Effect of the discussion frame on finding a compromise: A group decision experiment on the final disposal of removed soil outside Fukushima

Effect of the discussion frame on finding a compromise: A group decision experiment on the final disposal of removed soil outside Fukushima | 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 Effect of the discussion frame on finding a compromise: A group decision experiment on the final disposal of removed soil outside Fukushima Yume Souma, Yukihide Shibata, Mie Tsujimoto, Qinglin Cui, Takashi Nakazawa, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6290609/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Public deliberation is useful for finding an acceptable compromise, particularly when plural values are contradictory. This study addresses the case of the final disposal of removed soil outside Fukushima Prefecture, Japan, which requires public deliberation to untangle contradictory values but has not yet been implemented. Despite existing case reports and surveys targeting individual answers, a group decision experiment in a laboratory setting with rigorous manipulation is noteworthy for determining the conditions under which a group can find an acceptable compromise that reflects heterogeneous opinions. In a group decision experiment comprising four members, we manipulated the discussion frames: one was a controversial frame, whereby participants refuted each other in a dichotomous manner, and the other was an inclusive frame, whereby they contemplated both the pros and cons thoroughly. Each group decided whether to approve the final disposal outside Fukushima. The results indicated that the inclusive frame was more likely to facilitate compromise that reflected heterogeneous opinions than the controversial frame. Although group opinions shifted toward support for their decision with decreased variance in both conditions, participants in the inclusive frame condition rated their decisions more positively than those in the controversial condition. Notably, in the inclusive condition, participants evaluated conclusions favorably regardless of their initial opinions, while those in the controversial condition viewed decisions negatively when they conflicted with their initial opinions. These findings highlight the impact of discussion frames on finding a compromise and offer insights into designing effective public deliberation for environmental policy planning. public deliberation discussion frame finding a compromise group decision experiment final disposal of removed soil Figures Figure 1 Figure 2 Figure 3 1. Introduction Public decision-making, such as in terms of environmental management policy, calls for neither simply following the majority rule nor being pushed through by a loud minority (Gutmann and Thompson 2004 ; Smith 2009 ). It requires elaborating on both majority and minority opinions thoroughly, listening to different points of view, and finding a compromise that is acceptable to both sides, especially when reconciling controversial values is difficult, all of which are publicly important (Cohen 1989 ; Habermas 1988 ; Luskin et al. 2002 ; Steenbergen et al. 2003 ). This study addresses the case of the final disposal of removed soil outside Fukushima Prefecture, which entails burden distribution with conflicts of plural values, as described in the following section. Experimental examinations are a valuable tool to test the conditions under which people achieve constructive compromise, reflecting contradictory values, although practical experiences have affirmed such outcomes. Therefore, this study employs a method of group decision experiments developed in social psychology (c.f., Moscovici and Doise 1994 ; Moscovici and Zavalloni 1969 ) to investigate the conditions for achieving compromised decisions by conducting rigorous factor control and manipulation. Finding a compromise that both sides can accept is challenging in terms of burden distribution, particularly when contradictory values are in conflict. A practical tool for untangling such value conflicts is public discourse. It is crucial to engage the public, involving diverse citizens (Renn 2006 ). This approach can diminish conflicts, facilitate stakeholder and public learning, enhance support for project goals, and promote long-term decision implementation (Beierle 2002 ; de Vente et al. 2016 ). For instance, public deliberations have been observed in various contexts, such as sustainable societal policies and environmental master plans (Nakamura et al. 2024 ; Ohnuma et al. 2022 ). Issues involving clear common goals and minimal controversy help to reach a consensus in a broad direction and incorporate diverse opinions. However, implementing public deliberation sometimes fails; it can lead to unexpected or unintended adverse outcomes (Emery et al. 2015 ; Reed 2008 ). Therefore, determining the factors and conditions relevant to the failure or success of the discourse arena is vital. This study focuses on whether participants can find an acceptable compromise. Pluralistic values, including minority opinions, should be discussed and considered in public deliberations (Fishkin 2009 ; Ohnuma 2014 ). Discourse ethics (Habermas 1988 ) emphasize that citizens should impartially and sincerely elaborate on all opinions. Although numerous studies have advocated for its importance (e.g., Fishkin 2009 ; Lafont 2015 ; Parkinson 2003 ), it is not guaranteed in reality. Participants may stick to their positions of approval or disapproval, resulting in debates that are neither constructive nor productive. Few studies on public deliberation have empirically examined whether, how, and when discourse reflects heterogeneous opinions, including minority perspectives within a group (Hamlett and Cobb 2007; Mansbridge 1983 ). Therefore, it is essential to examine the conditions required to prevent unproductive debates. Empirical research has not sufficiently clarified the conditions that make a difference in public deliberation. However, studies on group experiments in social psychology have repeatedly demonstrated the strong influence of the majority and the frequent use of majority rule (Asch 1956 ; Carpini et al. 2004 ; Crano and Seyranian 2007 ; Davis 1973 ; Garcia et al. 2021 ; Hastie and Kameda 2005 ; Kameda 1991 ; Kameda et al. 2022 ; Kuroda et al. 2023 ; Mendelberg 2002 ; Mercier and Morin 2019 ; Paruzel-Czachura et al. 2024 ; Tanford and Penrod 1984 ). Several studies have shown that minorities within a group can influence the majority, albeit under limited conditions (Moscovici 1980 ; Moscovici et al. 1969 ; Nemeth 1981 ). Given these findings, the conceptualization of ways to arrive at a compromise during public deliberation is worthwhile. This study examines such conditions using a group decision experiment on the final disposal of removed soil outside Fukushima Prefecture. In this study, the success or failure of group decisions is judged based on whether the group finds a compromise acceptable to any member. We hypothesize that the discussion frame affects reaching a compromise, as discussed in Section 1.3 . For example, a discussion frame in which participants are divided between favoring and opposing may not work constructively, contrary to one in which they consider both sides. Hence, we manipulated discussion frames in the group decision experiment. Finally, from the findings of the experiment, we elucidate how the discussion frame can contribute to a compromise in public discourse. 1.1 The case of the final disposal of the removed soil outside Fukushima Prefecture 1.1.1 Outline of the issue The Fukushima Daiichi nuclear power plant accident occurred in March 2011, resulting in the release of large amounts of radioactive substances into the environment, thus causing environmental pollution. The Japanese government carried out decontamination work to reconstruct Fukushima Prefecture, which produced vast volumes of soil and other materials. The removed soil was initially placed in temporary storage sites in broad areas of Fukushima; however, to proceed with the restoration and reconstruction of Fukushima, a facility was necessary to manage and store the removed soil safely and centrally. Consequently, an interim storage facility was constructed in Okuma and Futaba, which are towns in Fukushima. The area of the interim storage facility is approximately 16 km², of which approximately 80% is private land owned by villagers (Ministry of the Environment 2023 ), where paddy fields and shrines existed, and many lived before the accident. The amount of removed soil and other materials delivered to the facility is approximately 14 million m³ (equivalent to the volume of approximately 28,000 25-swimming pools). Of the massive amount of removed soil, approximately 20% is high-concentration soil exceeding 8,000 Bq/kg, and 80% is low-concentration soil below 8,000 Bq/kg (Ministry of the Environment 2023 ). Regarding the removed soil and waste, the government must take the necessary measures to complete the final disposal outside Fukushima within 30 years from the start of transportation to the interim storage facility (by March 2045), in line with the Japan Environmental Storage & Safety Corporation Law (Law No. 44 of 2003, promulgated on May 16, 2003). However, a specific method or disposal site for the final disposal has not yet been determined. It is difficult to dispose of the large amount of removed soil outside Fukushima from the perspective of obtaining a site area. Therefore, the key to realizing final disposal outside Fukushima is to reduce the final disposal volume (Ministry of the Environment 2023 ). To ensure safety, the government is attempting to convert low-concentration soil below 8,000 Bq/kg into recycled material and promote its reuse under the condition that the management body and responsibility are guaranteed (Ministry of the Environment 2023 ). Low-concentration soil is usable for road construction and farmland development in raised earth foundations. Demonstration projects for reusing soil have been conducted in Minami-Soma City and Iitate Village in Fukushima, and safety has been confirmed in both projects (Baba 2022 ; Hasegawa 2021 ; Ministry of the Environment 2023 ). To implement the final disposal of the removed soil outside Fukushima and the reuse of low-radioactive soil, it is essential to foster public understanding and invite public discourse (Ministry of the Environment 2023 ). In other words, designing public engagement is required, in which a wide range of citizens discuss the issue of the removed soil (c.f., IAEA 2022 ). Hence, it would be worthwhile to provide insights into the design of a more useful dialogue. Previous studies on the removed soil have conducted surveys with questionnaires and interviews to explore the social acceptability of the final disposal and related factors (Murakami et al. 2024 ; Shirai et al. 2023 ; Takada et al. 2022 , 2024 , 2025 ). However, only a few studies have examined the content individuals discuss and the decisions they make when engaging in group discussions (Souma et al. 2022 , 2024 ). Therefore, we compare the decisions made through discussions on the removed soil issue in terms of reflecting both sides’ opinions. 1.1.2 Conjunctive argument points of the final disposal of the removed soil The final disposal of the removed soil involves a complex set of burden distributions that demands public understanding and consensus. Therefore, public deliberation not only on the final disposal in question but also on other related points is vital for making a comprehensive decision. Two arguments that are critical for burden distribution are summarized. The first point is the number of final disposal sites. Regardless of whether the final disposal of the removed soil is conducted outside Fukushima, selecting one or more final disposal sites is critical. Previous studies on the final disposal and reuse of the removed soil suggest that inequity is mitigated and is more acceptable at multiple sites than at a single site (Takada et al. 2022 ; Yokoyama et al. 2021 ). If the findings of these studies are robust, people are more likely to agree to final disposal at more than one location. However, some may argue that a single location is better because it reduces costs and concrete risks and enhances the efficiency of constructing a final disposal facility. Hence, the number of final disposal sites remains debatable. The second point relates to the reuse of the removed soil. As mentioned above, the Japanese government aims to reuse the low-concentration removed soil to realize final disposal outside Fukushima Prefecture. Regardless of how the safety of reuse has been scientifically confirmed in demonstration projects (Baba 2022 ; Hasegawa 2021 ; Ministry of the Environment 2023 ), reuse cannot be implemented unless residents living in nearby areas of the sites understand the safety measures and provide consent. In addition, the number and range of reuse sites constitute an argument. The number of sites can be single or multiple. Moreover, as the reuse of soil can be carried out throughout Japan in principle, it can also be conducted within Fukushima, which differs from final disposal. However, considering the residents of Okuma and Futaba towns in Fukushima who have borne the burden, as with final disposal, reuse should also be carried out outside Fukushima. In summary, the argument concerns whether the reuse of low-concentration soil should be carried out, and if so, whether it should be implemented at a single location or multiple locations, and whether the range should be nationwide, including or outside Fukushima. In sum, the central argument to be decided in the following experiment is whether to approve the final disposal outside Fukushima. Moreover, the number of final disposal sites and the reuse of the removed soil are conjunctive argument points. In the following experiment, decisions on both the central and conjunctive argument points are presented as discussion points and referred to in verifying whether a compromise can be found. It is assumed that if the central decision reflects one side but the decisions on conjunctive argument points adopt the other side’s views, the overall group conclusion is deemed a compromise. Note that, in the experiment, the central decision is mandatory, but decisions on conjunctive argument points are optional. 1.2 Effects of discussion frame on finding a compromise This study focuses on discussion frames as a factor in finding an acceptable compromise in group decisions. A discussion frame refers to the manner of communication understood among members (Black 2013 ), which can be transformed through the design of the dialogue forum under the organizer. This study adopted controversial and inclusive frames, which are commonly observed in public discourse. A controversial frame involves an explicit pro–con conflict, refuting the opposing opinions of each other, and a dichotomous choice, such as for or against. In contrast, an inclusive frame involves a thoughtful examination of both sides regardless of their positions. Although environmental management policy planning forums must be transparent and open (Bryson and Crosby 1996 ), such forums sometimes become debate-like, in which participants are divided into two sides and refute each other. In such controversial frames, participants often fail to reach a consensus (Nagel and Satoh 2019 ; Reiners 2023 ). Hence, inclusive frames have also been applied, whereby participants do not debate for or against but aim for mutual understanding (Ohnuma et al. 2019 ). The discussion frame in this study combines the posture of discussion (i.e., the mental preparedness that participants have during the discussion) and the options given for the decision, as the manner of communication and the set of options are mutually influential. In a controversial frame involving dichotomous debate and choice, participants would be less likely to find an acceptable compromise in the group because they are placed in a situation where they cannot easily admit to changing their opinions. Additionally, as participants attempt to justify their views, they may insist that only their opinions are correct regarding the central decision and conjunctive issues. Conversely, in an inclusive frame involving the examination of both sides’ opinions and mutual understanding, participants would be more likely to reach an acceptable compromise in the group. Moreover, even if the central decision reflects only one side, other views may be incorporated into conjunctive argument points. 1.3 Influence of group decision on the members Assuming that the discussion frame influences the finding of an acceptable compromise, its impact will likely extend to how participants evaluate the group’s conclusions. If participants find a compromise acceptable to both sides, the evaluation of the conclusion should be high, regardless of their initial opinions. Conversely,, when the conclusion reflects only one side’s opinion, the evaluation will likely vary depending on initial opinions. Previous studies have observed group polarization, whereby the average opinion within the group shifts toward the group’s decision, and the variance of opinions within the group decreases after discussion (Fishkin 2009 ; Fishkin and Luskin 2005 ; Gastil and Dillard 1999 ; Gerber et al. 2018 ; Lamm and Myers 1978 ; Moscovici and Zavalloni 1969 ; Sanders 2012 ). However, group polarization may occur solely because the group has reached a decision (Arima 2019 ), regardless of whether the conclusion is compromised. Conversely, if the group cannot reach a decision, the differences between opposing views may deepen, thereby increasing the variance of opinions. To examine the difference between group polarization and making an acceptable compromise, this study investigates whether opinion changes and participants’ evaluations of the conclusions differ across discussion frames. 1.4 Purpose This study aims to investigate a pivotal condition for finding an acceptable compromise in decision-making, employing a group decision experiment on the final disposal of removed soil outside Fukushima Prefecture. Precisely, the study manipulates the discussion and decision frames in the experiment and examines their effects on reaching an acceptable compromise that integrates controversial values. First, we compare the decision statements presented by participants between conditions. We predict that the central and conjunctive argument points are more likely to be incorporated into group decisions under the inclusive frame condition than under the controversial frame condition. Second, we examine the effects of discussion frames on opinion changes before and after the discussion. Opinion changes are explored to determine whether the average opinion within the group shifts to support the group’s decisions and whether the variance of opinions decreases. We predict that such a change will occur, regardless of the frame, once the group reaches a decision. Third, we examine the evaluation of the conclusions as an indicator of reaching an acceptable compromise that satisfies both sides’ opinions. We hypothesize that the evaluation will be rated higher in the inclusive condition than in the controversial condition, regardless of initial opinions, because the conclusions in the inclusive frame condition will incorporate both sides’ opinions, leading to a more acceptable compromise. 2. Methods 2.1 Experiment overview This study was approved by the Ethics Review Committee of the first author’s institution (Approval Code: R4-05) and was conducted between June and October 2023. Participants discussed and decided whether the final disposal of the removed soil outside Fukushima Prefecture was acceptable. In the experiment, we manipulated the discussion and decision frames: one was the controversial condition, characterized by clearly different positions, in which participants were instructed to refute the opponent, and the other was the inclusive condition, in which participants were instructed to consider both positions regardless of their initial opinion. Details regarding the manipulation of conditions are provided below. 2.1.1 Participants Each group consisted of four undergraduate students who met for the first time and were recruited through an experimental participant recruitment system (Sona Systems). Considering the statistical power and moderate effect size in the t-test (statistical power β = 0.80, effect size d = 0.50; Cohen 2016 ), a sample size of 16 groups, with 64 participants, was determined for each condition. Participants’ gender distribution was as follows: 70 males (controversial condition: 38, inclusive condition: 32), 57 females (controversial condition: 25, inclusive condition: 32), and 1 participant in the controversial condition who selected “non-binary/prefer not to answer.” None of the participants were from Fukushima, and their interest in and knowledge about decontaminated soil and final disposal were moderate in both conditions. Participants were uninformed about the details of the experiment until they arrived at the laboratory. The experimenter formed groups from participants who applied for the identified timeslots, and group assignments were balanced by the experimenter using pre-questionnaire responses. 2.1.2 Creation of informed materials regarding the final disposal of removed soil Before the discussion, participants received informational materials providing an overview of the removed soil and its final disposal. These materials, totaling 19 pages (Online Resource 1), were reviewed by experts from various fields, including radiation medicine, soil chemistry, environmental restoration, and risk communication. The experts ensured the information’s accuracy, neutrality, and validity, and we revised the materials until they were judged satisfactory. The materials provided details on the generation process of the removed soil, final disposal procedures, and statements from the mayors of Okuma and Futaba, where the interim storage facility is located. The arguments included the reuse of soil and the number of final disposal sites. Participants had access to the materials throughout the discussion. 2.1.3 Experimental procedure Upon arriving at the experimental room, participants received consent forms for participation and recording and signed them if they agreed. They then received the informational materials and watched a 10-minute instructional video corresponding to them. Subsequently, participants completed a questionnaire. Following this, a manner of discussion that differed between the conditions was introduced. The details of this process are provided below. Participants had five minutes for individual deliberation, recording their ideas on a sheet. Then, the discussion manner was reiterated, and participants were asked to record their conclusion on the “decision sheet” at the end of the discussion. Moreover, participants were told that one of the members would present their decision along with the reasons and process leading to it. A copy of the “decision sheet” was delivered to each group. The discussion lasted 40 minutes, with one of the members announcing the group’s decision and allowing for additional comments from others. Finally, participants completed a post-discussion questionnaire. 2.1.4 Condition manipulation To establish the discussion frame, manipulation was performed using several procedures. First, “position plates” were placed in front of participants in the controversial condition based on their responses to the pre-questionnaire, which asked whether they supported or opposed the final disposal of the removed soil outside Fukushima. In the controversial condition, participants were informed that the position on their plates corresponded to their pre-questionnaire response, which was their initial opinion. The “position plates” were visible to everyone, including participants. Although participants in the inclusive condition answered the question about supporting or opposing the final disposal outside Fukushima Prefecture the same as those in the controversial condition, “position plates” were not placed in front of them. Second, different manners of discussion were used for each condition. In the controversial condition, participants were instructed to “assert your position and persuade opponents with different opinions to be adopted as the group decision” and “decide whether to approve or disapprove the final disposal outside Fukushima Prefecture by the end of the discussion.” In the inclusive condition, participants were instructed to “consider both supportive and opposing stances on the final disposal of the removed soil, critically sift through the merit and demerit of the final disposal outside Fukushima Prefecture” and “decide what should be done by the end of the discussion.” Third, the “opinion sheets,” where participants wrote their ideas for individual deliberation before discussion, differed for each condition. In the controversial condition, participants were asked to fill in 1) their position on the final disposal outside Fukushima Prefecture (as written on the “position plate”), 2) arguments supporting their position, 3) assumed arguments from the opposing position, and 4) arguments to counter the assumed opponents’ arguments. In the inclusive condition, participants were asked to fill in 1) their position on the final disposal outside Fukushima (the same as the position they answered in the pre-discussion questionnaire), 2) the merits of the final disposal outside Fukushima Prefecture, 3) the demerits of the final disposal outside Fukushima, and 4) consider both supportive and opposing contentions, considering agreeable ideas to varied individuals with various stances. Finally, the “decision sheet” that included the choices for the decision differed by the conditions. In the controversial condition, the decision sheet had the options: “Approve,” “Disapprove,” or “Not decided” for the final disposal outside Fukushima. In the inclusive condition, the decision entry sheet contained options: “Proceed,” “Not proceed,” “Other” (entry specified contents), or “Not decided” with the final disposal outside Fukushima Prefecture. Participants in both conditions were asked to fill in their decisions as a group on the decision sheet until the end of the discussion. 2.2 Questionnaire Before the discussion, participants responded to a pre-discussion questionnaire. This questionnaire measured their opinions on the final disposal of the removed soil outside Fukushima Prefecture and relevant points. Items were rated on a 6-point Likert scale ranging from 1 (disapprove) to 6 (approve). In the following results section, we showed only one item, “Conducting the final disposal outside Fukushima Prefecture.” In the post-discussion questionnaire, participants rated their compliance with the discussion methods: 1) to assert their position and persuade opponents with different opinions to be adopted as the group decision, and 2) to consider both supportive and opposing stances on the final disposal of the removed soil, elaborating on the merits and demerits of the final disposal outside Fukushima Prefecture. They then provided their opinions on the final disposal and relevant points, similar to the pre-discussion questionnaire. Additionally, participants evaluated their group’s decisions as follows: 1) Overall, I think the conclusion is good, and 2) Considering the whole, I evaluate the conclusion as good. Ratings were on a 7-point Likert scale ranging from 1 (do not agree) to 7 (agree), comprising the “evaluation of decision” scale (Cronbach’s α = 0.97). The entire contents of the pre- and post-discussion questionnaires are presented in Online Resource 2. R version 4.2.3 was used for statistical analysis (Online Resource 3). 3. Results 3.1 Manipulation check We checked the manipulation using the responses to the post-discussion questionnaire. A multilevel linear regression analysis was conducted with the responses to each item as the dependent variable and the condition (0: controversial condition, 1: inclusive condition) as the predictor variable. Discussion groups were treated as random intercepts. Participants in the controversial condition (M = 4.03, SD = 1.50) exerted more effort in persuading others with opposing opinions than those in the inclusive condition (M = 2.78, SD = 1.43). However, no effect of condition was found on the second item ( β = 0.26, 95% CI = [-0.12, 0.65]). The responses were similar for the controversial (M = 4.98, SD = 1.13) and inclusive (M = 5.25, SD = 0.91) conditions. 3.2 Group decisions We examined the distribution of initial opinions on the final disposal of the removed soil outside Fukushima Prefecture before the discussions to compare the conditions. There were 45 supporters and 19 opponents in the controversial condition and 43 supporters and 21 opponents in the inclusive condition, indicating a roughly equal distribution between conditions. Table 1 presents the initial opinion distribution (number of supporters and opponents) and group decisions regarding the final disposal. Table 1 Distribution of the initial opinion and decision of each group Controversial condition Inclusive condition Distribution of the initial opinion (pros - cons) Decision (the final disposal outside Fukushima Prefecture) Distribution of the initial opinion (pros - cons) Decision (the final disposal outside Fukushima Prefecture) 4-0 Approval 4-0 Approval 4-0 Approval 4-0 Approval 4-0 Approval 4-0 Approval 4-0 Approval 3-1 Disapproval 4-0 Approval 3-1 Approval 3-1 Approval 3-1 Approval 3-1 Not decided 3-1 Approval 3-1 Not decided 3-1 Others 3-1 Not decided 3-1 Others 3-1 Not decided 3-1 Others 3-1 Not decided 2-2 Approval 2-2 Disapproval 2-2 Others 2-2 Approval 2-2 Others 2-2 Approval 2-2 Others 1-3 Disapproval 1-3 Disapproval 0-4 Disapproval 1-3 Approval Notably, 5 out of the 16 groups in the controversial condition did not reach a decision by the end of the discussion period, whereas all groups in the inclusive condition did. Instead, in the inclusive condition, six groups arrived at the “Other” conclusion, which involved neither approval nor disapproval of the final disposal outside Fukushima, thus compromising both sides. For example, some groups concluded that the burden of soil disposal should be shared within the entire Tohoku region or that disposal should take place in both uninhabited areas outside and within Fukushima Prefecture. Remarkably, one group detailed the procedure for selecting disposal sites. 3.3 Descriptions of decision statements After the discussion, a group member presented the group decision, which typically addressed the approval or disapproval of the final disposal outside Fukushima Prefecture and conjunctive argument points, such as the reuse of soil and the number of sites. In the following, we present examples of decision statements representing the differences between conditions from two perspectives: the structure of the decision statement and the relevance between the central decision and conjunctive argument points. The decision statements of all the groups are provided in Online Resource 4. Regarding the structure of the decision statement, in the controversial condition, many groups initially stated whether they approved or disapproved of the final disposal, followed by the reasons justifying their decision. For instance, in a group that decided to oppose, a group member said: “The conclusion as a group was opposition. There were opinions in favor of (the final disposal outside Fukushima Prefecture), including reducing the burden and leading people in other areas to further understand the disaster. However, as for the burden, counterarguments were made that this would increase the burden on other regions and that it would be difficult in reality. In addition, in Fukushima Prefecture, interim storage facilities are currently in good condition to manage the removed soil. We thought that there was no need to take the risk of transport ing the waste to other places, so the decision was opposed.” Conversely,, in the inclusive condition, although most groups also initially expressed their decision on the final disposal, they subsequently addressed the elaborations on the various arising opinions, the reasons for adopting these opinions, and the criteria for judgment in the sequence of the discussion. For instance, in a group that decided to proceed, the following was expressed: “We took a position in favor of the final disposal outside Fukushima Prefecture. Initially, the reasons for both supporters and opponents were discussed. The main reasons for the support were to avoid burdening Fukushima residents , [...] . The opposing reasons were that the municipalities receiving compensation to host nuclear facilities should bear responsibility for the facility’s installation. Additionally, the Tokyo Electric Power Company, which installed the nuclear power plant, should take responsibility. Hence, a group member of the opposition argued that the disposal site should be located in Fukushima Prefecture. However, considering that the Japanese government has promoted nuclear power plants nationwide, the idea that all Japanese citizens should bear responsibility was formed in our group. Then, the opinion as a group shifted toward not only conducting the final disposal in Fukushima Prefecture but also the distribution in the whole country.” Regarding the interconnections between the central decision and conjunctive argument points, the decision statements under the controversial condition were likely to separate the final disposal from the conjunctive argument points, such as the reuse of low-concentration soil. “We reached a decision, in principle, in favor of the final disposal site outside Fukushima. The initial opposing opinions [...]. In passing, we discussed where the burden of the reuse of low-concentration soil should be placed, and we generally agreed that the reuse should be borne by those outside Fukushima Prefecture.” This statement implied that the focus was directed toward whether to support or oppose the final disposal outside Fukushima and that conjunctive argument points, such as the reuse of low-concentration soil, were considered independently of the decision on the final disposal. Conversely, the decision statements from the inclusive condition indicated that they discussed issues associated with conjunctive argument points. “As a positive aspect, the key point was the distribution of the burden. Opposing opinions included concerns about the many people bearing the burden, dispersing risks, and uncertainty regarding finding host sites. […] In the end, the decision was to proceed with the final disposal outside Fukushima. Moreover, it was decided that Fukushima Prefecture would bear the entire burden of the reuse of low-concentration soil, while the soil subject to final disposal was distributed , except for Fukushima, based on population ratios. It was agreed that each prefecture would bear the cost of construction for the final disposal site, and the government would cover the transfer costs (for the removed soil).” The group, composed of an initial opinion of three in favor and one against, ultimately agreed with the final disposal outside Fukushima. However, the concerns raised by the opposing side were also considered in their decision to reuse low-radioactive-concentration soil within Fukushima Prefecture. 3.4 Opinion changes We conducted an analysis to assess opinion changes before and after the discussion, focusing on the averages and variances within the group. Results for “Conducting the final disposal outside Fukushima Prefecture” are presented here, and results for others are provided in Online Resource 5. Table 2 presents the average opinions before and after the discussions by condition. A multilevel linear regression analysis revealed that the 95% confidence intervals for each parameter crossed zero (the estimated effect of condition, time, and interaction were β = -0.45, 95% CI = [-1.17, 0.25], β = 0.11, 95% CI = [-0.52, 0.77], and β = 0.61, 95% CI = [-0.31, 1.54], respectively), meaning that no difference was found in either condition or time regarding the average opinions about the final disposal outside Fukushima. Table 2 Changes in the average opinions Controversial condition Inclusive condition Average of pre-opinion Average of post-opinion Average of pre-opinion Average of post-opinion Conducting the final disposal outside Fukushima Prefecture 4.14 4.25 3.69 4.42 The results may be influenced by the varying direction of opinion change depending on the group decision. Therefore, the averages for each group before and after the discussion were plotted based on the group’s decisions (Figure 1). The average opinions of many groups shifted toward supporting the group decisions. However, for groups under the controversial condition with the “Not decided” outcome and the inclusive condition with the “Other” outcome, the direction of opinion shifts varied among groups. Table 3 presents the variance within the group before and after the discussion by condition. The results of a multilevel linear regression analysis indicated that the 95% confidence intervals for each parameter crossed zero (β = 0.12, 95% CI = [-0.21, 0.46], β = -0.14, 95% CI = [-0.44, 0.17], β = -0.33, 95% CI = [-0.76, 0.09]), meaning that differences were not found in either condition or time regarding opinion variances. Table 3 Changes in the average of SD Controversial condition Inclusive condition Average of SD before discussion Average of SD after discussion Average of SD before discussion Average of SD after discussion Conducting the final disposal outside Fukushima Prefecture 1.16 1.02 1.29 0.81 The variance in opinions within the group before and after the discussion was plotted by the group’s decision (Figure 2), indicating a reduction in opinion variance after the discussion compared to before. However, under the controversial “Not decided” condition, the variance in opinions within the group increased after the discussion. This indicated that because participants with differing opinions on the final disposal outside Fukushima could not reach a consensus, they received more support for their initial positions through discussion. In other words, the gap between participants’ opinions widened, and division within the group was promoted. 3.5 Evaluation of the decision We examined how participants evaluated their decisions. The results of a multilevel linear regression analysis indicated that, compared to the controversial condition (M = 4.75, SD = 1.43), the inclusive condition (M = 5.59, SD = 1.23) had a more positive evaluation of the decision (β = 0.85, 95% CI = [0.28, 1.40]). To further examine the tendencies in these responses, average scores were calculated for each category created by the combination of conditions, group decisions, and initial opinions on the issue (Figure 3). In the controversial condition, participants whose initial opinions were supportive (i.e., “pros”) tended to have relatively low evaluations of the decision when the group’s conclusion was “Disapprove” or “Not decided.” In other words, participants whose opinions were not reflected in the group’s decisions were less likely to rate the group’s decisions positively. In the inclusive condition, evaluations of the decision were consistently high, regardless of individual initial opinions. This result suggested that, in the inclusive condition, participants who had opinions opposing their group’s conclusion were also more likely to accept it. 4. Discussion 4.1 Summary of results This study used a group decision experiment to investigate the effects of discussion and decision frames on finding a compromise on the removed soil issue. We manipulated the frames to be controversial and inclusive. Observations of the decision statement revealed that the inclusive condition was more likely than the controversial condition to reach a compromise on the final disposal of the removed soil. An instance of such an observation was that some groups found a compromise reflecting one side of the central decision and incorporating the other side into conjunctive argument points. The analysis of opinion changes indicated that opinions shifted regardless of the discussion frame, with the group’s average opinion changing toward supporting the decision and variance decreasing. Thus, group polarization occurred in both discussion frames. Nevertheless, as predicted, evaluations of the group’s conclusions were rated higher in the inclusive condition than in the controversial condition. Specifically, only in the controversial condition did evaluations tend to be lower when participants’ initial opinions were not reflected. 4.2 Interpretation of the results We attempt to interpret the results by integrating descriptive and statistical analyses. The inclusive condition tended to reflect plural opinions more than the controversial condition and yielded a more positive evaluation of the decision, whereas opinion changes occurred similarly in both conditions. Should we attribute these opinion changes simply to thinking that “it is good” based on the results? The results of the evaluations of the group’s conclusions provide a perspective on this question. Evaluations were higher in the inclusive condition than in the controversial condition. In the controversial condition, participants whose views were not reflected evaluated their decisions negatively, indicating a lack of acceptance. This result implies that while opinions may shift toward supporting the decision, they do not necessarily assess it positively or fully approve it when their opinions are not reflected. Conversely, in the inclusive frame, the decision was compromised, resulting in higher evaluations of the group’s decisions regardless of initial opinions. This result suggests that individuals with heterogeneous views can appreciate the group’s conclusion alike. Focusing on controversial frames, some groups could not reach a consensus (“Not decided”), and all these groups were composed of three pros and one con. Minorities in controversial frames persisted in advocating for their opinions and influencing the majority. This pattern is the opposite of conformity with the majority, which is repeatedly observed in group decisions (Asch 1956 ). However, the results indicated that group members who did not make a decision in the controversial condition rated their decisions lower than those in the inclusive condition, regardless of their initial position. Therefore, controversial frames would hinder finding an acceptable compromise and cause dissatisfaction with conclusions among group members. 4.3 Limitations Before discussing the contributions of this study, two limitations must be noted. First, participants were university students residing in urban areas, and none were from Fukushima Prefecture. Consequently, the lack of direct involvement in the removed soil issue may have promoted a more comprehensive discussion. Therefore, it is essential to consider whether individuals with high stakeholder involvement would discuss the same issue in a similar manner. However, given that the candidate sites for receiving the removed soil have not yet been decided, it is not feasible to engage such stakeholders, except for the Okuma and Futaba residents, in the discussion. Moreover, involving such stakeholders might trigger conflicts, divisions of opinion, a lack of consensus, and ethical concerns. This study could provide a prescription for these complications by examining the impact of discussion frames on the content and conclusions before determining the recipients of the removed soil. Additionally, to assess the effect of participants being students, it would be helpful to compare the findings of this study with those of a case study in which urban residents participated in workshops on the removed soil issue, thus reconsidering the conduct of public deliberation. Second, we found that the setting of the controversial frame was insufficient. The post-questionnaire revealed that participants in the controversial condition attempted to engage in discussions that considered both for and against positions to a similar extent as those in the inclusive condition. Despite contrivances such as presenting the pros and cons in front of participants in the controversial condition, it seemed difficult for them to immerse themselves in the dispute. Moreover, participants may not have held strong opinions on the issue, making it difficult to refute opposing views, especially in controversial conditions. These were the reasons for the unsatisfactory manipulation of this controversial condition. However, gathering individuals with firm opinions on the removed soil issue to participate in experiments is unrealistic. Considering these constraints, this study made the best possible effort to establish discussion frames. 4.4 Implication Despite these limitations, this study provides valuable insights worth considering not only for the specific case of the removed soil issue but also for public deliberation in environmental management policy planning. 4.4.1 Insights into the issue of the final disposal of removed soil Our study demonstrated that framing the controversy with a dichotomous choice resulted in only one side’s argument points being reflected in the decisions. Given this result, a concern arises that only the opinions of specific stakeholders are considered. For example, opposing the final disposal outside Fukushima Prefecture may disregard the opinions of Okuma and Futaba residents who wish for the disposal to occur outside the interim storage site and return to their hometowns. Furthermore, dichotomous scenarios might hinder consensus building, leading to impasses or “Not decided” outcomes. Contrastingly, the inclusive scenario, allowing for the “Other” option, facilitates finding an acceptable compromise and incorporating diverse perspectives, including Okuma and Futaba residents and those receiving the burdens of removed soil in the future. Although not all groups in the inclusive condition have reached such a conclusion, the inclusive discussion frame helps find a compromise. This inclusive scenario also enables the critical evaluation of the pros and cons of the issue, fostering comprehensive decision-making that considers various conjunctive argument points, even when deciding to approve or disapprove the final disposal outside Fukushima. Applying the inclusive discussion frame to public discourse on the removed soil issue is vital to settling the problem. Currently, no specific district has yet been decided upon to take over the reuse and final disposal of removed soil. Under such a situation, merely conducting public discourses is insufficient; instead, the way of conducting it needs to be carefully designed, in which a wide range of citizens can impartially examine both the pros and cons of final disposal outside Fukushima; be aware of various stakeholders, particularly the Okuma and Futaba residents who have borne the burden and those who will newly take on the burden; and find an acceptable compromise. This study suggests the significance and appropriateness of making the discourse arena into the inclusive frame, where participants engage in reflective deliberation regardless of their positions, whereas the discourse arena with a controversial frame prevents such reflective deliberation, leading to failure in finding an acceptable compromise and leaving the removed soil issue unresolved. Additionally, the pre-discussion questionnaire revealed that many participants held positive opinions about the offsite disposal of the removed soil. It is uncertain whether participants had a positive attitude before the experiment or developed their opinions by obtaining information on the removed soil issue. However, providing multifaceted information, such as scientific data on removed soil and current legislation, could deepen the understanding of final disposal outside Fukushima Prefecture. This insight is crucial for the implementation of final disposal. 4.4.2 Suggestions for public deliberation on environmental management This study conducted a group decision experiment using the case of removed soil issues and examined the effects of the discussion frame on finding an acceptable compromise reflecting plural opinions. It was found that inclusive frames were better at reaching a compromise, with participants rating their conclusions more positively than in controversial frames. These findings can be extended to public deliberations on broader environmental management policy planning, especially on contentious issues where conflicts exist among participants. Participants in this study were not confident in their opinions, even in the controversial frame condition, and they did not experience heavy conflict. Thereupon, it is anticipated that consensus may disappear if stakeholders with vested interests engage in a controversial manner. Especially in situations where conflicting interests exist among community members or between residents and the administration, failure to reach consensus not only impedes policy implementation but also divides communities and evokes resistance from residents. Hence, discussion frames should be carefully designed based on participants’ interests and the firmness of their opinions. The benefit of applying inclusive frames is that they allow group members to obtain a comprehensive view. Previous studies (c.f., Fishkin 2009 ; Fishkin and Luskin 2005 ; Gastil and Dillard 1999 ; Gerber et al. 2018 ; Sanders 2012 ) have demonstrated that public deliberation leads to opinion changes; however, they neither directly proved nor guaranteed that opinions deepened. To answer this question, this study analyzed both the central decision and conjunctive argument points and participants’ statements after making decisions. As a result, groups in the inclusive condition reached compromise solutions regarding the central decision, considered conjunctive argument points when determining the central decision, and organized discussions based on the pros and cons of the final disposal outside Fukushima instead of simply for or against positions. These trends may also occur when the inclusive discussion frame is applied to other cases; that is, it is plausible that opinions on the issue deepen individually and collectively, facilitating a comprehensive understanding and compromise. An inclusive discussion frame is crucial for topics involving various intertwined elements in environmental management policy and not only for policy planning vis-à-vis the removed soil issue. In this sense, we provide evidence by conducting multidimensional analyses using a rigorously manipulated experiment on public deliberations. Statements and Declarations Acknowledgments This work was partially supported by the Graduate Grant Program of the Graduate School of Humanities and Human Sciences, Hokkaido University, awarded to the first author. We would like to thank Editage (www.editage.jp) for English language editing. Funding This work was supported by the experimental assessment of diverse justice criteria toward the final repository of removal soil outside Fukushima Prefecture, Environment Research and Technology Development Fund [JPMEERF22S20907]; Hyper Democracy, Creative Revolutionary Technology Seeds for Science and Technology Innovation (CREST) by the Japan Science and Technology Agency (JST) [JPMJCR20D1]; the Consensus process for realizing common goods overcoming the divided society, Grants-in-Aid for Scientific Research (KAKEN) by the Japan Society for the Promotion of Science (JSPS) [23K22343]; and Exploration of Multiple Common Goods in Public Decision-Making: a group discussion experiment on the treatment of decontaminated soil, Grant-in-Aid for JSPS Fellows by JSPS [24KJ0296]. Competing Interests The authors declare no competing interests. Ethical Approval All procedures performed in studies involving human participants were conducted in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Ethics Review Committee of the Center for Experimental Research in Social Sciences, Hokkaido University (No. R4-05, 22 April 2022). Consent to Participate and Publish Before the start of the experiment, the researchers obtained participants’ consent in written form. The researchers distributed the consent forms individually, and consent was confirmed through participants’ signatures. This consent covered participation in the experiment, recording and filming during the discussions, and academic publication of anonymized data. Furthermore, because this study involved non-interventional research, all participants were fully informed in advance about the purpose of the research, the anonymization of their data, and the potential academic publication of the analysis results. Data, Materials, and/or Code Availability The datasets generated and/or analyzed during the current study are available in the Open Science Framework repository (https://osf.io/), [https://osf.io/uh2ae/?view_only=7692bc81c0ec43738945a0bdd134ef6c]. 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condition)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6290609/v1/899271efadf854fb549a1eeb.png"},{"id":81695382,"identity":"a43d7abe-3434-49af-839d-b5b7baad6a3e","added_by":"auto","created_at":"2025-04-30 11:57:04","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":112483,"visible":true,"origin":"","legend":"\u003cp\u003eAverage of SD by each group (left-hand side: controversial condition, right-hand side: inclusive condition)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6290609/v1/155650c98c501459ad9a3f76.png"},{"id":81693729,"identity":"16b6e3ee-dabc-4a7b-89bf-f13fd8877667","added_by":"auto","created_at":"2025-04-30 11:49:04","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":65106,"visible":true,"origin":"","legend":"\u003cp\u003eEvaluation of decision by each category (left-hand side: controversial condition, right-hand side: inclusive condition)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6290609/v1/41ebe6a838e976d6b7b98346.png"},{"id":82532322,"identity":"88852c5a-8982-4329-bddf-159a60237b68","added_by":"auto","created_at":"2025-05-12 14:54:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1252825,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6290609/v1/128d01e7-eb7e-40b7-b93c-6c99e0a1031e.pdf"},{"id":81693736,"identity":"8e1295f2-af3e-44d2-aaa1-dda42737f2eb","added_by":"auto","created_at":"2025-04-30 11:49:04","extension":"zip","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":3700524,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterials.zip","url":"https://assets-eu.researchsquare.com/files/rs-6290609/v1/2097548b362da837da3072bf.zip"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of the discussion frame on finding a compromise: A group decision experiment on the final disposal of removed soil outside Fukushima","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePublic decision-making, such as in terms of environmental management policy, calls for neither simply following the majority rule nor being pushed through by a loud minority (Gutmann and Thompson \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Smith \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). It requires elaborating on both majority and minority opinions thoroughly, listening to different points of view, and finding a compromise that is acceptable to both sides, especially when reconciling controversial values is difficult, all of which are publicly important (Cohen \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Habermas \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Luskin et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Steenbergen et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). This study addresses the case of the final disposal of removed soil outside Fukushima Prefecture, which entails burden distribution with conflicts of plural values, as described in the following section.\u003c/p\u003e \u003cp\u003eExperimental examinations are a valuable tool to test the conditions under which people achieve constructive compromise, reflecting contradictory values, although practical experiences have affirmed such outcomes. Therefore, this study employs a method of group decision experiments developed in social psychology (c.f., Moscovici and Doise \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Moscovici and Zavalloni \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1969\u003c/span\u003e) to investigate the conditions for achieving compromised decisions by conducting rigorous factor control and manipulation.\u003c/p\u003e \u003cp\u003eFinding a compromise that both sides can accept is challenging in terms of burden distribution, particularly when contradictory values are in conflict. A practical tool for untangling such value conflicts is public discourse. It is crucial to engage the public, involving diverse citizens (Renn \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). This approach can diminish conflicts, facilitate stakeholder and public learning, enhance support for project goals, and promote long-term decision implementation (Beierle \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; de Vente et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). For instance, public deliberations have been observed in various contexts, such as sustainable societal policies and environmental master plans (Nakamura et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Ohnuma et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Issues involving clear common goals and minimal controversy help to reach a consensus in a broad direction and incorporate diverse opinions.\u003c/p\u003e \u003cp\u003eHowever, implementing public deliberation sometimes fails; it can lead to unexpected or unintended adverse outcomes (Emery et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Reed \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Therefore, determining the factors and conditions relevant to the failure or success of the discourse arena is vital. This study focuses on whether participants can find an acceptable compromise.\u003c/p\u003e \u003cp\u003ePluralistic values, including minority opinions, should be discussed and considered in public deliberations (Fishkin \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Ohnuma \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Discourse ethics (Habermas \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1988\u003c/span\u003e) emphasize that citizens should impartially and sincerely elaborate on all opinions. Although numerous studies have advocated for its importance (e.g., Fishkin \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Lafont \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Parkinson \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), it is not guaranteed in reality. Participants may stick to their positions of approval or disapproval, resulting in debates that are neither constructive nor productive. Few studies on public deliberation have empirically examined whether, how, and when discourse reflects heterogeneous opinions, including minority perspectives within a group (Hamlett and Cobb 2007; Mansbridge \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). Therefore, it is essential to examine the conditions required to prevent unproductive debates.\u003c/p\u003e \u003cp\u003eEmpirical research has not sufficiently clarified the conditions that make a difference in public deliberation. However, studies on group experiments in social psychology have repeatedly demonstrated the strong influence of the majority and the frequent use of majority rule (Asch \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1956\u003c/span\u003e; Carpini et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Crano and Seyranian \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Davis \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1973\u003c/span\u003e; Garcia et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Hastie and Kameda \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Kameda \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Kameda et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Kuroda et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Mendelberg \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Mercier and Morin \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Paruzel-Czachura et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Tanford and Penrod \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1984\u003c/span\u003e). Several studies have shown that minorities within a group can influence the majority, albeit under limited conditions (Moscovici \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1980\u003c/span\u003e; Moscovici et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Nemeth \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1981\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eGiven these findings, the conceptualization of ways to arrive at a compromise during public deliberation is worthwhile. This study examines such conditions using a group decision experiment on the final disposal of removed soil outside Fukushima Prefecture. In this study, the success or failure of group decisions is judged based on whether the group finds a compromise acceptable to any member. We hypothesize that the discussion frame affects reaching a compromise, as discussed in Section \u003cspan refid=\"Sec6\" class=\"InternalRef\"\u003e1.3\u003c/span\u003e. For example, a discussion frame in which participants are divided between favoring and opposing may not work constructively, contrary to one in which they consider both sides. Hence, we manipulated discussion frames in the group decision experiment. Finally, from the findings of the experiment, we elucidate how the discussion frame can contribute to a compromise in public discourse.\u003c/p\u003e \u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003e1.1 The case of the final disposal of the removed soil outside Fukushima Prefecture\u003c/h2\u003e \u003cdiv id=\"Sec3\" class=\"Section3\"\u003e \u003ch2\u003e1.1.1 Outline of the issue\u003c/h2\u003e \u003cp\u003eThe Fukushima Daiichi nuclear power plant accident occurred in March 2011, resulting in the release of large amounts of radioactive substances into the environment, thus causing environmental pollution. The Japanese government carried out decontamination work to reconstruct Fukushima Prefecture, which produced vast volumes of soil and other materials. The removed soil was initially placed in temporary storage sites in broad areas of Fukushima; however, to proceed with the restoration and reconstruction of Fukushima, a facility was necessary to manage and store the removed soil safely and centrally. Consequently, an interim storage facility was constructed in Okuma and Futaba, which are towns in Fukushima.\u003c/p\u003e \u003cp\u003eThe area of the interim storage facility is approximately 16 km\u0026sup2;, of which approximately 80% is private land owned by villagers (Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), where paddy fields and shrines existed, and many lived before the accident. The amount of removed soil and other materials delivered to the facility is approximately 14\u0026nbsp;million m\u0026sup3; (equivalent to the volume of approximately 28,000 25-swimming pools). Of the massive amount of removed soil, approximately 20% is high-concentration soil exceeding 8,000 Bq/kg, and 80% is low-concentration soil below 8,000 Bq/kg (Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegarding the removed soil and waste, the government must take the necessary measures to complete the final disposal outside Fukushima within 30 years from the start of transportation to the interim storage facility (by March 2045), in line with the Japan Environmental Storage \u0026amp; Safety Corporation Law (Law No. 44 of 2003, promulgated on May 16, 2003). However, a specific method or disposal site for the final disposal has not yet been determined.\u003c/p\u003e \u003cp\u003eIt is difficult to dispose of the large amount of removed soil outside Fukushima from the perspective of obtaining a site area. Therefore, the key to realizing final disposal outside Fukushima is to reduce the final disposal volume (Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). To ensure safety, the government is attempting to convert low-concentration soil below 8,000 Bq/kg into recycled material and promote its reuse under the condition that the management body and responsibility are guaranteed (Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Low-concentration soil is usable for road construction and farmland development in raised earth foundations. Demonstration projects for reusing soil have been conducted in Minami-Soma City and Iitate Village in Fukushima, and safety has been confirmed in both projects (Baba \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Hasegawa \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo implement the final disposal of the removed soil outside Fukushima and the reuse of low-radioactive soil, it is essential to foster public understanding and invite public discourse (Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In other words, designing public engagement is required, in which a wide range of citizens discuss the issue of the removed soil (c.f., IAEA \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Hence, it would be worthwhile to provide insights into the design of a more useful dialogue.\u003c/p\u003e \u003cp\u003ePrevious studies on the removed soil have conducted surveys with questionnaires and interviews to explore the social acceptability of the final disposal and related factors (Murakami et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Shirai et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Takada et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2024\u003c/span\u003e, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). However, only a few studies have examined the content individuals discuss and the decisions they make when engaging in group discussions (Souma et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Therefore, we compare the decisions made through discussions on the removed soil issue in terms of reflecting both sides\u0026rsquo; opinions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e1.1.2 Conjunctive argument points of the final disposal of the removed soil\u003c/h2\u003e \u003cp\u003eThe final disposal of the removed soil involves a complex set of burden distributions that demands public understanding and consensus. Therefore, public deliberation not only on the final disposal in question but also on other related points is vital for making a comprehensive decision. Two arguments that are critical for burden distribution are summarized.\u003c/p\u003e \u003cp\u003eThe first point is the number of final disposal sites. Regardless of whether the final disposal of the removed soil is conducted outside Fukushima, selecting one or more final disposal sites is critical. Previous studies on the final disposal and reuse of the removed soil suggest that inequity is mitigated and is more acceptable at multiple sites than at a single site (Takada et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Yokoyama et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). If the findings of these studies are robust, people are more likely to agree to final disposal at more than one location. However, some may argue that a single location is better because it reduces costs and concrete risks and enhances the efficiency of constructing a final disposal facility. Hence, the number of final disposal sites remains debatable.\u003c/p\u003e \u003cp\u003eThe second point relates to the reuse of the removed soil. As mentioned above, the Japanese government aims to reuse the low-concentration removed soil to realize final disposal outside Fukushima Prefecture. Regardless of how the safety of reuse has been scientifically confirmed in demonstration projects (Baba \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Hasegawa \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Ministry of the Environment \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), reuse cannot be implemented unless residents living in nearby areas of the sites understand the safety measures and provide consent. In addition, the number and range of reuse sites constitute an argument. The number of sites can be single or multiple. Moreover, as the reuse of soil can be carried out throughout Japan in principle, it can also be conducted within Fukushima, which differs from final disposal. However, considering the residents of Okuma and Futaba towns in Fukushima who have borne the burden, as with final disposal, reuse should also be carried out outside Fukushima. In summary, the argument concerns whether the reuse of low-concentration soil should be carried out, and if so, whether it should be implemented at a single location or multiple locations, and whether the range should be nationwide, including or outside Fukushima.\u003c/p\u003e \u003cp\u003eIn sum, the central argument to be decided in the following experiment is whether to approve the final disposal outside Fukushima. Moreover, the number of final disposal sites and the reuse of the removed soil are conjunctive argument points. In the following experiment, decisions on both the central and conjunctive argument points are presented as discussion points and referred to in verifying whether a compromise can be found. It is assumed that if the central decision reflects one side but the decisions on conjunctive argument points adopt the other side\u0026rsquo;s views, the overall group conclusion is deemed a compromise. Note that, in the experiment, the central decision is mandatory, but decisions on conjunctive argument points are optional.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e1.2 Effects of discussion frame on finding a compromise\u003c/h2\u003e \u003cp\u003eThis study focuses on discussion frames as a factor in finding an acceptable compromise in group decisions. A discussion frame refers to the manner of communication understood among members (Black \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), which can be transformed through the design of the dialogue forum under the organizer. This study adopted controversial and inclusive frames, which are commonly observed in public discourse.\u003c/p\u003e \u003cp\u003eA controversial frame involves an explicit pro\u0026ndash;con conflict, refuting the opposing opinions of each other, and a dichotomous choice, such as for or against. In contrast, an inclusive frame involves a thoughtful examination of both sides regardless of their positions. Although environmental management policy planning forums must be transparent and open (Bryson and Crosby \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1996\u003c/span\u003e), such forums sometimes become debate-like, in which participants are divided into two sides and refute each other. In such controversial frames, participants often fail to reach a consensus (Nagel and Satoh \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Reiners \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Hence, inclusive frames have also been applied, whereby participants do not debate for or against but aim for mutual understanding (Ohnuma et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The discussion frame in this study combines the posture of discussion (i.e., the mental preparedness that participants have during the discussion) and the options given for the decision, as the manner of communication and the set of options are mutually influential.\u003c/p\u003e \u003cp\u003eIn a controversial frame involving dichotomous debate and choice, participants would be less likely to find an acceptable compromise in the group because they are placed in a situation where they cannot easily admit to changing their opinions. Additionally, as participants attempt to justify their views, they may insist that only their opinions are correct regarding the central decision and conjunctive issues.\u003c/p\u003e \u003cp\u003eConversely, in an inclusive frame involving the examination of both sides\u0026rsquo; opinions and mutual understanding, participants would be more likely to reach an acceptable compromise in the group. Moreover, even if the central decision reflects only one side, other views may be incorporated into conjunctive argument points.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e1.3 Influence of group decision on the members\u003c/h2\u003e \u003cp\u003eAssuming that the discussion frame influences the finding of an acceptable compromise, its impact will likely extend to how participants evaluate the group\u0026rsquo;s conclusions. If participants find a compromise acceptable to both sides, the evaluation of the conclusion should be high, regardless of their initial opinions. Conversely,, when the conclusion reflects only one side\u0026rsquo;s opinion, the evaluation will likely vary depending on initial opinions.\u003c/p\u003e \u003cp\u003ePrevious studies have observed group polarization, whereby the average opinion within the group shifts toward the group\u0026rsquo;s decision, and the variance of opinions within the group decreases after discussion (Fishkin \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fishkin and Luskin \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Gastil and Dillard \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Gerber et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Lamm and Myers \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1978\u003c/span\u003e; Moscovici and Zavalloni \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Sanders \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). However, group polarization may occur solely because the group has reached a decision (Arima \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), regardless of whether the conclusion is compromised. Conversely, if the group cannot reach a decision, the differences between opposing views may deepen, thereby increasing the variance of opinions. To examine the difference between group polarization and making an acceptable compromise, this study investigates whether opinion changes and participants\u0026rsquo; evaluations of the conclusions differ across discussion frames.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e1.4 Purpose\u003c/h2\u003e \u003cp\u003eThis study aims to investigate a pivotal condition for finding an acceptable compromise in decision-making, employing a group decision experiment on the final disposal of removed soil outside Fukushima Prefecture. Precisely, the study manipulates the discussion and decision frames in the experiment and examines their effects on reaching an acceptable compromise that integrates controversial values.\u003c/p\u003e \u003cp\u003eFirst, we compare the decision statements presented by participants between conditions. We predict that the central and conjunctive argument points are more likely to be incorporated into group decisions under the inclusive frame condition than under the controversial frame condition.\u003c/p\u003e \u003cp\u003eSecond, we examine the effects of discussion frames on opinion changes before and after the discussion. Opinion changes are explored to determine whether the average opinion within the group shifts to support the group\u0026rsquo;s decisions and whether the variance of opinions decreases. We predict that such a change will occur, regardless of the frame, once the group reaches a decision.\u003c/p\u003e \u003cp\u003eThird, we examine the evaluation of the conclusions as an indicator of reaching an acceptable compromise that satisfies both sides\u0026rsquo; opinions. We hypothesize that the evaluation will be rated higher in the inclusive condition than in the controversial condition, regardless of initial opinions, because the conclusions in the inclusive frame condition will incorporate both sides\u0026rsquo; opinions, leading to a more acceptable compromise.\u003c/p\u003e \u003c/div\u003e"},{"header":"2. Methods","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Experiment overview\u003c/h2\u003e\n \u003cp\u003eThis study was approved by the Ethics Review Committee of the first author\u0026rsquo;s institution (Approval Code: R4-05) and was conducted between June and October 2023. Participants discussed and decided whether the final disposal of the removed soil outside Fukushima Prefecture was acceptable. In the experiment, we manipulated the discussion and decision frames: one was the controversial condition, characterized by clearly different positions, in which participants were instructed to refute the opponent, and the other was the inclusive condition, in which participants were instructed to consider both positions regardless of their initial opinion. Details regarding the manipulation of conditions are provided below.\u003c/p\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.1 Participants\u003c/h2\u003e\n \u003cp\u003eEach group consisted of four undergraduate students who met for the first time and were recruited through an experimental participant recruitment system (Sona Systems). Considering the statistical power and moderate effect size in the t-test (statistical power \u0026beta;\u0026thinsp;=\u0026thinsp;0.80, effect size d\u0026thinsp;=\u0026thinsp;0.50; Cohen \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e), a sample size of 16 groups, with 64 participants, was determined for each condition. Participants\u0026rsquo; gender distribution was as follows: 70 males (controversial condition: 38, inclusive condition: 32), 57 females (controversial condition: 25, inclusive condition: 32), and 1 participant in the controversial condition who selected \u0026ldquo;non-binary/prefer not to answer.\u0026rdquo; None of the participants were from Fukushima, and their interest in and knowledge about decontaminated soil and final disposal were moderate in both conditions. Participants were uninformed about the details of the experiment until they arrived at the laboratory. The experimenter formed groups from participants who applied for the identified timeslots, and group assignments were balanced by the experimenter using pre-questionnaire responses.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.2 Creation of informed materials regarding the final disposal of removed soil\u003c/h2\u003e\n \u003cp\u003eBefore the discussion, participants received informational materials providing an overview of the removed soil and its final disposal. These materials, totaling 19 pages (Online Resource 1), were reviewed by experts from various fields, including radiation medicine, soil chemistry, environmental restoration, and risk communication. The experts ensured the information\u0026rsquo;s accuracy, neutrality, and validity, and we revised the materials until they were judged satisfactory. The materials provided details on the generation process of the removed soil, final disposal procedures, and statements from the mayors of Okuma and Futaba, where the interim storage facility is located. The arguments included the reuse of soil and the number of final disposal sites. Participants had access to the materials throughout the discussion.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.3 Experimental procedure\u003c/h2\u003e\n \u003cp\u003eUpon arriving at the experimental room, participants received consent forms for participation and recording and signed them if they agreed. They then received the informational materials and watched a 10-minute instructional video corresponding to them. Subsequently, participants completed a questionnaire. Following this, a manner of discussion that differed between the conditions was introduced. The details of this process are provided below.\u003c/p\u003e\n \u003cp\u003eParticipants had five minutes for individual deliberation, recording their ideas on a sheet. Then, the discussion manner was reiterated, and participants were asked to record their conclusion on the \u0026ldquo;decision sheet\u0026rdquo; at the end of the discussion. Moreover, participants were told that one of the members would present their decision along with the reasons and process leading to it. A copy of the \u0026ldquo;decision sheet\u0026rdquo; was delivered to each group. The discussion lasted 40 minutes, with one of the members announcing the group\u0026rsquo;s decision and allowing for additional comments from others. Finally, participants completed a post-discussion questionnaire.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e2.1.4 Condition manipulation\u003c/h2\u003e\n \u003cp\u003eTo establish the discussion frame, manipulation was performed using several procedures. First, \u0026ldquo;position plates\u0026rdquo; were placed in front of participants in the controversial condition based on their responses to the pre-questionnaire, which asked whether they supported or opposed the final disposal of the removed soil outside Fukushima. In the controversial condition, participants were informed that the position on their plates corresponded to their pre-questionnaire response, which was their initial opinion. The \u0026ldquo;position plates\u0026rdquo; were visible to everyone, including participants. Although participants in the inclusive condition answered the question about supporting or opposing the final disposal outside Fukushima Prefecture the same as those in the controversial condition, \u0026ldquo;position plates\u0026rdquo; were not placed in front of them.\u003c/p\u003e\n \u003cp\u003eSecond, different manners of discussion were used for each condition. In the controversial condition, participants were instructed to \u0026ldquo;assert your position and persuade opponents with different opinions to be adopted as the group decision\u0026rdquo; and \u0026ldquo;decide whether to approve or disapprove the final disposal outside Fukushima Prefecture by the end of the discussion.\u0026rdquo; In the inclusive condition, participants were instructed to \u0026ldquo;consider both supportive and opposing stances on the final disposal of the removed soil, critically sift through the merit and demerit of the final disposal outside Fukushima Prefecture\u0026rdquo; and \u0026ldquo;decide what should be done by the end of the discussion.\u0026rdquo;\u003c/p\u003e\n \u003cp\u003eThird, the \u0026ldquo;opinion sheets,\u0026rdquo; where participants wrote their ideas for individual deliberation before discussion, differed for each condition. In the controversial condition, participants were asked to fill in 1) their position on the final disposal outside Fukushima Prefecture (as written on the \u0026ldquo;position plate\u0026rdquo;), 2) arguments supporting their position, 3) assumed arguments from the opposing position, and 4) arguments to counter the assumed opponents\u0026rsquo; arguments. In the inclusive condition, participants were asked to fill in 1) their position on the final disposal outside Fukushima (the same as the position they answered in the pre-discussion questionnaire), 2) the merits of the final disposal outside Fukushima Prefecture, 3) the demerits of the final disposal outside Fukushima, and 4) consider both supportive and opposing contentions, considering agreeable ideas to varied individuals with various stances.\u003c/p\u003e\n \u003cp\u003eFinally, the \u0026ldquo;decision sheet\u0026rdquo; that included the choices for the decision differed by the conditions. In the controversial condition, the decision sheet had the options: \u0026ldquo;Approve,\u0026rdquo; \u0026ldquo;Disapprove,\u0026rdquo; or \u0026ldquo;Not decided\u0026rdquo; for the final disposal outside Fukushima. In the inclusive condition, the decision entry sheet contained options: \u0026ldquo;Proceed,\u0026rdquo; \u0026ldquo;Not proceed,\u0026rdquo; \u0026ldquo;Other\u0026rdquo; (entry specified contents), or \u0026ldquo;Not decided\u0026rdquo; with the final disposal outside Fukushima Prefecture. Participants in both conditions were asked to fill in their decisions as a group on the decision sheet until the end of the discussion.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Questionnaire\u003c/h2\u003e\n \u003cp\u003eBefore the discussion, participants responded to a pre-discussion questionnaire. This questionnaire measured their opinions on the final disposal of the removed soil outside Fukushima Prefecture and relevant points. Items were rated on a 6-point Likert scale ranging from 1 (disapprove) to 6 (approve). In the following results section, we showed only one item, \u0026ldquo;Conducting the final disposal outside Fukushima Prefecture.\u0026rdquo;\u003c/p\u003e\n \u003cp\u003eIn the post-discussion questionnaire, participants rated their compliance with the discussion methods: 1) to assert their position and persuade opponents with different opinions to be adopted as the group decision, and 2) to consider both supportive and opposing stances on the final disposal of the removed soil, elaborating on the merits and demerits of the final disposal outside Fukushima Prefecture. They then provided their opinions on the final disposal and relevant points, similar to the pre-discussion questionnaire. Additionally, participants evaluated their group\u0026rsquo;s decisions as follows: 1) Overall, I think the conclusion is good, and 2) Considering the whole, I evaluate the conclusion as good. Ratings were on a 7-point Likert scale ranging from 1 (do not agree) to 7 (agree), comprising the \u0026ldquo;evaluation of decision\u0026rdquo; scale (Cronbach\u0026rsquo;s \u0026alpha;\u0026thinsp;=\u0026thinsp;0.97).\u003c/p\u003e\n \u003cp\u003eThe entire contents of the pre- and post-discussion questionnaires are presented in Online Resource 2.\u003c/p\u003e\n \u003cp\u003eR version 4.2.3 was used for statistical analysis (Online Resource 3).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003e\u003cstrong\u003e3.1 Manipulation check\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe checked the manipulation using the responses to the post-discussion questionnaire. A multilevel linear regression analysis was conducted with the responses to each item as the dependent variable and the condition (0: controversial condition, 1: inclusive condition) as the predictor variable. Discussion groups were treated as random intercepts. Participants in the controversial condition (M = 4.03, SD = 1.50) exerted more effort in persuading others with opposing opinions than those in the inclusive condition (M = 2.78, SD = 1.43). However, no effect of condition was found on the second item (\u003cem\u003e\u0026beta;\u003c/em\u003e = 0.26, 95% CI = [-0.12, 0.65]). The responses were similar for the controversial (M = 4.98, SD = 1.13) and inclusive (M = 5.25, SD = 0.91) conditions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Group decisions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe examined the distribution of initial opinions on the final disposal of the removed soil outside Fukushima Prefecture before the discussions to compare the conditions. There were 45 supporters and 19 opponents in the controversial condition and 43 supporters and 21 opponents in the inclusive condition, indicating a roughly equal distribution between conditions. Table 1 presents the initial opinion distribution (number of supporters and opponents) and group decisions regarding the final disposal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e Distribution of the initial opinion and decision of each group\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"574\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" style=\"width: 280px;\"\u003e\n \u003cp\u003eControversial condition\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 280px;\"\u003e\n \u003cp\u003eInclusive condition\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003eDistribution of\u0026nbsp;\u003cbr\u003e\u0026nbsp;the initial opinion\u003cbr\u003e\u0026nbsp;(pros - cons)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDecision\u003cbr\u003e\u0026nbsp;(the final disposal outside Fukushima Prefecture)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003eDistribution of\u0026nbsp;\u003cbr\u003e\u0026nbsp;the initial opinion\u003cbr\u003e\u0026nbsp;(pros - cons)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDecision\u003cbr\u003e\u0026nbsp;(the final disposal outside Fukushima Prefecture)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDisapproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e4-0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eNot decided\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eNot decided\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eNot decided\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eNot decided\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e3-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eNot decided\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDisapproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e2-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eOthers\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1-3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDisapproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1-3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDisapproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e0-4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eDisapproval\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 15px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 113px;\"\u003e\n \u003cp\u003e1-3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 166px;\"\u003e\n \u003cp\u003eApproval\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eNotably, 5 out of the 16 groups in the controversial condition did not reach a decision by the end of the discussion period, whereas all groups in the inclusive condition did. Instead, in the inclusive condition, six groups arrived at the \u0026ldquo;Other\u0026rdquo; conclusion, which involved neither approval nor disapproval of the final disposal outside Fukushima, thus compromising both sides. For example, some groups concluded that the burden of soil disposal should be shared within the entire Tohoku region or that disposal should take place in both uninhabited areas outside and within Fukushima Prefecture. Remarkably, one group detailed the procedure for selecting disposal sites.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Descriptions of decision statements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter the discussion, a group member presented the group decision, which typically addressed the approval or disapproval of the final disposal outside Fukushima Prefecture and conjunctive argument points, such as the reuse of soil and the number of sites. In the following, we present examples of decision statements representing the differences between conditions from two perspectives: the structure of the decision statement and the relevance between the central decision and conjunctive argument points. The decision statements of all the groups are provided in Online Resource 4.\u003c/p\u003e\n\u003cp\u003eRegarding the structure of the decision statement, in the controversial condition, many groups initially stated whether they approved or disapproved of the final disposal, followed by the reasons justifying their decision. For instance, in a group that decided to oppose, a group member said:\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026ldquo;The conclusion as a group was opposition. There were opinions in favor of (the final disposal outside Fukushima Prefecture), including reducing the burden and leading people in other areas to further understand the disaster. However, as for the burden, counterarguments were made that this would increase the burden on other regions and that it would be difficult in reality. In addition, in Fukushima Prefecture, interim storage facilities are currently in good condition to manage the removed soil. We thought\u0026nbsp;\u003c/em\u003e\u003cem\u003ethat there was no need to take the risk of transport\u003c/em\u003e\u003cem\u003eing the waste to other places, so the decision was opposed.\u0026rdquo;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eConversely,, in the inclusive condition, although most groups also initially expressed their decision on the final disposal, they subsequently addressed the elaborations on the various arising opinions, the reasons for adopting these opinions, and the criteria for judgment in the sequence of the discussion. For instance, in a group that decided to proceed, the following was expressed:\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026ldquo;We took a position in favor of the final disposal outside Fukushima Prefecture. Initially,\u0026nbsp;\u003c/em\u003e\u003cem\u003ethe\u0026nbsp;\u003c/em\u003e\u003cem\u003ereasons for both supporters and opponents were discussed. The main reasons for the support were to avoid burdening Fukushima residents\u003c/em\u003e\u003cem\u003e, [...]\u003c/em\u003e\u003cem\u003e. The opposing reasons were that the municipalities receiving compensation to host nuclear facilities should bear responsibility for the facility\u0026rsquo;s installation. Additionally,\u0026nbsp;\u003c/em\u003e\u003cem\u003ethe Tokyo Electric Power\u003c/em\u003e\u003cem\u003e\u0026nbsp;Company, which installed the nuclear power plant, should take responsibility. Hence, a group member of\u0026nbsp;\u003c/em\u003e\u003cem\u003ethe\u0026nbsp;\u003c/em\u003e\u003cem\u003eopposition argued that the disposal site should be located in\u0026nbsp;\u003c/em\u003e\u003cem\u003eFukushima\u0026nbsp;\u003c/em\u003e\u003cem\u003ePrefecture. However, considering that the Japanese government\u0026nbsp;\u003c/em\u003e\u003cem\u003ehas promoted nuclear power plants nationwide, the\u0026nbsp;\u003c/em\u003e\u003cem\u003eidea that all Japanese citizens should bear responsibility was formed in our group. Then, the opinion as a group shifted toward not\u0026nbsp;\u003c/em\u003e\u003cem\u003eonly conducting the final disposal\u003c/em\u003e\u003cem\u003e\u0026nbsp;in Fukushima Prefecture but\u0026nbsp;\u003c/em\u003e\u003cem\u003ealso the distribution in\u0026nbsp;\u003c/em\u003e\u003cem\u003ethe whole country.\u0026rdquo;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eRegarding the interconnections between the central decision and conjunctive argument points, the decision statements under the controversial condition were likely to separate the final disposal from the conjunctive argument points, such as the reuse of low-concentration soil.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026ldquo;We reached a decision, in principle, in favor of the final disposal site outside Fukushima. The initial opposing opinions [...]. In passing, we discussed where the burden of the reuse of low-concentration soil should be placed, and we generally agreed that the reuse should be borne by those outside Fukushima Prefecture.\u0026rdquo;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis statement implied that the focus was directed toward whether to support or oppose the final disposal outside Fukushima and that conjunctive argument points, such as the reuse of low-concentration soil, were considered independently of the decision on the final disposal.\u003c/p\u003e\n\u003cp\u003eConversely, the decision statements from the inclusive condition indicated that they discussed issues associated with conjunctive argument points.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026ldquo;As a positive aspect, the key point was the distribution of the burden. Opposing opinions included concerns about\u0026nbsp;\u003c/em\u003e\u003cem\u003ethe\u0026nbsp;\u003c/em\u003e\u003cem\u003emany people bearing the burden, dispersing risks, and uncertainty regarding finding host sites. [\u0026hellip;] In the end, the decision was to proceed with the final disposal outside Fukushima. Moreover, it was decided that Fukushima Prefecture would bear the entire burden of the reuse of low-concentration soil, while the soil subject to final disposal was distributed\u003c/em\u003e\u003cem\u003e, except for Fukushima, based on population ratios.\u0026nbsp;\u003c/em\u003e\u003cem\u003eIt was agreed that each prefecture would bear the cost of construction for the final disposal site, and the government would cover the transfer costs (for the removed soil).\u0026rdquo;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe group, composed of an initial opinion of three in favor and one against, ultimately agreed with the final disposal outside Fukushima. However, the concerns raised by the opposing side were also considered in their decision to reuse low-radioactive-concentration soil within Fukushima Prefecture.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Opinion changes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe conducted an analysis to assess opinion changes before and after the discussion, focusing on the averages and variances within the group. Results for \u0026ldquo;Conducting the final disposal outside Fukushima Prefecture\u0026rdquo; are presented here, and results for others are provided in Online Resource 5.\u003c/p\u003e\n\u003cp\u003eTable 2 presents the average opinions before and after the discussions by condition. A multilevel linear regression analysis revealed that the 95% confidence intervals for each parameter crossed zero (the estimated effect of condition, time, and interaction were \u003cem\u003e\u0026beta;\u003c/em\u003e = -0.45, 95% CI = [-1.17, 0.25], \u003cem\u003e\u0026beta;\u003c/em\u003e = 0.11, 95% CI = [-0.52, 0.77], and \u003cem\u003e\u0026beta;\u003c/em\u003e = 0.61, 95% CI = [-0.31, 1.54], respectively), meaning that no difference was found in either condition or time regarding the average opinions about the final disposal outside Fukushima.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2\u003c/strong\u003e Changes in the average opinions\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"567\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003eControversial condition\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003eInclusive condition\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of\u0026nbsp;\u003cbr\u003e\u0026nbsp;pre-opinion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 95px;\"\u003e\n \u003cp\u003eAverage of\u0026nbsp;\u003cbr\u003e\u0026nbsp;post-opinion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of\u0026nbsp;\u003cbr\u003e\u0026nbsp;pre-opinion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of\u0026nbsp;\u003cbr\u003e\u0026nbsp;post-opinion\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 189px;\"\u003e\n \u003cp\u003eConducting the final disposal outside Fukushima Prefecture\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e4.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 95px;\"\u003e\n \u003cp\u003e4.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e3.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e4.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe results may be influenced by the varying direction of opinion change depending on the group decision. Therefore, the averages for each group before and after the discussion were plotted based on the group\u0026rsquo;s decisions (Figure 1). The average opinions of many groups shifted toward supporting the group decisions. However, for groups under the controversial condition with the \u0026ldquo;Not decided\u0026rdquo; outcome and the inclusive condition with the \u0026ldquo;Other\u0026rdquo; outcome, the direction of opinion shifts varied among groups.\u003c/p\u003e\n\u003cp\u003eTable 3 presents the variance within the group before and after the discussion by condition. The results of a multilevel linear regression analysis indicated that the 95% confidence intervals for each parameter crossed zero (\u0026beta; = 0.12, 95% CI = [-0.21, 0.46], \u0026beta; = -0.14, 95% CI = [-0.44, 0.17], \u0026beta; = -0.33, 95% CI = [-0.76, 0.09]), meaning that differences were not found in either condition or time regarding opinion variances.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3\u003c/strong\u003e Changes in the average of SD\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"567\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003e \u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003eControversial condition\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" style=\"width: 189px;\"\u003e\n \u003cp\u003eInclusive condition\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of SD before discussion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of SD after discussion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of SD before discussion\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003eAverage of SD after discussion\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 189px;\"\u003e\n \u003cp\u003eConducting the final disposal outside Fukushima Prefecture\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e1.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e1.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e1.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 94px;\"\u003e\n \u003cp\u003e0.81\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe variance in opinions within the group before and after the discussion was plotted by the group\u0026rsquo;s decision (Figure 2), indicating a reduction in opinion variance after the discussion compared to before. However, under the controversial \u0026ldquo;Not decided\u0026rdquo; condition, the variance in opinions within the group increased after the discussion. This indicated that because participants with differing opinions on the final disposal outside Fukushima could not reach a consensus, they received more support for their initial positions through discussion. In other words, the gap between participants\u0026rsquo; opinions widened, and division within the group was promoted.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5 Evaluation of the decision\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe examined how participants evaluated their decisions. The results of a multilevel linear regression analysis indicated that, compared to the controversial condition (M = 4.75, SD = 1.43), the inclusive condition (M = 5.59, SD = 1.23) had a more positive evaluation of the decision (\u0026beta; = 0.85, 95% CI = [0.28, 1.40]).\u003c/p\u003e\n\u003cp\u003eTo further examine the tendencies in these responses, average scores were calculated for each category created by the combination of conditions, group decisions, and initial opinions on the issue (Figure 3).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;In the controversial condition, participants whose initial opinions were supportive (i.e., \u0026ldquo;pros\u0026rdquo;) tended to have relatively low evaluations of the decision when the group\u0026rsquo;s conclusion was \u0026ldquo;Disapprove\u0026rdquo; or \u0026ldquo;Not decided.\u0026rdquo; In other words, participants whose opinions were not reflected in the group\u0026rsquo;s decisions were less likely to rate the group\u0026rsquo;s decisions positively. In the inclusive condition, evaluations of the decision were consistently high, regardless of individual initial opinions. This result suggested that, in the inclusive condition, participants who had opinions opposing their group\u0026rsquo;s conclusion were also more likely to accept it.\u0026nbsp;\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003ch2\u003e4.1 Summary of results\u003c/h2\u003e\u003cp\u003eThis study used a group decision experiment to investigate the effects of discussion and decision frames on finding a compromise on the removed soil issue. We manipulated the frames to be controversial and inclusive. Observations of the decision statement revealed that the inclusive condition was more likely than the controversial condition to reach a compromise on the final disposal of the removed soil. An instance of such an observation was that some groups found a compromise reflecting one side of the central decision and incorporating the other side into conjunctive argument points.\u003c/p\u003e\u003cp\u003eThe analysis of opinion changes indicated that opinions shifted regardless of the discussion frame, with the group’s average opinion changing toward supporting the decision and variance decreasing. Thus, group polarization occurred in both discussion frames. Nevertheless, as predicted, evaluations of the group’s conclusions were rated higher in the inclusive condition than in the controversial condition. Specifically, only in the controversial condition did evaluations tend to be lower when participants’ initial opinions were not reflected.\u003c/p\u003e\u003ch2\u003e4.2 Interpretation of the results\u003c/h2\u003e\u003cp\u003eWe attempt to interpret the results by integrating descriptive and statistical analyses. The inclusive condition tended to reflect plural opinions more than the controversial condition and yielded a more positive evaluation of the decision, whereas opinion changes occurred similarly in both conditions.\u003c/p\u003e\u003cp\u003eShould we attribute these opinion changes simply to thinking that “it is good” based on the results? The results of the evaluations of the group’s conclusions provide a perspective on this question. Evaluations were higher in the inclusive condition than in the controversial condition. In the controversial condition, participants whose views were not reflected evaluated their decisions negatively, indicating a lack of acceptance. This result implies that while opinions may shift toward supporting the decision, they do not necessarily assess it positively or fully approve it when their opinions are not reflected. Conversely, in the inclusive frame, the decision was compromised, resulting in higher evaluations of the group’s decisions regardless of initial opinions. This result suggests that individuals with heterogeneous views can appreciate the group’s conclusion alike.\u003c/p\u003e\u003cp\u003eFocusing on controversial frames, some groups could not reach a consensus (“Not decided”), and all these groups were composed of three pros and one con. Minorities in controversial frames persisted in advocating for their opinions and influencing the majority. This pattern is the opposite of conformity with the majority, which is repeatedly observed in group decisions (Asch \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). However, the results indicated that group members who did not make a decision in the controversial condition rated their decisions lower than those in the inclusive condition, regardless of their initial position. Therefore, controversial frames would hinder finding an acceptable compromise and cause dissatisfaction with conclusions among group members.\u003c/p\u003e\u003ch2\u003e4.3 Limitations\u003c/h2\u003e\u003cp\u003eBefore discussing the contributions of this study, two limitations must be noted. First, participants were university students residing in urban areas, and none were from Fukushima Prefecture. Consequently, the lack of direct involvement in the removed soil issue may have promoted a more comprehensive discussion. Therefore, it is essential to consider whether individuals with high stakeholder involvement would discuss the same issue in a similar manner. However, given that the candidate sites for receiving the removed soil have not yet been decided, it is not feasible to engage such stakeholders, except for the Okuma and Futaba residents, in the discussion. Moreover, involving such stakeholders might trigger conflicts, divisions of opinion, a lack of consensus, and ethical concerns. This study could provide a prescription for these complications by examining the impact of discussion frames on the content and conclusions before determining the recipients of the removed soil. Additionally, to assess the effect of participants being students, it would be helpful to compare the findings of this study with those of a case study in which urban residents participated in workshops on the removed soil issue, thus reconsidering the conduct of public deliberation.\u003c/p\u003e\u003cp\u003eSecond, we found that the setting of the controversial frame was insufficient. The post-questionnaire revealed that participants in the controversial condition attempted to engage in discussions that considered both for and against positions to a similar extent as those in the inclusive condition. Despite contrivances such as presenting the pros and cons in front of participants in the controversial condition, it seemed difficult for them to immerse themselves in the dispute. Moreover, participants may not have held strong opinions on the issue, making it difficult to refute opposing views, especially in controversial conditions. These were the reasons for the unsatisfactory manipulation of this controversial condition. However, gathering individuals with firm opinions on the removed soil issue to participate in experiments is unrealistic. Considering these constraints, this study made the best possible effort to establish discussion frames.\u003c/p\u003e\u003ch2\u003e4.4 Implication\u003c/h2\u003e\u003cp\u003eDespite these limitations, this study provides valuable insights worth considering not only for the specific case of the removed soil issue but also for public deliberation in environmental management policy planning.\u003c/p\u003e\u003ch2\u003e4.4.1 Insights into the issue of the final disposal of removed soil\u003c/h2\u003e\u003cp\u003eOur study demonstrated that framing the controversy with a dichotomous choice resulted in only one side’s argument points being reflected in the decisions. Given this result, a concern arises that only the opinions of specific stakeholders are considered. For example, opposing the final disposal outside Fukushima Prefecture may disregard the opinions of Okuma and Futaba residents who wish for the disposal to occur outside the interim storage site and return to their hometowns. Furthermore, dichotomous scenarios might hinder consensus building, leading to impasses or “Not decided” outcomes. Contrastingly, the inclusive scenario, allowing for the “Other” option, facilitates finding an acceptable compromise and incorporating diverse perspectives, including Okuma and Futaba residents and those receiving the burdens of removed soil in the future. Although not all groups in the inclusive condition have reached such a conclusion, the inclusive discussion frame helps find a compromise. This inclusive scenario also enables the critical evaluation of the pros and cons of the issue, fostering comprehensive decision-making that considers various conjunctive argument points, even when deciding to approve or disapprove the final disposal outside Fukushima.\u003c/p\u003e\u003cp\u003eApplying the inclusive discussion frame to public discourse on the removed soil issue is vital to settling the problem. Currently, no specific district has yet been decided upon to take over the reuse and final disposal of removed soil. Under such a situation, merely conducting public discourses is insufficient; instead, the way of conducting it needs to be carefully designed, in which a wide range of citizens can impartially examine both the pros and cons of final disposal outside Fukushima; be aware of various stakeholders, particularly the Okuma and Futaba residents who have borne the burden and those who will newly take on the burden; and find an acceptable compromise. This study suggests the significance and appropriateness of making the discourse arena into the inclusive frame, where participants engage in reflective deliberation regardless of their positions, whereas the discourse arena with a controversial frame prevents such reflective deliberation, leading to failure in finding an acceptable compromise and leaving the removed soil issue unresolved.\u003c/p\u003e\u003cp\u003eAdditionally, the pre-discussion questionnaire revealed that many participants held positive opinions about the offsite disposal of the removed soil. It is uncertain whether participants had a positive attitude before the experiment or developed their opinions by obtaining information on the removed soil issue. However, providing multifaceted information, such as scientific data on removed soil and current legislation, could deepen the understanding of final disposal outside Fukushima Prefecture. This insight is crucial for the implementation of final disposal.\u003c/p\u003e\u003ch2\u003e4.4.2 Suggestions for public deliberation on environmental management\u003c/h2\u003e\u003cp\u003eThis study conducted a group decision experiment using the case of removed soil issues and examined the effects of the discussion frame on finding an acceptable compromise reflecting plural opinions. It was found that inclusive frames were better at reaching a compromise, with participants rating their conclusions more positively than in controversial frames. These findings can be extended to public deliberations on broader environmental management policy planning, especially on contentious issues where conflicts exist among participants.\u003c/p\u003e\u003cp\u003eParticipants in this study were not confident in their opinions, even in the controversial frame condition, and they did not experience heavy conflict. Thereupon, it is anticipated that consensus may disappear if stakeholders with vested interests engage in a controversial manner. Especially in situations where conflicting interests exist among community members or between residents and the administration, failure to reach consensus not only impedes policy implementation but also divides communities and evokes resistance from residents. Hence, discussion frames should be carefully designed based on participants’ interests and the firmness of their opinions.\u003c/p\u003e\u003cp\u003eThe benefit of applying inclusive frames is that they allow group members to obtain a comprehensive view. Previous studies (c.f., Fishkin \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Fishkin and Luskin \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Gastil and Dillard \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Gerber et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Sanders \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) have demonstrated that public deliberation leads to opinion changes; however, they neither directly proved nor guaranteed that opinions deepened. To answer this question, this study analyzed both the central decision and conjunctive argument points and participants’ statements after making decisions. As a result, groups in the inclusive condition reached compromise solutions regarding the central decision, considered conjunctive argument points when determining the central decision, and organized discussions based on the pros and cons of the final disposal outside Fukushima instead of simply for or against positions. These trends may also occur when the inclusive discussion frame is applied to other cases; that is, it is plausible that opinions on the issue deepen individually and collectively, facilitating a comprehensive understanding and compromise.\u003c/p\u003e\u003cp\u003eAn inclusive discussion frame is crucial for topics involving various intertwined elements in environmental management policy and not only for policy planning vis-à-vis the removed soil issue. In this sense, we provide evidence by conducting multidimensional analyses using a rigorously manipulated experiment on public deliberations.\u003c/p\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was partially supported by the Graduate Grant Program of the Graduate School of Humanities and Human Sciences, Hokkaido University, awarded to the first author.\u003c/p\u003e\n\u003cp\u003eWe would like to thank Editage (www.editage.jp) for English language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the experimental assessment of diverse justice criteria toward the final repository of removal soil outside Fukushima Prefecture, Environment Research and Technology Development Fund [JPMEERF22S20907]; Hyper Democracy, Creative Revolutionary Technology Seeds for Science and Technology Innovation (CREST) by the Japan Science and Technology Agency (JST) [JPMJCR20D1]; the Consensus process for realizing common goods overcoming the divided society, Grants-in-Aid for Scientific Research (KAKEN) by the Japan Society for the Promotion of Science (JSPS) [23K22343]; and Exploration of Multiple Common Goods in Public Decision-Making: a group discussion experiment on the treatment of decontaminated soil, Grant-in-Aid for JSPS Fellows by JSPS [24KJ0296].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll procedures performed in studies involving human participants were conducted in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Ethics Review Committee of the Center for Experimental Research in Social Sciences, Hokkaido University (No. R4-05, 22 April 2022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate and Publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBefore the start of the experiment, the researchers obtained participants\u0026rsquo; consent in written form. The researchers distributed the consent forms individually, and consent was confirmed through participants\u0026rsquo; signatures. This consent covered participation in the experiment, recording and filming during the discussions, and academic publication of anonymized data.\u003c/p\u003e\n\u003cp\u003eFurthermore, because this study involved non-interventional research, all participants were fully informed in advance about the purpose of the research, the anonymization of their data, and the potential academic publication of the analysis results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData, Materials, and/or Code Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available in the Open Science Framework repository (https://osf.io/), [https://osf.io/uh2ae/?view_only=7692bc81c0ec43738945a0bdd134ef6c].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: Yume Souma, Susumu Ohnuma, Takashi Nakawzawa, Tomoyuki Tatsumi, and Yoshiko Arima; Data curation: Yume Souma, Yukihide Shibata, Mie Tsujimoto, Qinglin Cui, and Susumu Ohnuma; Formal Analysis: Yume Souma; Funding acquisition: Susumu Ohnuma; Investigation: Yume Souma, Yukihide Shibata, Mie Tsujimoto, Qinglin Cui, and Susumu Ohnuma; Methodology: Yume Souma and Susumu Ohnuma; Supervision: Susumu Ohnuma; Visualization: Yume Souma; Writing-original draft: Yume Souma; Writing-review and editing: Susumu Ohnuma, Takashi Nakawzawa, Tomoyuki Tatsumi, and Yoshiko Arima.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eArima Y (2019) Group as a de-polarizer of attitude. https://doi.org/10.31235/osf.io/bt5y7\u003c/li\u003e\n\u003cli\u003eAsch SE (1956) Studies of independence and conformity: I. 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Jpn J Psychol 91:378\u0026ndash;387. https://doi.org/10.4992/jjpsy.91.19048 (in Japanese)\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"public deliberation, discussion frame, finding a compromise, group decision experiment, final disposal of removed soil","lastPublishedDoi":"10.21203/rs.3.rs-6290609/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6290609/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePublic deliberation is useful for finding an acceptable compromise, particularly when plural values are contradictory. This study addresses the case of the final disposal of removed soil outside Fukushima Prefecture, Japan, which requires public deliberation to untangle contradictory values but has not yet been implemented. Despite existing case reports and surveys targeting individual answers, a group decision experiment in a laboratory setting with rigorous manipulation is noteworthy for determining the conditions under which a group can find an acceptable compromise that reflects heterogeneous opinions.\u003c/p\u003e \u003cp\u003eIn a group decision experiment comprising four members, we manipulated the discussion frames: one was a controversial frame, whereby participants refuted each other in a dichotomous manner, and the other was an inclusive frame, whereby they contemplated both the pros and cons thoroughly. Each group decided whether to approve the final disposal outside Fukushima.\u003c/p\u003e \u003cp\u003eThe results indicated that the inclusive frame was more likely to facilitate compromise that reflected heterogeneous opinions than the controversial frame. Although group opinions shifted toward support for their decision with decreased variance in both conditions, participants in the inclusive frame condition rated their decisions more positively than those in the controversial condition. Notably, in the inclusive condition, participants evaluated conclusions favorably regardless of their initial opinions, while those in the controversial condition viewed decisions negatively when they conflicted with their initial opinions.\u003c/p\u003e \u003cp\u003eThese findings highlight the impact of discussion frames on finding a compromise and offer insights into designing effective public deliberation for environmental policy planning.\u003c/p\u003e","manuscriptTitle":"Effect of the discussion frame on finding a compromise: A group decision experiment on the final disposal of removed soil outside Fukushima","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-30 11:48:59","doi":"10.21203/rs.3.rs-6290609/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7204f9b8-e6ef-441e-91d9-a352fe1aa9e7","owner":[],"postedDate":"April 30th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-05-12T14:53:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-30 11:48:59","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6290609","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6290609","identity":"rs-6290609","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}