseline and test trials for each eye condition. When both eyes were open, the percentages of correct responses averaged across the two dolphins were 92.2% for the baseline and 93.8% for the test trials, respectively. In contrast, for the single-eye condition, there were consistent differences between the left and right eyes for both baseline and test trials: they showed better performances for the right-eye-only condition than the left-eye-only condition (Mantel-Haenszel test: Peace, χ 2 (1) = 17.36, p < 0.001; Tino, χ 2 (1) = 24.36, p < 0.001). Next, Figure 10 shows the results of the congruency-based analysis of the test trials (see also Figure 6B). Comparing congruent and incongruent trials, the dolphins showed better accuracy for the congruent trials than the incongruent trials, except for "Bye" in Peace (Mantel-Haenszel test: "Bye", Peace, χ 2 (1) = 0.38, p = 0.541; Tino, χ 2 (1) = 11.41, p < 0.001; "Talk", Peace, χ 2 (1) = 11.01, p < 0.001; Tino, χ 2 (1) = 10.96, p < 0.001). In addition, when comparing the left- and right-eye-only conditions, they performed better on the congruent trials than the incongruent trials in the left-eye-only condition (see asterisks above the bars in Figure 10, χ 2 s(1) > 4.57, p s < 0.05). In contrast, the dolphins showed significantly higher performances regardless of congruency in the right-eye-only condition than in the left-eye-only condition, except for "Talk" in Tino (Breslow-Day test: "Bye", Peace, χ 2 (1) = 4.70, p = 0.030; Tino, χ 2 (1) = 4.10, p = 0.043; "Talk", Peace, χ 2 (1) = 13.95, p < 0.001; χ 2 (1) = 0.03, p = 0.857). The results of Experiment 5 are consistent with those of Experiment 4. The present results suggest that on which side of the dolphin's body the sign movement was presented, or more specifically, from which eye the input was coming, is critical for identifying the signs, especially those having different meanings between left-right mirror images. Was accurate identification difficult due to visual field restriction simply because the critical motion information of the sign was presented on the side of the occluded eye? Indeed, previous studies have shown that a blind spot exists in the anterior rostral region of the dolphin (Xitco et al., 2004). However, this visual field restriction account could not explain why there was no difference in performance between congruent and incongruent trials in the right-eye-only condition (except for "Talk" in Tino). In addition, recent studies have reported that dolphins see the area at the anterior rostrum, previously thought to be a blind spot. (Gunnars et al., 2021). Therefore, it would be better to assume that the observed differences were due to information processing after visual input from the eye. More clearly than in Experiment 4, Experiment 5 strongly suggests the possibility of lateralization of sign discrimination, especially discrimination of left-right mirror-image signs. Our results show the right-eye advantage in sign discrimination. In addition, the congruency effect on the discrimination of mirror-image signs was evident in the left-eye-only condition. In contrast, the dolphins performed better in the right-eye-only condition regardless of congruency. These results are consistent with previous studies reporting the right-eye (left-hemispheric) advantages in shape discrimination and visuospatial cognitive abilities in dolphins (Kilian et al., 2010). General Discussion In this study, we examined the visuospatial cognitive abilities of bottlenose dolphins by manipulating the spatial relationship between the trainer and the dolphins while discriminating gestural signs that had different meanings for left-right mirror images. We found two significant findings. First, the dolphins used an egocentric rather than an object-based frame of reference in recognizing the signs, and second, their recognition of signs was right-eye (left-hemispheric) dominant. We observed left-right reversed responses to "Talk" consistently in the condition of turning their backs to the trainer in Experiment 1 and in the inverted posture in Experiment 2. These results are strong evidence for using their body axis as a frame of reference. On the other hand, in "Bye", which required motor responses counter-corresponding to the movements of the signs, there were very few left-right reversed responses from the trainer's perspective. Although we interpreted these results as a correspondence between the sign movement and their motion direction, these could also be interpreted based on the egocentric frame of reference. In Experiment 3, we eliminated the non-arbitrary relationship between the sign and the dolphin's movement using shape signs instead of gestural signs. As a result, the dolphins showed significantly lower accuracy in the inverted posture. More interestingly, further analysis of the error responses revealed that the responses were not left-right reversed but instead that there were strong motion direction biases. These results were difficult to explain in either the egocentric or object-based reference frame but suggest that both of these reference frames may have influenced their responses. Some studies on visuospatial cognition in human children suggest that either egocentric or object-based frames are not used exclusively but interact with each other (Emerson, 1931; Suzuki et al., 1991). In the present study, it might be concluded that while the movement information of the signs facilitated the use of the egocentric frame in the dolphin's decision of swimming directions, the lack of this information (through the replacement of the gestural signs by the shape signs) led to an increased influence of the environmental reference frame. In addition, the pool in which Experiment 3 was conducted was relatively homogeneous internally, with few underwater landmarks available. If the environmental features were made more distinct, the dolphins might rely more heavily on the object-based frames. For example, suppose the dolphins are asked to swim up or down (toward the surface or the bottom of the pool) rather than left or right. Then, we could investigate the interaction between egocentric and object-based frames by testing them in standard (upright) and inverted postures in the water using shape signs for up and down directions. In the second test of Experiment 3, Thihra often responded to "×" and "●" after returning from the inverted posture to the standard upright posture. The trainer had not trained this behavior, but it occurred spontaneously during the test period. Captive dolphins in aquariums are generally well-trained by trainers and rarely change their posture during training or performance show. Therefore, as mentioned earlier, this behavior can be considered cognitive offloading resulting from the dolphin's attempt to solve the problem rather than "inappropriate" behavior due to disrupted control by the trainer. In addition to Thihra, although less frequently, the other dolphins sometimes showed similar behaviors, such as turning their head toward the trainer when the sign was presented from the body side in the landing condition in Experiment 4. Cognitive offloading is generally known to improve performance in humans by reducing the cognitive load (Risko & Gilbert, 2016). However, we did not find such a facilitating effect in Thihra; after returning to the standard posture, she always swam rightward. Cognitive offloading is associated with metacognition in humans (Dunn & Risko, 2015), but there are almost no studies of animal metacognition examined from the standpoint of cognitive offloading (cf. "spontaneous" information-seeking behavior; Call & Carpenter, 2001; Rosati & Santos, 2016). Further comparative studies on cognitive offloading will be necessary for the future. In Experiment 2, the dolphins showed worse performances for "Bye" in the inverted posture than in the upright posture. In contrast, they responded to "Bye" perfectly in Experiment 1, even in the dorsal posture (from the trainer's perspective). In Experiment 1, it was evident that the dorsal posture reversed the retinal image horizontally. However, the effect on the vertical axis of the image remains unclear. Unlike primates, dolphins have a wide horizontal visual field along the body axis (Mass & Supin, 2009) because their eyes are laterally oriented. Therefore, when the dolphins rotated 180 degrees around their body axis while maintaining an upright posture like in Experiment 1, their retinal image would be maintained vertically but reversed horizontally. On the other hand, the position of the trainer's head in the retinal image seems to be rostral (i.e., lower), as inferred from the posture of the dolphin on the right of Figure 2B: it is similar to how we humans look behind us by leaning backward. In other words, the vertical axis also might appear to be inverted. However, the dolphins' performances did not deteriorate in the dorsal posture in Experiment 1, suggesting that their retinal image in the dorsal posture might not be upside down. The discussion above may also be directly related to mental rotation. The worse performances for "Bye" and "Talk" in the inverted posture in Experiment 2 indicate that the 180-degree rotated mirror images were difficult to discriminate for them, consistent with the previous studies reporting mental rotation in cetaceans (Murayama & Tobayama, 1995; cf. DeLong et al., 2020). Our study might be unique because the body was rotated (perspective transformation) rather than the stimuli being rotated (object-based transformation). Some human studies have examined the effects of perspective transformation, such as tilting the head (Corballis et al., 1976, 1978). However, almost no studies have been conducted under conditions in which the whole body was rotated (e.g., standing on one's head or lying on one's back). Although these two transformations are functionally equivalent in image rotation on the retina, the effects of physical body rotation on visuospatial perception and cognition remain largely unknown. Like in the present study, the underwater environment may be just appropriate for examining these issues. Further research from the perspective of diving psychology is expected (e.g., Niewiedział et al., 2018). For object-based transformation, a video projection system could rotate the trainer's image and show it to the dolphins. It has been reported that dolphins can respond appropriately to the presentation of signs through video images (Herman et al., 1990; cf. Tomonaga & Sakurai, 2014). A comprehensive discussion comparing the results of object-based and perspective formations would provide further insights into the spatial cognitive abilities of cetaceans. Experiments 4 and 5 examined how the dolphins' performances changed on which side of their body or eye the sign movement was presented. Their performances were generally better when the side on which the sign movement occurred was the same as the side of the body or eye on which the sign was presented (congruent trials) than when it was not (incongruent trials). These results suggest that not only the static sign shape but also the dynamic aspect of the sign may be crucial for discrimination, especially for the signs with different meanings between left-right mirror images. It is known that in humans (e.g., Abrams & Christ, 2003; Pratt et al., 2010) and nonhuman animals (e.g., Matsuno & Tomonaga, 2006), the motion of an object can capture attention. Visuospatial attention to sign movements may play facilitating role in the discrimination of mirror-image signs by dolphins. However, further analyses in Experiments 4 and 5 revealed that this tendency was primarily restricted to conditions in which the signs were presented only to the left side of the body or to the left eye. When the signs were presented from the right side, the difference between congruent and incongruent trials often disappeared (see Figure 10): there was lateralization in the discrimination of mirror-image signs. Our results strongly suggest that shape and mirror-image discriminations in dolphins may be right-eye dominant, therefore, left-hemispheric dominant. Many studies on lateralization in cetaceans, including bottlenose dolphins, have recently accumulated (cf. Güntürkün et al., 2020). So far, right-eye (i.e., left-hemispheric) advantage has been reported in number discrimination (Kilian et al., 2005), shape discrimination (von Fersen et al., 2000; but see Matrai et al., 2019), visuospatial cognition (Kilian et al., 2000), and audio-visual tasks (Delfour & Marten, 2006). On the other hand, left-eye advantage has been reported in social behavior and social cognition (Thieltges et al., 2011; Karenina et al., 2010, 2013; Sakai et al., 2006b). In addition, behavioral laterality in the wild has also been studied intensively in recent years (Karenina et al., 2010, 2013; Kaplan et al., 2019; Sakai et al., 2006b; Siniscalchi et al., 2012). Our results added further findings to these studies and are consistent with the previous findings. Unlike other terrestrial mammals, including humans (Gunia et al., 2021; Hopkins et al., 1993; Patterson & Bradshaw, 1975; Piazza et al., 2006; Corballis et al., 2010; Priftis et al., 2003; Moeller et al., 2015), visuospatial processing is lateralized to the left hemisphere in bottlenose dolphins. However, the previous and our results would still be insufficient to confirm this conclusion. Furthermore, we cannot adequately address why the dolphin's hemispheric difference is different from other mammals. More research efforts are needed. Finally, we discuss the limitations of this study. The major weakness is the small number of participants. However, this is not limited to our study but is true for other studies on captive dolphins. This is a limitation derived from the circumstances of dolphins in captivity. Field studies might also have other limitations, such as visibility, accessibility, etc. The only way to overcome these limitations is to accumulate studies with small numbers of cases. Based on the findings accumulated in this way, we could conduct meta-analyses to develop testable hypotheses regarding visuospatial cognition and laterality in brain function in dolphins. Another hopeful strategy would be multi-institutional collaborations. This trend is rapidly progressing against the reproducibility crisis in psychology (Open Science Collaboration, 2015), and several projects (so-called ManyXs projects) have already launched in the area of comparative cognition in nonhuman primates, birds, and dogs (Alberghina et al., 2022; Lambert et al., 2022; ManyPrimates, 2019a, b). Although the current efforts mainly focus on replication studies, such a project could be applied to hypothesis-building or hypothesis-testing research in cetaceans, where the number of available individuals is inevitably limited in each facility. Future collaboration among researchers will be essential Declarations Acknowledgments The authors thank Mr. M. Soichi, H. Nitto, M. Kurita, and the Port of Nagoya Public Aquarium staff, and Mr. K. Kuroyanagi, M. Tsuchiya, K. Kawamoto, K. Saito, and the Minamichita Beachland Aquarium staff for their generous support of the present study. We especially thank Mr. K. Kanda, M. Dozaki, and Ms. N. Tsuzuki for their invaluable support of the present study and the preparation of the manuscript. Ethical Approval The experimental procedures were approved by each aquarium and adhered to the Ethical Guidelines for the Conduct of Research on Animals by Zoos and Aquariums issued by the World Association of Zoos and Aquariums (WAZA), the Code of Ethics issued by the Japanese Association of Zoos and Aquariums (JAZA), the Guidelines for Animal Experiments issued by the Japanese Society for Animal Psychology, and the Japanese Act on Welfare and Management of Animals. Competing interests The authors declare that they have no conflicts of interest. Authors' contributions M.T. conceived and designed the present study; M.T., Y. U-I., T. S., and N. S. performed the experiments, analyzed the data, and discussed the results. M.T. wrote the paper, and all authors commented on the manuscript. Funding This study was financially supported by JSPS-MEXT Grants-in-Aid for Scientific Research (23220006 and 15H05709). Availability of data and materials All the data used for this study are available from the supplementary material. References Alberghina, D., Bray, E., Buchsbaum, D., Byosiere, S. E., Espinosa, J., Gnanadesikan, G., … Stevens, J. R. (2022). ManyDogs project: a big team science approach to investigating canine behavior and cognition. PsyArXiv. https://doi.org/10.31234/osf.io/j82uc Abrams, R. A., & Christ, S. E. (2003). Motion onset captures attention. Psychological Science, 14 (5), 427–432. https://doi.org/10.1111/1467-9280.01458 Armitage, K. L., Bulley, A., & Redshaw, J. (2020). Developmental origins of cognitive offloading. Proceedings of the Royal Society B , 287 (1928), 20192927. https://doi.org/10.1098/rspb.2019.2927 Armitage, K. L., & Redshaw, J. (2022). Children boost their cognitive performance with a novel offloading technique. Child Development, 93 (1), 25–38. https://doi.org/10.1111/cdev.13664 Biro, D., Meade, J., & Guilford, T. (2004). Familiar route loyalty implies visual pilotage in the homing pigeon. Proceedings of the National Academy of Sciences , 101 (50), 17440–17443. https://doi.org/10.1073/pnas.0406984101 Call, J., & Carpenter, M. (2001). Do apes and children know what they have seen? Animal Cognition, 3 (4), 207–220. https://doi.org/10.1007/s100710100078 Camilli, G., & Hopkins, K. D. (1978). Applicability of chi-square to 2 × 2 contingency tables with small expected cell frequencies. Psychological Bulletin, 85 , 163–167. https://doi.org/10.1037/0033-2909.85.1.163 Connor, R., Mann, J., & Watson-Capps, J. (2006). A sex-specific affiliative contact behavior in Indian Ocean bottlenose dolphins, Tursiops sp . Ethology, 112 (7), 631–638. https://doi.org/10.1111/j.1439-0310.2006.01203.x Corballis, M. C. (1997). Mental rotation and the right hemisphere. Brain and Language, 57 (1), 100–121. https://doi.org/10.1006/brln.1997.1835 Corballis, M. C., Birse, K., Paggi, A., Manzoni, T., Pierpaoli, C., & Fabri, M. (2010). Mirror-image discrimination and reversal in the disconnected hemispheres. Neuropsychologia, 48 (6), 1664–1669. https://doi.org/10.1016/j.neuropsychologia.2010.02.011 Corballis, M. C., Nagourney, B. A., Shetzer, L. I., & Stefanatos, G. (1978). Mental rotation under head tilt: Factors influencing the location of the subjective reference frame. Perception & Psychophysics, 24 (3), 263–273. https://doi.org/10.3758/BF03206098 Corballis, M. C., Zbrodoff, J., & Roldan, C. E. (1976). What’s up in mental rotation? Perception & Psychophysics, 19 (6), 525–530. https://doi.org/10.3758/BF03211221 Delfour, F., & Marten, K. (2006). Lateralized visual behavior in bottlenose dolphins ( Tursiops truncatus ) performing audio-visual tasks: The right visual field advantage. Behavioural Processes , 71 (1), 41–50. https://doi.org/10.1016/j.beproc.2005.09.005 DeLong, C. M., Fellner, W., Wilcox, K. T., Odell, K., & Harley, H. E. (2020). Visual perception in a bottlenose dolphin ( Tursiops truncatus ): Successful recognition of 2-D objects rotated in the picture and depth planes. Journal of Comparative Psychology, 134 , 180–196. https://doi.org/10.1037/com0000207 Dudzinski, K., & Ribic, C. (2017). Pectoral fin contact as a mechanism for social bonding among dolphins. Animal Behavior and Cognition, 4 (1), 30–48. https://doi.org/10.12966/abc.03.02.2017 Dunn, T. L., & Risko, E. F. (2016). Toward a metacognitive account of cognitive offloading. Cognitive Science, 40 (5), 1080–1127. https://doi.org/10.1111/cogs.12273 Emerson, L. L. (1931). The effect of bodily orientation upon the young child's memory for position of objects. Child Development, 2 (2), 125–142. https://doi.org/10.2307/1125419 Farah, M. J. (1989). The neural basis of mental imagery. Trends in Neurosciences, 12 (10), 395–399. https://doi.org/10.1016/0166-2236(89)90079-9 Freas, C. A., & Cheng, K. (2022). The basis of navigation across species. Annual Review of Psychology, 73 (1), 217–241. https://doi.org/10.1146/annurev-psych-020821-111311 Fujita, K., & Matsuzawa, T. (1989). Comparison of the representational abilities of chimpanzees and humans. Primate Research, 5 (1), 58–74. https://doi.org/10.2354/psj.5.58 (Japanese text with English abstract) Furuya, I. (1998). Use of right-left cues in pigeons. Cognitive Studies, 5 (3), 77–86. https://doi.org/10.11225/jcss.5.3_77 (Japanese text with English abstract) Gaunet, F., & Berthoz, A. (2000). Mental rotation for spatial environment recognition. Brain Research. Cognitive Brain Research, 9 (1), 91–102. https://doi.org/10.1016/s0926-6410(99)00038-5 Gunnars, T. S., Barnes, M., Milner, R., Walker, K., Abramson, C., & Bruck, J. (2021). The visual field of the bottlenose dolphin ( Tursiops truncatus ). The Animal Behavior Society 2021 Virtual Meeting. Oral presentation. August 5, 2021. Güntürkün, O., Ströckens, F., & Ocklenburg, S. (2020). Brain lateralization: A comparative perspective. Physiological Reviews, 100 (3), 1019–1063. https://doi.org/10.1152/physrev.00006.2019 Hassett, T. C., Lord, V. K., & Hampton, R. R. (2022). Rhesus monkeys manipulate mental images. Cognition, 228 , 105225. https://doi.org/10.1016/j.cognition.2022.105225 Herman, L. M., Morrel-Samuels, P., & Pack, A. A. (1990). Bottlenosed dolphin and human recognition of veridical and degraded video displays of an artificial gestural language. Journal of Experimental Psychology. General, 119 (2), 215–230. https://doi.org/10.1037//0096-3445.119.2.215 Hollard, V. D., & Delius, J. D. (1982). Rotational invariance in visual pattern recognition by pigeons and humans. Science, 218 (4574), 804–806. https://doi.org/10.1126/science.7134976 Hopkins, W. D., Fagot, J., & Vauclair, J. (1993). Mirror-image matching and mental rotation problem solving by baboons ( Papio papio ): Unilateral input enhances performance. Journal of Experimental Psychology. General, 122 (1), 61–72. https://doi.org/10.1037//0096-3445.122.1.61 Huttenlocher, J., & Presson, C. C. (1973). Mental rotation and the perspective problem. Cognitive Psychology, 4 , 277–299. https://doi.org/10.1016/0010-0285(73)90015-7 Huttenlocher, J., & Presson, C. C. (1979). The coding and transformation of spatial information. Cognitive Psychology, 11 (3), 375–394. https://doi.org/10.1016/0010-0285(79)90017-3 Kaplan, J. D., Goodrich, S. Y., Melillo-Sweeting, K., & Reiss, D. (2019). Behavioural laterality in foraging bottlenose dolphins ( Tursiops truncatus ). Royal Society Open Science, 6 (11), 190929. https://doi.org/10.1098/rsos.190929 Karenina, K., Giljov, A., Baranov, V., Osipova, L., Krasnova, V., & Malashichev, Y. (2010). Visual laterality of calf–mother interactions in wild whales. PLOS ONE, 5 (11), e13787. https://doi.org/10.1371/journal.pone.0013787 Karenina, K., Giljov, A., Ivkovich, T., Burdin, A., & Malashichev, Y. (2013). Lateralization of spatial relationships between wild mother and infant orcas, Orcinus orca . Animal Behaviour, 86 (6), 1225–1231. https://doi.org/10.1016/j.anbehav.2013.09.025 Kilian, A., Fersen, L. von, & Güntürkün, O. (2005). Left hemispheric advantage for numerical abilities in the bottlenose dolphin. Behavioural Processes , 68 (2), 179–184. https://doi.org/10.1016/j.beproc.2004.11.003 Kilian, A., von Fersen, L., & Güntürkün, O. (2000). Lateralization of visuospatial processing in the bottlenose dolphin ( Tursiops truncatus ). Behavioural Brain Research, 116 (2), 211–215. https://doi.org/10.1016/s0166-4328(00)00273-4 Kosslyn, S. M. (1995). Mental imagery. In D. N. Osherson (Ed.), Visual cognition: An invitation to cognitive science, Vol. 2 , 2nd ed (pp. 267–296). The MIT Press. Lambert, M., Farrar, B., Garcia-Pelegrin, E., Reber, S., & Miller, R. (2022). ManyBirds: A multi-site collaborative Open Science approach to avian cognition and behavior research. Animal Behavior and Cognition, 9 (1), 133–152. http://dx.doi.org/10.26451/abc.09.01.11.2022 Lohmann, A., Delius, J. D., Hollard, V. D., & Friesel, M. F. (1988). Discrimination of shape reflections and shape orientations by Columba livia . Journal of Comparative Psychology (Washington, D.C.: 1983), 102 (1), 3–13. https://doi.org/10.1037/0735-7036.102.1.3 ManyPrimates (2019a). Establishing an infrastructure for collaboration in primate cognition research. PLOS ONE, 14 (10), e0223675. https://doi.org/10.1371/journal.pone.0223675 ManyPrimates (2019b). Collaborative open science as a way to reproducibility and new insights in primate cognition research. Japanese Psychological Review, 62 (3), 205–220. https://doi.org/10.24602/sjpr.62.3_205 Mass, A. M., & Supin, A. Ya. (2009). Vision. In W. F. Perrin, B. Würsig, & J. G. M. Thewissen (Eds.), Encyclopedia of Marine Mammals (Second Edition) (pp. 1200–1211). Academic Press. https://doi.org/10.1016/B978-0-12-373553-9.00275-3 Matrai, E., Hoffmann-Kuhnt, M., & Kwok, S. T. (2019). Lateralization in accuracy, reaction time and behavioral processes in a visual discrimination task in an Indo-Pacific bottlenose dolphin ( Tursiops aduncus ). Behavioural Processes , 162 , 112–118. https://doi.org/10.1016/j.beproc.2019.02.003 Matsuno, T., & Tomonaga, M. (2006). Visual search for moving and stationary items in chimpanzees ( Pan troglodytes ) and humans ( Homo sapiens ). Behavioural Brain Research, 172 (2), 219–232. https://doi.org/10.1016/j.bbr.2006.05.004 Mauck, B., & Dehnhardt, G. (1997). Mental rotation in a California sea lion ( Zalophus californianus ). Journal of Experimental Biology, 200 (9), 1309–1316. https://doi.org/10.1242/jeb.200.9.1309 Moeller, K., Willmes, K., & Klein, E. (2015). A review on functional and structural brain connectivity in numerical cognition. Frontiers in Human Neuroscience, 9 , 227. https://www.frontiersin.org/articles/ 10.3389/fnhum.2015.00227 Niewiedział, D., Kolańska, M., Dąbrowiecki, Z., Jerzemowski, M., Siermontowski, P., Kobos, Z., & Olszański, R. (2018). Psychological aspects of diving in selected theoretical and research perspectives. Polish Hyperbaric Research, 62 (1), 43–54. https://doi.org/10.2478/phr-2018-0003 Open Science Collaboration (2015). Estimating the reproducibility of psychological science. Science, 349 , aac4716. https://doi.org/10.1126/science.aac4716 Patterson, K., & Bradshaw, J. L. (1975). Differential hemispheric mediation of nonverbal visual stimuli. Journal of Experimental Psychology. Human Perception and Performance, 1 (3), 246–252. https://doi.org/10.1037//0096-1523.1.3.246 Piaget, J., & Inhelder, B. (1956). The child's conception of space . London: Routledge & Kegan Paul. Piazza, M., Mechelli, A., Price, C. J., & Butterworth, B. (2006). Exact and approximate judgements of visual and auditory numerosity: An fMRI study. Brain Research, 1106 (1), 177–188. https://doi.org/10.1016/j.brainres.2006.05.104 Poucet, B. (1993). Spatial cognitive maps in animals: New hypotheses on their structure and neural mechanisms. Psychological Review, 100 (2), 163–182. https://doi.org/10.1037/0033-295x.100.2.163 Pratt, J., Radulescu, P. V., Guo, R. M., & Abrams, R. A. (2010). It's alive! Animate motion captures visual attention. Psychological Science, 21 (11), 1724–1730. https://doi.org/10.1177/0956797610387440 Presson, C. C. (1982). Strategies in spatial reasoning. Journal of Experimental Psychology: Learning, Memory, and Cognition, 8 , 243–251. https://doi.org/10.1037/0278-7393.8.3.2430 Presson, C. C., & Somerville, S. C. (1985). Beyond egocentrism: A new look at the beginnings of spatial representation. In H. M. Wellman (Ed.), Children's searching: The development of search skill and spatial representation (pp. 1–26). Psychology Press. Priftis, K., Rusconi, E., Umiltà, C., & Zorzi, M. (2003). Pure agnosia for mirror stimuli after right inferior parietal lesion. Brain: A Journal of Neurology, 126 (Pt 4), 908–919. https://doi.org/10.1093/brain/awg075 Pylyshyn, Z. W. (2002). Mental imagery: In search of a theory. Behavioral and Brain Sciences, 25 (2), 157–182. https://doi.org/10.1017/S0140525X02000043 Risko, E. F., & Gilbert, S. J. (2016). Cognitive offloading. Trends in Cognitive Sciences, 20 (9), 676–688. https://doi.org/10.1016/j.tics.2016.07.002 Rosati, A. G., & Santos, L. R. (2016). Spontaneous metacognition in rhesus monkeys. Psychological Science, 27 (9), 1181–1191. https://doi.org/10.1177/0956797616653737 Sakai, M., Hishii, T., Takeda, S., & Kohshima, S. (2006a). Flipper rubbing behaviors in wild bottlenose dolphins ( Tursiops aduncus ). Marine Mammal Science, 22 (4), 966–978. https://doi.org/10.1111/j.1748-7692.2006.00082.x Sakai, M., Hishii, T., Takeda, S., & Kohshima, S. (2006b). Laterality of flipper rubbing behaviour in wild bottlenose dolphins ( Tursiops aduncus ): Caused by asymmetry of eye use? Behavioural Brain Research, 170 (2), 204–210. https://doi.org/10.1016/j.bbr.2006.02.018 Sakai, M., Morisaka, T., Kogi, K., Hishii, T., & Kohshima, S. (2010). Fine-scale analysis of synchronous breathing in wild Indo-Pacific bottlenose dolphins ( Tursiops aduncus ). Behavioural Processes , 83 (1), 48–53. https://doi.org/10.1016/j.beproc.2009.10.001 Shepard, R. N. (1978). The mental image. American Psychologist, 33 , 125–137. https://doi.org/10.1037/0003-066X.33.2.125 Shepard, R. N., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171 (3972), 701–703. https://doi.org/10.1126/science.171.3972.701 Siniscalchi, M., Dimatteo, S., Pepe, A. M., Sasso, R., & Quaranta, A. (2012). Visual lateralization in wild striped dolphins (Stenella coeruleoalba) in response to stimuli with different degrees of familiarity. PLoS One, 7 ( 1 ), e30001. https://doi.org/10.1371/journal.pone.0030001 Suzuki, T., Matsuzaki, Y., & Saeki, Y. (1991). Children's organization of a spatial array separated from its surroundings. Japanese Journal of Developmental Psychology, 1 (2), 128–135. https://doi.org/10.11201/jjdp.1.128 (Japanese text with English abstract) Tarpley, R. J., & Ridgway, S. H. (1994). Corpus callosum size in delphinid cetaceans. Brain, Behavior and Evolution, 44 (3), 156–165. https://doi.org/10.1159/000113587 Tcaci Popescu, S., & Wexler, M. (2012). Spontaneous body movements in spatial cognition. Frontiers in Psychology, 3 , 136. https://www.frontiersin.org/articles/ 10.3389/fpsyg.2012.00136 Thewissen, J. G. M. (2018). Brain. In B. Würsig, J. G. M. Thewissen, & K. M. Kovacs (Eds.), Encyclopedia of Marine Mammals (Third Edition) (pp. 137–140). Academic Press. https://doi.org/10.1016/B978-0-12-804327-1.00077-7 Thieltges, H., Lemasson, A., Kuczaj, S., Böye, M., & Blois-Heulin, C. (2011). Visual laterality in dolphins when looking at (un)familiar humans. Animal Cognition, 14 (2), 303–308. https://doi.org/10.1007/s10071-010-0354-5 Tomonaga, M., & Sakurai, N. (2014). Recognition of rotated video images of gestural signs by bottlenose dolphins [Unpublished raw data]. Minamichita Beachland Aquarium. Tomonaga, M., & Uwano, Y. (2010). Bottlenose dolphins' ( Tursiops truncatus ) theory of mind as demonstrated by responses to their trainers' attentional states. International Journal of Comparative Psychology, 23 (3). https://doi.org/10.46867/ijcp.2010.23.03.03 Tomonaga, M., Uwano, Y., Ogura, S., Chin, H., Dozaki, M., & Saito, T. (2015). Which person is my trainer? Spontaneous visual discrimination of human individuals by bottlenose dolphins ( Tursiops truncatus ). SpringerPlus, 4 (1), 352. https://doi.org/10.1186/s40064-015-1147-8 Tomonaga, M., Uwano, Y., & Saito, T. (2014). How dolphins see the world: A comparison with chimpanzees and humans. Scientific Reports, 4 , 3717. https://doi.org/10.1038/srep03717 von Fersen, L., Schall, U., & Güntürkün, O. (2000). Visual lateralization of pattern discrimination in the bottlenose dolphin ( Tursiops truncatus ). Behavioural Brain Research, 107 (1), 177–181. https://doi.org/10.1016/S0166-4328(99)00142-4 Wang, R. F., & Spelke, E. S. (2002). Human spatial representation: Insights from animals. Trends in Cognitive Sciences, 6 (9), 376–382. https://doi.org/10.1016/S1364-6613(02)01961-7 Williams, T. M. (2001). Intermittent swimming by mammals: a strategy for increasing energetic efficiency during diving. American Zoologist, 41 (2), 166–176. https://doi.org/10.1093/icb/41.2.166 Williams, R., Trites, A. W., & Bain, D. E. (2002). Behavioural responses of killer whales ( Orcinus orca ) to whale-watching boats: Opportunistic observations and experimental approaches. Journal of Zoology, 256 (2), 255–270. https://doi.org/10.1017/S0952836902000298 Xitco Jr., M. J., Gory, J. D., & Kuczaj II, S. A. (2004). Dolphin pointing is linked to the attentional behavior of a receiver. Animal Cognition, 7 , 231–238. https://doi.org/10.1007/s10071-004-0217-z Zacks, J. M., & Michelon, P. (2005). Transformations of visuospatial images. Behavioral and Cognitive Neuroscience Reviews, 4 (2), 96–118. https://doi.org/10.1177/1534582305281085 Zacks, J. M., Mires, J., Tversky, B., & Hazeltine, E. (2000). Mental spatial transformations of objects and perspective. Spatial Cognition and Computation, 2 (4), 315–332. https://doi.org/10.1023/A:1015584100204 Zapetis, M., & Szesciorka, A. (2018). Cetacean navigation. In J. Vonk & T. Shackelford (Eds.), Encyclopedia of Animal Cognition and Behavior (pp. 1–7). Springer International Publishing. https://doi.org/10.1007/978-3-319-47829-6_986-1 Additional Declarations No competing interests reported. Supplementary Files TableS1.pdf Table S1. Summary of sessions and trials for each experiment. TableS2.pdf Table S2. Summary of the statistical tests for each experiment. SupplementaryMaterialRawData.xlsx Supplementary File 1. Raw dataset for each experiment (xlsx format). SupplementaryFile2.docx Supplementary File 2. Explanation of Supplementary Video 1. Exp1QVentral3rdSession11signs.mpg Supplementary Video 1. The third session of the test with the ventral posture for Quick in Experiment 1. Cite Share Download PDF Status: Published Journal Publication published 15 Jun, 2023 Read the published version in Animal Cognition → Version 1 posted Editorial decision: Major revision 18 May, 2023 Reviews received at journal 07 Apr, 2023 Reviewers agreed at journal 04 Mar, 2023 Reviewers invited by journal 04 Mar, 2023 Editor assigned by journal 27 Feb, 2023 Submission checks completed at journal 22 Feb, 2023 First submitted to journal 20 Feb, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-2606167","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":178166967,"identity":"78be20e2-a0a7-486c-a992-6eb3e89291c2","order_by":0,"name":"Masaki Tomonaga","email":"data:image/png;base64,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","orcid":"","institution":"Japan Monkey Centre","correspondingAuthor":true,"prefix":"","firstName":"Masaki","middleName":"","lastName":"Tomonaga","suffix":""},{"id":178166968,"identity":"1f750853-5cda-430e-b9d6-b61d724125e3","order_by":1,"name":"Yuka Uwano-Ito","email":"","orcid":"","institution":"Port of Nagoya Public Aquarium","correspondingAuthor":false,"prefix":"","firstName":"Yuka","middleName":"","lastName":"Uwano-Ito","suffix":""},{"id":178166969,"identity":"fc2f4f5d-9421-4225-81f9-1b6723a350c1","order_by":2,"name":"Toyoshi Saito","email":"","orcid":"","institution":"Port of Nagoya Public Aquarium","correspondingAuthor":false,"prefix":"","firstName":"Toyoshi","middleName":"","lastName":"Saito","suffix":""},{"id":178166970,"identity":"48626512-8730-4fab-8ae7-d35aafeda0d8","order_by":3,"name":"Natsuko Sakurai","email":"","orcid":"","institution":"Minamichita Beachland Aquarium","correspondingAuthor":false,"prefix":"","firstName":"Natsuko","middleName":"","lastName":"Sakurai","suffix":""}],"badges":[],"createdAt":"2023-02-20 05:14:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-2606167/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-2606167/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10071-023-01799-6","type":"published","date":"2023-06-15T21:13:03+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":33426712,"identity":"3cd16b6d-6464-40bb-94c1-fe4f7122ba52","added_by":"auto","created_at":"2023-02-24 21:25:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":464409,"visible":true,"origin":"","legend":"\u003cp\u003eExamples of gestural signs used at Port of Nagoya Public Aquarium. These signs were used as the test signs. See also Supplementary Video 1 for the other signs.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/87b16ac4ed0d30d400b70211.png"},{"id":33426929,"identity":"ca7bafb6-353f-43bd-9ade-6286a5a06fe2","added_by":"auto","created_at":"2023-02-24 21:41:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1049231,"visible":true,"origin":"","legend":"\u003cp\u003eTesting setup for each experiment. (A) Testing setup in Tomonaga et al. (2010), Left: the trainer standing in front, right: the trainer standing back. (B) Experiment 1, left: ventral posture, right: dorsal posture. (C) Experiment 2, left: standard upright posture (dorsal up), right: inverted posture (ventral up). (D) Experiment 3, left: upright posture, right: inverted posture. The trainer held the shape sign \"●\". (E) Experiment 4, left: front, right: right side. (F) Experiment 5, left: both-eyes condition, right: left-eye-only condition.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/c1784aa9bb74009943fb561b.png"},{"id":33426451,"identity":"63a1853b-0913-4d3e-9ad6-5d722facec5d","added_by":"auto","created_at":"2023-02-24 21:09:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":18911,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the test trials for Experiment 1. Double-quotations indicate the gestural signs. \u003cem\u003eItalics\u003c/em\u003e indicate the dolphin participants. Asterisks beneath each bar indicate the results of binomial tests, and those above the bars indicate the results of Chi-square tests; ***: \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001, ***: \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.01, *: \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.05. V: ventral posture, D: dorsal posture.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/31c8a7643548db2d447afdcf.png"},{"id":33426593,"identity":"aa74bdfc-5ac7-444f-8551-9e7f0f8be105","added_by":"auto","created_at":"2023-02-24 21:17:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34775,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the test trials for Experiment 2. Up: upright posture, Inv: inverted posture.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/700fe06e28101e71cfe69676.png"},{"id":33426788,"identity":"692654a9-dd1c-4b1b-a689-25222de76280","added_by":"auto","created_at":"2023-02-24 21:33:07","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":17628,"visible":true,"origin":"","legend":"\u003cp\u003eResults of Experiment 3. Left: the first test, right: the second test. BL: baseline trials.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/16bd5f00e3940d0371840c21.png"},{"id":33852098,"identity":"46e1f56f-d900-430f-be36-0d6c0a304a2b","added_by":"auto","created_at":"2023-03-06 16:45:34","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":55481,"visible":true,"origin":"","legend":"\u003cp\u003eDefinition of \"congruency\" in (A) Experiments 4 and (B) 5. See details in the text.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/38c5e056e37c1329e9f4c9a5.png"},{"id":33852089,"identity":"5021a3a3-e093-441e-a4b2-d4edd97709a5","added_by":"auto","created_at":"2023-03-06 16:45:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":19418,"visible":true,"origin":"","legend":"\u003cp\u003eResults of Experiment 4: Mean accuracy for each position in the main test, separately for baseline (BL) and test trials. F: front, L: left side, R: right side.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/e7d7c0c46c08008f4dc10004.png"},{"id":33426597,"identity":"a8997912-dc29-4c0c-9b31-1ee4f619bab3","added_by":"auto","created_at":"2023-02-24 21:17:07","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":44134,"visible":true,"origin":"","legend":"\u003cp\u003eResults of Experiment 4: Results of the test trials as a function of the trainer’s position and congruency. Asterisks between the left and right conditions indicate the results of Mantel-Haenszel test. C: congruent trials, I: Incongruent trials.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/651e4db6d582e127d897c095.png"},{"id":33426715,"identity":"709f8d15-f881-46e9-af0b-c94fec93245b","added_by":"auto","created_at":"2023-02-24 21:25:07","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":15762,"visible":true,"origin":"","legend":"\u003cp\u003eResults of Experiment 5: Mean accuracy for each eye condition, separately for baseline (BL) and test trials. B: both eyes, L: left eye only, R: right eye only.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/0abe35ec228d9b72a59f391f.png"},{"id":33426601,"identity":"0541d9a0-14d8-48d1-869b-33446cd72259","added_by":"auto","created_at":"2023-02-24 21:17:07","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":50804,"visible":true,"origin":"","legend":"\u003cp\u003eResults of Experiment 5: Results of the test trials as a function of the single eye conditions and congruency. Asterisks between the left and right conditions indicate the results of Mantel-Haenszel test.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/740c81b53abd3ed2653cd5fd.png"},{"id":44731215,"identity":"58fbcf56-dd20-4dbf-b2d9-2d66f49ca9d0","added_by":"auto","created_at":"2023-10-16 21:40:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2204971,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/55d45098-2ddc-4e1f-a8eb-332f476b9304.pdf"},{"id":33426928,"identity":"bd996685-78f5-43da-b650-543d91781fdb","added_by":"auto","created_at":"2023-02-24 21:41:07","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":212323,"visible":true,"origin":"","legend":"\u003cp\u003eTable S1. Summary of sessions and trials for each experiment.\u003c/p\u003e","description":"","filename":"TableS1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/74fa2d4f0d447607d5c40aa3.pdf"},{"id":33426459,"identity":"b844a404-d725-494e-b300-f21ada304447","added_by":"auto","created_at":"2023-02-24 21:09:07","extension":"pdf","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":380773,"visible":true,"origin":"","legend":"\u003cp\u003eTable S2. Summary of the statistical tests for each experiment.\u003c/p\u003e","description":"","filename":"TableS2.pdf","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/f837eb795c0f7a03829440b0.pdf"},{"id":33426790,"identity":"d74c1c19-38dd-458e-be39-142bc087641c","added_by":"auto","created_at":"2023-02-24 21:33:07","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":210890,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary File 1. Raw dataset for each experiment (xlsx format).\u003c/p\u003e","description":"","filename":"SupplementaryMaterialRawData.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/2a35c001e182e000a019e4e2.xlsx"},{"id":33426717,"identity":"3a095b18-a358-4050-b34b-0ddbb306be12","added_by":"auto","created_at":"2023-02-24 21:25:07","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":14226,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary File 2. Explanation of Supplementary Video 1.\u003c/p\u003e","description":"","filename":"SupplementaryFile2.docx","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/e21a8f4b46bce687913412d4.docx"},{"id":33426464,"identity":"ab3727aa-198c-48a0-85bc-5056208d102f","added_by":"auto","created_at":"2023-02-24 21:09:15","extension":"mpg","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":147914752,"visible":true,"origin":"","legend":"\u003cp\u003eSupplementary Video 1. The third session of the test with the ventral posture for Quick in Experiment 1.\u003c/p\u003e","description":"","filename":"Exp1QVentral3rdSession11signs.mpg","url":"https://assets-eu.researchsquare.com/files/rs-2606167/v1/84525b1496795b2f9ef812a2.mpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Left or right, that is the question: Use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncates)","fulltext":[{"header":"Introduction","content":"\u003cp\u003eCetaceans such as dolphins exhibit a variety of postures underwater and on the surface. Not only do they swim with their body axis horizontally, but their body axis is vertical during deep dives or spy hops (Williams, 2001; Williams et al., 2001, 2002). In addition, when rubbing with other individuals, they sometimes flip their body upside down (Dudzinski \u0026amp; Ribic, 2017; Sakai et al., 2006a, b). How do they perceive and recognize this three-dimensional space during moving freely underwater? It is evident that echolocation plays an essential role in dolphins\u0026apos; navigation (Zapetis \u0026amp; Szesciorka, 2018), but they may also utilize visual cues, especially in shallower waters or within short distances (e.g., positional relationships with other individuals; Connor et al., 2006; Karenina et al., 2010, 2013). The fact that they show rubbing and synchronous breathing with specific individuals more frequently than others would suggest their use of visual cues (Sakai et al., 2006a, 2010).\u003c/p\u003e\n\u003cp\u003eAmong various aspects of spatial cognition in bottlenose dolphins, the present study mainly focused on the visual recognition of left-right relationships. In humans, it has been known that the body axis (or perspective) of the self plays an important role in the development of visuospatial cognition (Piaget \u0026amp; Inhelder, 1956; but see Presson \u0026amp; Sommerville, 1985, for further discussion). This is exemplified in the classic \u0026quot;three-mountain\u0026quot; problem. In this task, children are presented with models of three differently shaped mountains arranged spatially and asked what those mountains look like from a different perspective than the children\u0026apos;s. Children\u0026apos;s responses change developmentally from \u0026quot;egocentric,\u0026quot; in which they focus on their own perspective from any position to \u0026quot;decentralized,\u0026quot; in which they understand the relationship between different perspectives and visibility (Piaget \u0026amp; Inhelder, 1956).\u003c/p\u003e\n\u003cp\u003eOn the other hand, another important task related to spatial cognition is \u0026quot;mental rotation\u0026quot; (Shepard \u0026amp; Metzler, 1971). When observers discriminate or make a same-different judgment of mirror-reversed images (such as p vs. q), accuracy and speed deteriorate as a function of the angle of stimulus presentation. In particular, a linear increase in reaction times as a function of stimulus rotation has been robustly replicated in humans, suggesting that we mentally rotate the representation of these stimuli. Thus, it has been argued that such mental representations are image-like (Farah, 1989; Koslyn, 1995; Shepard, 1978; but see Pylysyn, 2002).\u003c/p\u003e\n\u003cp\u003eBoth these two tasks are similar in that they involve manipulations of spatial images. However, there is also a critical difference: they involve different spatial transformations (Presson, 1982; Zacks \u0026amp; Michelon, 2005; Zacks et al., 2000). The three-mountain problem, also known as the \u0026quot;perspective-taking task,\u0026quot; requires a mental transformation of the observer\u0026apos;s perspective. In contrast, the mental rotation task requires not a perspective transformation but a spatial transformation of objects (within the mental image). And this disparity in spatial transformations constitutes the basis for the variation in task performances and the developmental processes underlying them. (e.g., Huttenlocher \u0026amp; Presson, 1973, 1979).\u003c/p\u003e\n\u003cp\u003eHow, then, is visuospatial ability in nonhuman animals? So far, there are very few systematic studies on this topic from the comparative perspective except for the studies on navigation and cognitive maps (Biro et al., 2004; Freas \u0026amp; Cheng, 2022; Poucet, 1993; Wang \u0026amp; Spelke, 2002). Among these few studies, for example, Furuya (1998) conducted a series of experiments on pigeons and showed that they might use the egocentric frame of reference to perform the left-right discrimination task within a relatively small Skinner box. The mental rotation has also been studied in pigeons, monkeys, chimpanzees, sea lions, and dolphins, but the results are mixed (Delius \u0026amp; Hollard, 1995; Fujita \u0026amp; Matsuzawa, 1989; Hassett et al., 2022; Hollard \u0026amp; Delius, 1982; Mauck \u0026amp; Dehnhardt, 1997; Murayama \u0026amp; Tobayama, 1995; Lohman et al., 1988; see also DeLong et al., 2020). Some studies found changes in performance according to the angle of stimulus rotation (Hassett et al., 2022; Mauck \u0026amp; Dehnhardt, 1997; Murayama \u0026amp; Tobayama, 1995), whereas others did not (Fujita \u0026amp; Matsuzawa, 1989; Hollard \u0026amp; Delius, 1982).\u003c/p\u003e\n\u003cp\u003eThe present study aimed to examine the visuospatial perception in captive bottlenose dolphins by focusing on gestural signs used for them. Gestural signs used in dolphin training and performance shows vary from aquarium to aquarium. Some signs involve moving both hands at the same time. The other signs use only one hand irrespective of the left or right, but some have different meanings depending on which hand is used. For example, at the Port of Nagoya Public Aquarium, Japan, in response to the sign \u0026quot;Right-Talk\u0026quot; (hereafter, we use double quotation marks to indicate the name of the sign), in which the trainer holds his/her right hand out to the side at the waist and rotates it around the wrist, the dolphins produce a specific sound. On the other hand, they produce a different sound to the same action with the left hand (\u0026quot;Left-Talk\u0026quot;, Figure 1). Also, in response to the sign \u0026quot;Right-Bye\u0026quot;, in which only the right hand is waved at shoulder height like a bye-bye gesture, the dolphins swim slowly to the left from the trainer\u0026apos;s perspective (or to the right from the dolphins\u0026apos; perspective) while flapping their left flippers (the opposite direction for the left hand, \u0026quot;Left-Bye\u0026quot;). Tomonaga et al. (2010) studied the dolphins that had already acquired the responses to these signs to investigate their understanding of human\u0026apos;s attentional state. When the trainer turned his/her back to the dolphin during presenting the sign (Figure 2A), the accuracy was significantly worse than when the trainer faced the dolphins. Tomonaga et al. concluded that the trainer\u0026apos;s attentional state (e.g., loss of eye contact) did not significantly affect the performance declines observed in their study. Instead, they suggested that the impairments in sign comprehension resulted from the trainer\u0026apos;s left-right reversal.\u003c/p\u003e\n\u003cp\u003eInspired by Tomonaga et al.\u0026apos;s study (2010), the present study further examined left-right discrimination using gestural signs in bottlenose dolphins by manipulating the spatial relationships between dolphins and trainers in various ways. What frames of reference do dolphins use to recognize mirror-image gestural signs, that is, to distinguish between left and right? As spatial frames of reference, Zacks and Michelon (2005) proposed three frames; an egocentric frame, an object-based frame, and an environment-based frame. The egocentric frame locates objects in the external world around one\u0026apos;s own body\u0026apos;s coordinate system. An egocentric reference frame is one in which objects are located relative to axes defined with respect to the self. This frame corresponds to what Piaget called egocentricity (Piaget \u0026amp; Inhelder, 1956). On the other hand, an object-based frame locates things relative to axes defined with respect to a specific object in the environment, for example, a trainer facing dolphins or a landmark such as an artificial rock in a swimming pool. If the dolphins in Tomonaga et al.\u0026apos;s study could have used the object-based frame, they would have understood the signs according to the body axis of the trainer, but the results were negative. And finally, an environment-based frame locates \u0026quot;things relative to axes defined with respect to a fixed space (Zacks \u0026amp; Michelson, 2005; p.98)\u0026quot;, such as major and minor axes of elliptical pools or geographic directions (north, south, east, west).\u003c/p\u003e\n\u003cp\u003eOf the two types of spatial transformations, perspective and object-based transformations, we adopted the object-based transformation in this study. However, unlike in the studies on mental rotation, since it was impossible to apply transformation directly to objects, that is, to physically rotate a real trainer to present signs (cf. Tomonaga \u0026amp; Sakurai, 2014), we manipulated the postures of the dolphins. Our participant dolphins usually faced the trainer in a vertical posture with their heads above the surface (see Figure 1). In Experiment 1, the dolphins stood upright with their dorsal side facing the trainer and responded to various signs (Figure 2B). In this posture, the body axis did not change from the standard (frontal or ventral) posture, but their retinal images rotated 180 degrees. In Experiment 2, the dolphins responded to the signs shown from the underwater exhibit area while keeping their body axis horizontal underwater. They were tested in two postures: upright, with the ventral side facing downward (standard), and inverted, with the dorsal side facing downward (Figure 2C). In the inverted posture, not only were the retinal images inverted, but their bodies also rotated physically. In humans, when the head is tilted or the body is laid at 90 degrees (prone posture) during the mental rotation experiments, the response profile is also shifted in the direction of the axis of the retina (Corballis et al., 1976, 1978). Thus, these two experiments could provide insights into whether the axis on the retinal coordinates or the body axis is dominant for the dolphin\u0026apos;s visuospatial cognition.\u003c/p\u003e\n\u003cp\u003eIn Experiments 1 and 2, the dolphins had to discriminate left and right of the trainer. In addition, they also had to decide which side they moved in response to \u0026quot;Bye\u0026quot;. In the case of \u0026quot;Bye\u0026quot; at Nagoya Port Aquarium and \u0026quot;High-Speed Run (HSR)\u0026quot; (swimming at high speed in the direction in which the trainer extends her arm) at Minamichita Beachland Aquarium, there are non-arbitrary relationships between the directions of the trainer\u0026apos;s sign and the dolphins\u0026apos; movement. Therefore, in Experiment 3, we trained the dolphins to swim to the left and right using point-symmetric shapes based on arbitrary relationships, i.e., \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot;, instead of the gestural signs for \u0026quot;HSR\u0026quot; (Figure 2D). Using these graphic signs, we examined the effect of postural inversion on their decisions regarding swimming directions.\u003c/p\u003e\n\u003cp\u003eGestural signs in which only one hand moves can be identified by paying attention to the shape of the sign and which side of the body the movement of the sign is on from the dolphin\u0026apos;s perspective. In Experiment 4, the dolphins landed at the poolside, and the trainer presented signs from either the left or right side of them (Figure 2E). For example, if \u0026quot;Right-Talk\u0026quot; (the trainer waves her right hand) is presented in the standard (frontal) position, the hand movement is made on the left side of the body and vice versa from the dolphins\u0026apos; perspective. If the dolphins focus solely on the side of their body where the sign movement takes place, regardless of the trainer\u0026apos;s waving hand, then when \u0026quot;Right-Talk\u0026quot; is presented on the right side of their body, they would respond as if \u0026quot;Left-Talk\u0026quot; had been presented (see Figure 6A).\u003c/p\u003e\n\u003cp\u003eThe presentation of a sign on one side of the dolphin\u0026apos;s body is analogous to presenting a sign to only one eye from the standard frontal position. In the final experiment (Experiment 5), one eye was covered using an eyecup (Figure 2F). It is known that the optic nerve fibers of bottlenose dolphins completely cross at the optic chiasm (Ridgway, 1986; Tarpley \u0026amp; Ridgway, 1994; Thewissen, 2009), suggesting that all information input to the right eye is initially sent to only the left hemisphere. If it is more critical which eye sees a moving sign, rather than whether the sign moves at left or right, then, for example, seeing \u0026quot;Right-Talk\u0026quot; with the right eye would result in \u0026quot;Left-Talk\u0026quot; response (see Figure 6B).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition, it is also known that primates, including humans, have a left visual field (i.e., right-hemispheric) advantage in visuospatial tasks such as mental rotation and perspective taking (e.g., Corballis, 1997; Corblis et al., 2010; Gunia et al., 2021). On the other hand, it has been reported that dolphins showed a right-eye advantage (left-hemispheric advantage) in visuospatial tasks (Kilian et al., 2000). Experiments 4 and 5 also examined the differences in responses to signs presented on either side of the body and to either the left or right eye.\u003c/p\u003e"},{"header":"General Methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants and setting.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present study was conducted at the two aquariums. At the Port of Nagoya Public Aquarium (PNPA) in Nagoya City, Aichi, Japan, four adult male bottlenose dolphins (\u003cem\u003eTursiops truncates\u003c/em\u003e), Eagle, Peace, Quick, and Tino, participated (Experiments 1, 2, 4, and 5). They were all wild-born and approximately 11\u0026ndash;14 years old at the beginning of the present study. They usually received four 15-minute sessions of husbandry, performance, and cognitive training tasks (Tomonaga et al., 2010, 2014, 2015). There were six pools for dolphins varied in size at PNPA, and the dolphin participants were kept in one of these pools according to the breeding management plans. Experimental sessions were conducted in one of these pools in coordination with other public programs of the aquarium.\u003c/p\u003e\n\u003cp\u003eAt the Minamichita Beachland Aquarium (MCBA), Mihama Town, Aichi, Japan, two adult female bottlenose dolphins, Neri and Thihra, participated in Experiment 3. They were also wild-born and approximately ten years old at the beginning of the present study. According to the breeding management plans, they lived in a pool in the dolphin exhibit area (approximately 13m in diameter x 3m in depth). They also participated in daily 15-min public programs. The experiment was also conducted in this pool.\u003c/p\u003e\n\u003cp\u003eWe did not conduct any food deprivations during the present study in both aquariums.\u003c/p\u003e\n\u003cp\u003eGeneral Procedures\u003c/p\u003e\n\u003cp\u003eDetailed procedures for each experiment are described in the Methods section of each experiment. This section describes the procedures common to all experiments.\u003c/p\u003e\n\u003cp\u003eTwo trainers typically conducted experimental sessions except for Experiment 2 (three trainers). The first trainer presented signs to the dolphin, and the second trainer instructed the first trainer which sign to present and recorded the dolphin\u0026apos;s responses. The first trainer initially had the dolphin maintain a waiting posture for the sign. If the waiting posture was not standard, the sign for that posture was presented first. When the dolphin\u0026apos;s posture became stable, the first trainer presented the sign instructed by the second trainer. Both trainers simultaneously and independently judged whether the dolphin responded correctly to the sign. The experimental sessions were recorded by a video camera, and if the two trainers\u0026apos; judgments differed, the video recordings were checked, and then corrected responses were coded. The dolphin\u0026apos;s responses were judged from the trainer\u0026apos;s perspective. If the dolphin\u0026apos;s response was correct, a whistle was sounded, followed by a food reward (fish pieces) according to the reinforcement schedule set for each experiment. Several trainers conducted the experiments, but the trainer\u0026apos;s role was fixed within a session. Experimental sessions consisting of several trials were conducted once to several times per day.\u003c/p\u003e\n\u003cp\u003eData Analysis\u003c/p\u003e\n\u003cp\u003eAs noted above, the dolphin\u0026apos;s responses were coded in real-time. To check for reliability, the first author also coded responses based on video recordings for about two sessions per individual in each experiment (approximately 13% of the available video recordings). The resulting agreement rate was 99% for the entire study.\u003c/p\u003e\n\u003cp\u003eDue to the small number of dolphins participating in each experiment, all statistical analyses were performed individually. Binomial tests were performed on the results for each experimental condition where the chance probability was set at 0.5. Chi-square tests were also performed to compare two conditions, such as the control and experimental conditions. We did not apply Yates\u0026apos; corrections to the chi-square test statistics even though the contingency tables had small cell frequencies (e.g., Camilli \u0026amp; Hopkins, 1978). In addition, Mantel-Haenszel and Breslow-Day tests were performed for the data of stratified 2x2 tables (Experiments 4 and 5). The results of the statistical tests for each experiment are indicated by asterisks in each graph and summarized in Table S2.\u003c/p\u003e\n\u003cp\u003eThe datasets for each experiment are attached as Supplementary Material.\u003c/p\u003e"},{"header":"Experiment 1","content":"\u003cp\u003eIn Experiment 1, the dolphins were presented with signs in an upright posture with their backs toward the trainer (dorsal posture, right of Figure 2B). In this posture, there was no change in the body axis relative to the standard upright (ventral) posture (both were vertical) but the dolphins looked up at the trainer from the dorsal direction, and the retinal image rotated 180 degrees.\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eExperiment 1 was conducted at PNPA. The three dolphins, Eagle, Peace, and Quick participated in this experiment. Eleven different signs were used in this experiment (see Supplementary Video 1). Four of the 11 signs were used for test trials: the left and right \u0026quot;Bye\u0026quot; and the left and right \u0026quot;Talk\u0026quot; (see Figure 1). The experiment began with the test in the standard ventral posture, followed by preliminary training in the dorsal posture without test trials, and then the test in the dorsal posture. The number of sessions conducted in each condition differed for each dolphin: the ventral posture test (left of Figure 2A) was conducted for a minimum of three sessions (11 trials per session), the dorsal posture pretraining was conducted for at least three sessions (15 trials), and the dorsal posture test (15 trials) was conducted for at least eight sessions, respectively. The number of sessions in each condition is summarized in Table S1.\u003c/p\u003e\n\u003cp\u003eIn this experiment, food rewards were given for correct responses on each trial. During the dorsal posture training and testing, the dolphins responded in the dorsal posture for three consecutive trials, receiving a food reward for each correct response. After every three trials, they were returned to the standard posture, provided with an additional food reward, and then re-positioned in the dorsal posture to continue the experiment. Correct responses in the dorsal posture were judged from the trainer\u0026apos;s perspective.\u003c/p\u003e\n\u003cp\u003eResults and Discussion\u003c/p\u003e\n\u003cp\u003eBaseline-trial performances were very high for all individuals, 98.7% on average for the ventral posture testing, 99.3% for the dorsal posture training, and 95.9% for the dorsal posture testing. Figure 3 shows the results of the test trials separately for the two signs. Error responses were categorized into Reversed responses, in which the left-right correspondence was reversed (from the trainer\u0026apos;s perspective), and Others (responses to other signs or no response). Asterisks at the bottom of each column indicate the results of binomial tests. Those at the top between the ventral and dorsal postures indicate the results of chi-square tests conducted between conditions.\u003c/p\u003e\n\u003cp\u003eRegarding \u0026quot;Bye\u0026quot;, all dolphins but Eagle showed perfect performances from the trainer\u0026apos;s perspective, even in the dorsal posture. For example, if the trainer showed \u0026quot;Right-Bye\u0026quot; with his/her right hand to the dolphins in the dorsal posture, they swam slowly to the left from the trainer\u0026apos;s perspective, flapping their right flipper. Eagle showed error responses in all trials of \u0026quot;Bye\u0026quot;, but most of them were responses to \u0026quot;Talk\u0026quot; or returning to the ventral (standard) posture.\u003c/p\u003e\n\u003cp\u003eAll dolphins showed very high performances on \u0026quot;Talk\u0026quot; in the ventral posture, but in the dorsal posture, they predominantly showed error responses (Eagle, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 16.00, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 14.32, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Quick, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 14.00, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). In addition, for Peace and Quick, most error responses were left-right reversed \u0026quot;Talk\u0026quot; responses. For Eagle, the responses to \u0026quot;Left-Talk\u0026quot; were more frequent in the \u0026quot;Right-Talk\u0026quot; trials, whereas he often produced different sounds from neither \u0026quot;Left-Talk\u0026quot; nor \u0026quot;Right-Talk\u0026quot; responses in the \u0026quot;Left-Talk\u0026quot; trials.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor Peace and Quick, when responding to \u0026quot;Talk\u0026quot; in the dorsal posture, they frequently showed left-right reversed responses from the trainer\u0026apos;s perspective. These results suggest that the trainer\u0026apos;s signs were seen as reversed from the dolphins\u0026apos; perspective. On the other hand, for \u0026quot;Bye\u0026quot;, correct responses were maintained from the trainer\u0026apos;s perspective, suggesting that the dolphins might have used a different strategy to recognize \u0026quot;Bye\u0026quot;. In contrast to \u0026quot;Talk\u0026quot;, \u0026quot;Bye\u0026quot; required a directional response, i.e., swimming in the opposite direction of the trainer\u0026apos;s waving hand. This correspondence is not arbitrary, making it difficult to distinguish whether the dolphins judged the swimming direction based on the reversed correspondence to the movement of the sign or their body axis.\u003c/p\u003e\n\u003cp\u003eAs for Eagle, he showed more other responses to the test signs than left-right reversed responses in the dorsal posture. However, it is clear that the dorsal posture itself, which was not the standard posture, had little disturbing effects on his performance because his responses during the baseline trials in the dorsal posture (93.1%) were as high as the other dolphins (97.6%). Instead, these results might suggest that the dorsal posture altered retinal images of \u0026quot;Talk\u0026quot; and \u0026quot;Bye\u0026quot;, resulting in disrupted left-right discrimination.\u003c/p\u003e"},{"header":"Experiment 2","content":"\u003cp\u003eIn Experiment 2, the dolphins responded to signs presented from the underground exhibit area or observation window by maintaining a posture with their body axis horizontal underwater. The dolphins were tested in a standard upright posture with the dorsal side facing upward (left of Figure 2C) and an inverted posture with the ventral side facing upward (right of Figure 2C). In the inverted posture, the retinal image rotated 180 degrees around the body axis, and the body was also inverted against the gravity axis.\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eExperiment 2 was also conducted at PNPA, and Peace and Quick participated. The experiment was conducted in the pools with a glass wall on the underwater exhibit area or observation windows.\u003c/p\u003e\n\u003cp\u003eThis experiment was conducted with three trainers: the first and second trainers stood near the exhibit area (or window), and the third trainer stood poolside above the water, communicating with each other via walkie-talkies. Each trial began with the third trainer at the poolside holding the dolphins upright. On instruction from the first trainer standing in front of the exhibit area, the third trainer showed the sign to the dolphins to go to the underwater exhibit area. A suction cup was placed on the glass surface from the trainer\u0026apos;s side, and the dolphins waited for signs in a standard upright posture in front of this suction cup (Figure 2C). The first trainer presented the sign in the upright posture condition, while in the inverted posture condition, the dolphins were initially rotated 180 degrees by the sign of the first trainer, and then the test sign was presented. Immediately after the response to the sign, the first trainer sounded a whistle regardless of whether the response was correct or incorrect. The dolphins kept the waiting posture at the suction cup again until the next sign was presented. Four trials were conducted successively, and the dolphins were instructed to return to the water surface. The third trainer gave food rewards to the dolphins that came to the surface (regardless of accuracy in each trial). The same posture was maintained within this four-trial block, and the upright and inverted postures were alternated between blocks. The second trainer provided instructions on signs to be presented to the first trainer and recorded the dolphins\u0026apos; behavior.\u003c/p\u003e\n\u003cp\u003eIn Experiment 2, eight different signs were used, including the test signs. The experiment was first conducted where no test signs were presented in the inverted posture (pretest), followed by the main test in which the test signs were presented both in the upright and inverted postures. The pretest consisted of 16 sessions, and the main test consisted of 28. Each session consisted of 16 trials (i.e., four blocks). Since Peace did not complete one main test session, he was given one additional session (see Table S1).\u003c/p\u003e\n\u003cp\u003eResults and Discussion\u003c/p\u003e\n\u003cp\u003eIn the pretest, both dolphins showed high accuracy in upright and inverted postures (96.9% on average). However, Quick had difficulty making \u0026quot;Left-Talk\u0026quot; sounds underwater, with an accuracy of 12.5%. They also showed accurate baseline-trial performance on the main test (98.8%). The results of the test trials during the main test are shown in Figure 4. Both dolphins responded correctly to \u0026quot;Bye\u0026quot; in the inverted posture significantly better than the chance level (binominal testes, \u003cem\u003ep\u003c/em\u003es \u0026lt; 0.01), but the accuracies were significantly lower than in the upright position (Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 7.54, \u003cem\u003ep\u003c/em\u003e = 0.006; Quick, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 4.46, \u003cem\u003ep\u003c/em\u003e = 0.035). For \u0026quot;Talk,\u0026quot; Quick performed poorly on \u0026quot;Left-Talk\u0026quot; in the main test (0% correct in both upright and inverted postures; see the \u0026quot;Talk\u0026quot;/Up bar in Figure 4). However, even under these constraints, both dolphins performed significantly worse in the inverted posture than in the upright posture (Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 25.34, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Quick, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 11.65, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001), and the majority of error responses were left-right reversed responses (except for Quick\u0026apos;s responses to \u0026quot;Left-Talk\u0026quot;).\u003c/p\u003e\n\u003cp\u003eIn the inverted posture of this experiment, the trainer appeared to rotate 180 degrees from the dolphin\u0026apos;s perspective. Thus, the dolphins had to discriminate 180-degree rotated mirror-image figures in the test trials, as in the mental rotation experiments, which is difficult even for humans. This object-based transformation might have affected the discrimination between \u0026quot;Left-Bye\u0026quot; and \u0026quot;Right-Bye\u0026quot;. For \u0026quot;Talk\u0026quot;, the left-right reversed responses were frequently observed in the inverted posture as in Experiment 1. These results suggest that the trainer\u0026apos;s vertical direction (upright or inverted) was not so important in discriminating between \u0026quot;Left-Talk\u0026quot; and \u0026quot;Right-Talk\u0026quot;. Alternatively, a critical cue for the discrimination might be whether the sign movement occurred on the left or right side with respect to the dolphins\u0026apos; body axis.\u003c/p\u003e"},{"header":"Experiment 3","content":"\u003cp\u003eIn Experiments 1 and 2, in contrast to \u0026quot;Talk\u0026quot;, the dolphins showed more \u0026quot;correct\u0026quot; responses to \u0026quot;Bye\u0026quot; from the trainer\u0026apos;s perspective. These results suggest that the dolphins might have matched their moving direction simply to the opposite side of the sign movement presented by the trainer. In Experiment 3, we presented point-symmetric geometric forms such as \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot; instead of gestural signs to investigate the effects of postures on dolphins\u0026apos; responses to these signs. Using these graphic signs, we could examine whether the dolphins decided their left-right movements in terms of egocentric or object-based coordinates (for example, the trainer or landmarks in the pool).\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eWe conducted Experiment 3 at MCBA, where two dolphins, Neri and Thihra, received two different tests. The experiments were conducted with two trainers in a pool with an underwater exhibit area (Figure 2D). The first trainer presented signs and recorded the dolphin\u0026apos;s behavior at the exhibit area. The second trainer at the poolside above the water surface sent the dolphin underwater and gave food rewards for every correct response. These trainers communicated with each other using walkie-talkies.\u003c/p\u003e\n\u003cp\u003eAs mentioned earlier, a sign called \u0026quot;HSR\u0026quot;, where the dolphins swim at high speed in the direction in which the trainer extends her arm horizontally was being used at MCBA. In this experiment, we replaced \u0026quot;HSR\u0026quot; with geometric forms; cross (\u0026times;) for \u0026quot;Left-HSR\u0026quot; and filled circle (●) for \u0026quot;Right-HSR\u0026quot;. Each shape was colored black and approximately 40 cm in size. For the control condition, filled square (◾) was also replaced with the non-directional sign \u0026quot;Yes\u0026quot; (the trainer shook his/her head up and down, and the dolphins also shook their heads up and down in response). The training for matching between the shapes and responses was incorporated into routine husbandry training and performance-show training.\u003c/p\u003e\n\u003cp\u003eIn both tests, postural conditions varied randomly between sessions. The first test was conducted with five signs, including \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot;. Gestural signs of \u0026quot;HSR\u0026quot; and \u0026quot;◾\u0026quot; were not used in the first test. Each session consisted of 5 trials, and 24 sessions for each postural condition were conducted. The second test was conducted with eight signs, including gestural left and right \u0026quot;HSRs\u0026quot; and \u0026quot;◾\u0026quot;. This second test was done to examine the possibility that the worse performances in the inverted posture of the first test were due to a deterioration of shape discrimination and worse responses to gestural \u0026quot;HSR\u0026quot; in the inverted posture. Due to a breeding program, only Thihra participated in this test. Each session consisted of 6 trials, and 48 sessions for each postural condition were conducted.\u003c/p\u003e\n\u003cp\u003eResults and Discussion\u003c/p\u003e\n\u003cp\u003eThe training for matching between the graphic signs and responses took approximately a month. Figure 5 shows the results of the test sessions. In the first test, the dolphins performed very accurately during the baseline trials (99.3% on average). The average percentage of correct responses to \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot; in the upright posture was 76.0%, not a perfect response, but significantly better than the chance level (binomial tests: \u003cem\u003ep\u003c/em\u003es \u0026lt; 0.001; see Figure 5 and Table S2). In contrast, in the inverted posture, accuracies from the trainer\u0026apos;s perspective were significantly lower for both dolphins (Neri, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 5.44, \u003cem\u003ep\u003c/em\u003e = 0.020; Thihra, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 8.71, \u003cem\u003ep\u003c/em\u003e = 0.003). They showed a strong response bias toward either the left or right direction (Neri toward the left and Thihra toward the right). In the second test, the inverted posture did not disrupt Thihra\u0026apos;s performances on \u0026quot;HSR\u0026quot; and \u0026quot;◾\u0026quot;. In contrast, she responded to \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot; significantly worse in the inverted than upright posture, as in the first test (\u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 17.42, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). Interestingly, when \u0026quot;\u0026times;\u0026quot; or \u0026quot;●\u0026quot; was presented in the inverted posture, Thihra often returned to the standard upright posture and swam to either the left or right (in this case, these responses were coded as incorrect even though the direction corresponded to the sign). Such responses were observed in 45.7% (16/35) of the incorrect responses. Furthermore, these responses were observed significantly more frequently on the test trials with \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot; than on the baseline trials and the test trials with \u0026quot;◾\u0026quot; in the inverted posture (33.3% vs. 1.7%, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 62.07, \u003cem\u003ep\u003c/em\u003e \u0026lt;0.001).\u003c/p\u003e\n\u003cp\u003eIn contrast to the previous experiments, the dolphins did not consistently show \u0026quot;correct\u0026quot; or left-right reversed responses in the inverted posture. Instead, they showed strong directional biases or \u0026quot;inappropriate\u0026quot; responses to the graphic signs, suggesting that the correspondence of movement to the left and right was disrupted under the testing condition. If the dolphins used the egocentric frame as the basis for the motion directions, then the inverted posture should have caused left-right reversed responses. On the other hand, if the reference frame was based on the trainer\u0026apos;s position (i.e., object-based frame), they should have swum in the \u0026quot;correct\u0026quot; directions from the trainer\u0026apos;s perspective, even in the inverted posture. The results of the present experiment did not fit either of these criteria, suggesting that these two reference frames might have influenced each other. Some studies suggest that even in human children, these two perspectives interactively affected performances during the three-mountain problem and related tasks (Emerson, 1931; Suzuki et al., 1991). The interactions between egocentric and object-based frames of reference will need to be further investigated with more dolphins in the future.\u003c/p\u003e\n\u003cp\u003eIn the second test, Thihra frequently swam to either side after returning to the standard upright posture when \u0026quot;\u0026times;\u0026quot; or \u0026quot;●\u0026quot; was presented in the inverted posture. In this experiment, such behavior was treated as \u0026quot;incorrect\u0026quot; because the experimenter could not adequately control her behavior, but it might be a kind of adaptive behavior for her. Since she had difficulty judging the direction of swimming in the inverted posture, she might have returned \u0026quot;spontaneously\u0026quot; to the upright posture and judged the direction again. It has been reported that human children older than six years also spontaneously physically rotate stimuli and maps and tilt their heads during mental rotation and map reading tasks (Armitage et al., 2020; Armitage \u0026amp; Redshaw, 2021; cf. Tcaci Popescu \u0026amp; Wexler, 2012). Such behavior is often called cognitive offloading (Risko \u0026amp; Gilbert, 2016). Cognitive offloading is defined as \u0026quot;the use of physical action to alter the information processing requirements of a task so as to reduce cognitive demand\u0026quot; (Risko \u0026amp; Gilbert, 2016, p. 676). Thihra\u0026apos;s behavior in this experiment could also be considered cognitive offloading.\u003c/p\u003e"},{"header":"Experiment 4","content":"\u003cp\u003eIn Experiments 1 and 2, the responses to \u0026quot;Talk\u0026quot; were reversed in the dorsal and inverted postures. From these results, we suggested that the left-right reversal of retinal images may have influenced the responses to \u0026quot;Talk\u0026quot;. However, if these results were further examined together with those of \u0026quot;Bye\u0026quot;, it would be suggested that a critical cue had been whether the \u0026quot;movement\u0026quot; of the trainer\u0026apos;s sign was presented on the left or right side of the dolphin\u0026apos;s body axis. In Experiment 4, to explore this possibility, the dolphins landed at the poolside, and the trainer him/herself moved to either the left or right side of the dolphin\u0026apos;s body and presented the signs from there (Figure 2E).\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eExperiment 4 was conducted at PNPA, and Eagle, Peace, and Quick participated. Experimental sessions were conducted in pools with a large poolside or shallow area where the dolphins could land. In each trial, the first trainer presented the sign to the dolphins to land at the poolside. Then, the trainer presented the sign kneeling in front of the dolphins or on their left or right side (near the dolphin\u0026apos;s eye; right of Figure 2E). When the response to the sign was correct, the first trainer blew the whistle immediately. After three consecutive trials with the landing position, the dolphins were returned to the pool and given food rewards regardless of whether the responses were correct or incorrect. The dolphins returned to the landing site again for the following three consecutive trials.\u003c/p\u003e\n\u003cp\u003eIn this experiment, only \u0026quot;Talk\u0026quot; was used as the test signs, and six different signs were used, including the test signs. The experiment began with baseline training, where the first trainer always presented the signs in front of the dolphin. Each session consisted of 12 trials, and the dolphins received four (for Eagle and Peace) or eight sessions (for Quick) of this training. After the baseline training, they received eight pretest sessions (5 trials per session) in which the signs were presented not only in front but also from the left and right sides of the body. The dolphins then completed 2\u0026ndash;4 sessions (30\u0026ndash;48 trials) of re-training before the main test. The main test consisted of 15 trials per session and 32 sessions individually. The position of the first trainer randomly changed from trial to trial in the pretest and main test.\u003c/p\u003e\n\u003cp\u003eResults and Discussion\u003c/p\u003e\n\u003cp\u003eThe dolphins showed 96.9%, 93.3%, and 98.2% correct responses on average for baseline training, pretest, and re-training before the main test, respectively. Figure 7 shows the mean accuracy for each position in the main test, separately for baseline and test trials. When the signs were presented from the front, the overall accuracy was 97.7% on average. The dolphins performed better for the signs from the right side than the left, except for the baseline trials in Quick. However, this difference was significant only for Eagle (Mantel-Haenszel test: \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 5.68, \u003cem\u003ep\u003c/em\u003e = 0.017).\u003c/p\u003e\n\u003cp\u003eWe conducted a more detailed analysis of the test trials. As shown in Figure 6A, when the trainer placed in front of the dolphins and presented \u0026quot;Right-Talk\u0026quot;, the trainer\u0026apos;s hand moved at the left side of the dolphins\u0026apos; body and vice versa. On the other hand, if, for example, the trainer placed on the left side and presented \u0026quot;Talk\u0026quot;, the hand movement was presented from the left side of the body whether it was \u0026quot;Left-Talk\u0026quot; or \u0026quot;Right-Talk\u0026quot;. In the case of \u0026quot;Right-Talk\u0026quot;, the trainer\u0026apos;s hand moved at the left side of the body as in the front condition (congruent), while in the case of \u0026quot;Left-Talk\u0026quot;, the hand moved at the opposite side (left side) of the body from the front condition (incongruent). Based on these congruency relationships between sign movement and presentation side, the test trials were classified into two types, congruent and incongruent. Figure 8 summarizes the results of these analyses. Except for the left side in Peace, the dolphins performed better on the congruent trials than the incongruent trials, and all the incorrect responses were left-right reversed responses. These differences were significant except for the right side in Eagle (Eagle, left, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 24.00, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Peace, left, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 12.68, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001, right, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 24.00, p \u0026lt; 0.001; Quick, left, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 19.33, p \u0026lt; 0.001, right, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 8.00, p = 0.005).\u0026nbsp;Furthermore, when the results for the left and right sides were combined and then analyzed, the accuracy was significantly higher for the congruent trials than incongruent trials for Eagle and Quick (Mantel-Haenszel test: Eagle,\u0026nbsp;\u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 20.68, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Quick, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 22.55, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;We further examined whether there was a difference in the accuracy of test trials between the left and right sides based on congruency. As a result, we found significant differences for Eagle and Peace, but only Eagle showed better performance on the right side than on the left side (Breslow-Day test: \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 4.69, \u003cem\u003ep\u003c/em\u003e = 0.030). These results indicate that mirror-image discrimination of the signs was easier on the right body side than the left side for Eagle.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The results of this experiment suggest that in recognizing mirror-image signs like \u0026quot;Talk\u0026quot;, the dolphins might pay more attention to which side of the body the sign\u0026apos;s movement occurred rather than discriminating mirror-image patterns of the sign\u0026apos;s shape. This conclusion is consistent with the previous experiments. However, given that the dolphins did recognize the baseline signs presented from the side of the body, it is evident that they did not recognize gestural signs only by movement. Therefore, it would be suggested that the dolphins recognized static shapes of \u0026quot;Talk\u0026quot; but did not properly pay attention to which hand was used. They might have understood the \u0026quot;meaning\u0026quot; of the signs based solely on movement information. Previous studies showed that dolphins could understand gestural signs even when they were presented with only the movements using point-light displays (Herman et al., 1990). The present results suggest that the role of static shape information of the signs also needs to be examined in more detail.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;In this experiment, the dolphins showed better performance from the right side of the body compared to the left side. Although this difference was significant only for Eagle, none of the dolphins exhibited an opposite pattern (i.e., better performance from the left side; see Figures 7 and 8). As mentioned in the introduction, since the optic nerves cross completely at the optic chiasm (Ridgway, 1986), the sign presentation from the side implies prioritized information input to the eye on that side (and thus initially to the opposite cerebral hemisphere). Several studies have suggested the right-eye (left-hemispheric) advantage in shape discrimination and visuospatial abilities in bottlenose dolphins (Delfour \u0026amp; Marten, 2006; Kilian et al., 2000, 2005; von Fersen et al., 2000). The present results indicate that the right-eye advantage in visuospatial cognition in bottlenose dolphins needs further investigation.\u003c/p\u003e"},{"header":"Experiment 5","content":"\u003cp\u003eAlthough the results of Experiment 4 suggested a right-eye advantage in the discrimination of signs and mirror-image patterns, these were not so robust. The weak evidence may be due to the influence of sign presentation from unusual positions. Furthermore, the information input from the opposite eye might not have been completely blocked, even though the signs were presented from the side of the body. Therefore, in the final experiment, we addressed this issue by testing the dolphins facing the trainer in the standard upright posture but with one eye covered with an eyecup (Figure 2F).\u003c/p\u003e\n\u003cp\u003eMethods\u003c/p\u003e\n\u003cp\u003eThis experiment was conducted at PNPA, and the two dolphins, Peace and Tino, participated. Tino participated in this study for the first time but has participated in several cognitive experiments (Tomonaga et al., 2010, 2014, 2015). A silicone suction cup was used as an eyecup to cover one eye (Figure 2F). The eyecup was connected to a PVC ring (30 cm in diameter) with a string, which was hooked onto the dolphin\u0026apos;s rostrum during the experiment. This was done to prevent the dolphin from accidentally swallowing the eyecups when detached from the body. Three experimental conditions were prepared: one in which both eyes were open and the other two in which only one of the eyes was open. In the single-eye condition, one eye was covered with an eyecup, and a dummy eyecup was placed in a position that did not interfere with the forward visual field of the other eye (right of Figure 2F). In both-eyes condition, two dummy eyecups were also placed near the eyes (see left of Figure 2F). These dummy cups were used to eliminate the possibility that wearing the eyecup itself could affect performance.\u003c/p\u003e\n\u003cp\u003eThis experiment was conducted with two trainers. The trainer always presented the signs to the dolphin in the normal upright posture (Figure 2F). The experiment was conducted with ten different signs, including four test signs; one session consisted of 12 trials, and the eyecup conditions were randomly changed across sessions. The first trainer initially held the dolphin upright and then presented the signs. After the three consecutive trials (trial blocks), food rewards were given to the dolphin regardless of whether the responses were correct or incorrect. The second trainer gave instructions for the signs to the first trainer and recorded the dolphin\u0026apos;s responses. Sixteen sessions were conducted for each eyecup condition, totaling 48 sessions.\u003c/p\u003e\n\u003cp\u003eAs in Experiment 4, we defined congruency based on the sides of the sign movement and the open eye (Figure 6B). For example, in the right-eye-only condition, \u0026quot;Left-Talk\u0026quot; and \u0026quot;Left-Bye\u0026quot; were congruent because the sign movement of these signs occurred on the right side of the body, whereas \u0026quot;Right-Talk\u0026quot; and \u0026quot;Right-Eye\u0026quot; were incongruent because the sign movement occurred on the left side of the body.\u003c/p\u003e\n\u003cp\u003eResults and Discussion\u003c/p\u003e\n\u003cp\u003eFigure 9 shows the performance on baseline and test trials for each eye condition. When both eyes were open, the percentages of correct responses averaged across the two dolphins were 92.2% for the baseline and 93.8% for the test trials, respectively. In contrast, for the single-eye condition, there were consistent differences between the left and right eyes for both baseline and test trials: they showed better performances for the right-eye-only condition than the left-eye-only condition (Mantel-Haenszel test: Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 17.36, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; Tino, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 24.36, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001).\u003c/p\u003e\n\u003cp\u003eNext, Figure 10 shows the results of the congruency-based analysis of the test trials (see also Figure 6B). Comparing congruent and incongruent trials, the dolphins showed better accuracy for the congruent trials than the incongruent trials, except for \u0026quot;Bye\u0026quot; in Peace (Mantel-Haenszel test: \u0026quot;Bye\u0026quot;, Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 0.38, p = 0.541; Tino, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 11.41, p \u0026lt; 0.001; \u0026quot;Talk\u0026quot;, Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 11.01, p \u0026lt; 0.001; Tino, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 10.96, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001). In addition, when comparing the left- and right-eye-only conditions, they performed better on the congruent trials than the incongruent trials in the left-eye-only condition (see asterisks above the bars in Figure 10, \u0026chi;\u003csup\u003e2\u003c/sup\u003es(1) \u0026gt; 4.57, \u003cem\u003ep\u003c/em\u003es \u0026lt; 0.05). In contrast, the dolphins showed significantly higher performances regardless of congruency in the right-eye-only condition than in the left-eye-only condition, except for \u0026quot;Talk\u0026quot; in Tino (Breslow-Day test: \u0026quot;Bye\u0026quot;, Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 4.70, \u003cem\u003ep\u003c/em\u003e = 0.030; Tino, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 4.10, \u003cem\u003ep\u003c/em\u003e = 0.043; \u0026quot;Talk\u0026quot;, Peace, \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 13.95, \u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001; \u0026chi;\u003csup\u003e2\u003c/sup\u003e(1) = 0.03, \u003cem\u003ep\u003c/em\u003e = 0.857).\u003c/p\u003e\n\u003cp\u003eThe results of Experiment 5 are consistent with those of Experiment 4. The present results suggest that on which side of the dolphin\u0026apos;s body the sign movement was presented, or more specifically, from which eye the input was coming, is critical for identifying the signs, especially those having different meanings between left-right mirror images. Was accurate identification difficult due to visual field restriction simply because the critical motion information of the sign was presented on the side of the occluded eye? Indeed, previous studies have shown that a blind spot exists in the anterior rostral region of the dolphin (Xitco et al., 2004). However, this visual field restriction account could not explain why there was no difference in performance between congruent and incongruent trials in the right-eye-only condition (except for \u0026quot;Talk\u0026quot; in Tino). In addition, recent studies have reported that dolphins see the area at the anterior rostrum, previously thought to be a blind spot. (Gunnars et al., 2021). Therefore, it would be better to assume that the observed differences were due to information processing after visual input from the eye.\u003c/p\u003e\n\u003cp\u003eMore clearly than in Experiment 4, Experiment 5 strongly suggests the possibility of lateralization of sign discrimination, especially discrimination of left-right mirror-image signs. Our results show the right-eye advantage in sign discrimination. In addition, the congruency effect on the discrimination of mirror-image signs was evident in the left-eye-only condition. In contrast, the dolphins performed better in the right-eye-only condition regardless of congruency. These results are consistent with previous studies reporting the right-eye (left-hemispheric) advantages in shape discrimination and visuospatial cognitive abilities in dolphins (Kilian et al., 2010).\u003c/p\u003e"},{"header":"General Discussion","content":"\u003cp\u003eIn this study, we examined the visuospatial cognitive abilities of bottlenose dolphins by manipulating the spatial relationship between the trainer and the dolphins while discriminating gestural signs that had different meanings for left-right mirror images. We found two significant findings. First, the dolphins used an egocentric rather than an object-based frame of reference in recognizing the signs, and second, their recognition of signs was right-eye (left-hemispheric) dominant.\u003c/p\u003e\n\u003cp\u003eWe observed left-right reversed responses to \u0026quot;Talk\u0026quot; consistently in the condition of turning their backs to the trainer in Experiment 1 and in the inverted posture in Experiment 2. These results are strong evidence for using their body axis as a frame of reference. On the other hand, in \u0026quot;Bye\u0026quot;, which required motor responses counter-corresponding to the movements of the signs, there were very few left-right reversed responses from the trainer\u0026apos;s perspective. Although we interpreted these results as a correspondence between the sign movement and their motion direction, these could also be interpreted based on the egocentric frame of reference.\u003c/p\u003e\n\u003cp\u003eIn Experiment 3, we eliminated the non-arbitrary relationship between the sign and the dolphin\u0026apos;s movement using shape signs instead of gestural signs. As a result, the dolphins showed significantly lower accuracy in the inverted posture. More interestingly, further analysis of the error responses revealed that the responses were not left-right reversed but instead that there were strong motion direction biases. These results were difficult to explain in either the egocentric or object-based reference frame but suggest that both of these reference frames may have influenced their responses. Some studies on visuospatial cognition in human children suggest that either egocentric or object-based frames are not used exclusively but interact with each other (Emerson, 1931; Suzuki et al., 1991). In the present study, it might be concluded that while the movement information of the signs facilitated the use of the egocentric frame in the dolphin\u0026apos;s decision of swimming directions, the lack of this information (through the replacement of the gestural signs by the shape signs) led to an increased influence of the environmental reference frame.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition, the pool in which Experiment 3 was conducted was relatively homogeneous internally, with few underwater landmarks available. If the environmental features were made more distinct, the dolphins might rely more heavily on the object-based frames. For example, suppose the dolphins are asked to swim up or down (toward the surface or the bottom of the pool) rather than left or right. Then, we could investigate the interaction between egocentric and object-based frames by testing them in standard (upright) and inverted postures in the water using shape signs for up and down directions.\u003c/p\u003e\n\u003cp\u003eIn the second test of Experiment 3, Thihra often responded to \u0026quot;\u0026times;\u0026quot; and \u0026quot;●\u0026quot; after returning from the inverted posture to the standard upright posture. The trainer had not trained this behavior, but it occurred spontaneously during the test period. Captive dolphins in aquariums are generally well-trained by trainers and rarely change their posture during training or performance show. Therefore, as mentioned earlier, this behavior can be considered cognitive offloading resulting from the dolphin\u0026apos;s attempt to solve the problem rather than \u0026quot;inappropriate\u0026quot; behavior due to disrupted control by the trainer. In addition to Thihra, although less frequently, the other dolphins sometimes showed similar behaviors, such as turning their head toward the trainer when the sign was presented from the body side in the landing condition in Experiment 4. Cognitive offloading is generally known to improve performance in humans by reducing the cognitive load (Risko \u0026amp; Gilbert, 2016). However, we did not find such a facilitating effect in Thihra; after returning to the standard posture, she always swam rightward. Cognitive offloading is associated with metacognition in humans (Dunn \u0026amp; Risko, 2015), but there are almost no studies of animal metacognition examined from the standpoint of cognitive offloading (cf. \u0026quot;spontaneous\u0026quot; information-seeking behavior; Call \u0026amp; Carpenter, 2001; Rosati \u0026amp; Santos, 2016). Further comparative studies on cognitive offloading will be necessary for the future.\u003c/p\u003e\n\u003cp\u003eIn Experiment 2, the dolphins showed worse performances for \u0026quot;Bye\u0026quot; in the inverted posture than in the upright posture. In contrast, they responded to \u0026quot;Bye\u0026quot; perfectly in Experiment 1, even in the dorsal posture (from the trainer\u0026apos;s perspective). In Experiment 1, it was evident that the dorsal posture reversed the retinal image horizontally. However, the effect on the vertical axis of the image remains unclear. Unlike primates, dolphins have a wide horizontal visual field along the body axis (Mass \u0026amp; Supin, 2009) because their eyes are laterally oriented. Therefore, when the dolphins rotated 180 degrees around their body axis while maintaining an upright posture like in Experiment 1, their retinal image would be maintained vertically but reversed horizontally. On the other hand, the position of the trainer\u0026apos;s head in the retinal image seems to be rostral (i.e., lower), as inferred from the posture of the dolphin on the right of Figure 2B: it is similar to how we humans look behind us by leaning backward. In other words, the vertical axis also might appear to be inverted. However, the dolphins\u0026apos; performances did not deteriorate in the dorsal posture in Experiment 1, suggesting that their retinal image in the dorsal posture might not be upside down.\u003c/p\u003e\n\u003cp\u003eThe discussion above may also be directly related to mental rotation. The worse performances for \u0026quot;Bye\u0026quot; and \u0026quot;Talk\u0026quot; in the inverted posture in Experiment 2 indicate that the 180-degree rotated mirror images were difficult to discriminate for them, consistent with the previous studies reporting mental rotation in cetaceans (Murayama \u0026amp; Tobayama, 1995; cf. DeLong et al., 2020). Our study might be unique because the body was rotated (perspective transformation) rather than the stimuli being rotated (object-based transformation). Some human studies have examined the effects of perspective transformation, such as tilting the head (Corballis et al., 1976, 1978). However, almost no studies have been conducted under conditions in which the whole body was rotated (e.g., standing on one\u0026apos;s head or lying on one\u0026apos;s back). Although these two transformations are functionally equivalent in image rotation on the retina, the effects of physical body rotation on visuospatial perception and cognition remain largely unknown. Like in the present study, the underwater environment may be just appropriate for examining these issues. Further research from the perspective of diving psychology is expected (e.g., Niewiedział et al., 2018).\u003c/p\u003e\n\u003cp\u003eFor object-based transformation, a video projection system could rotate the trainer\u0026apos;s image and show it to the dolphins. It has been reported that dolphins can respond appropriately to the presentation of signs through video images (Herman et al., 1990; cf. Tomonaga \u0026amp; Sakurai, 2014). A comprehensive discussion comparing the results of object-based and perspective formations would provide further insights into the spatial cognitive abilities of cetaceans.\u003c/p\u003e\n\u003cp\u003eExperiments 4 and 5 examined how the dolphins\u0026apos; performances changed on which side of their body or eye the sign movement was presented. Their performances were generally better when the side on which the sign movement occurred was the same as the side of the body or eye on which the sign was presented (congruent trials) than when it was not (incongruent trials). These results suggest that not only the static sign shape but also the dynamic aspect of the sign may be crucial for discrimination, especially for the signs with different meanings between left-right mirror images. It is known that in humans (e.g., Abrams \u0026amp; Christ, 2003; Pratt et al., 2010) and nonhuman animals (e.g., Matsuno \u0026amp; Tomonaga, 2006), the motion of an object can capture attention. Visuospatial attention to sign movements may play facilitating role in the discrimination of mirror-image signs by dolphins.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHowever, further analyses in Experiments 4 and 5 revealed that this tendency was primarily restricted to conditions in which the signs were presented only to the left side of the body or to the left eye. When the signs were presented from the right side, the difference between congruent and incongruent trials often disappeared (see Figure 10): there was lateralization in the discrimination of mirror-image signs. Our results strongly suggest that shape and mirror-image discriminations in dolphins may be right-eye dominant, therefore, left-hemispheric dominant.\u003c/p\u003e\n\u003cp\u003eMany studies on lateralization in cetaceans, including bottlenose dolphins, have recently accumulated (cf. G\u0026uuml;nt\u0026uuml;rk\u0026uuml;n et al., 2020). So far, right-eye (i.e., left-hemispheric) advantage has been reported in number discrimination (Kilian et al., 2005), shape discrimination (von Fersen et al., 2000; but see Matrai et al., 2019), visuospatial cognition (Kilian et al., 2000), and audio-visual tasks (Delfour \u0026amp; Marten, 2006). On the other hand, left-eye advantage has been reported in social behavior and social cognition (Thieltges et al., 2011; Karenina et al., 2010, 2013; Sakai et al., 2006b). In addition, behavioral laterality in the wild has also been studied intensively in recent years (Karenina et al., 2010, 2013; Kaplan et al., 2019; Sakai et al., 2006b; Siniscalchi et al., 2012). Our results added further findings to these studies and are consistent with the previous findings. Unlike other terrestrial mammals, including humans (Gunia et al., 2021; Hopkins et al., 1993; Patterson \u0026amp; Bradshaw, 1975; Piazza et al., 2006; Corballis et al., 2010; Priftis et al., 2003; Moeller et al., 2015), visuospatial processing is lateralized to the left hemisphere in bottlenose dolphins. However, the previous and our results would still be insufficient to confirm this conclusion. Furthermore, we cannot adequately address why the dolphin\u0026apos;s hemispheric difference is different from other mammals. More research efforts are needed.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Finally, we discuss the limitations of this study. The major weakness is the small number of participants. However, this is not limited to our study but is true for other studies on captive dolphins. This is a limitation derived from the circumstances of dolphins in captivity. Field studies might also have other limitations, such as visibility, accessibility, etc. The only way to overcome these limitations is to accumulate studies with small numbers of cases. Based on the findings accumulated in this way, we could conduct meta-analyses to develop testable hypotheses regarding visuospatial cognition and laterality in brain function in dolphins.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAnother hopeful strategy would be multi-institutional collaborations. This trend is rapidly progressing against the reproducibility crisis in psychology (Open Science Collaboration, 2015), and several projects (so-called \u003cem\u003eManyXs\u003c/em\u003e projects) have already launched in the area of comparative cognition in nonhuman primates, birds, and dogs (Alberghina et al., 2022; Lambert et al., 2022; ManyPrimates, 2019a, b). Although the current efforts mainly focus on replication studies, such a project could be applied to hypothesis-building or hypothesis-testing research in cetaceans, where the number of available individuals is inevitably limited in each facility. Future collaboration among researchers will be essential\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank Mr. M. Soichi, H. Nitto, M. Kurita, and the Port of Nagoya Public Aquarium staff, and Mr. K. Kuroyanagi, M. Tsuchiya, K. Kawamoto, K. Saito, and the Minamichita Beachland Aquarium staff for their generous support of the present study. We especially thank Mr. K. Kanda, M. Dozaki, and Ms. N. Tsuzuki for their invaluable support of the present study and the preparation of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe experimental procedures were approved by each aquarium and adhered to the \u003cem\u003eEthical Guidelines for the Conduct of Research on Animals by Zoos and Aquariums\u003c/em\u003e issued by the World Association of Zoos and Aquariums (WAZA), the \u003cem\u003eCode of Ethics\u003c/em\u003e issued by the Japanese Association of Zoos and Aquariums (JAZA), the \u003cem\u003eGuidelines for Animal Experiments\u003c/em\u003e issued by the Japanese Society for Animal Psychology, and the Japanese Act on Welfare and Management of Animals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eM.T. conceived and designed the present study; M.T., Y. U-I., T. S., and N. S. performed the experiments, analyzed the data, and discussed the results. M.T. wrote the paper, and all authors commented on the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was financially supported by JSPS-MEXT Grants-in-Aid for Scientific Research (23220006 and 15H05709).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the data used for this study are available from the supplementary material.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAlberghina, D., Bray, E., Buchsbaum, D., Byosiere, S. E., Espinosa, J., Gnanadesikan, G., \u0026hellip; Stevens, J. R. (2022). ManyDogs project: a big team science approach to investigating canine behavior and cognition. PsyArXiv. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.31234/osf.io/j82uc\u003c/span\u003e\u003cspan address=\"10.31234/osf.io/j82uc\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbrams, R. A., \u0026amp; Christ, S. E. (2003). Motion onset captures attention. Psychological Science, \u003cem\u003e14\u003c/em\u003e(5), 427\u0026ndash;432. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/1467-9280.01458\u003c/span\u003e\u003cspan address=\"10.1111/1467-9280.01458\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArmitage, K. L., Bulley, A., \u0026amp; Redshaw, J. (2020). Developmental origins of cognitive offloading. \u003cem\u003eProceedings of the Royal Society B\u003c/em\u003e, \u003cem\u003e287\u003c/em\u003e(1928), 20192927. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1098/rspb.2019.2927\u003c/span\u003e\u003cspan address=\"10.1098/rspb.2019.2927\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArmitage, K. L., \u0026amp; Redshaw, J. (2022). Children boost their cognitive performance with a novel offloading technique. Child Development, \u003cem\u003e93\u003c/em\u003e(1), 25\u0026ndash;38. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/cdev.13664\u003c/span\u003e\u003cspan address=\"10.1111/cdev.13664\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBiro, D., Meade, J., \u0026amp; Guilford, T. (2004). Familiar route loyalty implies visual pilotage in the homing pigeon. \u003cem\u003eProceedings of the National Academy of Sciences\u003c/em\u003e, \u003cem\u003e101\u003c/em\u003e(50), 17440\u0026ndash;17443. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1073/pnas.0406984101\u003c/span\u003e\u003cspan address=\"10.1073/pnas.0406984101\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCall, J., \u0026amp; Carpenter, M. (2001). Do apes and children know what they have seen? Animal Cognition, \u003cem\u003e3\u003c/em\u003e(4), 207\u0026ndash;220. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s100710100078\u003c/span\u003e\u003cspan address=\"10.1007/s100710100078\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCamilli, G., \u0026amp; Hopkins, K. D. (1978). Applicability of chi-square to 2\u0026ensp;\u0026times;\u0026ensp;2 contingency tables with small expected cell frequencies. Psychological Bulletin, \u003cem\u003e85\u003c/em\u003e, 163\u0026ndash;167. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/0033-2909.85.1.163\u003c/span\u003e\u003cspan address=\"10.1037/0033-2909.85.1.163\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eConnor, R., Mann, J., \u0026amp; Watson-Capps, J. (2006). A sex-specific affiliative contact behavior in Indian Ocean bottlenose dolphins, \u003cem\u003eTursiops sp\u003c/em\u003e. Ethology, \u003cem\u003e112\u003c/em\u003e(7), 631\u0026ndash;638. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1439-0310.2006.01203.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1439-0310.2006.01203.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorballis, M. C. (1997). Mental rotation and the right hemisphere. Brain and Language, \u003cem\u003e57\u003c/em\u003e(1), 100\u0026ndash;121. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1006/brln.1997.1835\u003c/span\u003e\u003cspan address=\"10.1006/brln.1997.1835\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorballis, M. C., Birse, K., Paggi, A., Manzoni, T., Pierpaoli, C., \u0026amp; Fabri, M. (2010). Mirror-image discrimination and reversal in the disconnected hemispheres. Neuropsychologia, \u003cem\u003e48\u003c/em\u003e(6), 1664\u0026ndash;1669. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.neuropsychologia.2010.02.011\u003c/span\u003e\u003cspan address=\"10.1016/j.neuropsychologia.2010.02.011\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorballis, M. C., Nagourney, B. A., Shetzer, L. I., \u0026amp; Stefanatos, G. (1978). Mental rotation under head tilt: Factors influencing the location of the subjective reference frame. Perception \u0026amp; Psychophysics, \u003cem\u003e24\u003c/em\u003e(3), 263\u0026ndash;273. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3758/BF03206098\u003c/span\u003e\u003cspan address=\"10.3758/BF03206098\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCorballis, M. C., Zbrodoff, J., \u0026amp; Roldan, C. E. (1976). What\u0026rsquo;s up in mental rotation? Perception \u0026amp; Psychophysics, \u003cem\u003e19\u003c/em\u003e(6), 525\u0026ndash;530. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3758/BF03211221\u003c/span\u003e\u003cspan address=\"10.3758/BF03211221\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDelfour, F., \u0026amp; Marten, K. (2006). Lateralized visual behavior in bottlenose dolphins (\u003cem\u003eTursiops truncatus\u003c/em\u003e) performing audio-visual tasks: The right visual field advantage. \u003cem\u003eBehavioural Processes\u003c/em\u003e, \u003cem\u003e71\u003c/em\u003e(1), 41\u0026ndash;50. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.beproc.2005.09.005\u003c/span\u003e\u003cspan address=\"10.1016/j.beproc.2005.09.005\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDeLong, C. M., Fellner, W., Wilcox, K. T., Odell, K., \u0026amp; Harley, H. E. (2020). Visual perception in a bottlenose dolphin (\u003cem\u003eTursiops truncatus\u003c/em\u003e): Successful recognition of 2-D objects rotated in the picture and depth planes. Journal of Comparative Psychology, \u003cem\u003e134\u003c/em\u003e, 180\u0026ndash;196. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/com0000207\u003c/span\u003e\u003cspan address=\"10.1037/com0000207\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDudzinski, K., \u0026amp; Ribic, C. (2017). Pectoral fin contact as a mechanism for social bonding among dolphins. Animal Behavior and Cognition, \u003cem\u003e4\u003c/em\u003e(1), 30\u0026ndash;48. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.12966/abc.03.02.2017\u003c/span\u003e\u003cspan address=\"10.12966/abc.03.02.2017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDunn, T. L., \u0026amp; Risko, E. F. (2016). Toward a metacognitive account of cognitive offloading. Cognitive Science, \u003cem\u003e40\u003c/em\u003e(5), 1080\u0026ndash;1127. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/cogs.12273\u003c/span\u003e\u003cspan address=\"10.1111/cogs.12273\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEmerson, L. L. (1931). The effect of bodily orientation upon the young child's memory for position of objects. Child Development, \u003cem\u003e2\u003c/em\u003e(2), 125\u0026ndash;142. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2307/1125419\u003c/span\u003e\u003cspan address=\"10.2307/1125419\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFarah, M. J. (1989). The neural basis of mental imagery. Trends in Neurosciences, \u003cem\u003e12\u003c/em\u003e(10), 395\u0026ndash;399. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0166-2236(89)90079-9\u003c/span\u003e\u003cspan address=\"10.1016/0166-2236(89)90079-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFreas, C. A., \u0026amp; Cheng, K. (2022). The basis of navigation across species. Annual Review of Psychology, \u003cem\u003e73\u003c/em\u003e(1), 217\u0026ndash;241. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1146/annurev-psych-020821-111311\u003c/span\u003e\u003cspan address=\"10.1146/annurev-psych-020821-111311\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFujita, K., \u0026amp; Matsuzawa, T. (1989). Comparison of the representational abilities of chimpanzees and humans. Primate Research, \u003cem\u003e5\u003c/em\u003e(1), 58\u0026ndash;74. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2354/psj.5.58\u003c/span\u003e\u003cspan address=\"10.2354/psj.5.58\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (Japanese text with English abstract)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFuruya, I. (1998). Use of right-left cues in pigeons. Cognitive Studies, \u003cem\u003e5\u003c/em\u003e(3), 77\u0026ndash;86. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.11225/jcss.5.3_77\u003c/span\u003e\u003cspan address=\"10.11225/jcss.5.3_77\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (Japanese text with English abstract)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGaunet, F., \u0026amp; Berthoz, A. (2000). Mental rotation for spatial environment recognition. Brain Research. Cognitive Brain Research, \u003cem\u003e9\u003c/em\u003e(1), 91\u0026ndash;102. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/s0926-6410(99)00038-5\u003c/span\u003e\u003cspan address=\"10.1016/s0926-6410(99)00038-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGunnars, T. S., Barnes, M., Milner, R., Walker, K., Abramson, C., \u0026amp; Bruck, J. (2021). The visual field of the bottlenose dolphin (\u003cem\u003eTursiops truncatus\u003c/em\u003e). The Animal Behavior Society 2021 Virtual Meeting. Oral presentation. August 5, 2021.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eG\u0026uuml;nt\u0026uuml;rk\u0026uuml;n, O., Str\u0026ouml;ckens, F., \u0026amp; Ocklenburg, S. (2020). Brain lateralization: A comparative perspective. Physiological Reviews, \u003cem\u003e100\u003c/em\u003e(3), 1019\u0026ndash;1063. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1152/physrev.00006.2019\u003c/span\u003e\u003cspan address=\"10.1152/physrev.00006.2019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHassett, T. C., Lord, V. K., \u0026amp; Hampton, R. R. (2022). Rhesus monkeys manipulate mental images. Cognition, \u003cem\u003e228\u003c/em\u003e, 105225. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cognition.2022.105225\u003c/span\u003e\u003cspan address=\"10.1016/j.cognition.2022.105225\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerman, L. M., Morrel-Samuels, P., \u0026amp; Pack, A. A. (1990). Bottlenosed dolphin and human recognition of veridical and degraded video displays of an artificial gestural language. Journal of Experimental Psychology. General, \u003cem\u003e119\u003c/em\u003e(2), 215\u0026ndash;230. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037//0096-3445.119.2.215\u003c/span\u003e\u003cspan address=\"10.1037//0096-3445.119.2.215\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHollard, V. D., \u0026amp; Delius, J. D. (1982). Rotational invariance in visual pattern recognition by pigeons and humans. Science, \u003cem\u003e218\u003c/em\u003e(4574), 804\u0026ndash;806. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1126/science.7134976\u003c/span\u003e\u003cspan address=\"10.1126/science.7134976\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHopkins, W. D., Fagot, J., \u0026amp; Vauclair, J. (1993). Mirror-image matching and mental rotation problem solving by baboons (\u003cem\u003ePapio papio\u003c/em\u003e): Unilateral input enhances performance. Journal of Experimental Psychology. General, \u003cem\u003e122\u003c/em\u003e(1), 61\u0026ndash;72. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037//0096-3445.122.1.61\u003c/span\u003e\u003cspan address=\"10.1037//0096-3445.122.1.61\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuttenlocher, J., \u0026amp; Presson, C. C. (1973). Mental rotation and the perspective problem. Cognitive Psychology, \u003cem\u003e4\u003c/em\u003e, 277\u0026ndash;299. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0010-0285(73)90015-7\u003c/span\u003e\u003cspan address=\"10.1016/0010-0285(73)90015-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuttenlocher, J., \u0026amp; Presson, C. C. (1979). The coding and transformation of spatial information. Cognitive Psychology, \u003cem\u003e11\u003c/em\u003e(3), 375\u0026ndash;394. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0010-0285(79)90017-3\u003c/span\u003e\u003cspan address=\"10.1016/0010-0285(79)90017-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKaplan, J. D., Goodrich, S. Y., Melillo-Sweeting, K., \u0026amp; Reiss, D. (2019). Behavioural laterality in foraging bottlenose dolphins (\u003cem\u003eTursiops truncatus\u003c/em\u003e). Royal Society Open Science, \u003cem\u003e6\u003c/em\u003e(11), 190929. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1098/rsos.190929\u003c/span\u003e\u003cspan address=\"10.1098/rsos.190929\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarenina, K., Giljov, A., Baranov, V., Osipova, L., Krasnova, V., \u0026amp; Malashichev, Y. (2010). Visual laterality of calf\u0026ndash;mother interactions in wild whales. PLOS ONE, \u003cem\u003e5\u003c/em\u003e(11), e13787. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1371/journal.pone.0013787\u003c/span\u003e\u003cspan address=\"10.1371/journal.pone.0013787\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarenina, K., Giljov, A., Ivkovich, T., Burdin, A., \u0026amp; Malashichev, Y. (2013). Lateralization of spatial relationships between wild mother and infant orcas, \u003cem\u003eOrcinus orca\u003c/em\u003e. Animal Behaviour, \u003cem\u003e86\u003c/em\u003e(6), 1225\u0026ndash;1231. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.anbehav.2013.09.025\u003c/span\u003e\u003cspan address=\"10.1016/j.anbehav.2013.09.025\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKilian, A., Fersen, L. von, \u0026amp; G\u0026uuml;nt\u0026uuml;rk\u0026uuml;n, O. (2005). Left hemispheric advantage for numerical abilities in the bottlenose dolphin. \u003cem\u003eBehavioural Processes\u003c/em\u003e, \u003cem\u003e68\u003c/em\u003e(2), 179\u0026ndash;184. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.beproc.2004.11.003\u003c/span\u003e\u003cspan address=\"10.1016/j.beproc.2004.11.003\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKilian, A., von Fersen, L., \u0026amp; G\u0026uuml;nt\u0026uuml;rk\u0026uuml;n, O. (2000). Lateralization of visuospatial processing in the bottlenose dolphin (\u003cem\u003eTursiops truncatus\u003c/em\u003e). Behavioural Brain Research, \u003cem\u003e116\u003c/em\u003e(2), 211\u0026ndash;215. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/s0166-4328(00)00273-4\u003c/span\u003e\u003cspan address=\"10.1016/s0166-4328(00)00273-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKosslyn, S. M. (1995). Mental imagery. In D. N. Osherson (Ed.), \u003cem\u003eVisual cognition: An invitation to cognitive science, Vol. 2\u003c/em\u003e, \u003cem\u003e2nd ed\u003c/em\u003e (pp.\u0026nbsp;267\u0026ndash;296). The MIT Press.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLambert, M., Farrar, B., Garcia-Pelegrin, E., Reber, S., \u0026amp; Miller, R. (2022). ManyBirds: A multi-site collaborative Open Science approach to avian cognition and behavior research. Animal Behavior and Cognition, \u003cem\u003e9\u003c/em\u003e(1), 133\u0026ndash;152. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://dx.doi.org/10.26451/abc.09.01.11.2022\u003c/span\u003e\u003cspan address=\"10.26451/abc.09.01.11.2022\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLohmann, A., Delius, J. D., Hollard, V. D., \u0026amp; Friesel, M. F. (1988). Discrimination of shape reflections and shape orientations by \u003cem\u003eColumba livia\u003c/em\u003e. Journal of Comparative Psychology (Washington, D.C.: 1983), \u003cem\u003e102\u003c/em\u003e(1), 3\u0026ndash;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/0735-7036.102.1.3\u003c/span\u003e\u003cspan address=\"10.1037/0735-7036.102.1.3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eManyPrimates (2019a). Establishing an infrastructure for collaboration in primate cognition research. PLOS ONE, \u003cem\u003e14\u003c/em\u003e(10), e0223675. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1371/journal.pone.0223675\u003c/span\u003e\u003cspan address=\"10.1371/journal.pone.0223675\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eManyPrimates (2019b). Collaborative open science as a way to reproducibility and new insights in primate cognition research. Japanese Psychological Review, \u003cem\u003e62\u003c/em\u003e(3), 205\u0026ndash;220. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.24602/sjpr.62.3_205\u003c/span\u003e\u003cspan address=\"10.24602/sjpr.62.3_205\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMass, A. M., \u0026amp; Supin, A. Ya. (2009). Vision. In W. F. Perrin, B. W\u0026uuml;rsig, \u0026amp; J. G. M. Thewissen (Eds.), \u003cem\u003eEncyclopedia of Marine Mammals (Second Edition)\u003c/em\u003e (pp.\u0026nbsp;1200\u0026ndash;1211). Academic Press. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/B978-0-12-373553-9.00275-3\u003c/span\u003e\u003cspan address=\"10.1016/B978-0-12-373553-9.00275-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatrai, E., Hoffmann-Kuhnt, M., \u0026amp; Kwok, S. T. (2019). Lateralization in accuracy, reaction time and behavioral processes in a visual discrimination task in an Indo-Pacific bottlenose dolphin (\u003cem\u003eTursiops aduncus\u003c/em\u003e). \u003cem\u003eBehavioural Processes\u003c/em\u003e, \u003cem\u003e162\u003c/em\u003e, 112\u0026ndash;118. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.beproc.2019.02.003\u003c/span\u003e\u003cspan address=\"10.1016/j.beproc.2019.02.003\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatsuno, T., \u0026amp; Tomonaga, M. (2006). Visual search for moving and stationary items in chimpanzees (\u003cem\u003ePan troglodytes\u003c/em\u003e) and humans (\u003cem\u003eHomo sapiens\u003c/em\u003e). Behavioural Brain Research, \u003cem\u003e172\u003c/em\u003e(2), 219\u0026ndash;232. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bbr.2006.05.004\u003c/span\u003e\u003cspan address=\"10.1016/j.bbr.2006.05.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMauck, B., \u0026amp; Dehnhardt, G. (1997). Mental rotation in a California sea lion (\u003cem\u003eZalophus californianus\u003c/em\u003e). Journal of Experimental Biology, \u003cem\u003e200\u003c/em\u003e(9), 1309\u0026ndash;1316. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1242/jeb.200.9.1309\u003c/span\u003e\u003cspan address=\"10.1242/jeb.200.9.1309\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoeller, K., Willmes, K., \u0026amp; Klein, E. (2015). A review on functional and structural brain connectivity in numerical cognition. Frontiers in Human Neuroscience, \u003cem\u003e9\u003c/em\u003e, 227. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.frontiersin.org/articles/\u003c/span\u003e\u003cspan address=\"https://www.frontiersin.org/articles/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fnhum.2015.00227\u003c/span\u003e\u003cspan address=\"10.3389/fnhum.2015.00227\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNiewiedział, D., Kolańska, M., Dąbrowiecki, Z., Jerzemowski, M., Siermontowski, P., Kobos, Z., \u0026amp; Olszański, R. (2018). Psychological aspects of diving in selected theoretical and research perspectives. Polish Hyperbaric Research, \u003cem\u003e62\u003c/em\u003e(1), 43\u0026ndash;54. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2478/phr-2018-0003\u003c/span\u003e\u003cspan address=\"10.2478/phr-2018-0003\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOpen Science Collaboration (2015). Estimating the reproducibility of psychological science. Science, \u003cem\u003e349\u003c/em\u003e, aac4716. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1126/science.aac4716\u003c/span\u003e\u003cspan address=\"10.1126/science.aac4716\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePatterson, K., \u0026amp; Bradshaw, J. L. (1975). Differential hemispheric mediation of nonverbal visual stimuli. Journal of Experimental Psychology. Human Perception and Performance, \u003cem\u003e1\u003c/em\u003e(3), 246\u0026ndash;252. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037//0096-1523.1.3.246\u003c/span\u003e\u003cspan address=\"10.1037//0096-1523.1.3.246\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePiaget, J., \u0026amp; Inhelder, B. (1956). \u003cem\u003eThe child's conception of space\u003c/em\u003e. London: Routledge \u0026amp; Kegan Paul.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePiazza, M., Mechelli, A., Price, C. J., \u0026amp; Butterworth, B. (2006). Exact and approximate judgements of visual and auditory numerosity: An fMRI study. Brain Research, \u003cem\u003e1106\u003c/em\u003e(1), 177\u0026ndash;188. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.brainres.2006.05.104\u003c/span\u003e\u003cspan address=\"10.1016/j.brainres.2006.05.104\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePoucet, B. (1993). Spatial cognitive maps in animals: New hypotheses on their structure and neural mechanisms. Psychological Review, \u003cem\u003e100\u003c/em\u003e(2), 163\u0026ndash;182. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/0033-295x.100.2.163\u003c/span\u003e\u003cspan address=\"10.1037/0033-295x.100.2.163\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePratt, J., Radulescu, P. V., Guo, R. M., \u0026amp; Abrams, R. A. (2010). It's alive! Animate motion captures visual attention. Psychological Science, \u003cem\u003e21\u003c/em\u003e(11), 1724\u0026ndash;1730. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1177/0956797610387440\u003c/span\u003e\u003cspan address=\"10.1177/0956797610387440\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePresson, C. C. (1982). Strategies in spatial reasoning. Journal of Experimental Psychology: Learning, Memory, and Cognition, \u003cem\u003e8\u003c/em\u003e, 243\u0026ndash;251. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/0278-7393.8.3.2430\u003c/span\u003e\u003cspan address=\"10.1037/0278-7393.8.3.2430\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePresson, C. C., \u0026amp; Somerville, S. C. (1985). Beyond egocentrism: A new look at the beginnings of spatial representation. In H. M. Wellman (Ed.), \u003cem\u003eChildren's searching: The development of search skill and spatial representation\u003c/em\u003e (pp.\u0026nbsp;1\u0026ndash;26). Psychology Press.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePriftis, K., Rusconi, E., Umilt\u0026agrave;, C., \u0026amp; Zorzi, M. (2003). Pure agnosia for mirror stimuli after right inferior parietal lesion. Brain: A Journal of Neurology, \u003cem\u003e126\u003c/em\u003e(Pt 4), 908\u0026ndash;919. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/brain/awg075\u003c/span\u003e\u003cspan address=\"10.1093/brain/awg075\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePylyshyn, Z. W. (2002). Mental imagery: In search of a theory. Behavioral and Brain Sciences, \u003cem\u003e25\u003c/em\u003e(2), 157\u0026ndash;182. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1017/S0140525X02000043\u003c/span\u003e\u003cspan address=\"10.1017/S0140525X02000043\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRisko, E. F., \u0026amp; Gilbert, S. J. (2016). Cognitive offloading. Trends in Cognitive Sciences, \u003cem\u003e20\u003c/em\u003e(9), 676\u0026ndash;688. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tics.2016.07.002\u003c/span\u003e\u003cspan address=\"10.1016/j.tics.2016.07.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRosati, A. G., \u0026amp; Santos, L. R. (2016). Spontaneous metacognition in rhesus monkeys. Psychological Science, \u003cem\u003e27\u003c/em\u003e(9), 1181\u0026ndash;1191. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1177/0956797616653737\u003c/span\u003e\u003cspan address=\"10.1177/0956797616653737\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSakai, M., Hishii, T., Takeda, S., \u0026amp; Kohshima, S. (2006a). Flipper rubbing behaviors in wild bottlenose dolphins (\u003cem\u003eTursiops aduncus\u003c/em\u003e). Marine Mammal Science, \u003cem\u003e22\u003c/em\u003e(4), 966\u0026ndash;978. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1111/j.1748-7692.2006.00082.x\u003c/span\u003e\u003cspan address=\"10.1111/j.1748-7692.2006.00082.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSakai, M., Hishii, T., Takeda, S., \u0026amp; Kohshima, S. (2006b). Laterality of flipper rubbing behaviour in wild bottlenose dolphins (\u003cem\u003eTursiops aduncus\u003c/em\u003e): Caused by asymmetry of eye use? Behavioural Brain Research, \u003cem\u003e170\u003c/em\u003e(2), 204\u0026ndash;210. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bbr.2006.02.018\u003c/span\u003e\u003cspan address=\"10.1016/j.bbr.2006.02.018\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSakai, M., Morisaka, T., Kogi, K., Hishii, T., \u0026amp; Kohshima, S. (2010). Fine-scale analysis of synchronous breathing in wild Indo-Pacific bottlenose dolphins (\u003cem\u003eTursiops aduncus\u003c/em\u003e). \u003cem\u003eBehavioural Processes\u003c/em\u003e, \u003cem\u003e83\u003c/em\u003e(1), 48\u0026ndash;53. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.beproc.2009.10.001\u003c/span\u003e\u003cspan address=\"10.1016/j.beproc.2009.10.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShepard, R. N. (1978). The mental image. American Psychologist, \u003cem\u003e33\u003c/em\u003e, 125\u0026ndash;137. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1037/0003-066X.33.2.125\u003c/span\u003e\u003cspan address=\"10.1037/0003-066X.33.2.125\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShepard, R. N., \u0026amp; Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, \u003cem\u003e171\u003c/em\u003e(3972), 701\u0026ndash;703. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1126/science.171.3972.701\u003c/span\u003e\u003cspan address=\"10.1126/science.171.3972.701\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSiniscalchi, M., Dimatteo, S., Pepe, A. M., Sasso, R., \u0026amp; Quaranta, A. (2012). Visual lateralization in wild striped dolphins \u003cem\u003e(Stenella coeruleoalba)\u003c/em\u003e in response to stimuli with different degrees of familiarity. PLoS One, \u003cem\u003e7\u003c/em\u003e(\u003cem\u003e1\u003c/em\u003e), e30001. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1371/journal.pone.0030001\u003c/span\u003e\u003cspan address=\"10.1371/journal.pone.0030001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSuzuki, T., Matsuzaki, Y., \u0026amp; Saeki, Y. (1991). Children's organization of a spatial array separated from its surroundings. Japanese Journal of Developmental Psychology, \u003cem\u003e1\u003c/em\u003e(2), 128\u0026ndash;135. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.11201/jjdp.1.128\u003c/span\u003e\u003cspan address=\"10.11201/jjdp.1.128\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (Japanese text with English abstract)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTarpley, R. J., \u0026amp; Ridgway, S. H. (1994). Corpus callosum size in delphinid cetaceans. Brain, Behavior and Evolution, \u003cem\u003e44\u003c/em\u003e(3), 156\u0026ndash;165. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1159/000113587\u003c/span\u003e\u003cspan address=\"10.1159/000113587\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTcaci Popescu, S., \u0026amp; Wexler, M. (2012). Spontaneous body movements in spatial cognition. Frontiers in Psychology, \u003cem\u003e3\u003c/em\u003e, 136. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.frontiersin.org/articles/\u003c/span\u003e\u003cspan address=\"https://www.frontiersin.org/articles/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3389/fpsyg.2012.00136\u003c/span\u003e\u003cspan address=\"10.3389/fpsyg.2012.00136\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThewissen, J. G. M. (2018). Brain. In B. W\u0026uuml;rsig, J. G. M. Thewissen, \u0026amp; K. M. Kovacs (Eds.), \u003cem\u003eEncyclopedia of Marine Mammals (Third Edition)\u003c/em\u003e (pp.\u0026nbsp;137\u0026ndash;140). Academic Press. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/B978-0-12-804327-1.00077-7\u003c/span\u003e\u003cspan address=\"10.1016/B978-0-12-804327-1.00077-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eThieltges, H., Lemasson, A., Kuczaj, S., B\u0026ouml;ye, M., \u0026amp; Blois-Heulin, C. (2011). Visual laterality in dolphins when looking at (un)familiar humans. Animal Cognition, \u003cem\u003e14\u003c/em\u003e(2), 303\u0026ndash;308. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10071-010-0354-5\u003c/span\u003e\u003cspan address=\"10.1007/s10071-010-0354-5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTomonaga, M., \u0026amp; Sakurai, N. (2014). \u003cem\u003eRecognition of rotated video images of gestural signs by bottlenose dolphins\u003c/em\u003e [Unpublished raw data]. Minamichita Beachland Aquarium.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTomonaga, M., \u0026amp; Uwano, Y. (2010). Bottlenose dolphins' (\u003cem\u003eTursiops truncatus\u003c/em\u003e) theory of mind as demonstrated by responses to their trainers' attentional states. International Journal of Comparative Psychology, \u003cem\u003e23\u003c/em\u003e(3). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.46867/ijcp.2010.23.03.03\u003c/span\u003e\u003cspan address=\"10.46867/ijcp.2010.23.03.03\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTomonaga, M., Uwano, Y., Ogura, S., Chin, H., Dozaki, M., \u0026amp; Saito, T. (2015). Which person is my trainer? Spontaneous visual discrimination of human individuals by bottlenose dolphins (\u003cem\u003eTursiops truncatus\u003c/em\u003e). SpringerPlus, \u003cem\u003e4\u003c/em\u003e(1), 352. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/s40064-015-1147-8\u003c/span\u003e\u003cspan address=\"10.1186/s40064-015-1147-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTomonaga, M., Uwano, Y., \u0026amp; Saito, T. (2014). How dolphins see the world: A comparison with chimpanzees and humans. Scientific Reports, \u003cem\u003e4\u003c/em\u003e, 3717. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1038/srep03717\u003c/span\u003e\u003cspan address=\"10.1038/srep03717\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003evon Fersen, L., Schall, U., \u0026amp; G\u0026uuml;nt\u0026uuml;rk\u0026uuml;n, O. (2000). Visual lateralization of pattern discrimination in the bottlenose dolphin (\u003cem\u003eTursiops truncatus\u003c/em\u003e). Behavioural Brain Research, \u003cem\u003e107\u003c/em\u003e(1), 177\u0026ndash;181. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0166-4328(99)00142-4\u003c/span\u003e\u003cspan address=\"10.1016/S0166-4328(99)00142-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang, R. F., \u0026amp; Spelke, E. S. (2002). Human spatial representation: Insights from animals. Trends in Cognitive Sciences, \u003cem\u003e6\u003c/em\u003e(9), 376\u0026ndash;382. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S1364-6613(02)01961-7\u003c/span\u003e\u003cspan address=\"10.1016/S1364-6613(02)01961-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliams, T. M. (2001). Intermittent swimming by mammals: a strategy for increasing energetic efficiency during diving. American Zoologist, \u003cem\u003e41\u003c/em\u003e(2), 166\u0026ndash;176. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1093/icb/41.2.166\u003c/span\u003e\u003cspan address=\"10.1093/icb/41.2.166\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliams, R., Trites, A. W., \u0026amp; Bain, D. E. (2002). Behavioural responses of killer whales (\u003cem\u003eOrcinus orca\u003c/em\u003e) to whale-watching boats: Opportunistic observations and experimental approaches. Journal of Zoology, \u003cem\u003e256\u003c/em\u003e(2), 255\u0026ndash;270. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1017/S0952836902000298\u003c/span\u003e\u003cspan address=\"10.1017/S0952836902000298\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXitco Jr., M. J., Gory, J. D., \u0026amp; Kuczaj II, S. A. (2004). Dolphin pointing is linked to the attentional behavior of a receiver. Animal Cognition, \u003cem\u003e7\u003c/em\u003e, 231\u0026ndash;238. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s10071-004-0217-z\u003c/span\u003e\u003cspan address=\"10.1007/s10071-004-0217-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZacks, J. M., \u0026amp; Michelon, P. (2005). Transformations of visuospatial images. Behavioral and Cognitive Neuroscience Reviews, \u003cem\u003e4\u003c/em\u003e(2), 96\u0026ndash;118. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1177/1534582305281085\u003c/span\u003e\u003cspan address=\"10.1177/1534582305281085\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZacks, J. M., Mires, J., Tversky, B., \u0026amp; Hazeltine, E. (2000). Mental spatial transformations of objects and perspective. Spatial Cognition and Computation, \u003cem\u003e2\u003c/em\u003e(4), 315\u0026ndash;332. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1023/A:1015584100204\u003c/span\u003e\u003cspan address=\"10.1023/A:1015584100204\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZapetis, M., \u0026amp; Szesciorka, A. (2018). Cetacean navigation. In J. Vonk \u0026amp; T. Shackelford (Eds.), \u003cem\u003eEncyclopedia of Animal Cognition and Behavior\u003c/em\u003e (pp.\u0026nbsp;1\u0026ndash;7). Springer International Publishing. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/978-3-319-47829-6_986-1\u003c/span\u003e\u003cspan address=\"10.1007/978-3-319-47829-6_986-1\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"animal-cognition","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"anco","sideBox":"Learn more about [Animal Cognition](http://link.springer.com/journal/10071)","snPcode":"10071","submissionUrl":"https://submission.nature.com/new-submission/10071/3","title":"Animal Cognition","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-2606167/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-2606167/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHow do bottlenose dolphins visually perceive the space around them? In particular, what coordinates do they use as a frame of reference for left-right perception? To address this question, we examined the dolphin's responses to various manipulations of the spatial relationship between the dolphin and the trainer by using gestural signs for actions given by the trainer, which have different meanings in the left and right hands. When the dolphins were tested with their backs to the trainer (Experiment 1) or in an inverted position underwater (Experiments 2 and 3), correct responses from the trainer's perspective were maintained for signs related to movement direction instructions. In contrast, reversed responses were frequently observed for signs that required different sounds for the left and right hands. When the movement direction instructions were presented with symmetrical graphic signs such as \"\u0026times;\" and \"●\", accuracy decreased in the inverted posture (Experiment 3). Furthermore, when the signs for sounds were presented from either the left or right side of the dolphin's body, performance was better when the side of the sign movement coincided with the body side on which it was presented than when it was mismatched (Experiment 4). In the final experiment, when one eye was covered with an eyecup, the results showed that, as in the case of body-side presentation, performance was better when the open eye coincided with the side on which the sign movement was presented. These results indicate that dolphins used the egocentric frame for visuospatial cognition. In addition, they showed better performances when the gestural signs were presented to the right eye, suggesting a left-hemispheric advantage in the dolphin's visuospatial cognition.\u003c/p\u003e","manuscriptTitle":"Left or right, that is the question: Use of egocentric frame of reference and the right-eye advantage for understanding gestural signs in bottlenose dolphins (Tursiops truncates)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-02-24 21:09:02","doi":"10.21203/rs.3.rs-2606167/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2023-05-18T06:59:29+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-04-07T21:26:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"4d2df22e-bcc9-4536-a247-366ca5b096ff","date":"2023-03-04T17:58:08+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-03-04T12:14:30+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-02-27T05:36:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2023-02-22T18:05:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Animal Cognition","date":"2023-02-20T05:06:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"animal-cognition","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"anco","sideBox":"Learn more about [Animal Cognition](http://link.springer.com/journal/10071)","snPcode":"10071","submissionUrl":"https://submission.nature.com/new-submission/10071/3","title":"Animal Cognition","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a0a4a869-25c7-4caf-9573-539282e62e95","owner":[],"postedDate":"February 24th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2023-10-16T21:23:30+00:00","versionOfRecord":{"articleIdentity":"rs-2606167","link":"https://doi.org/10.1007/s10071-023-01799-6","journal":{"identity":"animal-cognition","isVorOnly":false,"title":"Animal Cognition"},"publishedOn":"2023-06-15 21:13:03","publishedOnDateReadable":"June 15th, 2023"},"versionCreatedAt":"2023-02-24 21:09:02","video":"","vorDoi":"10.1007/s10071-023-01799-6","vorDoiUrl":"https://doi.org/10.1007/s10071-023-01799-6","workflowStages":[]},"version":"v1","identity":"rs-2606167","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-2606167","identity":"rs-2606167","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}