Bilingualism and cognition: The impact of age of acquisition, language use and proficiency in healthy older adults

Bilingualism and cognition: The impact of age of acquisition, language use and proficiency in healthy older adults | 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 Article Bilingualism and cognition: The impact of age of acquisition, language use and proficiency in healthy older adults Sergio Grueso, Gonzalo Sánchez-Benavides, Miguel Santos-Santos, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7796112/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 Background The positive effect of bilingualism, especially later in life, is typically attributed to its role as a cognitive reserve factor. However, evidence supporting such benefits remains inconclusive or appears limited to certain populations, tasks, or cognitive domains. Some of these inconsistencies may stem from the tendency to define bilingualism as a dichotomous variable, rather than considering the multiple factors that contribute to the bilingual experience. Our study investigates the impact of bilingualism on cognition in cognitively unimpaired older adults, focusing on age of language acquisition (AoA), proficiency, and usage throughout life. Method We analyzed data from 2415 cognitively unimpaired individuals (aged 45–74) from the Alzheimer's and Families (ALFA) study. We included Mini-Mental State Examination to assess global cognition, semantic fluency for lexical retrieval, Memory Binding Test for verbal episodic memory, and WAIS-IV subtests for processing speed and visual-motor coordination (Coding), visual-spatial reasoning (Visual Puzzles), non-verbal abstract reasoning (Matrix Reasoning), verbal short-term memory (Digit Span Forward) and working memory and attention (Digit Span Backward and Sequencing). We defined three groups based on AoA (Early/Late) and proficiency (High/Low) of Catalan: 1) Early High-Proficiency bilinguals (n = 1559); 2) Late High-Proficiency bilinguals (n = 537); and 3) Late Low-Proficiency bilinguals, primarily Spanish-dominant (n = 319). We also analyzed the effect of the language of assessment (Spanish or Catalan) on cognitive performance. Results We found that both Early and Late High-Proficiency bilingual groups outperformed Late Low-Proficiency bilinguals in verbal fluency and processing speed. Additionally, Early High-Proficiency bilinguals scored significantly higher in verbal short-term memory than both Late AoA groups. Conclusion Our findings highlight that the cognitive effects of bilingualism in aging are not uniform but rather domain-specific and that bilingualism, particularly when characterized by high proficiency, can serve as a meaningful contributor to cognitive reserve. Biological sciences/Neuroscience Biological sciences/Psychology Social science/Psychology bilingualism aging cognitive aging cognitive reserve bilingual advantage Figures Figure 1 Figure 2 Background Despite a growing body of research on the cognitive advantages of bilingualism, evidence for a positive effect remains inconclusive or appears limited to specific populations, tests, or cognitive domains [1–4]. This is especially relevant in the context of aging, where the nature of the protective role of bilingualism against cognitive decline continues to be debated [5,6]. Among the reasons for this inconsistency across studies, it has been suggested that the lack of replication of research findings may stem from the complex nature of bilingualism, which is a highly diverse and dynamic experience shaped by substantial individual differences. For instance, factors such as age of acquisition (AoA), language proficiency, frequency of use, and language-switching practices, can all influence neural structures and cognitive outcomes [1,7–9]. These findings highlight that bilingualism’s effects on cognition are complex and highly individualized, challenging the traditional dichotomy between a monolithic view of bilingualism and monolingualism. Bilingualism, cognitive reserve, and aging Investigating the potential positive effects of bi- and multilingualism on cognition is crucial for understanding the underlying mechanisms that may protect against cognitive impairment and dementia. This is not only a theoretical question but also has important implications for policies related to healthy aging and the reduction of age-related disorders [10–12]. Indeed, in recent years, there has been a notable increase in studies exploring the potential cognitive benefits of speaking multiple languages in patients with neurodegenerative diseases. One of the first examples was a study conducted in Canada by Bialystok et al. [13] that showed a 4-year delay in Alzheimer’s Disease (AD) onset for bilinguals, compared to monolingual peers. Craik et al. later confirmed the same time gap in a follow-up study of the same sample [14]. Other studies followed their work, replicating their results of bilingualism delaying effect on AD in other cultural backgrounds as India [15], Belgium [16], China [17] and the US [18]. This effect has been reported in different meta-analysis [19–21] and there is also evidence of delaying effects of bilingualism in MCI population [22–24]. Other studies also showed a reduced incidence of MCI [25] and AD [26] in multilingual countries (for a review, see [6]). However, the bilingual advantage in cognitive decline and dementia prevention has not been consistently observed across all research findings [27,28]. The positive effect of bilingualism against cognitive decline and dementia has often been attributed to the concept of cognitive reserve. According to Stern et al., cognitive reserve is defined as the discrepancy between the level of age-related neural deterioration and the extent of cognitive impairment [29]. It encompasses the brain's ability to adapt and reorganize through processes such as increased efficiency, capacity, and flexibility of neural networks in response to aging, damage, or disease. These adaptive mechanisms have also been suggested for bilingualism [5,6,30]. However, the relationship between bilingualism and cognitive reserve remains complex, particularly when considering the interaction between brain health and cognitive performance. Although, some researchers suggest that the bilingual advantage may be more evident in older adults, compared to young bilinguals, as age-related cognitive decline provides greater opportunity for bilingualism to generate a protective effect [31]. For example, Grant et al. proposed that the previously reported bilingual advantage in episodic memory among older adults, can be explained by enhanced prefrontal function, better preservation of posterior brain regions, and increased connectivity between prefrontal and posterior areas [32], suggesting that the advantages in episodic memory and executive control among bilinguals may be due to the overlap between brain regions associated with cognitive reserve and those involved in memory and language. Meta-analyses show mixed evidence for a bilingual advantage in executive functions among older adults. Degirmenci et al. [33], reported that benefits appear limited to inhibitory control in individuals aged 65–75, with no consistent effects on working memory or task-switching, largely due to variability in language experience, tasks, and participant characteristics. Similarly, Ware et al. found that the reliability of the bilingual advantage on cognition depends on the type of test employed, suggesting that it is not an all-or-nothing phenomenon [4]. Despite some evidence indicating that bilingualism may contribute to cognitive reserve and healthy aging, we need a clearer understanding of the specific aspects of the bilingual language experience that offer the greatest protective benefits against neurocognitive decline. Bilingual Language Experience Different variables associated with bilingualism have been proposed as key factors influencing the reliability of its effects on cognition. Indeed, there has been growing interest in exploring how differences in bilingual language experiences including AoA of a second language (L2), L2 proficiency, and daily language use, particularly in terms of frequency and switching practices, can influence both language-related processes and executive control [1,8,34,35]. However, these variables have been primarily explored in young adults, and studies involving cognitively unimpaired older individuals remain limited. The evidence regarding the effect of AoA on executive control is mixed. In this regard, studies with children showed that early bilinguals performed better in conflict monitoring [36]. Others have shown that young early bilinguals may experience reduced task-switching costs [37], while late bilinguals with frequent language use may show a greater advantage in conflict resolution [38]. Additionally, Torres et al. found that earlier L2 AoA was associated with better performance on the Digit Span Backward subtest [39], while Schroeder and Marian reported that early L2 AoA was linked to enhanced episodic recall [40]. Language proficiency is another important aspect of the bilingual language experience that has been demonstrated to influence executive control [41]. In particular, it has been shown that higher L2 proficiency predicted better executive control performance [42,43] and is associated with better conflict monitoring [44]. Some studies have found that bilinguals tend to have smaller vocabulary sizes and perform worse in picture naming and fluency tests [45,46], but in letter fluency tests, that require higher executive control demands, high proficiency bilinguals outperformed low proficiency bilinguals [47]. Finally, Rosselli et al. found that bilinguals with high proficiency in both their L1 and L2 scored higher on most executive function tests than those with low proficiency in both languages, while bilinguals proficient in only one language (L1 or L2) scored in between these two groups [48]. Bilinguals differ not only in proficiency and AoA, but also in language usage, another key variable in defining bilingualism. Contextual factors can lead individuals who acquired two languages early in life to primarily use only one, while late L2 AoA bilinguals may shift their dominant language over time. Therefore, it is essential to examine language usage alongside other factors such as AoA and language proficiency. Research on executive control indicates that active use of both languages is associated with enhanced goal maintenance and conflict monitoring [49]. Other studies suggest that performance in switching tasks may be influenced by the frequency of daily language switching [50,51]. Additionally, other studies have found enhanced task-switching performance among active bilinguals, but no significant differences on the Simon task between passive bilinguals and monolinguals [52]. Although these variables have primarily been explored in younger individuals and the findings remain inconclusive, they are highly relevant to our study, as they will guide our analysis in defining the language profile of participants in our large sample of cognitively unimpaired older adults. The present study In this study, we investigated the impact of language experience on cognitive aging by analyzing the cognitive performance of cognitively unimpaired individuals aged 45–74 years from the ALFA study [53], focusing on age of acquisition, proficiency, and language use. The cohort, recruited in Catalonia (Spain), provides considerable variability in linguistic backgrounds due to the co-official status of Catalan and Spanish. According to the Statistical Institute of Catalonia, in 2023 the region had a population of approximately 7.9 million inhabitants. In the 45–74 age group, 93.9% of individuals report understanding Catalan, 84% can read it, 79.7% are able to speak it and 62.5% can write it. With respect to first language, 34% of middle-aged adults (45–64 years) identify Catalan and 44.7% identify Spanish, whereas in the older population (> 65 years), the proportions shift to 40.6% for Catalan and 45.4% for Spanish [54]. For the purposes of this study, three language profiles were defined: Early High-Proficiency bilinguals, who acquired both languages in early childhood; Late High-Proficiency bilinguals, who acquired Catalan after Spanish but attained high proficiency; and Late Low-Proficiency bilinguals, who primarily use Spanish and exhibit limited active competence in Catalan. These group distinctions establish the framework for the hypotheses addressed in the present work. Our analysis focuses on both linguistic and non-linguistic cognitive domains, which enables us to test the hypothesis that, for non-linguistic cognitive domains, Early High-Proficiency bilinguals should outperform Late Low-Proficiency bilinguals, the latter of whom we consider to have a profile more similar to monolinguals. Late High-Proficiency bilinguals will fall in the middle, given the influential role of the L2 AoA. In particular, we expect that for non-verbal abstract reasoning, visuospatial reasoning, working memory and processing speed, Early High-Proficiency bilinguals should outperform Late Low-Proficiency bilinguals, as higher language proficiency is associated with better executive control, particularly in working memory and conflict monitoring [42,44]. Additionally, AoA also plays a role in cognitive flexibility and conflict monitoring [36,39,55], and in the active use of the two languages [42,56]. For Late High-Proficiency bilinguals, we expect an effect of AoA, which might be counteracted by the positive effect of higher language proficiency and active use of the two languages, bringing their performance closer to that of Early High-Proficiency bilinguals. As for tests with a verbal or linguistic component, we hypothesized that while bilingualism may support the maintenance of episodic memory in older adulthood through its positive effects on executive functioning [3,4,6,33,40,42], this advantage would be reduced or absent in tests that place high demands on lexical processing, such as free recall of words, due to bilinguals’ known disadvantages in lexical access and retrieval [40,57]. Additionally, this disadvantage should be more evident for verbal fluency, which relies heavier on a linguistic component. We anticipate that Late Low-Proficiency bilinguals who primarily use one language may perform similarly to, or even better than, highly proficient bilinguals (both early and late) as previous research has shown a bilingual disadvantage in tests involving lexical retrieval [33,39,45,58] Regarding the relationship between bilingual language variables, early AoA is expected to be related to higher proficiency in L2. However, late bilinguals who frequently use both languages may still exhibit cognitive advantages compared to other late bilinguals with passive exposure to Catalan [38]. Overall, we expect higher L2 proficiency, earlier L2 AoA, and active use of both Spanish and Catalan to be associated with better executive control in healthy older adults. This is likely due to the lifelong engagement in language control mechanisms, which may enhance general executive control [2,59]. Methods Participants Participants were selected from the database of the ALFA parent cohort, established by the Barcelonaβeta Brain Research Center [53]. The original aim of the ALFA parent cohort study was to prospectively follow a cohort of cognitively unimpaired individuals, most of whom are offspring of AD patients. To achieve this, the inclusion criteria for enrolment in the study were: (1) being a Spanish and/or Catalan speaker; (2) aged between 45 and 74 years; and (3) providing consent to study procedures and tests, which included a clinical interview, lifestyle and health questionnaires, cognitive assessments, and blood tests for genotyping. Exclusion criteria were: (1) cognitive performance not meeting the prespecified cutoffs of Mini-Mental State Examination [60,61] (MMSE) < 26, or Memory Impairment Screen [62,63] < 6, or Time-Orientation subtest of the Barcelona Test II [64] < 68, or verbal semantic fluency [65,66] (animals) 0; or (3) The presence of a) major psychiatric disorders, b) severe auditory or visual disorders, c) neurodevelopmental and/or psychomotor disorder, d) significant disease that could interfere with cognition, e) neurological disorders or brain injury that could affect participant’s cognition and f) suspected pattern of family history of autosomal dominant AD [53]. According to these inclusion and exclusion criteria, 2743 participants were recruited [53]. For the present study, we excluded 81 participants with missing data on the language use questionnaire, 28 participants without L2 AoA information and 129 participants who reported using languages other than Spanish or Catalan. An additional three were removed due to missing age or Semantic Fluency data, resulting in 2502 participants for subsequent analyses. Data extraction and variable selection For this study, we extracted the following information from 2502 participants (See Table S1 in Additional File for descriptive statistics of sociodemographic variables, language and cognitive profile of the sample): a. Sociodemographic data. We collected participant's age, years of education and sex. b. Neuropsychological test scores. For cognitive assessment, we included the following tests: (1) MMSE [60,61] for global cognition; (2) Semantic Fluency test (animals), for verbal fluency [65,66]; (3) the Memory Binding Test (MBT) [68] to assess verbal episodic memory; (4) from the Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV) [69] the Matrix Reasoning subtest for non-verbal abstract reasoning; (5) the Visual Puzzles subtest for visuospatial reasoning; (6) the Digit Span subtest to assess verbal short-term and working memory; and (7) the Coding subtest for processing speed and visual-motor coordination. Participants could choose whether to perform the neuropsychological assessment in Catalan or Spanish. For further details on the evaluation procedure, see [53]. c. Language profile. The language history was collected fromparticipants with a questionnaire that was created ad-hoc for the study. For a similar version, see Calabria et al. [70]. The information collected for Spanish and Catalan was: ● Age of language acquisition. Participants were asked about the time they began speaking each language. ● Language proficiency. This was collected as self-reported proficiency for speaking, comprehension, reading, and writing in each language using a five-point scale (1 = not at all, 2 = low, 3 = fairly good, 4 = good, and 5 = very good) ● Language use. Participants were asked about which language they preferred to use in three different contexts among four options: “Spanish”, “Catalan”, “No preference between Catalan and Spanish” and “Other languages”. Specifically, the information gathered for each participant in the three contexts was: seven items regarding childhood, they were asked about the language usually spoken with (1) their mother; (2) their father; (3) other family members living with them; (4) other extended family members; (5) friends and neighbours; (6) friends at school; and (7) the language in which they received their education. In five items regarding current social language use, participants were asked which language they use (1) at home (with a partner, children, etc.); (2) with other family members; (3) at work; (4) with friends or neighbours; and (5) in other social contexts such as the bank or supermarket. Finally, three items regarding internal language use, including the language they use when (1) talking to themselves; (2) performing arithmetic operations or counting; and (3) for insulting or swearing. Participants who reported using languages other than Spanish or Catalan were excluded from the study (See Table S2 Additional File for full questions). d. Cognitive Reserve Questionnaire (CRQ) [71] . This consists of 8 items that evaluate the educational background, occupational complexity, social and physical activities and cultural and intellectual pursuits. The 8 items generate a score that serves as a quantitative proxy of cognitive reserve, maximum total score is 25 points and the items are: (1) formal education (0-5 points); (2) parental formal education (0-2 points); (3) attendance to courses (0-3 points); (4) occupation (0-4 points); (5) musical education (0-2 points); (6) languages spoken (0-3 points); (7) frequency of reading (0-4 points); and (8) cognitively stimulating activities (0-2 points). To control the effect of cognitive reserve, we computed an adjusted cognitive reserve score by removing the language and education items in order to avoid correcting multiple times for education or language profiles. Statistical analysis First, we grouped our sample based on Catalan proficiency and AoA. To define participant groups based on their bilingual language experience, variables with minimal variability were excluded, as they were unlikely to contribute meaningfully to group differentiation. Specifically, Catalan comprehension and reading proficiency, Spanish AoA, and all Spanish proficiency measures. Group classification was performed using fixed thresholds applied to AoA of Catalan (in years) and Proficiency as the mean self-reported value of Writing and Speaking proficiencies. Participants with Catalan proficiency scores of 3 or lower were categorized as having low proficiency, whereas those with scores of 4 or above were classified as having high proficiency. Based on previous literature [33,38,45,72,73], the age of 6 was chosen as the cutoff for early Catalan AoA, as key brain and executive function developments occur in early childhood, often before formal schooling. Those who acquired Catalan at age 6 or later were classified as late bilinguals. This procedure resulted in four theoretically interpretable language profile groups: (1) Early High-Proficiency Bilinguals (n=1559); (2) Early Low-Proficiency Bilinguals (n=537); (3) Late High-Proficiency Bilinguals (n=319); and (4) Late Low-Proficiency Bilinguals (n=87). Participants in the Early Low-Proficiency Bilingual group were excluded from further analyses since native exposure is unlikely to result in low proficiency [24,33,55], specially in the context of Catalonia due to constant exposure to both Catalan and Spanish [24,74]. Their classification likely reflected data entry or self-reporting errors. The final sample was 2415 participants. Second, we conducted an Analysis of Variance (ANOVA) aimed to identify differences in language and sociodemographic variables (age, years of education and cognitive reserve) across the three language profile groups. Normality was assessed using the Shapiro-Wilk test, and homogeneity of variances using Levene’s test. Due to violations of homogeneity and unequal group sizes, we employed Welch’s ANOVA, which is robust to heteroscedasticity and unequal sample sizes, with language profile group as the between-subjects factor. Although traditional ANOVA assumes normality, Welch’s ANOVA is robust to moderate violations, particularly in larger samples. Omega squared (ω²) was used to estimate effect sizes. When Welch’s ANOVA yielded significant effects, Games-Howell post hoc tests were conducted to perform pairwise comparisons, as this method is specifically designed to handle unequal variances and sample sizes. In addition, a Chi-squared test of independence was conducted to examine potential differences in sex distribution across the three language profile groups. Third, an Analysis of Covariance (ANCOVA) with multiple covariates was conducted to examine the effects of language profile group (3 levels) and the language of assessment (Catalan or Spanish), controlling for age, years of education, sex, and adjusted cognitive reserve score, on 13 neuropsychological test scores: (1) MMSE; (2) Semantic Fluency; (3) MBT Total Free Recall; (4) MBT Total Paired Recall; (5) MBT Total Delayed Paired Recall; (6) MBT Total Delayed Free Recall; (7) WAIS-IV Coding; (8) WAIS-IV Matrix Reasoning; (9) WAIS-IV Visual Puzzles; (10) WAIS-IV Digit Span Total Score; (11) Digit Span Forward; (12) Digit Span Backward; and (13) Digit Span Sequencing. To enable direct comparisons across different cognitive measures and groups, z-scores were computed within the whole sample for all test scores. Most participants in the Early High-Proficiency and Late Low-Proficiency bilingual groups completed the assessments in their dominant language. Only a small subset of Late Low-Proficiency bilinguals opted to complete the assessment in Catalan, their non-dominant language and 41% of participants in the Late High-Proficiency group chose to be assessed in Catalan, despite Spanish being their first acquired language. The ANCOVA model included main effects of language profile group and language of assessment, as well as their interaction (language profile group × language of assessment). Type III sums of squares were used to accommodate unbalanced group sizes and interaction effects. Effect sizes were reported as partial eta squared (η²ₚ). When significant main effects or interactions were found, pairwise comparisons of estimated marginal means were conducted using the emmeans package in R, with p-values adjusted using the Holm method to control for multiple comparisons. We observed unequal variances (Levene's test, p < .05) in MBT Total Delayed Free Recall, WAIS Matrix Reasoning, and Digit Span Sequencing. To address this, we used squared transformation, which most effectively improved variance homogeneity for each affected variable. For MMSE and MBT Total Paired Recall, none of the transformations successfully corrected variance inequality. MMSE scores were likely influenced by a ceiling effect due to the exclusion criterion (scores < 26), and MBT Paired Recall scores were left-skewed. For these variables, we applied robust ANCOVA using heteroscedasticity-consistent standard errors (HC3) via the Anova() function from the car package [75] in R (Type III sums of squares, robust = TRUE), allowing valid inference despite violations of homoscedasticity and normality. For all other variables, Levene’s tests were non-significant ( p > .05), indicating homogeneity of variances. All analyses were performed using R software [76]. Results Sociodemographic variables For age, we found a statistically significant difference among the groups, F (2, 778.71) = 28.15, p < .001, ω² = .022, with mean ages ranging from 54 to 57 years and a standard deviation of approximately 6 years. Post hoc comparisons revealed that Late High-Proficiency bilinguals had significantly higher age than Early High-Proficiency bilinguals ( p < .001) and Late Low-Proficiency bilinguals ( p < .001) with no significant differences between the later two ( p = .596). We also found significant differences among the groups in years of education, F (2, 745.09) = 50.14, p < .001, ω² = .039. Post hoc comparisons showed that both high-proficiency bilingual groups had similar years of education ( p = .08), but the Late Low-Proficiency bilinguals had significantly lower education than Early High-Proficiency bilinguals ( p < .001) and Late High-Proficiency bilinguals ( p < .001). For the adjusted CRQ scores, results showed a significant effect of group, F (2, 742.56) = 44.69, p < .001, ω² = .035. Post hoc comparisons showed that both high-proficiency bilingual groups had similar adjusted CRQ scores ( p = .589), but the Late Low-Proficiency bilinguals had significantly lower adjusted CRQ scores than Early High-Proficiency bilinguals ( p < .001) and Late High-Proficiency bilinguals ( p < .001). A Chi-squared test of independence indicated that sex was not significantly associated with language profile group, χ²(2, N = 2415) = 2.66, p = .264. Overall, significant differences emerged across all sociodemographic variables except sex, with high-proficiency bilinguals showing higher educational attainment and cognitive reserve scores than low-proficiency bilinguals (Table 1 ). Table 1 Group comparison in sociodemographic and language variables. Variable Early High n = 1559 Late High n = 537 Late Low n = 319 p-value ω² Early High vs Late High Early High vs Late Low Late High vs Late Low Sex (M/F) 586/973 189/348 130/189 .264* - - - - Age (years) 56.29 ± 6.78 53.9 ± 6.28 55.92 ± 6.08 < .001 .022 < .001 .596 < .001 Years of Education 13.64 ± 3.43 14 ± 3.31 11.69 ± 3.5 < .001 .039 .08 < .001 < .001 CRQ Adjusted Score 10.47 ± 2.72 10.34 ± 2.52 8.82 ± 2.89 < .001 .035 .589 < .001 < .001 Catalan AoA 1.1 ± 0.56 18.62 ± 8.35 24.44 ± 12.19 < .001 .593 < .001 < .001 < .001 Comprehension (1–5) 4.97 ± 0.16 4.95 ± 0.23 4.56 ± 0.72 < .001 .042 .038 < .001 < .001 Reading (1–5) 4.96 ± 0.21 4.89 ± 0.45 4.24 ± 0.98 < .001 .068 < .001 < .001 < .001 Speaking (1–5) 4.95 ± 0.22 4.77 ± 0.45 3.16 ± 0.96 < .001 .326 < .001 < .001 < .001 Writing (1–5) 4.78 ± 0.5 4.66 ± 0.56 2.14 ± 0.91 < .001 .514 < .001 < .001 < .001 Spanish AoA 3.22 ± 2.84 1 ± 0.06 1 ± 0.06 < .001 .281 < .001 < .001 .916 Comprehension (1–5) 4.96 ± 0.19 4.99 ± 0.11 4.94 ± 0.26 < .001 .010 < .001 .166 < .001 Reading (1–5) 4.96 ± 0.19 4.99 ± 0.11 4.94 ± 0.23 < .001 .010 < .001 .297 .001 Speaking (1–5) 4.92 ± 0.3 4.99 ± 0.14 4.91 ± 0.34 < .001 .022 < .001 .916 < .001 Writing (1–5) 4.93 ± 0.27 4.98 ± 0.15 4.9 ± 0.33 < .001 .014 < .001 .147 < .001 Note: Early High = Early AoA High-Proficiency Bilinguals; Late High = Late AoA High-Proficiency Bilinguals; Late Low = Late AoA Low-Proficiency Bilinguals; M = Male; F = Female; AoA = Age of Acquisition; CRQ = Cognitive Reserve Questionnaire. Values are presented as mean (± SD). Post hoc results are for Games-Howell tests. Effect sizes were estimated with omega squared (ω²). An asterisk indicates p-values are for Chi-squared Test (Χ²). Dash (-) indicates not applicable. Language profile Catalan. For AoA, all groups differed significantly as expected since groups were based on this measure, F (2, 533.14) = 1760.28, p < .001, ω² = .593. Similarly, for language proficiency we found statistically significant differences in all domains: speaking, F (2, 569.55) = 585.69, p < .001, ω² = .326; oral comprehension, F (2, 596.33) = 53.55, p < .001, ω² = .042; writing, F (2, 653.32) = 1279.33, p < .001, ω² = .514; and reading, F (2, 567.56) = 89.7, p < .001, ω² = .068 (Table 1 ). Spanish. The mean AoA and proficiency values indicated native-like acquisition across all groups and domains with minimal variability. Despite that, we found significant differences across the three groups in AoA, F (2, 1304.71) = 473.02, p < .001, ω² = .281, and for language proficiency domains: speaking, F (2, 790.74) = 27.97, p < .001, ω² = .022; oral comprehension, F (2, 764.47) = 12.87, p < .001, ω² = .010; writing, F (2, 771.48) = 18.13, p < .001, ω² = .014; and reading, F (2, 770.38) = 12.91, p < .001, ω² = .010 (Table 1 ). Language use. Most of the Early High-Proficiency bilinguals reported a high preference for Catalan during childhood (87%) and adulthood (72%) with some reporting a bilingual preference in adulthood (22%). In contrast, Late Low-Proficiency bilinguals reported a high preference for Spanish during childhood (97%) and adulthood (75%) with some reporting a bilingual preference in adulthood (18%). The Late High-Proficiency bilinguals also reported a high preference for Spanish in childhood (93%) but a more balance preference between the two languages in adulthood, with 27% having a preference for Spanish, 30% for Catalan and 43% for both languages. These percentages are mean values across all contexts from childhood and adulthood, for specific results of each group in different contexts across their lifespan see Fig. 1 and Table S3 in Additional File. Cognitive measures The results of the comparison across all cognitive measures for the three language profile groups are summarized in Fig. 2 . MMSE. The results indicated no significant main effects of language profile group, F (2, 2405) = 1.98, p = .138, η²ₚ = .002, or language of assessment, F (1, 2405) = 0.25, p = .619, η²ₚ < .001. The interaction term between language profile group and language of assessment was not significant, F (2, 2405) = 1.28, p = .279, η²ₚ = .001. Semantic fluency. The results showed a significant main effect of language profile group, F (2, 2405) = 7.39, p < .001, η²ₚ = .006. Post-hoc comparisons showed that Late Low-Proficiency bilinguals performed significantly worse than both Late High-Proficiency bilinguals, t = -3.54, p < .001, and Early High-Proficiency bilinguals, t = -3.74, p < .001. No significant difference was found between Early High-Proficiency bilinguals and Late High-Proficiency bilinguals, t = -0.05, p = .960. Additionally, a significant main effect of language of assessment was observed, with participants evaluated in Spanish scoring higher than those evaluated in Catalan, F (1, 2405) = 4.81, p = .028, η²ₚ = .002. The interaction between language profile group and language of assessment was not significant, F (2, 2490) = 1.99, p = .137, η²ₚ = .002. Memory Binding Test. For the total immediate paired recall score, results indicated no significant main effects of language profile group, F (2, 2405) = 2.07, p = .126, η²ₚ = .002 or language of assessment, F (1, 2405) = 2.27, p = .132, η²ₚ < .001. Additionally, the interaction term was not significant, F (2, 2405) = 2.09, p = .124, η²ₚ = .002. Similarly, total delayed paired recall score results showed no significant main effect of language profile group, F (2, 2405) = 1.59, p = .203, η²ₚ = .001, or language of assessment, F (1, 2405) = 1.20, p = .273, η²ₚ < .001. The interaction between language profile group and language of assessment was also not significant, F (2, 2405) = 0.81, p = .443, η²ₚ < .001. Regarding the total immediate free recall score, the analysis showed a significant main effect of language profile group, F (2, 2405) = 3.31, p = .036, η²ₚ = .003, but not language of assessment, F (1, 2405) = 0.20, p = .657, η²ₚ < .001. The interaction between language profile group and language of assessment was also not significant, F (2, 2405) = 0.05, p = .955, η²ₚ < .001. None of the post hoc comparisons between groups was significant. For the total delayed free recall score, results showed no significant main effect of language profile group, F (2, 2405) = 1.83, p = .161, η²ₚ = .002, or language of assessment, F (1, 2405) = 1.47, p = .225, η²ₚ < .001. The interaction between language profile group and language of assessment was also not significant, F (2, 2405) = 1.18, p = .309, η²ₚ < .001. WAIS-IV Coding. Results revealed a significant main effect of language profile group, F (2, 2405) = 20.23, p < .001, η²ₚ = .017 and language of assessment, F (1, 2405) = 4.21, p = .040, η²ₚ = .002, with Catalan assessments having significantly higher scores than Spanish assessments. The interaction between language profile group and language of assessment was not significant, F (2, 2405) = 2.26, p = .104, η²ₚ = .002. Post hoc analyses showed that Late Lower-Proficiency bilinguals performed significantly worse than both Late High-Proficiency bilinguals ( t = -3.05, p = .005) and Early High-Proficiency bilinguals ( t = -4.37, p < .001). However, no significant differences were found between Early High-Proficiency bilinguals and Late High-Proficiency bilinguals ( t = 1.67, p = .094). WAIS-IV Visual Puzzles. Results showed no significant main effects of language profile group, F (2, 2405) = 0.07, p = .928, η²ₚ < .001, or language of assessment, F (1, 2405) = 0.19, p = .660, η²ₚ < .001. The interaction between language profile group and language of assessment was not significant, F (2, 2405) = 0.42, p = .766, η²ₚ < .001. WAIS-IV Matrix Reasoning. Results showed no significant main effects of language profile group, F (2, 2405) = 1.64, p = .193, η²ₚ = .001, but it was significant for language of assessment, F (1, 2405) = 5.48, p = .019, η²ₚ = .002, with Catalan assessments having significantly higher scores than Spanish assessments. However, the interaction between language profile group and language of assessment was not significant, F (2, 2405) = 1.72, p = .179, η²ₚ = .001. WAIS-IV Digit Span. For the total score of WAIS-IV Digit Span, results revealed no significant main effects of language profile group, F (2, 2405) = 2.37, p = .093, η²ₚ = .002), but significant main effects of language of assessment, F (1, 2405) = 3.99, p = .046, η²ₚ = .002), with Spanish assessments having higher scores than Catalan assessments. Results also showed a significant interaction between language profile group and language of assessment, F (2, 2405) = 3.55, p = .028, η²ₚ = .003. Post hoc comparisons showed that there were no statistical differences between language profile groups in Spanish assessments (all p -values > .05). However, in Catalan assessments, Early High-Proficiency bilinguals score significantly higher than Late High-Proficiency bilinguals, t = 3.85, p = .002 and Late Low-Proficiency bilinguals, t = 3.17, p = .018. There were no significant differences between Late Low-Proficiency bilinguals and Late High-Proficiency bilinguals ( t = -1.05, p = .999). For the Digit Span Forward, there was not a significant main effect of language profile groups, F (2, 2405) = 2.01, p = .134, η²ₚ = .002, but the main effect of language of assessment was significant, F (1, 2405) = 11.15, p < .001, η²ₚ = .005, with Spanish assessments having higher scores than Catalan assessments. Also, the interaction effect was significant, F (2, 2405) = 8.74, p .05). However, in Catalan assessments, Early High-Proficiency bilinguals score significantly higher than Late High-Proficiency bilinguals, t = 4.36, p = .002 and Late Low-Proficiency bilinguals, t = 3.57, p = .004. There were no significant differences between Late Low-Proficiency bilinguals and Late High-Proficiency bilinguals, t = -1.17, p = .999. For the Digit Span Backward, results indicated no significant main effect of language profile group, F (2, 2405) = 1.53, p = .216, η²ₚ = .001, or of language of assessment, F (1, 2405) = 0.45, p = .501, η²ₚ < .001. The interaction between language profile group and language of assessment was also not significant, F (2, 2405) = 1.99, p = .136, η²ₚ = .002. Finally, for the Digit Span Sequencing, there was no significant main effect of language profile groups, F (2, 2405) = 2.06, p = .127, η²ₚ = .002, or language of assessment, F (1, 2405) = 0.94, p = .331, η²ₚ < .001. The interaction between language profile groups and language of assessment was not significant, F (2, 2405) = 0.246, p = .782, η²ₚ < .001. Discussion In this study, we investigated how language experience, primarily defined by AoA and language proficiency, influences cognition by examining differences between language groups across multiple cognitive domains. To this aim, we analyzed a large sample of cognitive data from the ALFA study cohort [53]. Our results indicate that cognitive test performance was influenced by language profile and, to some extent, by type of cognitive domain (linguistic vs. non-linguistic). Additionally, we found an effect of the language of assessment, which can affect test performance and potentially mask bilingual advantages. Non-linguistic domain In the non-linguistic domain, we predicted that Early High-Proficiency bilinguals would outperform Late Low-Proficiency bilinguals on tests involving attention and executive control, due to the combined benefits of early AoA, high language proficiency, and active use of both languages. We further expected that Late High-Proficiency bilinguals would show intermediate performance, with the negative effects of later AoA potentially offset by the benefits of higher proficiency and frequent language use. Our results suggest that both high-proficiency bilingual groups, regardless of their AoA, outperformed the Late Low-Proficiency bilinguals on the Coding subtest of the WAIS-IV. This subtest is associated with multiple cognitive processes, including processing speed, visual-motor coordination, short-term memory, and incidental learning. As such, it is difficult to determine whether the combined effects of AoA and language proficiency target a specific underlying cognitive process involved in test performance. However, performance on tests that directly assess verbal short-term memory suggest a distinct effect of AoA. Specifically, Early High-Proficiency bilinguals outperformed both Late High-Proficiency and Late Low-Proficiency bilinguals on the overall Digit Span score, an effect driven primarily by higher performance on the Digit Span Forward subtest. The patterns observed in both tests may reflect differences in the specific executive functions each test engages, and in the underlying cognitive processes supporting those functions, as well as the degree of bilingualism needed to attain a measurable cognitive benefit. While the Digit Span tests primarily assess verbal short-term memory, the group differences observed in the Coding subtest may more directly reflect enhanced processing speed rather than broader working memory advantages. Alternatively, rather than attributing the differences solely to specific cognitive processes or benefits, it is possible that the results are better explained by the degree of bilingual experience required to detect an effect. Notably, the Early High-Proficiency bilinguals, who had the highest level of bilingual exposure and use, may be more sensitive to subtle cognitive advantages, thus making group differences more detectable in this subgroup. Interestingly, no significant differences were observed between the groups on the Digit Span Backward or Sequencing tests. Although the high-proficiency bilinguals showed an advantage in tests involving speed and attentional control, as evidenced in both the Coding and Digit Span Forward tests, this benefit did not extend to more demanding working memory tests such as Digit Span Backward and Sequencing. This suggests that the cognitive advantage may lie more in attentional processing and speed than in the manipulation and maintenance aspects of working memory. No significant differences were found in other non-linguistic tests, such as the Visual Puzzles and Matrix Reasoning subtests of the WAIS-IV, which assess non-verbal abstract reasoning and visuospatial reasoning. Similarly, no differences were observed on the MMSE, which is expected given that scores below 26 were part of the exclusion criteria. This suggests that any modulation associated with bilingualism may be selective and specific to certain cognitive domains and tests, rather than reflecting a generalized enhancement of cognition. Indeed, the evidence for a bilingual advantage in these cognitive domains remains mixed, suggesting that speaking a second language may not have a direct impact on these cognitive processes, or that the benefits may be specific to certain language profiles or test characteristics. For instance, a meta-analysis reported a bilingual advantage in abstract and symbolic reasoning, however, the studies included primarily involved young participants [77]. Regarding working memory, there are studies reporting small to moderate bilingual advantages in this domain [77–79], however, other meta-analyses reported a null effect of bilingualism on working memory. For example, Degirmenci et al. found no clear evidence of a bilingual advantage in the updating domain, which is closely related to working memory, in healthy older adults [33]. Similarly, Lehtonen et al. reported that the already small effect sizes observed in working memory tests disappeared after correcting for publication bias [45]. Notably, in one study, monolinguals even outperformed bilinguals on the Digit Span Backward test [39]. Taken together, these results suggest that lifelong use of a second language, including continued use later in life, may modulate cognitive performance, though not uniformly across all domains. Our findings are consistent with those reported by Gallo et al. regarding the relationship between L2 proficiency and the efficiency of the attentional network [42]. They found that in healthy older adults, increasing levels of L2 proficiency predicted lower reaction times in incongruent trials of the Flanker test, while increasing years since L2 acquisition also predicted lower reaction times, but with a smaller beneficial impact. To some extent, this aligns with previous studies that have suggested that bilinguals are overall faster in performing tests that measured processing speed [3]. For example, in the Attention Network Test (ANT) [80], Costa et al. found that bilinguals were overall faster [81]. Desideri and Bonifacci also found better conflict performance and faster reaction times for bilingual adults on the ANT [82]. In another study, both early and late Chinese-English bilinguals had an advantage in conflict resolution compared to monolinguals on the ANT, with early bilinguals showing the greatest advantage [38]. Woumans et al. also found that bilinguals were faster on the ANT and exhibited a smaller congruency effect in the Simon task compared to monolinguals [16]. In the context of these results, tasks such as the Stroop, Flanker, and Simon were thought to measure enhanced inhibition. However, many findings were inconsistent with a simple inhibitory control explanation. For example, bilinguals often outperform monolinguals on congruent trials in conflict tasks where no inhibition is required, as well as on incongruent trials [6,59]. While the bilingual advantage was initially attributed to enhanced inhibitory control, some researchers now propose a broader framework of attentional control or increased processing efficiency [59,83]. Hilchey and Klein suggested that faster reaction times might reflect general processing speed rather than specific executive functioning advantages [84]. Linguistic domain For verbal episodic memory performance, we found no significant differences across language profile groups or language of assessment for any of the MBT measures. These results are in agreement with our hypothesis that potential cognitive benefits do not extend uniformly to all cognitive domains, particularly those evaluated with a test that relies on a verbal or linguistic component. For instance, Fernandes et al. found that bilingual older adults recalled fewer words than age-matched monolinguals in a free recall test, likely due to the high lexical demands of the test [85]. To some extent, this supports the idea that a verbal disadvantage can counteract the executive control benefits associated with bilingualism [86], and that when the verbal component is reduced, the bilingual advantage becomes more evident [40]. Nevertheless, verbal fluency results were not in line with our hypothesis. Both high-proficiency bilingual groups performed significantly better than the Late Low-Proficiency bilinguals. This finding contrasts with the broader literature, which typically associates bilingualism with disadvantages in lexical retrieval tests. Such disadvantages are often attributed to reduced exposure to each individual language compared to a monolingual speaker, and increased lexical interference from the constantly activated non-target language [45,57]. However, some studies have reported exceptions and mixed findings [87]. Costumero et al. found that while both monolingual and bilingual groups experienced cognitive decline, including in semantic fluency, over a 7-month follow-up period, monolinguals showed a greater overall cognitive decline than bilinguals, suggesting more preserved performance in bilingual individuals [88]. In cross-sectional studies, when bilinguals are matched with monolinguals on vocabulary size as a proxy for language proficiency, they either outperform [89] or perform comparably to monolinguals [47,90]. Similarly, Patra et al. reported no significant differences in a semantic fluency test between Bengali-English bilinguals and English monolinguals matched on receptive vocabulary, age, education, and non-verbal intelligence [91]. In the same way that cognitive benefits associated with bilingualism may be domain- and test-specific, potential disadvantages may also be limited to particular contexts. For example, Bialystok et al. reported that monolinguals produced more words only when compared with low-proficiency bilinguals, while no significant differences were observed between monolinguals and high-proficiency bilinguals [47]. Our results exemplify this by demonstrating performance differences within the bilingual population based on their proficiency levels, with Early and Late High-Proficiency groups scoring similarly in the semantic fluency test and outperforming the Late Low-Proficiency bilingual group. Language of assessment In the semantic fluency test, participants assessed in Spanish produced more words on average than those assessed in Catalan, suggesting that lexical retrieval is facilitated when the test is administered in the participant’s dominant language. This effect was most pronounced among late bilinguals. A similar pattern emerged in verbal short-term memory evaluated with the Digit Span Forward test, with Spanish assessments having better results than Catalan assessments, again driven by the performance of both late AoA bilingual groups. Prior research has showed better digit span performance in participant first language [92] or language of schooling [93,94], which was Spanish for both late AoA bilingual groups. In addition, the interaction between group and language of assessment was significant in both Digit Span and Digit Span Forward. While no significant group differences were found in Spanish assessments, Catalan assessments revealed that Early High-Proficiency bilinguals outperformed both late AoA groups. This suggests that even in relatively simple cognitive tests, verbal processing demands in a bilingual's L2 may subtly hinder performance, particularly when rapid lexical access is required, which can directly impact performance of late AoA bilinguals despite high L2 proficiency. Language of assessment also influenced performance in non-verbal tests such as Coding and Matrix Reasoning from the WAIS-IV. This was not anticipated in our hypotheses. Interestingly, these effects appear to be driven by the small group of Late Low-Proficiency participants who completed the assessment in Catalan. Given the small size of this subgroup and the unexpected direction of the effect, the finding is difficult to interpret and may reflect sample variability or other uncontrolled factors, rather than cognitive differences. Influence of bilingual language experience on cognitive performance The results from the verbal short-term memory tests suggest a specific advantage for early bilinguals. Early AoA is typically associated with greater advantages due to increase experience of controlling two languages. For example, in one study early AoA bilinguals exhibited significantly smaller interference cost on the Flanker test compared to late bilinguals and monolinguals [55]. Additionally, the observed benefits of early AoA may result from the combined effects of earlier exposure, enhanced proficiency, and subsequently greater frequency of use across both languages. In a study with Spanish-Catalan bilinguals, higher frequency of language use was associated with better working memory and phonemic fluency, measured as a composite score including Letter–Number Sequencing, Corsi, phonemic fluency, and Digit Span tests [74]. Interestingly, greater language use was also linked to increased white matter deterioration, yet participants maintained equivalent cognitive performance across domains, suggesting a cognitive reserve effect. Although they did not include direct measures of language proficiency or AoA, the sample was composed of highly educated Spanish-Catalan bilinguals that likely overlaps with the high-proficiency bilingual profiles identified in our study. While early AoA is strongly associated with higher language proficiency and active use of both languages that may lead to a better cognitive performance, specially in some specific domains such as verbal short-term memory, high proficiency itself was also linked to cognitive benefits, even among bilinguals with a late AoA. This implies that language proficiency may have an independent effect on cognition. In our study, high proficiency in both Spanish and Catalan was closely linked to more frequent and active bilingual language use in adulthood. This relationship is expected, as greater language use is likely to support and reinforce language proficiency, and viceversa [1,9,49,56,95,96]. While the relationship may be bidirectional, meaning that high proficiency may promote greater language use, and frequent use may reinforce proficiency, both scenarios suggest a positive feedback loop in bilingual language engagement. The specific type of proficiency may also be an important factor, in a previous study, Calabria et al. found that self-reported Catalan proficiency in speaking was the most important variable when calculating a bilingualism composite score that ranged from passive to active bilingualism [24]. Similarly, production measures of proficiency in Catalan, rather than comprehension measures, were most strongly associated with cognitive benefits in our study. In summary, our results indicate that high-proficiency Spanish-Catalan bilingual older adults who actively use both languages showed enhanced cognitive performance in specific domains compared to passive, Spanish-dominant bilinguals. These findings underscore the idea that the degree and nature of bilingual engagement, rather than just being bilingual, are key factors driving these cognitive benefits [6,24,97–99]. Our research contributes to the growing body of evidence that supports the unique and beneficial role of specific aspects of bilingual experience to both cognitive and neural reserve, which have been consistently associated with protective effects against age-related cognitive decline and enhanced resilience in the face of MCI or AD [5,6,98,100,101]. Additionally, our findings suggest that the benefits of lifelong L2 use are domain- and test-specific, highlighting that the bilingual advantage largely depends on specific aspects of language experience and how bilingualism is defined and measured. Our study has several limitations. First, self-reported measures of language use and proficiency are subject to bias and may not fully capture bilingual experience. Future research should incorporate standardized instruments such as The Language and Social Background Questionnaire (LSBQ) [102] or the Language Experience and Proficiency Questionnaire (LEAP-Q) [103,104] alongside objective proficiency measures. Second, although Holm-adjusted pairwise comparisons were applied within each cognitive domain, we did not correct for multiple testing across the 13 separate ANCOVAs, leaving a potential for inflated Type I error. Finally, bilingualism does not exist in isolation and its effects on cognition can be confounded or influenced by socioeconomic status [59,105] or other lifestyle factors such as occupational complexity or engaging in physical, intellectual and social activities as well as music training [6,73,97,106]. In our study, we attempted to account for these potential confounding variables with a proxy of cognitive reserve measured with the CRQ, which includes questions about the educational background, occupational complexity, social and physical activities and cultural and intellectual pursuits [71]. However, future research should include more detailed measures of socioeconomic status and lifestyle factors to further isolate the effects of bilingualism. Conclusions In conclusion, our findings highlight that the cognitive effects of bilingualism in aging are not uniform but domain-specific, with benefits most evident in tasks involving attentional control and processing speed, rather than across all cognitive domains. Moreover, the extent of cognitive benefits depends on specific aspects of the bilingual experience, such as language proficiency and AoA. These results have both theoretical and clinical implications. Theoretically, they deepen our understanding of the relationship between cognition, bilingualism, and aging within the framework of cognitive reserve. Clinically, they inform best practices for assessing language and cognitive deficits in bilingual individuals and suggest that second language use may serve as a valuable strategy for preventing cognitive decline and could be potentially integrated into cognitive training programs. Abbreviations AoA:Age of Acquisition; ALFA: Alzheimer’s and Families; AD: Alzheimer’s Disease; MCI: Mild Cognitive Impairment; CR: Cognitive Reserve; L1: first language; L2: second language; MMSE: Mini-Mental State Examination; MBT: Memory Binding Test; TFR: Total Free Recall; TPR: Total Paired recall; TDFR: Total Delayed Free Recall; TDPR: Total Delayed Paired Recall; WAIS: Wechsler Adult Intelligence Scale; CRQ: Cognitive Reserve Questionnaire; ANOVA: Analysis of Variance; ANCOVA: Analysis of Covariance; ANT: Attention Network Test. Declarations Acknowledgments This publication is part of the ALFA study. The authors would like to express their most sincere gratitude to the ALFA project participants, without whom this research would have not been possible. Collaborators of the ALFA study are: Clara Abadías, Müge Akinci, Andrea Ambite, Federica Anastasi, Ricardo Aquite, Sara Aragó, Eider Arenaza Urquijo, Kahina Baouche, Ricardo Berbería, Annabella Beteta, Marco Bianchi, Helena Blasco, Anna Brugulat-Serrat, Raffaele Cacciaglia, Jordi Camí, Fernanda Campos Strazzi, Lidia Canals Gispert, Alba Cañas, Diego Cascales, José Contador, Marta Crous-Bou, Irene Cumplido, Rafael Dal-Ré, Marina de Diego, Neus de la Cruz-Sanchez, Marta del Campo, Carme Deulofeu, Ruth Dominguez, Maria Emilio, Isabel Estragués, Tavia Evans, Carles Falcón, Karine Fauria, Marta Félez, Aida Fernandez, Alba Fernández Bonet, Ana Fernández-Arcos, Elisabeth Ferrer i Mairal, Jordi Freixa, Sherezade Fuentes, Clara Gallay, Marina García, Manuel Garfia, Fernando Gaston Rossi, Patricia Genius, Juan Domingo Gispert, José María González de Echávarri, Armand González-Escalante, Xavier Gotsens, Nina Gramunt Fombuena, Laura Gusó, Ana Harris, Laura Hernandez, Felipe Hernández-Villamizar, Gema Huesa, Jordi Huguet, Laura Iglesias, Esther Jiménez, Michalis Kassinopoulos, Iva Knezevic, Maria León, Aldana Lizarraga, David López-Martos, Ferran Lugo, Paula Marne, Carlota Medina, Francisco Javier Meléndez, Tania Menchón, Marta Milà Alomà, Carolina Minguillón, José Luis Molinuevo, Cristina Mustata, Irene Navalpotro, Grégory Operto, Paula Ortiz, Eva Palacios, Eleni Palpatzis, Wiesje Pelkmans, Jordi Peña-Casanova, Isabel Perez, Aitana Plaza, Albina Polo, Clara Porta, Sandra Pradas, Aleix Puig, Andreea Rădoi, Jaume Roca Alcaraz, Albert Rodrigo-Pares, Noelia Rodríguez de Guzmán Gallego, Blanca Rodríguez-Fernández, Maria Roman, Sarata Sall Sall, Gemma Salvadó, Mireia Sánchez, Pau Sánchez, Sabrina Segundo, Mahnaz Shekari, Lluis Solsona, Anna Soteras, Laura Stankeviciute, Marc Suárez, Pilar Tartière-González, Laia Tenas, Javier Torres-Torronteras, Núria Tort Clotet, Elisabet Zhan Travesset Muntada, David Vállez, Montserrat Vilà, Marc Vilanova, Natalia Vilor-Tejedor. Author contributions Conceptualization: SG; MC; Methodology: SG; MC; Formal analysis: SG; Resources: GS; OG; Data curation: GS; OG; Writing – original draft: SG; MC; Writing – review & editing: SG; GS; OG; MS; LS; FP; MC; Visualization: SG; Supervision: FP; MC; Project administration: MC; OG.; Funding acquisition: MC. All the authors contributed to the revisions of the manuscript and read and approved the submitted version of the manuscript. Funding The research leading to these results has received funding from “la Caixa” Foundation, under agreement LCF/PR/SC22/68000001. Additional funding was obtained from: Fondo de Investigación Sanitaria (FIS), Instituto de Salud Carlos III under grant PI12/00326. Additional support has been received from the Universities and Research Secretariat, Ministry of Business and Knowledge of the Catalan Government under the grant no. 2021 SGR 00913. This work is part of the project PID2023-149755OB-I00, funded by the Ministry of Science and Innovation, the State Research Agency 10.13039/501100011033 and the European Regional Development Fund FEDER, EU. MS is employed by Hospital de la Santa Creu i Sant Pau. His research is supported by funding from the Spanish Institute of Health Carlos III co-funded by the European Union (Juan Rodés research grant JR18-00018; Fondo de investigación sanitaria grant PI19/00882), the Department of Research and Universities from the Generalitat de Catalunya (2021 SGR 00979), the Alzheimer’s Association clinician scientist fellowship (AACSF-22-972945), and the National Institutes of Health (R01AG080470). FP is partially funded by UCLH Biomedical Research Centre. GSB is supported by the Instituto de Salud Carlos III (ISCIII) through the project CP23/00039 (Miguel Servet contract). Availability of data and materials The data that support the findings of this study are available from the corresponding author, upon reasonable request. Ethics approval and consent to participate This study used anonymized data provided by the Barcelona Beta Research Center (BBRC) as part of the ALFA study. The ALFA study protocol was approved by the independent Ethics Committee Parc de Salut Mar Barcelona and registered at ClinicalTrials.gov (ALFA Identifier: NCT01835717). It was conducted in accordance with the directives of the Spanish Law 14/2007, of 3rd of July, on Biomedical Research (Ley 14/2007 de Investigación Biomédica). All participating subjects signed the study’s informed consent form, which was approved by the Independent Ethics Committee ‘Parc de Salut Mar’, Barcelona. The study was conducted according to the Declaration of Helsinki. References de Bruin A. Not All Bilinguals Are the Same: A Call for More Detailed Assessments and Descriptions of Bilingual Experiences. 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The Language Experience and Proficiency Questionnaire (LEAP-Q): assessing language profiles in bilinguals and multilinguals. J Speech Lang Hear Res JSLHR. 2007;50:940–67. Calvo A, Bialystok E. Independent effects of bilingualism and socioeconomic status on language ability and executive functioning. Cognition. 2014;130:278–88. Bak TH. The impact of bilingualism on cognitive ageing and dementia: Finding a path through a forest of confounding variables. Linguist Approaches Biling. 2016;6:205–26. Additional Declarations No competing interests reported. Supplementary Files AdditionalFile.docx Additional file 1: Table S1: Descriptive statistics for sociodemographic variables, language and cognitive profile. Legend: MMSE: Mini-Mental State Examination; CRQ: Cognitive Reserve Questionnaire; MBT: Memory Binding Test; WAIS: Wechsler Adult Intelligence Scale. Table S2: Language Use Questionnaire. Table S3: Language Use Questionnaire answers in percentages. 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1","display":"","copyAsset":false,"role":"figure","size":174872,"visible":true,"origin":"","legend":"\u003cp\u003ePercentages of language use responses by language profile group. Late Low: Late Low-Proficiency bilinguals; Late High: Late High-Proficiency bilinguals; Early High: Early High-Proficiency bilinguals.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7796112/v1/88d1da1771efcf63466940a3.png"},{"id":95914403,"identity":"edbaea82-010d-440c-bfe5-5fae7106189b","added_by":"auto","created_at":"2025-11-14 11:13:14","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":171450,"visible":true,"origin":"","legend":"\u003cp\u003eEstimated marginal means of cognitive test scores by language profile and language of assessment, adjusted for covariates.\u003cstrong\u003e \u003c/strong\u003eAoA: Age of acquisition; MMSE: Mini-Mental State Examination; MBT: Memory Binding Test; TFR: Total Free Recall; TPR: Total Paired recall; TDFR: Total Delayed Free Recall; TDPR: Total Delayed Paired Recall. Error bars represent standard errors of the adjusted means. S vs. C* indicates a significant difference in language of assessment for that variable. An asterisk indicates a significant difference between language profile (\u003cem\u003ep\u003c/em\u003e \u0026lt; .05).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7796112/v1/77839a3dd485ee815dd386f6.png"},{"id":99797215,"identity":"77d05b4d-4e4f-4360-a5c6-f1a169b5af5e","added_by":"auto","created_at":"2026-01-08 13:45:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1451653,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7796112/v1/ebf280d1-ba77-42a6-beca-f0c0fb05bf53.pdf"},{"id":95914406,"identity":"d39f104d-df88-4144-bfa7-518ae2dd90ab","added_by":"auto","created_at":"2025-11-14 11:13:14","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":15059,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAdditional file 1: Table S1: \u003c/strong\u003eDescriptive statistics for sociodemographic variables, language and cognitive profile. Legend: MMSE: Mini-Mental State Examination; CRQ: Cognitive Reserve Questionnaire; MBT: Memory Binding Test; WAIS: Wechsler Adult Intelligence Scale.\u003cstrong\u003e Table S2: \u003c/strong\u003eLanguage Use Questionnaire. \u003cstrong\u003eTable S3: \u003c/strong\u003eLanguage Use Questionnaire answers in percentages.\u003c/p\u003e","description":"","filename":"AdditionalFile.docx","url":"https://assets-eu.researchsquare.com/files/rs-7796112/v1/912f35072252e250bc232dd3.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Bilingualism and cognition: The impact of age of acquisition, language use and proficiency in healthy older adults","fulltext":[{"header":"Background","content":"\u003cp\u003eDespite a growing body of research on the cognitive advantages of bilingualism, evidence for a positive effect remains inconclusive or appears limited to specific populations, tests, or cognitive domains [1\u0026ndash;4]. This is especially relevant in the context of aging, where the nature of the protective role of bilingualism against cognitive decline continues to be debated [5,6].\u003c/p\u003e\u003cp\u003eAmong the reasons for this inconsistency across studies, it has been suggested that the lack of replication of research findings may stem from the complex nature of bilingualism, which is a highly diverse and dynamic experience shaped by substantial individual differences. For instance, factors such as age of acquisition (AoA), language proficiency, frequency of use, and language-switching practices, can all influence neural structures and cognitive outcomes [1,7\u0026ndash;9]. These findings highlight that bilingualism\u0026rsquo;s effects on cognition are complex and highly individualized, challenging the traditional dichotomy between a monolithic view of bilingualism and monolingualism.\u003c/p\u003e\n\u003ch3\u003eBilingualism, cognitive reserve, and aging\u003c/h3\u003e\n\u003cp\u003eInvestigating the potential positive effects of bi- and multilingualism on cognition is crucial for understanding the underlying mechanisms that may protect against cognitive impairment and dementia. This is not only a theoretical question but also has important implications for policies related to healthy aging and the reduction of age-related disorders [10\u0026ndash;12].\u003c/p\u003e\u003cp\u003eIndeed, in recent years, there has been a notable increase in studies exploring the potential cognitive benefits of speaking multiple languages in patients with neurodegenerative diseases. One of the first examples was a study conducted in Canada by Bialystok et al. [13] that showed a 4-year delay in Alzheimer\u0026rsquo;s Disease (AD) onset for bilinguals, compared to monolingual peers. Craik et al. later confirmed the same time gap in a follow-up study of the same sample [14]. Other studies followed their work, replicating their results of bilingualism delaying effect on AD in other cultural backgrounds as India [15], Belgium [16], China [17] and the US [18]. This effect has been reported in different meta-analysis [19\u0026ndash;21] and there is also evidence of delaying effects of bilingualism in MCI population [22\u0026ndash;24]. Other studies also showed a reduced incidence of MCI [25] and AD [26] in multilingual countries (for a review, see [6]). However, the bilingual advantage in cognitive decline and dementia prevention has not been consistently observed across all research findings [27,28].\u003c/p\u003e\u003cp\u003eThe positive effect of bilingualism against cognitive decline and dementia has often been attributed to the concept of cognitive reserve. According to Stern et al., cognitive reserve is defined as the discrepancy between the level of age-related neural deterioration and the extent of cognitive impairment [29]. It encompasses the brain's ability to adapt and reorganize through processes such as increased efficiency, capacity, and flexibility of neural networks in response to aging, damage, or disease. These adaptive mechanisms have also been suggested for bilingualism [5,6,30].\u003c/p\u003e\u003cp\u003eHowever, the relationship between bilingualism and cognitive reserve remains complex, particularly when considering the interaction between brain health and cognitive performance. Although, some researchers suggest that the bilingual advantage may be more evident in older adults, compared to young bilinguals, as age-related cognitive decline provides greater opportunity for bilingualism to generate a protective effect [31]. For example, Grant et al. proposed that the previously reported bilingual advantage in episodic memory among older adults, can be explained by enhanced prefrontal function, better preservation of posterior brain regions, and increased connectivity between prefrontal and posterior areas [32], suggesting that the advantages in episodic memory and executive control among bilinguals may be due to the overlap between brain regions associated with cognitive reserve and those involved in memory and language.\u003c/p\u003e\u003cp\u003eMeta-analyses show mixed evidence for a bilingual advantage in executive functions among older adults. Degirmenci et al. [33], reported that benefits appear limited to inhibitory control in individuals aged 65\u0026ndash;75, with no consistent effects on working memory or task-switching, largely due to variability in language experience, tasks, and participant characteristics. Similarly, Ware et al. found that the reliability of the bilingual advantage on cognition depends on the type of test employed, suggesting that it is not an all-or-nothing phenomenon [4].\u003c/p\u003e\u003cp\u003eDespite some evidence indicating that bilingualism may contribute to cognitive reserve and healthy aging, we need a clearer understanding of the specific aspects of the bilingual language experience that offer the greatest protective benefits against neurocognitive decline.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eBilingual Language Experience\u003c/h2\u003e\u003cp\u003eDifferent variables associated with bilingualism have been proposed as key factors influencing the reliability of its effects on cognition. Indeed, there has been growing interest in exploring how differences in bilingual language experiences including AoA of a second language (L2), L2 proficiency, and daily language use, particularly in terms of frequency and switching practices, can influence both language-related processes and executive control [1,8,34,35]. However, these variables have been primarily explored in young adults, and studies involving cognitively unimpaired older individuals remain limited.\u003c/p\u003e\u003cp\u003eThe evidence regarding the effect of AoA on executive control is mixed. In this regard, studies with children showed that early bilinguals performed better in conflict monitoring [36]. Others have shown that young early bilinguals may experience reduced task-switching costs [37], while late bilinguals with frequent language use may show a greater advantage in conflict resolution [38]. Additionally, Torres et al. found that earlier L2 AoA was associated with better performance on the Digit Span Backward subtest [39], while Schroeder and Marian reported that early L2 AoA was linked to enhanced episodic recall [40].\u003c/p\u003e\u003cp\u003eLanguage proficiency is another important aspect of the bilingual language experience that has been demonstrated to influence executive control [41]. In particular, it has been shown that higher L2 proficiency predicted better executive control performance [42,43] and is associated with better conflict monitoring [44]. Some studies have found that bilinguals tend to have smaller vocabulary sizes and perform worse in picture naming and fluency tests [45,46], but in letter fluency tests, that require higher executive control demands, high proficiency bilinguals outperformed low proficiency bilinguals [47]. Finally, Rosselli et al. found that bilinguals with high proficiency in both their L1 and L2 scored higher on most executive function tests than those with low proficiency in both languages, while bilinguals proficient in only one language (L1 or L2) scored in between these two groups [48].\u003c/p\u003e\u003cp\u003eBilinguals differ not only in proficiency and AoA, but also in language usage, another key variable in defining bilingualism. Contextual factors can lead individuals who acquired two languages early in life to primarily use only one, while late L2 AoA bilinguals may shift their dominant language over time. Therefore, it is essential to examine language usage alongside other factors such as AoA and language proficiency. Research on executive control indicates that active use of both languages is associated with enhanced goal maintenance and conflict monitoring [49]. Other studies suggest that performance in switching tasks may be influenced by the frequency of daily language switching [50,51]. Additionally, other studies have found enhanced task-switching performance among active bilinguals, but no significant differences on the Simon task between passive bilinguals and monolinguals [52].\u003c/p\u003e\u003cp\u003eAlthough these variables have primarily been explored in younger individuals and the findings remain inconclusive, they are highly relevant to our study, as they will guide our analysis in defining the language profile of participants in our large sample of cognitively unimpaired older adults.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eThe present study\u003c/h3\u003e\n\u003cp\u003eIn this study, we investigated the impact of language experience on cognitive aging by analyzing the cognitive performance of cognitively unimpaired individuals aged 45\u0026ndash;74 years from the ALFA study [53], focusing on age of acquisition, proficiency, and language use. The cohort, recruited in Catalonia (Spain), provides considerable variability in linguistic backgrounds due to the co-official status of Catalan and Spanish. According to the Statistical Institute of Catalonia, in 2023 the region had a population of approximately 7.9\u0026nbsp;million inhabitants. In the 45\u0026ndash;74 age group, 93.9% of individuals report understanding Catalan, 84% can read it, 79.7% are able to speak it and 62.5% can write it. With respect to first language, 34% of middle-aged adults (45\u0026ndash;64 years) identify Catalan and 44.7% identify Spanish, whereas in the older population (\u0026gt;\u0026thinsp;65 years), the proportions shift to 40.6% for Catalan and 45.4% for Spanish [54].\u003c/p\u003e\u003cp\u003eFor the purposes of this study, three language profiles were defined: Early High-Proficiency bilinguals, who acquired both languages in early childhood; Late High-Proficiency bilinguals, who acquired Catalan after Spanish but attained high proficiency; and Late Low-Proficiency bilinguals, who primarily use Spanish and exhibit limited active competence in Catalan. These group distinctions establish the framework for the hypotheses addressed in the present work.\u003c/p\u003e\u003cp\u003eOur analysis focuses on both linguistic and non-linguistic cognitive domains, which enables us to test the hypothesis that, for non-linguistic cognitive domains, Early High-Proficiency bilinguals should outperform Late Low-Proficiency bilinguals, the latter of whom we consider to have a profile more similar to monolinguals. Late High-Proficiency bilinguals will fall in the middle, given the influential role of the L2 AoA.\u003c/p\u003e\u003cp\u003eIn particular, we expect that for non-verbal abstract reasoning, visuospatial reasoning, working memory and processing speed, Early High-Proficiency bilinguals should outperform Late Low-Proficiency bilinguals, as higher language proficiency is associated with better executive control, particularly in working memory and conflict monitoring [42,44]. Additionally, AoA also plays a role in cognitive flexibility and conflict monitoring [36,39,55], and in the active use of the two languages [42,56]. For Late High-Proficiency bilinguals, we expect an effect of AoA, which might be counteracted by the positive effect of higher language proficiency and active use of the two languages, bringing their performance closer to that of Early High-Proficiency bilinguals.\u003c/p\u003e\u003cp\u003e As for tests with a verbal or linguistic component, we hypothesized that while bilingualism may support the maintenance of episodic memory in older adulthood through its positive effects on executive functioning [3,4,6,33,40,42], this advantage would be reduced or absent in tests that place high demands on lexical processing, such as free recall of words, due to bilinguals\u0026rsquo; known disadvantages in lexical access and retrieval [40,57]. Additionally, this disadvantage should be more evident for verbal fluency, which relies heavier on a linguistic component. We anticipate that Late Low-Proficiency bilinguals who primarily use one language may perform similarly to, or even better than, highly proficient bilinguals (both early and late) as previous research has shown a bilingual disadvantage in tests involving lexical retrieval [33,39,45,58]\u003c/p\u003e\u003cp\u003eRegarding the relationship between bilingual language variables, early AoA is expected to be related to higher proficiency in L2. However, late bilinguals who frequently use both languages may still exhibit cognitive advantages compared to other late bilinguals with passive exposure to Catalan [38].\u003c/p\u003e\u003cp\u003eOverall, we expect higher L2 proficiency, earlier L2 AoA, and active use of both Spanish and Catalan to be associated with better executive control in healthy older adults. This is likely due to the lifelong engagement in language control mechanisms, which may enhance general executive control [2,59].\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eParticipants were selected from the database of the ALFA parent cohort, established by the Barcelonaβeta Brain Research Center [53]. The original aim of the ALFA parent cohort study was to prospectively follow a cohort of cognitively unimpaired individuals, most of whom are offspring of AD patients. To achieve this, the inclusion criteria for enrolment in the study were: (1) being a Spanish and/or Catalan speaker; (2) aged between 45 and 74 years; and (3) providing consent to study procedures and tests, which included a clinical interview, lifestyle and health questionnaires, cognitive assessments, and blood tests for genotyping.\u003c/p\u003e\n\u003cp\u003eExclusion criteria were: (1) cognitive performance not meeting the prespecified cutoffs of Mini-Mental State Examination [60,61] (MMSE) \u0026lt; 26, or Memory Impairment Screen [62,63] \u0026lt; 6, or Time-Orientation subtest of the Barcelona Test II [64] \u0026lt; 68, or verbal semantic fluency [65,66] (animals) \u0026lt; 12; (2) Clinical Dementia Rating scale [67] \u0026gt; 0; or (3) The presence of a) major psychiatric disorders, b) severe auditory or visual disorders, c) neurodevelopmental and/or psychomotor disorder, d) significant disease that could interfere with cognition, e) neurological disorders or brain injury that could affect participant’s cognition and f) suspected pattern of family history of autosomal dominant AD [53]. \u003c/p\u003e\n\u003cp\u003eAccording to these inclusion and exclusion criteria, 2743 participants were recruited [53]. For the present study, we excluded 81 participants with missing data on the language use questionnaire, 28 participants without L2 AoA information and 129 participants who reported using languages other than Spanish or Catalan. An additional three were removed due to missing age or Semantic Fluency data, resulting in 2502 participants for subsequent analyses.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData extraction and variable selection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor this study, we extracted the following information from 2502 participants (See Table S1 in Additional File for descriptive statistics of sociodemographic variables, language and cognitive profile of the sample):\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ea. Sociodemographic data. \u003c/strong\u003eWe collected participant's age, years of education and sex.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb. Neuropsychological test scores. \u003c/strong\u003eFor cognitive assessment, we included the following tests: (1) MMSE [60,61] for global cognition; (2) Semantic Fluency test (animals), for verbal fluency [65,66]; (3) the Memory Binding Test (MBT) [68] to assess verbal episodic memory; (4) from the Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV) [69] the Matrix Reasoning subtest for non-verbal abstract reasoning; (5) the Visual Puzzles subtest for visuospatial reasoning; (6) the Digit Span subtest to assess verbal short-term and working memory; and (7) the Coding subtest for processing speed and visual-motor coordination. Participants could choose whether to perform the neuropsychological assessment in Catalan or Spanish. For further details on the evaluation procedure, see [53].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ec. Language profile. \u003c/strong\u003eThe language history was collected fromparticipants with a questionnaire that was created ad-hoc for the study. For a similar version, see Calabria et al. [70]. The information collected for Spanish and Catalan was: \u003c/p\u003e\n\u003cp\u003e● \u003cstrong\u003eAge of language acquisition. \u003c/strong\u003eParticipants were asked about the time they began speaking each language. \u003c/p\u003e\n\u003cp\u003e● \u003cstrong\u003eLanguage proficiency. \u003c/strong\u003eThis was collected as self-reported proficiency for speaking, comprehension, reading, and writing in each language using a five-point scale (1 = not at all, 2 = low, 3 = fairly good, 4 = good, and 5 = very good)\u003c/p\u003e\n\u003cp\u003e● \u003cstrong\u003eLanguage use. \u003c/strong\u003eParticipants were asked about which language they preferred to use in three different contexts among four options: “Spanish”, “Catalan”, “No preference between Catalan and Spanish” and “Other languages”. Specifically, the information gathered for each participant in the three contexts was: seven items regarding childhood, they were asked about the language usually spoken with (1) their mother; (2) their father; (3) other family members living with them; (4) other extended family members; (5) friends and neighbours; (6) friends at school; and (7) the language in which they received their education. In five items regarding current social language use, participants were asked which language they use (1) at home (with a partner, children, etc.); (2) with other family members; (3) at work; (4) with friends or neighbours; and (5) in other social contexts such as the bank or supermarket. Finally, three items regarding internal language use, including the language they use when (1) talking to themselves; (2) performing arithmetic operations or counting; and (3) for insulting or swearing. Participants who reported using languages other than Spanish or Catalan were excluded from the study (See Table S2 Additional File for full questions).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ed. Cognitive Reserve Questionnaire (CRQ) \u003c/strong\u003e[71]\u003cstrong\u003e. \u003c/strong\u003eThis consists of 8 items that evaluate the educational background, occupational complexity, social and physical activities and cultural and intellectual pursuits. The 8 items generate a score that serves as a quantitative proxy of cognitive reserve, maximum total score is 25 points and the items are: (1) formal education (0-5 points); (2) parental formal education (0-2 points); (3) attendance to courses (0-3 points); (4) occupation (0-4 points); (5) musical education (0-2 points); (6) languages spoken (0-3 points); (7) frequency of reading (0-4 points); and (8) cognitively stimulating activities (0-2 points). To control the effect of cognitive reserve, we computed an adjusted cognitive reserve score by removing the language and education items in order to avoid correcting multiple times for education or language profiles.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFirst, we grouped our sample based on Catalan proficiency and AoA. To define participant groups based on their bilingual language experience, variables with minimal variability were excluded, as they were unlikely to contribute meaningfully to group differentiation. Specifically, Catalan comprehension and reading proficiency, Spanish AoA, and all Spanish proficiency measures.\u003c/p\u003e\n\u003cp\u003eGroup classification was performed using fixed thresholds applied to AoA of Catalan (in years) and Proficiency as the mean self-reported value of Writing and Speaking proficiencies. Participants with Catalan proficiency scores of 3 or lower were categorized as having low proficiency, whereas those with scores of 4 or above were classified as having high proficiency. Based on previous literature [33,38,45,72,73], the age of 6 was chosen as the cutoff for early Catalan AoA, as key brain and executive function developments occur in early childhood, often before formal schooling. Those who acquired Catalan at age 6 or later were classified as late bilinguals. This procedure resulted in four theoretically interpretable language profile groups: (1) Early High-Proficiency Bilinguals (n=1559); (2) Early Low-Proficiency Bilinguals (n=537); (3) Late High-Proficiency Bilinguals (n=319); and (4) Late Low-Proficiency Bilinguals (n=87). Participants in the Early Low-Proficiency Bilingual group were excluded from further analyses since native exposure is unlikely to result in low proficiency [24,33,55], specially in the context of Catalonia due to constant exposure to both Catalan and Spanish [24,74]. Their classification likely reflected data entry or self-reporting errors. The final sample was 2415 participants.\u003c/p\u003e\n\u003cp\u003eSecond, we conducted an Analysis of Variance (ANOVA) aimed to identify differences in language and sociodemographic variables (age, years of education and cognitive reserve) across the three language profile groups. Normality was assessed using the Shapiro-Wilk test, and homogeneity of variances using Levene’s test. Due to violations of homogeneity and unequal group sizes, we employed Welch’s ANOVA, which is robust to heteroscedasticity and unequal sample sizes, with language profile group as the between-subjects factor. Although traditional ANOVA assumes normality, Welch’s ANOVA is robust to moderate violations, particularly in larger samples. Omega squared (ω²) was used to estimate effect sizes. When Welch’s ANOVA yielded significant effects, Games-Howell post hoc tests were conducted to perform pairwise comparisons, as this method is specifically designed to handle unequal variances and sample sizes. In addition, a Chi-squared test of independence was conducted to examine potential differences in sex distribution across the three language profile groups.\u003c/p\u003e\n\u003cp\u003eThird, an Analysis of Covariance (ANCOVA) with multiple covariates was conducted to examine the effects of language profile group (3 levels) and the language of assessment (Catalan or Spanish), controlling for age, years of education, sex, and adjusted cognitive reserve score, on 13 neuropsychological test scores: (1) MMSE; (2) Semantic Fluency; (3) MBT Total Free Recall; (4) MBT Total Paired Recall; (5) MBT Total Delayed Paired Recall; (6) MBT Total Delayed Free Recall; (7) WAIS-IV Coding; (8) WAIS-IV Matrix Reasoning; (9) WAIS-IV Visual Puzzles; (10) WAIS-IV Digit Span Total Score; (11) Digit Span Forward; (12) Digit Span Backward; and (13) Digit Span Sequencing. To enable direct comparisons across different cognitive measures and groups, z-scores were computed within the whole sample for all test scores. Most participants in the Early High-Proficiency and Late Low-Proficiency bilingual groups completed the assessments in their dominant language. Only a small subset of Late Low-Proficiency bilinguals opted to complete the assessment in Catalan, their non-dominant language and 41% of participants in the Late High-Proficiency group chose to be assessed in Catalan, despite Spanish being their first acquired language. The ANCOVA model included main effects of language profile group and language of assessment, as well as their interaction (language profile group × language of assessment). Type III sums of squares were used to accommodate unbalanced group sizes and interaction effects. Effect sizes were reported as partial eta squared (η²ₚ). When significant main effects or interactions were found, pairwise comparisons of estimated marginal means were conducted using the emmeans package in R, with p-values adjusted using the Holm method to control for multiple comparisons.\u003c/p\u003e\n\u003cp\u003eWe observed unequal variances (Levene's test, \u003cem\u003ep\u003c/em\u003e \u0026lt; .05) in MBT Total Delayed Free Recall, WAIS Matrix Reasoning, and Digit Span Sequencing. To address this, we used squared transformation, which most effectively improved variance homogeneity for each affected variable. For MMSE and MBT Total Paired Recall, none of the transformations successfully corrected variance inequality. MMSE scores were likely influenced by a ceiling effect due to the exclusion criterion (scores \u0026lt; 26), and MBT Paired Recall scores were left-skewed. For these variables, we applied robust ANCOVA using heteroscedasticity-consistent standard errors (HC3) via the Anova() function from the car package [75] in R (Type III sums of squares, robust = TRUE), allowing valid inference despite violations of homoscedasticity and normality. For all other variables, Levene’s tests were non-significant (\u003cem\u003ep\u003c/em\u003e \u0026gt; .05), indicating homogeneity of variances. All analyses were performed using R software [76]. \u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003eSociodemographic variables\u003c/h2\u003e\n \u003cp\u003eFor age, we found a statistically significant difference among the groups, \u003cem\u003eF\u003c/em\u003e(2, 778.71)\u0026thinsp;=\u0026thinsp;28.15, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .022, with mean ages ranging from 54 to 57 years and a standard deviation of approximately 6 years. Post hoc comparisons revealed that Late High-Proficiency bilinguals had significantly higher age than Early High-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001) and Late Low-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001) with no significant differences between the later two (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.596). We also found significant differences among the groups in years of education, \u003cem\u003eF\u003c/em\u003e(2, 745.09)\u0026thinsp;=\u0026thinsp;50.14, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .039. Post hoc comparisons showed that both high-proficiency bilingual groups had similar years of education (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.08), but the Late Low-Proficiency bilinguals had significantly lower education than Early High-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001) and Late High-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001). For the adjusted CRQ scores, results showed a significant effect of group, \u003cem\u003eF\u003c/em\u003e(2, 742.56)\u0026thinsp;=\u0026thinsp;44.69, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .035. Post hoc comparisons showed that both high-proficiency bilingual groups had similar adjusted CRQ scores (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.589), but the Late Low-Proficiency bilinguals had significantly lower adjusted CRQ scores than Early High-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001) and Late High-Proficiency bilinguals (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001). A Chi-squared test of independence indicated that sex was not significantly associated with language profile group, \u0026chi;\u0026sup2;(2, N\u0026thinsp;=\u0026thinsp;2415)\u0026thinsp;=\u0026thinsp;2.66, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.264. Overall, significant differences emerged across all sociodemographic variables except sex, with high-proficiency bilinguals showing higher educational attainment and cognitive reserve scores than low-proficiency bilinguals (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eGroup comparison in sociodemographic and language variables.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVariable\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEarly High n\u0026thinsp;=\u0026thinsp;1559\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLate High n\u0026thinsp;=\u0026thinsp;537\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLate Low n\u0026thinsp;=\u0026thinsp;319\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u0026omega;\u0026sup2;\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEarly High vs Late High\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEarly High vs Late Low\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLate High vs Late Low\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSex (M/F)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e586/973\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e189/348\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e130/189\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.264*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.29\u0026thinsp;\u0026plusmn;\u0026thinsp;6.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e53.9\u0026thinsp;\u0026plusmn;\u0026thinsp;6.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e55.92\u0026thinsp;\u0026plusmn;\u0026thinsp;6.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.596\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eYears of Education\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.64\u0026thinsp;\u0026plusmn;\u0026thinsp;3.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14\u0026thinsp;\u0026plusmn;\u0026thinsp;3.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.69\u0026thinsp;\u0026plusmn;\u0026thinsp;3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.039\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCRQ Adjusted Score\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.47\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.34\u0026thinsp;\u0026plusmn;\u0026thinsp;2.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.82\u0026thinsp;\u0026plusmn;\u0026thinsp;2.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.589\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCatalan\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAoA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.62\u0026thinsp;\u0026plusmn;\u0026thinsp;8.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.44\u0026thinsp;\u0026plusmn;\u0026thinsp;12.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.593\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eComprehension (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e.038\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReading (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.068\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpeaking (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.77\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.326\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWriting (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.78\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.514\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSpanish\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAoA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.281\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.916\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eComprehension (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.166\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReading (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.010\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.297\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpeaking (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.916\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWriting (1\u0026ndash;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e.147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;.001\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cem\u003eNote:\u0026nbsp;\u003c/em\u003eEarly High = Early AoA High-Proficiency Bilinguals; Late High = Late AoA High-Proficiency Bilinguals; Late Low = Late AoA Low-Proficiency Bilinguals; M = Male; F = Female; AoA = Age of Acquisition; CRQ = Cognitive Reserve Questionnaire. Values are presented as mean (\u0026plusmn; SD). Post hoc results are for Games-Howell tests. Effect sizes were estimated with omega squared (\u0026omega;\u0026sup2;). An asterisk indicates p-values are for Chi-squared Test (\u0026Chi;\u0026sup2;). Dash (-) indicates not applicable.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eLanguage profile\u003c/h2\u003e\n \u003cp\u003e\u003cstrong\u003eCatalan.\u003c/strong\u003e For AoA, all groups differed significantly as expected since groups were based on this measure, \u003cem\u003eF\u003c/em\u003e(2, 533.14)\u0026thinsp;=\u0026thinsp;1760.28, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .593. Similarly, for language proficiency we found statistically significant differences in all domains: speaking, \u003cem\u003eF\u003c/em\u003e(2, 569.55)\u0026thinsp;=\u0026thinsp;585.69, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .326; oral comprehension, \u003cem\u003eF\u003c/em\u003e(2, 596.33)\u0026thinsp;=\u0026thinsp;53.55, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .042; writing, \u003cem\u003eF\u003c/em\u003e(2, 653.32)\u0026thinsp;=\u0026thinsp;1279.33, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .514; and reading, \u003cem\u003eF\u003c/em\u003e(2, 567.56)\u0026thinsp;=\u0026thinsp;89.7, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .068 (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSpanish.\u003c/strong\u003e The mean AoA and proficiency values indicated native-like acquisition across all groups and domains with minimal variability. Despite that, we found significant differences across the three groups in AoA, \u003cem\u003eF\u003c/em\u003e(2, 1304.71)\u0026thinsp;=\u0026thinsp;473.02, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .281, and for language proficiency domains: speaking, \u003cem\u003eF\u003c/em\u003e(2, 790.74)\u0026thinsp;=\u0026thinsp;27.97, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .022; oral comprehension, \u003cem\u003eF\u003c/em\u003e(2, 764.47)\u0026thinsp;=\u0026thinsp;12.87, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .010; writing, \u003cem\u003eF\u003c/em\u003e(2, 771.48)\u0026thinsp;=\u0026thinsp;18.13, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .014; and reading, \u003cem\u003eF\u003c/em\u003e(2, 770.38)\u0026thinsp;=\u0026thinsp;12.91, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026omega;\u0026sup2; = .010 (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eLanguage use.\u003c/strong\u003e Most of the Early High-Proficiency bilinguals reported a high preference for Catalan during childhood (87%) and adulthood (72%) with some reporting a bilingual preference in adulthood (22%). In contrast, Late Low-Proficiency bilinguals reported a high preference for Spanish during childhood (97%) and adulthood (75%) with some reporting a bilingual preference in adulthood (18%). The Late High-Proficiency bilinguals also reported a high preference for Spanish in childhood (93%) but a more balance preference between the two languages in adulthood, with 27% having a preference for Spanish, 30% for Catalan and 43% for both languages. These percentages are mean values across all contexts from childhood and adulthood, for specific results of each group in different contexts across their lifespan see Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e and Table S3 in Additional File.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eCognitive measures\u003c/h2\u003e\n \u003cp\u003eThe results of the comparison across all cognitive measures for the three language profile groups are summarized in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eMMSE.\u003c/strong\u003e The results indicated no significant main effects of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.98, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.138, \u0026eta;\u0026sup2;ₚ = .002, or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;0.25, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.619, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction term between language profile group and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.28, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.279, \u0026eta;\u0026sup2;ₚ = .001.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eSemantic fluency.\u003c/strong\u003e The results showed a significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;7.39, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026eta;\u0026sup2;ₚ = .006. Post-hoc comparisons showed that Late Low-Proficiency bilinguals performed significantly worse than both Late High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e = -3.54, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, and Early High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e = -3.74, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001. No significant difference was found between Early High-Proficiency bilinguals and Late High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e = -0.05, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.960. Additionally, a significant main effect of language of assessment was observed, with participants evaluated in Spanish scoring higher than those evaluated in Catalan, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;4.81, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.028, \u0026eta;\u0026sup2;ₚ = .002. The interaction between language profile group and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2490)\u0026thinsp;=\u0026thinsp;1.99, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.137, \u0026eta;\u0026sup2;ₚ = .002.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eMemory Binding Test.\u003c/strong\u003e For the total immediate paired recall score, results indicated no significant main effects of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.07, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.126, \u0026eta;\u0026sup2;ₚ = .002 or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;2.27, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.132, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. Additionally, the interaction term was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.09, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.124, \u0026eta;\u0026sup2;ₚ = .002.\u003c/p\u003e\n \u003cp\u003eSimilarly, total delayed paired recall score results showed no significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.59, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.203, \u0026eta;\u0026sup2;ₚ = .001, or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;1.20, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.273, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile group and language of assessment was also not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;0.81, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.443, \u0026eta;\u0026sup2;ₚ \u0026lt; .001.\u003c/p\u003e\n \u003cp\u003eRegarding the total immediate free recall score, the analysis showed a significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;3.31, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.036, \u0026eta;\u0026sup2;ₚ = .003, but not language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;0.20, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.657, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile group and language of assessment was also not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;0.05, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.955, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. None of the post hoc comparisons between groups was significant.\u003c/p\u003e\n \u003cp\u003eFor the total delayed free recall score, results showed no significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.83, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.161, \u0026eta;\u0026sup2;ₚ = .002, or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;1.47, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.225, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile group and language of assessment was also not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.18, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.309, \u0026eta;\u0026sup2;ₚ \u0026lt; .001.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eWAIS-IV Coding.\u003c/strong\u003e Results revealed a significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;20.23, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026eta;\u0026sup2;ₚ = .017 and language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;4.21, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.040, \u0026eta;\u0026sup2;ₚ = .002, with Catalan assessments having significantly higher scores than Spanish assessments. The interaction between language profile group and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.26, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.104, \u0026eta;\u0026sup2;ₚ = .002. Post hoc analyses showed that Late Lower-Proficiency bilinguals performed significantly worse than both Late High-Proficiency bilinguals (\u003cem\u003et\u003c/em\u003e = -3.05, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.005) and Early High-Proficiency bilinguals (\u003cem\u003et\u003c/em\u003e = -4.37, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;.001). However, no significant differences were found between Early High-Proficiency bilinguals and Late High-Proficiency bilinguals (\u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1.67, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.094).\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eWAIS-IV Visual Puzzles.\u003c/strong\u003e Results showed no significant main effects of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;0.07, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.928, \u0026eta;\u0026sup2;ₚ \u0026lt; .001, or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;0.19, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.660, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile group and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;0.42, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.766, \u0026eta;\u0026sup2;ₚ \u0026lt; .001.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eWAIS-IV Matrix Reasoning.\u003c/strong\u003e Results showed no significant main effects of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.64, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.193, \u0026eta;\u0026sup2;ₚ = .001, but it was significant for language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;5.48, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.019, \u0026eta;\u0026sup2;ₚ = .002, with Catalan assessments having significantly higher scores than Spanish assessments. However, the interaction between language profile group and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.72, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.179, \u0026eta;\u0026sup2;ₚ = .001.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eWAIS-IV Digit Span.\u003c/strong\u003e For the total score of WAIS-IV Digit Span, results revealed no significant main effects of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.37, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.093, \u0026eta;\u0026sup2;ₚ = .002), but significant main effects of language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;3.99, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.046, \u0026eta;\u0026sup2;ₚ = .002), with Spanish assessments having higher scores than Catalan assessments. Results also showed a significant interaction between language profile group and language of assessment, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;3.55, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.028, \u0026eta;\u0026sup2;ₚ = .003. Post hoc comparisons showed that there were no statistical differences between language profile groups in Spanish assessments (all \u003cem\u003ep\u003c/em\u003e-values\u0026thinsp;\u0026gt;\u0026thinsp;.05). However, in Catalan assessments, Early High-Proficiency bilinguals score significantly higher than Late High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3.85, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.002 and Late Low-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3.17, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.018. There were no significant differences between Late Low-Proficiency bilinguals and Late High-Proficiency bilinguals (\u003cem\u003et\u003c/em\u003e = -1.05, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.999).\u003c/p\u003e\n \u003cp\u003eFor the Digit Span Forward, there was not a significant main effect of language profile groups, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.01, p\u0026thinsp;=\u0026thinsp;.134, \u0026eta;\u0026sup2;ₚ = .002, but the main effect of language of assessment was significant, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;11.15, p\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026eta;\u0026sup2;ₚ = .005, with Spanish assessments having higher scores than Catalan assessments. Also, the interaction effect was significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;8.74, p\u0026thinsp;\u0026lt;\u0026thinsp;.001, \u0026eta;\u0026sup2;ₚ = .007. Post hoc comparisons showed that there were no statistical differences between language profile groups in Spanish assessments (all \u003cem\u003ep\u003c/em\u003e-values\u0026thinsp;\u0026gt;\u0026thinsp;.05). However, in Catalan assessments, Early High-Proficiency bilinguals score significantly higher than Late High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;4.36, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.002 and Late Low-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;3.57, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.004. There were no significant differences between Late Low-Proficiency bilinguals and Late High-Proficiency bilinguals, \u003cem\u003et\u003c/em\u003e = -1.17, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.999.\u003c/p\u003e\n \u003cp\u003eFor the Digit Span Backward, results indicated no significant main effect of language profile group, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.53, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.216, \u0026eta;\u0026sup2;ₚ = .001, or of language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;0.45, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.501, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile group and language of assessment was also not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;1.99, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.136, \u0026eta;\u0026sup2;ₚ = .002.\u003c/p\u003e\n \u003cp\u003eFinally, for the Digit Span Sequencing, there was no significant main effect of language profile groups, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;2.06, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.127, \u0026eta;\u0026sup2;ₚ = .002, or language of assessment, \u003cem\u003eF\u003c/em\u003e(1, 2405)\u0026thinsp;=\u0026thinsp;0.94, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.331, \u0026eta;\u0026sup2;ₚ \u0026lt; .001. The interaction between language profile groups and language of assessment was not significant, \u003cem\u003eF\u003c/em\u003e(2, 2405)\u0026thinsp;=\u0026thinsp;0.246, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.782, \u0026eta;\u0026sup2;ₚ \u0026lt; .001.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we investigated how language experience, primarily defined by AoA and language proficiency, influences cognition by examining differences between language groups across multiple cognitive domains. To this aim, we analyzed a large sample of cognitive data from the ALFA study cohort [53]. Our results indicate that cognitive test performance was influenced by language profile and, to some extent, by type of cognitive domain (linguistic vs. non-linguistic). Additionally, we found an effect of the language of assessment, which can affect test performance and potentially mask bilingual advantages.\u003c/p\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003eNon-linguistic domain\u003c/h2\u003e\u003cp\u003eIn the non-linguistic domain, we predicted that Early High-Proficiency bilinguals would outperform Late Low-Proficiency bilinguals on tests involving attention and executive control, due to the combined benefits of early AoA, high language proficiency, and active use of both languages. We further expected that Late High-Proficiency bilinguals would show intermediate performance, with the negative effects of later AoA potentially offset by the benefits of higher proficiency and frequent language use.\u003c/p\u003e\u003cp\u003eOur results suggest that both high-proficiency bilingual groups, regardless of their AoA, outperformed the Late Low-Proficiency bilinguals on the Coding subtest of the WAIS-IV. This subtest is associated with multiple cognitive processes, including processing speed, visual-motor coordination, short-term memory, and incidental learning. As such, it is difficult to determine whether the combined effects of AoA and language proficiency target a specific underlying cognitive process involved in test performance. However, performance on tests that directly assess verbal short-term memory suggest a distinct effect of AoA. Specifically, Early High-Proficiency bilinguals outperformed both Late High-Proficiency and Late Low-Proficiency bilinguals on the overall Digit Span score, an effect driven primarily by higher performance on the Digit Span Forward subtest.\u003c/p\u003e\u003cp\u003eThe patterns observed in both tests may reflect differences in the specific executive functions each test engages, and in the underlying cognitive processes supporting those functions, as well as the degree of bilingualism needed to attain a measurable cognitive benefit. While the Digit Span tests primarily assess verbal short-term memory, the group differences observed in the Coding subtest may more directly reflect enhanced processing speed rather than broader working memory advantages. Alternatively, rather than attributing the differences solely to specific cognitive processes or benefits, it is possible that the results are better explained by the degree of bilingual experience required to detect an effect. Notably, the Early High-Proficiency bilinguals, who had the highest level of bilingual exposure and use, may be more sensitive to subtle cognitive advantages, thus making group differences more detectable in this subgroup.\u003c/p\u003e\u003cp\u003eInterestingly, no significant differences were observed between the groups on the Digit Span Backward or Sequencing tests. Although the high-proficiency bilinguals showed an advantage in tests involving speed and attentional control, as evidenced in both the Coding and Digit Span Forward tests, this benefit did not extend to more demanding working memory tests such as Digit Span Backward and Sequencing. This suggests that the cognitive advantage may lie more in attentional processing and speed than in the manipulation and maintenance aspects of working memory.\u003c/p\u003e\u003cp\u003eNo significant differences were found in other non-linguistic tests, such as the Visual Puzzles and Matrix Reasoning subtests of the WAIS-IV, which assess non-verbal abstract reasoning and visuospatial reasoning. Similarly, no differences were observed on the MMSE, which is expected given that scores below 26 were part of the exclusion criteria. This suggests that any modulation associated with bilingualism may be selective and specific to certain cognitive domains and tests, rather than reflecting a generalized enhancement of cognition. Indeed, the evidence for a bilingual advantage in these cognitive domains remains mixed, suggesting that speaking a second language may not have a direct impact on these cognitive processes, or that the benefits may be specific to certain language profiles or test characteristics. For instance, a meta-analysis reported a bilingual advantage in abstract and symbolic reasoning, however, the studies included primarily involved young participants [77]. Regarding working memory, there are studies reporting small to moderate bilingual advantages in this domain [77\u0026ndash;79], however, other meta-analyses reported a null effect of bilingualism on working memory. For example, Degirmenci et al. found no clear evidence of a bilingual advantage in the updating domain, which is closely related to working memory, in healthy older adults [33]. Similarly, Lehtonen et al. reported that the already small effect sizes observed in working memory tests disappeared after correcting for publication bias [45]. Notably, in one study, monolinguals even outperformed bilinguals on the Digit Span Backward test [39].\u003c/p\u003e\u003cp\u003eTaken together, these results suggest that lifelong use of a second language, including continued use later in life, may modulate cognitive performance, though not uniformly across all domains. Our findings are consistent with those reported by Gallo et al. regarding the relationship between L2 proficiency and the efficiency of the attentional network [42]. They found that in healthy older adults, increasing levels of L2 proficiency predicted lower reaction times in incongruent trials of the Flanker test, while increasing years since L2 acquisition also predicted lower reaction times, but with a smaller beneficial impact. To some extent, this aligns with previous studies that have suggested that bilinguals are overall faster in performing tests that measured processing speed [3]. For example, in the Attention Network Test (ANT) [80], Costa et al. found that bilinguals were overall faster [81]. Desideri and Bonifacci also found better conflict performance and faster reaction times for bilingual adults on the ANT [82]. In another study, both early and late Chinese-English bilinguals had an advantage in conflict resolution compared to monolinguals on the ANT, with early bilinguals showing the greatest advantage [38]. Woumans et al. also found that bilinguals were faster on the ANT and exhibited a smaller congruency effect in the Simon task compared to monolinguals [16]. In the context of these results, tasks such as the Stroop, Flanker, and Simon were thought to measure enhanced inhibition. However, many findings were inconsistent with a simple inhibitory control explanation. For example, bilinguals often outperform monolinguals on congruent trials in conflict tasks where no inhibition is required, as well as on incongruent trials [6,59]. While the bilingual advantage was initially attributed to enhanced inhibitory control, some researchers now propose a broader framework of attentional control or increased processing efficiency [59,83]. Hilchey and Klein suggested that faster reaction times might reflect general processing speed rather than specific executive functioning advantages [84].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003eLinguistic domain\u003c/h2\u003e\u003cp\u003e For verbal episodic memory performance, we found no significant differences across language profile groups or language of assessment for any of the MBT measures. These results are in agreement with our hypothesis that potential cognitive benefits do not extend uniformly to all cognitive domains, particularly those evaluated with a test that relies on a verbal or linguistic component. For instance, Fernandes et al. found that bilingual older adults recalled fewer words than age-matched monolinguals in a free recall test, likely due to the high lexical demands of the test [85]. To some extent, this supports the idea that a verbal disadvantage can counteract the executive control benefits associated with bilingualism [86], and that when the verbal component is reduced, the bilingual advantage becomes more evident [40].\u003c/p\u003e\u003cp\u003e Nevertheless, verbal fluency results were not in line with our hypothesis. Both high-proficiency bilingual groups performed significantly better than the Late Low-Proficiency bilinguals. This finding contrasts with the broader literature, which typically associates bilingualism with disadvantages in lexical retrieval tests. Such disadvantages are often attributed to reduced exposure to each individual language compared to a monolingual speaker, and increased lexical interference from the constantly activated non-target language [45,57].\u003c/p\u003e\u003cp\u003eHowever, some studies have reported exceptions and mixed findings [87]. Costumero et al. found that while both monolingual and bilingual groups experienced cognitive decline, including in semantic fluency, over a 7-month follow-up period, monolinguals showed a greater overall cognitive decline than bilinguals, suggesting more preserved performance in bilingual individuals [88]. In cross-sectional studies, when bilinguals are matched with monolinguals on vocabulary size as a proxy for language proficiency, they either outperform [89] or perform comparably to monolinguals [47,90]. Similarly, Patra et al. reported no significant differences in a semantic fluency test between Bengali-English bilinguals and English monolinguals matched on receptive vocabulary, age, education, and non-verbal intelligence [91]. In the same way that cognitive benefits associated with bilingualism may be domain- and test-specific, potential disadvantages may also be limited to particular contexts. For example, Bialystok et al. reported that monolinguals produced more words only when compared with low-proficiency bilinguals, while no significant differences were observed between monolinguals and high-proficiency bilinguals [47]. Our results exemplify this by demonstrating performance differences within the bilingual population based on their proficiency levels, with Early and Late High-Proficiency groups scoring similarly in the semantic fluency test and outperforming the Late Low-Proficiency bilingual group.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003eLanguage of assessment\u003c/h2\u003e\u003cp\u003e In the semantic fluency test, participants assessed in Spanish produced more words on average than those assessed in Catalan, suggesting that lexical retrieval is facilitated when the test is administered in the participant\u0026rsquo;s dominant language. This effect was most pronounced among late bilinguals. A similar pattern emerged in verbal short-term memory evaluated with the Digit Span Forward test, with Spanish assessments having better results than Catalan assessments, again driven by the performance of both late AoA bilingual groups. Prior research has showed better digit span performance in participant first language [92] or language of schooling [93,94], which was Spanish for both late AoA bilingual groups. In addition, the interaction between group and language of assessment was significant in both Digit Span and Digit Span Forward. While no significant group differences were found in Spanish assessments, Catalan assessments revealed that Early High-Proficiency bilinguals outperformed both late AoA groups. This suggests that even in relatively simple cognitive tests, verbal processing demands in a bilingual's L2 may subtly hinder performance, particularly when rapid lexical access is required, which can directly impact performance of late AoA bilinguals despite high L2 proficiency.\u003c/p\u003e\u003cp\u003e Language of assessment also influenced performance in non-verbal tests such as Coding and Matrix Reasoning from the WAIS-IV. This was not anticipated in our hypotheses. Interestingly, these effects appear to be driven by the small group of Late Low-Proficiency participants who completed the assessment in Catalan. Given the small size of this subgroup and the unexpected direction of the effect, the finding is difficult to interpret and may reflect sample variability or other uncontrolled factors, rather than cognitive differences.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003eInfluence of bilingual language experience on cognitive performance\u003c/h2\u003e\u003cp\u003e The results from the verbal short-term memory tests suggest a specific advantage for early bilinguals. Early AoA is typically associated with greater advantages due to increase experience of controlling two languages. For example, in one study early AoA bilinguals exhibited significantly smaller interference cost on the Flanker test compared to late bilinguals and monolinguals [55]. Additionally, the observed benefits of early AoA may result from the combined effects of earlier exposure, enhanced proficiency, and subsequently greater frequency of use across both languages. In a study with Spanish-Catalan bilinguals, higher frequency of language use was associated with better working memory and phonemic fluency, measured as a composite score including Letter\u0026ndash;Number Sequencing, Corsi, phonemic fluency, and Digit Span tests [74]. Interestingly, greater language use was also linked to increased white matter deterioration, yet participants maintained equivalent cognitive performance across domains, suggesting a cognitive reserve effect. Although they did not include direct measures of language proficiency or AoA, the sample was composed of highly educated Spanish-Catalan bilinguals that likely overlaps with the high-proficiency bilingual profiles identified in our study.\u003c/p\u003e\u003cp\u003eWhile early AoA is strongly associated with higher language proficiency and active use of both languages that may lead to a better cognitive performance, specially in some specific domains such as verbal short-term memory, high proficiency itself was also linked to cognitive benefits, even among bilinguals with a late AoA. This implies that language proficiency may have an independent effect on cognition. In our study, high proficiency in both Spanish and Catalan was closely linked to more frequent and active bilingual language use in adulthood. This relationship is expected, as greater language use is likely to support and reinforce language proficiency, and viceversa [1,9,49,56,95,96]. While the relationship may be bidirectional, meaning that high proficiency may promote greater language use, and frequent use may reinforce proficiency, both scenarios suggest a positive feedback loop in bilingual language engagement. The specific type of proficiency may also be an important factor, in a previous study, Calabria et al. found that self-reported Catalan proficiency in speaking was the most important variable when calculating a bilingualism composite score that ranged from passive to active bilingualism [24]. Similarly, production measures of proficiency in Catalan, rather than comprehension measures, were most strongly associated with cognitive benefits in our study.\u003c/p\u003e\u003cp\u003eIn summary, our results indicate that high-proficiency Spanish-Catalan bilingual older adults who actively use both languages showed enhanced cognitive performance in specific domains compared to passive, Spanish-dominant bilinguals. These findings underscore the idea that the degree and nature of bilingual engagement, rather than just being bilingual, are key factors driving these cognitive benefits [6,24,97\u0026ndash;99]. Our research contributes to the growing body of evidence that supports the unique and beneficial role of specific aspects of bilingual experience to both cognitive and neural reserve, which have been consistently associated with protective effects against age-related cognitive decline and enhanced resilience in the face of MCI or AD [5,6,98,100,101]. Additionally, our findings suggest that the benefits of lifelong L2 use are domain- and test-specific, highlighting that the bilingual advantage largely depends on specific aspects of language experience and how bilingualism is defined and measured.\u003c/p\u003e\u003cp\u003eOur study has several limitations. First, self-reported measures of language use and proficiency are subject to bias and may not fully capture bilingual experience. Future research should incorporate standardized instruments such as The Language and Social Background Questionnaire (LSBQ) [102] or the Language Experience and Proficiency Questionnaire (LEAP-Q) [103,104] alongside objective proficiency measures. Second, although Holm-adjusted pairwise comparisons were applied within each cognitive domain, we did not correct for multiple testing across the 13 separate ANCOVAs, leaving a potential for inflated Type I error. Finally, bilingualism does not exist in isolation and its effects on cognition can be confounded or influenced by socioeconomic status [59,105] or other lifestyle factors such as occupational complexity or engaging in physical, intellectual and social activities as well as music training [6,73,97,106]. In our study, we attempted to account for these potential confounding variables with a proxy of cognitive reserve measured with the CRQ, which includes questions about the educational background, occupational complexity, social and physical activities and cultural and intellectual pursuits [71]. However, future research should include more detailed measures of socioeconomic status and lifestyle factors to further isolate the effects of bilingualism.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, our findings highlight that the cognitive effects of bilingualism in aging are not uniform but domain-specific, with benefits most evident in tasks involving attentional control and processing speed, rather than across all cognitive domains. Moreover, the extent of cognitive benefits depends on specific aspects of the bilingual experience, such as language proficiency and AoA. These results have both theoretical and clinical implications. Theoretically, they deepen our understanding of the relationship between cognition, bilingualism, and aging within the framework of cognitive reserve. Clinically, they inform best practices for assessing language and cognitive deficits in bilingual individuals and suggest that second language use may serve as a valuable strategy for preventing cognitive decline and could be potentially integrated into cognitive training programs.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eAoA:Age of Acquisition; ALFA: Alzheimer’s and Families; AD: Alzheimer’s Disease; MCI: Mild Cognitive Impairment; CR: Cognitive Reserve; L1: first language; L2: second language; MMSE: Mini-Mental State Examination; MBT: Memory Binding Test; TFR: Total Free Recall; TPR: Total Paired recall; TDFR: Total Delayed Free Recall; TDPR: Total Delayed Paired Recall; WAIS: Wechsler Adult Intelligence Scale; CRQ: Cognitive Reserve Questionnaire; ANOVA: Analysis of Variance; ANCOVA: Analysis of Covariance; ANT: Attention Network Test.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis publication is part of the ALFA study. The authors would like to express their most sincere gratitude to the ALFA project participants, without whom this research would have not been possible.\u0026nbsp;Collaborators of the ALFA study are: Clara Abadías, Müge Akinci, Andrea Ambite, Federica Anastasi, Ricardo Aquite, Sara Aragó, Eider Arenaza Urquijo, Kahina Baouche, Ricardo Berbería, Annabella Beteta, Marco Bianchi, Helena Blasco, Anna Brugulat-Serrat, Raffaele Cacciaglia, Jordi Camí, Fernanda Campos Strazzi, Lidia Canals Gispert, Alba Cañas, Diego Cascales, José Contador, Marta Crous-Bou, Irene Cumplido, Rafael Dal-Ré, Marina de Diego, Neus de la Cruz-Sanchez, Marta del Campo, Carme Deulofeu, Ruth Dominguez, Maria Emilio, Isabel Estragués, Tavia Evans, Carles Falcón, Karine Fauria, Marta Félez, Aida Fernandez, Alba Fernández Bonet, Ana Fernández-Arcos, Elisabeth Ferrer i Mairal, Jordi Freixa, Sherezade Fuentes, Clara Gallay, Marina García, Manuel Garfia, Fernando Gaston Rossi, Patricia Genius, Juan Domingo Gispert, José María González de Echávarri, Armand González-Escalante, Xavier Gotsens, Nina Gramunt Fombuena, Laura Gusó, Ana Harris, Laura Hernandez, Felipe Hernández-Villamizar, Gema Huesa, Jordi Huguet, Laura Iglesias, Esther Jiménez, Michalis Kassinopoulos, Iva Knezevic, Maria León, Aldana Lizarraga, David López-Martos, Ferran Lugo, Paula Marne, Carlota Medina, Francisco Javier Meléndez, Tania Menchón, Marta Milà Alomà, Carolina Minguillón, José Luis Molinuevo, Cristina Mustata, Irene Navalpotro, Grégory Operto, Paula Ortiz, Eva Palacios, Eleni Palpatzis, Wiesje Pelkmans, Jordi Peña-Casanova, Isabel Perez, Aitana Plaza, Albina Polo, Clara Porta, Sandra Pradas, Aleix Puig, Andreea Rădoi, Jaume Roca Alcaraz, Albert Rodrigo-Pares, Noelia Rodríguez de Guzmán Gallego, Blanca Rodríguez-Fernández, Maria Roman, Sarata Sall Sall, Gemma Salvadó, Mireia Sánchez, Pau Sánchez, Sabrina Segundo, Mahnaz Shekari, Lluis Solsona, Anna Soteras, Laura Stankeviciute, Marc Suárez, Pilar Tartière-González, Laia Tenas, Javier Torres-Torronteras, Núria Tort Clotet, Elisabet Zhan Travesset Muntada, David Vállez, Montserrat Vilà, Marc Vilanova, Natalia Vilor-Tejedor.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: SG; MC; Methodology: SG; MC; Formal analysis: SG; Resources: GS; OG; Data curation: GS; OG; Writing – original draft: SG; MC; Writing – review \u0026amp; editing: SG; GS; OG; MS; LS; FP; MC; Visualization: SG; Supervision: FP; MC; Project administration: MC; OG.; Funding acquisition: MC. All the authors contributed to the revisions of the manuscript and read and approved the submitted version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe research leading to these results has received funding from “la Caixa” Foundation, under agreement LCF/PR/SC22/68000001. Additional funding was obtained from: Fondo de Investigación Sanitaria (FIS), Instituto de Salud Carlos III under grant PI12/00326. Additional support has been received from the Universities and Research Secretariat, Ministry of Business and Knowledge of the Catalan Government under the grant no. 2021 SGR 00913. This work is part of the project PID2023-149755OB-I00, funded by the Ministry of Science and Innovation, the State Research Agency 10.13039/501100011033 and the European Regional Development Fund FEDER, EU. MS is employed by Hospital de la Santa Creu i Sant Pau. His research is supported by funding from the Spanish Institute of Health Carlos III co-funded by the European Union (Juan Rodés research grant JR18-00018; Fondo de investigación sanitaria grant PI19/00882), the Department of Research and Universities from the Generalitat de Catalunya (2021 SGR 00979), the Alzheimer’s Association clinician scientist fellowship (AACSF-22-972945), and the National Institutes of Health (R01AG080470). FP is partially funded by UCLH Biomedical Research Centre. GSB is supported by the Instituto de Salud Carlos III (ISCIII) through the project CP23/00039 (Miguel Servet contract).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author, upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study used anonymized data provided by the Barcelona Beta Research Center (BBRC) as part of the ALFA study. The ALFA study protocol was approved by the independent Ethics Committee Parc de Salut Mar Barcelona and registered at ClinicalTrials.gov (ALFA Identifier: NCT01835717). It was conducted in accordance with the directives of the Spanish Law 14/2007, of 3rd of July, on Biomedical Research (Ley 14/2007 de Investigación Biomédica). All participating subjects signed the study’s informed consent form, which was approved by the Independent Ethics Committee ‘Parc de Salut Mar’, Barcelona. The study was conducted according to the Declaration of Helsinki.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ede Bruin A. Not All Bilinguals Are the Same: A Call for More Detailed Assessments and Descriptions of Bilingual Experiences. Behav Sci. 2019;9:33.\u003c/li\u003e\n\u003cli\u003eLehtonen M, Fyndanis V, Jylkk\u0026auml; J. The relationship between bilingual language use and executive functions. Nat Rev Psychol. 2023;2:360\u0026ndash;73.\u003c/li\u003e\n\u003cli\u003evan den Noort M, Struys E, Bosch P, Jaswetz L, Perriard B, Yeo S, et al. Does the Bilingual Advantage in Cognitive Control Exist and If So, What Are Its Modulating Factors? A Systematic Review. Behav Sci. 2019;9:27.\u003c/li\u003e\n\u003cli\u003eWare AT, Kirkovski M, Lum JAG. 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Linguist Approaches Biling. 2021;11:459\u0026ndash;83.\u003c/li\u003e\n\u003cli\u003eRami L, Valls-Pedret C, Bartr\u0026eacute;s-Faz D, Caprile C, Sol\u0026eacute;-Padull\u0026eacute;s C, Castellv\u0026iacute; M, et al. Cognitive reserve questionnaire. Scores obtained in a healthy elderly population and in one with Alzheimer\u0026rsquo;s disease. Rev Neurol. 2011;52:195\u0026ndash;201.\u003c/li\u003e\n\u003cli\u003eBonfieni M, Branigan HP, Pickering MJ, Sorace A. Cognitive control in bilinguals: Effects of language experience and individual variability. Biling Lang Cogn. 2020;23:219\u0026ndash;30.\u003c/li\u003e\n\u003cli\u003eDonnelly S, Brooks PJ, Homer BD. Is there a bilingual advantage on interference-control tasks? A multiverse meta-analysis of global reaction time and interference cost. Psychon Bull Rev. 2019;26:1122\u0026ndash;47.\u003c/li\u003e\n\u003cli\u003eSol\u0026eacute;-Padull\u0026eacute;s C, Cattaneo G, Cabello-Toscano M, Mulet-Pons L, Vaqu\u0026eacute;-Alc\u0026aacute;zar L, Roca-Ventura A, et al. Use of Multiple Languages Provides Cognitive Reserve Amidst Age-Related White Matter Changes. J Gerontol Ser B. 2025;80:gbaf064.\u003c/li\u003e\n\u003cli\u003eFox J, Weisberg S. An R Companion to Applied Regression. SAGE Publications; 2019.\u003c/li\u003e\n\u003cli\u003eR Core Team. R: A language and environment for statistical computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2023. Available from: https://www.R-project.org/\u003c/li\u003e\n\u003cli\u003eAdesope OO, Lavin T, Thompson T, Ungerleider C. A Systematic Review and Meta-Analysis of the Cognitive Correlates of Bilingualism. Rev Educ Res. 2010;80:207\u0026ndash;45.\u003c/li\u003e\n\u003cli\u003eGrundy JG, Anderson JAE, Bialystok E. Neural correlates of cognitive processing in monolinguals and bilinguals. Ann N Y Acad Sci. 2017;1396:183\u0026ndash;201.\u003c/li\u003e\n\u003cli\u003eMonnier C, Boich\u0026eacute; J, Armandon P, Baudoin S, Bellocchi S. Is bilingualism associated with better working memory capacity? A meta-analysis. Int J Biling Educ Biling. 2022;25:2229\u0026ndash;55.\u003c/li\u003e\n\u003cli\u003eFan J, McCandliss BD, Sommer T, Raz A, Posner MI. Testing the Efficiency and Independence of Attentional Networks. J Cogn Neurosci. 2002;14:340\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eCosta A, Hern\u0026aacute;ndez M, Sebasti\u0026aacute;n-Gall\u0026eacute;s N. Bilingualism aids conflict resolution: Evidence from the ANT task. Cognition. 2008;106:59\u0026ndash;86.\u003c/li\u003e\n\u003cli\u003eDesideri L, Bonifacci P. Verbal and Nonverbal Anticipatory Mechanisms in Bilinguals. J Psycholinguist Res. 2018;47:719\u0026ndash;39.\u003c/li\u003e\n\u003cli\u003eZhou B, Krott A. Data trimming procedure can eliminate bilingual cognitive advantage. Psychon Bull Rev. 2016;23:1221\u0026ndash;30.\u003c/li\u003e\n\u003cli\u003eHilchey MD, Klein RM. Are there bilingual advantages on nonlinguistic interference tasks? Implications for the plasticity of executive control processes. Psychon Bull Rev. 2011;18:625\u0026ndash;58.\u003c/li\u003e\n\u003cli\u003eFernandes MA, Craik F, Bialystok E, Kreuger S. Effects of bilingualism, aging, and semantic relatedness on memory under divided attention. Can J Exp Psychol Rev Can Psychol Exp. 2007;61:128\u0026ndash;41.\u003c/li\u003e\n\u003cli\u003eWodniecka Z, Craik FIM, Luo L, Bialystok E. Does bilingualism help memory? Competing effects of verbal ability and executive control. Int J Biling Educ Biling. 2010;13:575\u0026ndash;95.\u003c/li\u003e\n\u003cli\u003eGiovannoli J, Martella D, Casagrande M. Executive functioning during verbal fluency tasks in bilinguals: A systematic review. 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J Speech Lang Hear Res JSLHR. 2007;50:940\u0026ndash;67.\u003c/li\u003e\n\u003cli\u003eCalvo A, Bialystok E. Independent effects of bilingualism and socioeconomic status on language ability and executive functioning. Cognition. 2014;130:278\u0026ndash;88.\u003c/li\u003e\n\u003cli\u003eBak TH. The impact of bilingualism on cognitive ageing and dementia: Finding a path through a forest of confounding variables. Linguist Approaches Biling. 2016;6:205\u0026ndash;26.\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":"bilingualism, aging, cognitive aging, cognitive reserve, bilingual advantage","lastPublishedDoi":"10.21203/rs.3.rs-7796112/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7796112/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eThe positive effect of bilingualism, especially later in life, is typically attributed to its role as a cognitive reserve factor. However, evidence supporting such benefits remains inconclusive or appears limited to certain populations, tasks, or cognitive domains. Some of these inconsistencies may stem from the tendency to define bilingualism as a dichotomous variable, rather than considering the multiple factors that contribute to the bilingual experience. Our study investigates the impact of bilingualism on cognition in cognitively unimpaired older adults, focusing on age of language acquisition (AoA), proficiency, and usage throughout life.\u003c/p\u003e\u003ch2\u003eMethod\u003c/h2\u003e\u003cp\u003eWe analyzed data from 2415 cognitively unimpaired individuals (aged 45\u0026ndash;74) from the Alzheimer's and Families (ALFA) study. We included Mini-Mental State Examination to assess global cognition, semantic fluency for lexical retrieval, Memory Binding Test for verbal episodic memory, and WAIS-IV subtests for processing speed and visual-motor coordination (Coding), visual-spatial reasoning (Visual Puzzles), non-verbal abstract reasoning (Matrix Reasoning), verbal short-term memory (Digit Span Forward) and working memory and attention (Digit Span Backward and Sequencing). We defined three groups based on AoA (Early/Late) and proficiency (High/Low) of Catalan: 1) Early High-Proficiency bilinguals (n\u0026thinsp;=\u0026thinsp;1559); 2) Late High-Proficiency bilinguals (n\u0026thinsp;=\u0026thinsp;537); and 3) Late Low-Proficiency bilinguals, primarily Spanish-dominant (n\u0026thinsp;=\u0026thinsp;319). We also analyzed the effect of the language of assessment (Spanish or Catalan) on cognitive performance.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003e We found that both Early and Late High-Proficiency bilingual groups outperformed Late Low-Proficiency bilinguals in verbal fluency and processing speed. Additionally, Early High-Proficiency bilinguals scored significantly higher in verbal short-term memory than both Late AoA groups.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eOur findings highlight that the cognitive effects of bilingualism in aging are not uniform but rather domain-specific and that bilingualism, particularly when characterized by high proficiency, can serve as a meaningful contributor to cognitive reserve.\u003c/p\u003e","manuscriptTitle":"Bilingualism and cognition: The impact of age of acquisition, language use and proficiency in healthy older adults","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-14 11:13:09","doi":"10.21203/rs.3.rs-7796112/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":"2cc0c1e9-18eb-4117-8d7f-16c4c5afffbd","owner":[],"postedDate":"November 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57955089,"name":"Biological sciences/Neuroscience"},{"id":57955090,"name":"Biological sciences/Psychology"},{"id":57955091,"name":"Social science/Psychology"}],"tags":[],"updatedAt":"2026-01-07T11:54:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-14 11:13:09","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7796112","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7796112","identity":"rs-7796112","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}