Cognates are advantaged over non-cognates in early bilingual expressive vocabulary development.

Bilinguals need to learn two words for most concepts. These words are called translation equivalents, and those that also sound similar (e.g., banana-banane) are called cognates. Research has consistently shown that children and adults process and name cognates more easily than non-cognates. The present study explored if there is such an advantage for cognate production in bilinguals' early vocabulary development. Longitudinal expressive vocabulary data were collected from 47 English-French bilinguals starting at 16-20 months up to 27 months (a total of 219 monthly administrations in both English and French). Children produced a greater proportion of cognates than non-cognates, and the interval between producing a word and its translation equivalent was about 10-15 days shorter for cognates than for non-cognates. The findings suggest that cognate learning is facilitated in early bilingual vocabulary development, such that phonological overlap supports bilinguals in learning phonologically similar words across their two languages.

Gesture development in infancy: Effects of gender but not bilingualism.

Gesture is an important communication tool that provides insight into infants' early language and cognitive development and predicts later language skills. While bilingual school-age children have been reported to gesture more than monolinguals, there is a lack of research examining gesture use in infants exposed to more than one language. In this preregistered study, we compared three groups of 14-month-old infants (N = 150) learning French and/or English: bilinguals (hearing a second language at least 25% of the time), exposed (hearing a second language 10%-24% of the time), and monolinguals (hearing one language 90% of the time or more). Parent-reported use of communicative gestures was gathered from the MacArthur-Bates Communicative Development Inventories (CDI). Results showed that the three language groups had similarly sized gesture repertoires, suggesting that language exposure did not affect gesture development at this age. However, a gender effect was found, where girls produced more types of gestures than boys. Overall, these results suggest that gender, but not language exposure, contributes to differences in gesture development in infancy.

Improving the generalizability of infant psychological research: The ManyBabies model.

Yarkoni's analysis clearly articulates a number of concerns limiting the generalizability and explanatory power of psychological findings, many of which are compounded in infancy research. ManyBabies addresses these concerns via a radically collaborative, large-scale and open approach to research that is grounded in theory-building, committed to diversification, and focused on understanding sources of variation.

Multilingual toddlers' vocabulary development in two languages: Comparing bilinguals and trilinguals.

Many children grow up hearing multiple languages, learning words in each. How does the number of languages being learned affect multilinguals' vocabulary development? In a pre-registered study, we compared productive vocabularies of bilingual (n = 170) and trilingual (n = 20) toddlers aged 17-33 months growing up in a bilingual community where both French and English are spoken. We hypothesized that because trilinguals have reduced input in French and English due to time spent hearing their third language, they would have smaller French-English vocabulary sizes than bilinguals. Trilinguals produced on average 2/3 of the number of words in these languages that bilinguals did: however, this difference was not statistically robust due to large levels of variability. Follow-up analyses did, however, indicate a relationship between input quantity and vocabulary size. Our results indicate that similar factors contribute to vocabulary development across toddlers regardless of the number of languages being acquired.

Code-switching in parents' everyday speech to bilingual infants.

Code-switching is a common phenomenon in bilingual communities, but little is known about bilingual parents' code-switching when speaking to their infants. In a pre-registered study, we identified instances of code-switching in day-long at-home audio recordings of 21 French-English bilingual families in Montreal, Canada, who provided recordings when their infant was 10 and 18 months old. Overall, rates of infant-directed code-switching were low, averaging 7 times per hour (6 times per 1,000 words) at 10 months and increasing to 28 times per hour (18 times per 1,000 words) at 18 months. Parents code-switched more between sentences than within a sentence; this pattern was even more pronounced when infants were 18 months than when they were 10 months. The most common apparent reasons for code-switching were to bolster their infant's understanding and to teach vocabulary words. Combined, these results suggest that bilingual parents code-switch in ways that support successful bilingual language acquisition.

Quebec-based Parents' Attitudes Towards Childhood Multilingualism: Evaluative Dimensions and Potential Predictors.

This is the first large-scale, quantitative study of the evaluative dimensions and potential predictors of Quebec-based parents' attitudes towards childhood multilingualism. Such attitudes are assumed to constitute a determinant of parental language choices, and thereby influence children's multilingual development. The newly-developed Attitudes towards Childhood Multilingualism Questionnaire was used to gather data from 825 participants raising an infant/toddler aged 0-4 years with multiple languages in the home. The results revealed three separate dimensions: status and solidarity (the same dimensions found in attitudes towards individual languages) as well as cognitive development (not previously attested as a separate dimension). Participants' approach to promoting multilingualism (specifically, whether they used the one-person-one-language-approach) and the combination of languages transmitted (specifically, whether this included a heritage language) correlated significantly with parental attitudes towards childhood multilingualism. Parents' linguistic background and location within Quebec were not significant predictors of attitudes. The paper discusses implications and directions for further research.

Bilingual children judge moral, social, and language violations as less transgressive than monolingual children.

Learning the rules and expectations that govern our social interactions is one of the major challenges of development. The current study examined whether bilingualism is associated with differences in children's developing social knowledge. We presented 54 4- to 6-year-old monolingual and bilingual children with vignettes of moral transgressions (e.g., hitting), social transgressions (e.g., wearing pants on one's head), and language transgressions (e.g., calling a common object by a nonsense word) and asked about their permissibility. In line with previous research findings, results demonstrate that all children evaluated moral violations more harshly than conventional violations. Notably, however, bilingual children were more permissive of violations across moral, social, and language domains than monolingual children. These findings yield new insights into the role of early experience in the development of social knowledge. We propose that bilinguals' unique linguistic and social experiences influence their understanding of moral and conventional rules.

Fine-tuning language discrimination: Bilingual and monolingual infants' detection of language switching.

The ability to differentiate between two languages sets the stage for bilingual learning. Infants can discriminate languages when hearing long passages, but language switches often occur on short time scales with few cues to language identity. As bilingual infants begin learning sequences of sounds and words, how do they detect the dynamics of two languages? In two studies using the head-turn preference procedure, we investigated whether infants (n = 44) can discriminate languages at the level of individual words. In Study 1, bilingual and monolingual 8- to 12-month-olds were tested on their detection of single-word language switching in lists of words (e.g., "dog… lait [fr. milk]"). In Study 2, they were tested on language switching within sentences (e.g., "Do you like the lait?"). We found that infants were unable to detect language switching in lists of words, but the results were inconclusive about infants' ability to detect language switching within sentences. No differences were observed between bilinguals and monolinguals. Given that bilingual proficiency eventually requires detection of sound sequences across two languages, more research will be needed to conclusively understand when and how this skill emerges. Materials, data, and analysis scripts are available at https://osf.io/9dtwn/.

The development of gaze following in monolingual and bilingual infants: A multi-laboratory study.

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non-verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word-learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze-following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6- to 9-month-old and 229 12- to 15-month-old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities, and both groups showed age-related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on-screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

What do bilingual infants actually hear? Evaluating measures of language input to bilingual-learning 10-month-olds.

Examining how bilingual infants experience their dual language input is important for understanding bilingual language acquisition. To assess these language experiences, researchers typically conduct language interviews with caregivers. However, little is known about the reliability of these parent reports in describing how bilingual children actually experience dual language input. Here, we explored the quantitative nature of dual language input to bilingual infants. Furthermore, we described some of the heterogeneity of bilingual exposure in a sample of French-English bilingual families. Participants were 21 families with a 10-month-old infant residing in Montréal, Canada. First, we conducted language interviews with the caregivers. Then, each family completed three full-day recordings at home using the Language Environment Analysis recording system. Results showed that children's proportion exposure to each language was consistent across the two measurement approaches, indicating that parent reports are reliable for assessing a bilingual child's language experiences. Further exploratory analyses revealed three unique findings: (a) there can be considerable variability in the absolute amount of input among infants hearing the same proportion of input, (b) infants can hear different proportions of language input when considering infant-directed versus overheard speech, (c) proportion of language input can vary by day, depending on who is caring for the infant. We conclude that collecting naturalistic recordings is complementary to parent-report measures for assessing infant's language experiences and for establishing bilingual profiles.

Statistical learning of multiple speech streams: A challenge for monolingual infants.

Language acquisition depends on the ability to detect and track the distributional properties of speech. Successful acquisition also necessitates detecting changes in those properties, which can occur when the learner encounters different speakers, topics, dialects, or languages. When encountering multiple speech streams with different underlying statistics but overlapping features, how do infants keep track of the properties of each speech stream separately? In four experiments, we tested whether 8-month-old monolingual infants (N = 144) can track the underlying statistics of two artificial speech streams that share a portion of their syllables. We first presented each stream individually. We then presented the two speech streams in sequence, without contextual cues signaling the different speech streams, and subsequently added pitch and accent cues to help learners track each stream separately. The results reveal that monolingual infants experience difficulty tracking the statistical regularities in two speech streams presented sequentially, even when provided with contextual cues intended to facilitate separation of the speech streams. We discuss the implications of our findings for understanding how infants learn and separate the input when confronted with multiple statistical structures.

Bilingual infants control their languages as they listen.

Infants growing up in bilingual homes learn two languages simultaneously without apparent confusion or delay. However, the mechanisms that support this remarkable achievement remain unclear. Here, we demonstrate that infants use language-control mechanisms to preferentially activate the currently heard language during listening. In a naturalistic eye-tracking procedure, bilingual infants were more accurate at recognizing objects labeled in same-language sentences ("Find the dog!") than in switched-language sentences ("Find the chien!"). Measurements of infants' pupil size over time indicated that this resulted from increased cognitive load during language switches. However, language switches did not always engender processing difficulties: the switch cost was reduced or eliminated when the switch was from the nondominant to the dominant language, and when it crossed a sentence boundary. Adults showed the same patterns of performance as infants, even though target words were simple and highly familiar. Our results provide striking evidence from infancy to adulthood that bilinguals monitor their languages for efficient comprehension. Everyday practice controlling two languages during listening is likely to explain previously observed bilingual cognitive advantages across the lifespan.

Building a collaborative Psychological Science: Lessons learned from ManyBabies 1.

The field of infancy research faces a difficult challenge: some questions require samples that are simply too large for any one lab to recruit and test. ManyBabies aims to address this problem by forming large-scale collaborations on key theoretical questions in developmental science, while promoting the uptake of Open Science practices. Here, we look back on the first project completed under the ManyBabies umbrella - ManyBabies 1 - which tested the development of infant-directed speech preference. Our goal is to share the lessons learned over the course of the project and to articulate our vision for the role of large-scale collaborations in the field. First, we consider the decisions made in scaling up experimental research for a collaboration involving 100+ researchers and 70+ labs. Next, we discuss successes and challenges over the course of the project, including: protocol design and implementation, data analysis, organizational structures and collaborative workflows, securing funding, and encouraging broad participation in the project. Finally, we discuss the benefits we see both in ongoing ManyBabies projects and in future large-scale collaborations in general, with a particular eye towards developing best practices and increasing growth and diversity in infancy research and psychological science in general. Throughout the paper, we include first-hand narrative experiences, in order to illustrate the perspectives of researchers playing different roles within the project. While this project focused on the unique challenges of infant research, many of the insights we gained can be applied to large-scale collaborations across the broader field of psychology.

Bilingual toddlers' comprehension of mixed sentences is asymmetrical across their two languages.

In bilingual language environments, infants and toddlers listen to two separate languages during the same key years that monolingual children listen to just one and bilinguals rarely learn each of their two languages at the same rate. Learning to understand language requires them to cope with challenges not found in monolingual input, notably the use of two languages within the same utterance (e.g., Do you like the perro? or ¿Te gusta el doggy?). For bilinguals of all ages, switching between two languages can reduce the efficiency in real-time language processing. But language switching is a dynamic phenomenon in bilingual environments, presenting the young learner with many junctures where comprehension can be derailed or even supported. In this study, we tested 20 Spanish-English bilingual toddlers (18- to 30-months) who varied substantially in language dominance. Toddlers' eye movements were monitored as they looked at familiar objects and listened to single-language and mixed-language sentences in both of their languages. We found asymmetrical switch costs when toddlers were tested in their dominant versus non-dominant language, and critically, they benefited from hearing nouns produced in their dominant language, independent of switching. While bilingualism does present unique challenges, our results suggest a united picture of early monolingual and bilingual learning. Just like monolinguals, experience shapes bilingual toddlers' word knowledge, and with more robust representations, toddlers are better able to recognize words in diverse sentences.

Labels or Concepts? The Development of Semantic Networks in Bilingual Two-Year-Olds.

The adult lexicon links concepts and labels with related meanings (e.g., dog-cat). How do children's encounters with concepts versus labels contribute to semantic development? Three studies investigated semantic priming in 40 monolinguals and 32 bilinguals, who have similar experience with concepts but different experience with labels (i.e., monolinguals hear "dog," bilinguals hear "dog" and "chien"). Similarities in performance across monolinguals and bilinguals at age 24 months, as well as across bilinguals' two languages at age 30 months, support the position that encounters with concepts contribute more to early semantic development than encounters with labels. Findings also suggest that the effects of semantic priming are challenging to observe at 24 months but are strong in bilinguals by age 30 months.

Uh and euh signal novelty for monolinguals and bilinguals: evidence from children and adults.

Previous research suggests that English monolingual children and adults can use speech disfluencies (e.g., uh) to predict that a speaker will name a novel object. To understand the origins of this ability, we tested 48 32-month-old children (monolingual English, monolingual French, bilingual English-French; Study 1) and 16 adults (bilingual English-French; Study 2). Our design leveraged the distinct realizations of English (uh) versus French (euh) disfluencies. In a preferential-looking paradigm, participants saw familiar-novel object pairs (e.g., doll-rel), labeled in either Fluent ("Look at the doll/rel!"), Disfluent Language-consistent ("Look at thee uh doll/rel!"), or Disfluent Language-inconsistent ("Look at thee euh doll/rel!") sentences. All participants looked more at the novel object when hearing disfluencies, irrespective of their phonetic realization. These results suggest that listeners from different language backgrounds harness disfluencies to comprehend day-to-day speech, possibly by attending to their lengthening as a signal of speaker uncertainty. Stimuli and data are available at .

Bilingualism affects 9-month-old infants' expectations about how words refer to kinds.

Infants are precocious word learners, and seem to possess systematic expectations about how words refer to object kinds. For example, while monolingual infants show a one-to-one mapping bias (e.g. mutual exclusivity), expecting each object to have only one basic level label, previous research has shown that this is less robust in bi- and multilinguals aged 1.5 years and older. This study examined the early origins of such one-to-one mapping biases by comparing monolingual and bilingual 9-10-month-olds' expectations about the relationship between labels and object kinds. In a violation of expectation paradigm, infants heard a speaker name hidden objects with either one label ('I see a mouba! I see a mouba!') or two labels ('I see a camo! I see a tenda!'). An occluder moved to reveal two objects that were either identical or of different kinds. Monolingual infants looked longest when two labels were associated with identical objects, and when one label was associated with objects of different kinds, showing that they found these outcomes unexpected. This replicated previous findings showing that monolinguals expect that distinct words label distinct object kinds (Dewar & Xu, ). Bilinguals looked equally to the outcomes regardless of the number of labels, showing no such expectations. This finding indicates that bilingualism influences young infants' expectations about how words refer to kinds, and more broadly supports the position that language experience contributes to the development of word learning heuristics.

Monolingual and bilingual children's social preferences for monolingual and bilingual speakers.

Past research has shown that young monolingual children exhibit language-based social biases: they prefer native language to foreign language speakers. The current research investigated how children's language preferences are influenced by their own bilingualism and by a speaker's bilingualism. Monolingual and bilingual 4- to 6-year-olds heard pairs of adults (a monolingual and a bilingual, or two monolinguals) and chose the person with whom they wanted to be friends. Whether they were from a largely monolingual or a largely bilingual community, monolingual children preferred monolingual to bilingual speakers, and native language to foreign language speakers. In contrast, bilingual children showed similar affiliation with monolingual and bilingual speakers, as well as for monolingual speakers using their dominant versus non-dominant language. Exploratory analyses showed that individual bilinguals displayed idiosyncratic patterns of preference. These results reveal that language-based preferences emerge from a complex interaction of factors, including preference for in-group members, avoidance of out-group members, and characteristics of the child as they relate to the status of the languages within the community. Moreover, these results have implications for bilingual children's social acceptance by their peers.

Bilingualism changes children's beliefs about what is innate.

Young children engage in essentialist reasoning about natural kinds, believing that many traits are innately determined. This study investigated whether personal experience with second language acquisition could alter children's essentialist biases. In a switched-at-birth paradigm, 5- and 6-year-old monolingual and simultaneous bilingual children expected that a baby's native language, an animal's vocalizations, and an animal's physical traits would match those of a birth rather than of an adoptive parent. We predicted that sequential bilingual children, who had been exposed to a new language after age 3, would show greater understanding that languages are learned. Surprisingly, sequential bilinguals showed reduced essentialist beliefs about all traits: they were significantly more likely than other children to believe that human language, animal vocalizations, and animal physical traits would be learned through experience rather than innately endowed. These findings suggest that bilingualism in the preschool years can profoundly change children's essentialist biases.