Previous developmental studies reported bilinguals’ Theory of Mind (ToM; the ability to take on another's perspective) develops differently than monolinguals. We conducted a scoping review to evaluate how researchers assess bilinguals’ ToM and whether they characterize bilinguals’ lived experiences. We analyzed 53 publications examining ToM in bilinguals, with most papers studying children (n = 42; 79%). We identified 96 different tasks used across these 53 papers. The most common are 46 (48%) cases of the false-belief task, a cognitive-focused task using story vignettes. Few tasks target other types of ToM, such as ToM in social settings or taking others’ emotional perspectives. Furthermore, only half of the papers reported language history (n = 28, 53%) and exposure (n = 25, 47%), limiting the inferrability of ToM and language experiences. Expanding how we study ToM in bilinguals will improve our understanding of the intersection of bilingualism and ToM.

Previous research has shown that non-Māori Speaking New Zealanders have extensive latent knowledge of Māori, despite not being able to speak it. This knowledge plausibly derives from a memory store of Māori forms (Oh et al., 2020; Panther et al., 2023). Modelling suggests that this ‘proto-lexicon’ includes not only Māori words, but also word-parts; however, this suggestion has not yet been tested experimentally.

We present the results of a new experiment in which non-Māori speaking New Zealanders and non-New Zealanders were asked to segment a range of Māori words into parts. We show that the degree to which segmentations of non-Māori speakers correlate to the segmentations of two fluent speakers of Māori is stronger among New Zealanders than non-New Zealanders. This research adds to the growing evidence that even in a largely ‘monolingual’ population, there is evidence of latent bilingualism through long-term exposure to a second language.

This study investigated whether non-native English speakers showed a processing advantage for high-frequency multiword units (multiword frequency effects), and whether the effects differed between native and non-native speakers. Such a difference has been identified in relation to single-word processing. Native English speakers and intermediate learners of English with languages of different scripts (native speakers of Japanese and German) judged whether English multiword units were grammatical. A significant processing advantage was identified for both native and non-native participants. More importantly, the multiword frequency effects were stronger among non-native than native speakers. The discrepancy persisted even after including individual vocabulary knowledge as a predictor in the mixed-effect models. Furthermore, there was no significant different impact of the effects between two non-native groups, even though German participants responded quicker than Japanese participants. This indicates that the varying influence between L1 and L2 could be explained by within-language, not between-language, variables.

No studies have investigated the neural correlates of Number and Person agreement processing in bilinguals. Because a previous fMRI study showed difference in L1 and L2 morphosyntactic processing of L1 Turkish–L2 Persian bilinguals, it was of interest whether this difference can be specifically attributed to Number or Person processing. Therefore, we reanalyzed these data at the whole-brain level, revealing a selective response for Number Violations in the pars opercularis (PO), whereas Number and Person Violations activated the posterior superior temporal gyrus (pSTG). These results support the decomposition of agreement projections and their neuroanatomical substrates in bilinguals and confirm the involvement of systematically different feature-checking and feature-mapping mechanisms in Number and Person agreement but shared mechanisms between L1 and L2. Moreover, at variance with previous reports, Number Violations evoked more effects than Person Violations in pSTG, suggesting qualitatively different processing underlying R-expression and pronominal controllers.

In applied linguistics generally and bilingualism research in particular, psychological variables remain a much under-investigated sub-category of individual differences compared with cognitive ones. To better understand the under-researched psychological effects of bilingualism, this study investigated well-being, a psychological construct, based on a big-data survey. Drawing upon a national survey (N = 12,582), we examined the influence of bilingualism (operationalised as foreign language (FL) proficiency) and 13 sociobiographical variables (e.g., socio-economic status, SES) on well-being. Among these 14 initial independent variables, perceived social fairness, SES, and health emerged as important predictors for well-being, with FL proficiency and national language (NL) proficiency as potentially important predictors; crucially, FL proficiency was more important than NL proficiency. As the first systematic attempt to link bilingualism with well-being, our study advocates (1) a more holistic perspective towards language (including NL and FL(s)) in any bilingual context and (2) fuller use of effect sizes.

Previous research has shown that bilingual speakers may be more tolerant to ambiguity, they might perceive situations of ambiguity more interesting, challenging and desirable (e.g., Dewaele & Li, 2013). To our knowledge, no data are available addressing the question whether the language in use can have an effect on the personality trait of tolerance of ambiguity (ToA). This study investigated whether and how reading statements in a second language (L2), as opposed to the native language (L1), affects ToA. 387 Italian–English bilingual adults completed a questionnaire measuring levels of ToA either in English or Italian. Results revealed that processing information in L2 promoted higher scores of ToA overall and in sentences that were related to challenging perspectives and change. Age, gender and L2 proficiency were significant predictors of higher ToA scores. This study offers new evidence that processing information in a L2 can affect tolerance of ambiguous situations.

The aim of the study is to explore the differential effects of neurodegenerative disorders on cross-language interference and facilitation, by comparing the performance in a bilingual Stroop task of Catalan–Spanish bilinguals with different neurodegenerative disorders [Mild Cognitive Impairment (MCI), n = 16; Alzheimer's disease (AD), n = 16; and Parkinson's disease (PD), n = 16)] and healthy controls (n = 14). Interference is the difference in naming latencies between the incongruent (colour words not matching with their ink colour) and control (non-colour words) conditions. Facilitation is the difference between the control and congruent conditions (colour words matching with their ink colour).

The results showed that AD and MCI patients, but not PD, showed a larger interference effect than healthy controls. Nevertheless, the patient groups showed the same facilitation effect as healthy controls.

The contribution of cortical and subcortical brain areas to cross-language interference suppression is discussed in relation to the type of brain degeneration.

BAbSANT (Bilingual Abstract Semantic Associative Network Training) is a novel, theoretically motivated approach to anomia therapy for bilingual persons with aphasia (BPWA). We report on a Russian-dominant, Russian–English BPWA, who was trained on abstract English and Russian words. We hypothesized both within- and cross-language generalization when the non-dominant language was trained, and only within-language generalization when the dominant language was trained. We also hypothesized that cross-language generalization is modulated by nonverbal cognitive control. Results revealed that when English abstract words were trained, within-language generalization to concrete words and cross-language generalization to Russian abstract words was observed, confirming our first hypothesis. However, our second hypothesis was not confirmed. When Russian was trained, direct effects of treatment and within- or cross-language generalization effects were not observed. Our third hypothesis was confirmed. Results from cognitive control tasks from this individual suggest a role of nonverbal cognitive control on cross-language treatment outcomes.

Contraction of want to to wanna is sometimes possible (e.g., Who do you want to/wanna stay with ___ ?), but sometimes impossible (e.g., Who do you want ___ to/*wanna stay?). This contrast is attributable to the grammatical constraint that a wh-trace blocks the contraction of want and to. Most first language (L1) and second language (L2) acquisition studies testing learner knowledge of this constraint have used elicited production tasks and focused on adult participants, with inconsistent results. Using a child-friendly acceptability judgment task, the current study shows that children as young as 3;11 and both child and adult L2 learners have target-like knowledge of the constraint on wanna contraction. This result is in line with the position that L1 acquisition, child L2 acquisition, and adult L2 acquisition are qualitatively similar.

Bilinguals experience processing costs when comprehending code-switches, yet the magnitude of the cost fluctuates depending on numerous factors. We tested whether switch costs vary based on the frequency of different types of code-switches, as estimated from natural corpora of bilingual speech and text. Spanish–English bilinguals in the U.S. read single-language and code-switched sentences in a self-paced task. Sentence regions containing code-switches were read more slowly than single-language control regions, consistent with the idea that integrating a code-switch poses a processing challenge. Crucially, more frequent code-switches elicited significantly smaller costs both within and across most classes of switch types (e.g., within verb phrases and when comparing switches at verb-phrase and noun-phrase sites). The results suggest that, in addition to learning distributions of syntactic and semantic patterns, bilinguals develop finely tuned expectations about code-switching behavior – representing one reason why code-switching in naturalistic contexts may not be particularly costly.

Personal pronouns can potentially be resolved in logical syntax by means of variable binding (VB) or at the discourse-representational level through coreference assignment (CR). Previous research suggests that real-time reference resolution is guided more strongly by discourse-level cues in a non-native language (L2) than in a native language (L1). Here we use the VB/CR distinction to further test this hypothesis. Using eye-movement monitoring during reading and a complementary questionnaire task, we compared L1 German and L1 Russian/L2 German speakers’ resolution of object pronouns. While both our participant groups ultimately preferred CR over VB interpretations, only the L2 participants showed evidence of favouring a sentence-external CR antecedent from early on during processing. Our L1 group, by contrast, favoured a VB antecedent during processing. The observed L1/L2 processing differences reveal divergent antecedent search strategies, with L2 but not L1 speakers being primarily guided by discourse-level cues during real-time comprehension.

Previous research suggests that child HSs’ performance in offline linguistic tasks is typically worse than their age-matched monolingual peers and is modulated by linguistic and child-level factors. This study examined the comprehension and production of three Mandarin non-canonical structures in 5- to 9-year-old Mandarin–English heritage children and Mandarin-speaking monolingual children, including an online processing task. Results showed that heritage children had different performance in production and offline comprehension across structures compared to monolinguals. In online processing, they showed sensitivity to different cues similarly to monolinguals but took longer to revise initial misinterpretations. Within heritage children, we found that presence of morphosyntactic cues facilitated performance across tasks while cross-linguistic influence was only identified in production and offline comprehension but not in online processing. Additionally, input quantity predicted their production and offline comprehension accuracy of non-canonical structures, whereas age modulated their production. Lastly, online processing was not modulated by age nor input.

In adulthood, novel words are commonly encountered in the context of sequential language learning, and to a lesser extent, when learning a new word in one's native language. Paired-associate (PAL) and cross-situational word learning (CSWL) paradigms have been studied separately, under distinct theoretical umbrellas, limiting the understanding of the mechanisms underlying the learning process in each. We tested 126 monolinguals and 111 bilinguals on PAL and CSWL, manipulating familiarity and measuring verbal working memory. Results revealed highly similar learning performance across groups, both demonstrating better performance in PAL than in CSWL, similar sensitivity to familiarity, and similar reliance on phonological working memory. We observed a trend such that bilinguals outperformed monolinguals in PAL but not in CSWL, but this trend was weak. Findings indicate limited effects of bilingualism on word learning in adulthood and suggest highly similar word learning mechanisms in learners with different linguistic experiences.

When a bilingual speaker has a larger linguistic sub-system in their L1 than their L2, how are L1 categories mapped to the smaller set of L2 categories? This article investigates this “subset scenario” (Escudero, 2005) through an analysis of laterals in highly proficient bilinguals (Scottish Gaelic L1, English L2). Gaelic has three lateral phonemes and English has one. We examine acoustics and articulation (using ultrasound tongue imaging) of lateral production in speakers’ two languages. Our results suggest that speakers do not copy a relevant Gaelic lateral into their English, instead maintaining language-specific strategies, with speakers also producing English laterals with positional allophony. These results show that speakers develop a separate production strategy for their L2. Our results advance models such as the L2LP which has mainly considered perception data, and also contribute articulatory data to this area of study.

Semantic feature-based treatments (SFTs) are effective rehabilitation strategies for word retrieval deficits in bilinguals with aphasia (BWA). However, few studies have prospectively evaluated the effects of key parameters of these interventions on treatment outcomes. This study examined the influence of intervention-level (i.e., treatment language and treatment sessions), individual-level (baseline naming severity and age), and stimulus-level (i.e., lexical frequency, phonological length, and phonological neighborhood density) factors on naming improvement in a treated and untreated language for 34 Spanish–English BWA who completed 40 hours of SFT. Results revealed significant improvement over time in both languages. In the treated language, individuals who received therapy in their L1 improved more. Additionally, higher pre-treatment naming scores predicted greater response to treatment. Finally, a frequency effect on baseline naming accuracy and phonological effects on accuracy over time were associated with differential treatment gains. These findings indicate that multilevel factors are influential predictors of bilingual treatment outcomes.

Bilingualism has been shown to contribute to increased resilience against cognitive aging. One of the key brain structures linked to memory and dementia symptom onset, the hippocampus, has been observed to adapt in response to bilingual experience – at least in healthy individuals. However, in the context of neurodegenerative pathology, it is yet unclear what role previous bilingual experience might have in terms of sustaining integrity of this structure or related behavioral correlates. The present study adds to the limited cohort of research on the effects of bilingualism on neurocognitive outcomes in Mild Cognitive Impairment (MCI) using structural brain data. We investigate whether bilingual language experience (operationalized as language entropy) results in graded neurocognitive adaptations within a cohort of bilinguals diagnosed with MCI. Results reveal a non-linear effect of bilingual language entropy on hippocampal volume, although they do not predict episodic memory performance, nor age of MCI diagnosis.

Text comprehension frequently demands the resolution of no longer plausible interpretations to build an accurate situation model, an ability that might be especially challenging during second language comprehension. Twenty-two native English speakers (L1) and twenty-two highly proficient non-native English speakers (L2) were presented with short narratives in English. Each text required the evaluation and revision of an initial prediction. Eye movements in the text and a comprehension sentence indicated less efficient performance in the L2 than in L1 comprehension, in both inferential evaluation and revision. Interestingly, these effects were determined by individual differences in inhibitory control and linguistic proficiency. Higher inhibitory control reduced the time rereading previous parts of the text (better evaluation) as well as revisiting the text before answering the sentence (better revision) in L2 comprehenders, whereas higher proficiency reduced the time in the sentence when the story was coherent, suggesting better general comprehension in both languages.

While research in heritage language phonology has found that transfer from the majority language can lead to divergent attainment in adult heritage language grammars, the extent to which language transfer develops during a heritage speaker's lifespan is understudied. To explore such cross-linguistic transfer, I examine the rate of glottalization between consonant-to-vowel sequences at word junctures produced by child and adult Spanish heritage speakers (i.e., HSs) in both languages. My results show that, in Spanish, child HSs produce greater rates of vowel-initial glottal phonation than their age-matched monolingually-raised Spanish counterparts, suggesting that the Spanish child HSs’ grammars are more permeable to transfer than those of the adult HSs. In English, child and adult HSs show similarly low rates of glottal phonation when compared to their age-matched monolingually-raised English speakers’ counterparts. The findings for English can be explained by either an account of transfer at the individual level or the community level.

To test effects of German on anticipation in Vietnamese, we recorded eye-movements during comprehension and manipulated i) verb constraints (different vs. similar in German and Vietnamese) and ii) classifier constraints (absent in German). In each of two experiments, participants listened to Vietnamese sentences like “Mai mặc một chiếc áo.” (‘Mai wears a [classifier] shirt.’), while viewing four objects. Between experiments, we contrasted bilingual background: L1 Vietnamese–L2 German late bilinguals (Experiment 1) and heritage speakers of Vietnamese in Germany (Experiment 2). Both groups anticipated verb-compatible and classifier-compatible objects upon hearing the verb/classifier. However, when the (verb) constraints differed (e.g., Vietnamese: mặc ‘wear (a shirt/#earrings)’ – German: tragen ‘wear (a shirt/earrings)’), the heritage speakers were distracted by the object (earrings) compatible with the German (but not the Vietnamese) verb constraints. These results demonstrate that competing information in the two languages can interfere with anticipation in heritage speakers.