Sometimes larger, sometimes smaller: Measuring vocabulary in monolingual and bilingual infants and toddlers.

Vocabulary size is a crucial early indicator of language development, for both monolingual and bilingual children. Assessing vocabulary in bilingual children is complex because they learn words in two languages, and there remains significant controversy about how to best measure their vocabulary size, especially in relation to monolinguals. This study compared monolingual vocabulary with different metrics of bilingual vocabulary, including combining vocabulary across languages to count either the number of words or the number of concepts lexicalized and assessing vocabulary in a single language. Data were collected from parents of 743 infants and toddlers aged 8-33 months learning French and/or English, using the MacArthur-Bates Communicative Development Inventories. The results showed that the nature and magnitude of monolingual-bilingual differences depended on how bilinguals' vocabulary was measured. Compared with monolinguals, bilinguals had larger expressive and receptive word vocabularies, similarly sized receptive concept vocabularies and smaller expressive concept vocabularies. Bilinguals' single-language vocabularies were smaller than monolinguals' vocabularies. The study highlights the need to better understand the role of translation equivalents in bilingual vocabulary development and the potential developmental differences in receptive and expressive vocabularies.

Are translation equivalents special? Evidence from simulations and empirical data from bilingual infants.

The acquisition of translation equivalents is often considered a special component of bilingual children's vocabulary development, as bilinguals have to learn words that share the same meaning across their two languages. This study examined three contrasting accounts for bilingual children's acquisition of translation equivalents relative to singlets (i.e., words that are first labels for a referent): the Avoidance Account whereby translation equivalents are harder to learn, the Preference Account whereby translation equivalents are easier to learn, and the Neutral Account whereby translation equivalents and singlets are learned similarly. To adjudicate between these accounts, Study 1 explored patterns of translation equivalent learning under a novel computational model - the Bilingual Vocabulary Model - which quantifies translation equivalent knowledge as a function of the probability of learning words in each language, and includes a bias parameter that varies the difficulty of learning translation equivalents according to each account. Study 2 tested model-derived predictions against vocabulary data from 200 French-English bilingual children aged 18-33 months. Results showed a close match between the model predictions and bilingual children's patterns of translation equivalent learning. At smaller vocabulary sizes, data matched the Preference Account, while at larger vocabulary sizes they matched the Neutral Account. Our findings show that patterns of translation equivalent learning emerge predictably from the word learning process, and potentially reveal a qualitative shift in translation equivalent learning as bilingual children develop and learn more words.

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.

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.

Brief Report: Vocabulary and Grammatical Skills of Bilingual Children with Autism Spectrum Disorders at School Age.

We examined the lexical and grammatical skills of monolingual and bilingual school-age children with autism spectrum disorders (ASD). Thirteen monolingual and thirteen bilingual children with ASD without intellectual disability, were compared on standardized measures of vocabulary and morphology. Findings revealed that bilingual children performed in the average monolingual range on a standardized receptive vocabulary test and slightly below the average range on a standardized morphological task in their dominant language. Prior work indicates that bilingual exposure is not detrimental for early language development in children with autism. The current findings suggest that at school age, bilinguals with ASD show similar language development patterns as those described in the literature on typically-developing bilinguals.

Can Bilingualism Mitigate Set-Shifting Difficulties in Children With Autism Spectrum Disorders?

This study investigated the effects of bilingualism on set-shifting and working memory in children with autism spectrum disorders (ASD). Bilinguals with ASD were predicted to display a specific bilingual advantage in set-shifting, but not working memory, relative to monolinguals with ASD. Forty 6- to 9-year-old children participated (20 ASD, 20 typically-developing). Set-shifting was measured using a computerized dimensional change card sort (DCCS) task, and by parent report of executive functioning in daily life. Results showed an advantage for bilingual relative to monolingual children with ASD on the DCCS task, but not for set-shifting in daily life. Working memory was similar for bilinguals and monolinguals with ASD. These findings suggest that bilingualism may mitigate some set-shifting difficulties in children with ASD.

Bilingual children with autism spectrum disorders: The impact of amount of language exposure on vocabulary and morphological skills at school age.

Studies of bilingual children with Autism Spectrum Disorders (ASD) have focused on early language development using parent report measures. However, the effect of bilingual exposure on more complex linguistic abilities is unknown. In the current study, we examined the impact of amount of language exposure on vocabulary and morphological skills in school-aged children with ASD who did not have intellectual disability. Forty-seven typically developing children and 30 children with ASD with varying exposure to French participated in the study. We investigated the impact of amount of language exposure, nonverbal IQ, age, and working memory on language abilities via regression analyses. Current amount of language exposure was the strongest predictor of both vocabulary skills (accounting for 62% of the variance) and morphological skills (accounting for 49% of the variance), for both typically-developing children and children with ASD. These findings highlight the central role amount of language exposure plays in vocabulary and morphological development for children with ASD, as it does for typically-developing children. In addition, they provide further evidence that, when provided with adequate language exposure, many children with ASD are capable of acquiring two languages. Autism Research 2018, 11: 1667-1678. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: We studied typically developing children and children with ASD living in a bilingual society who had varying exposure to French (ranging from bilinguals to monolinguals). We investigated the impact of amount of language exposure, nonverbal IQ, age, and working memory on their vocabulary and morphological skills. Current amount of language exposure was the strongest predictor of language skills in both groups of children. Findings indicate that when provided with adequate language exposure, many children with ASD are capable of acquiring two languages.

Children's referential understanding of novel words and parent labeling behaviors: similarities across children with and without autism spectrum disorders.

This study examined two facets of the use of social cues for early word learning in parent-child dyads, where children had an Autism Spectrum Disorder (ASD) or were typically developing. In Experiment 1, we investigated word learning and generalization by children with ASD (age range: 3;01-6;02) and typically developing children (age range: 1;02-4;09) who were matched on language ability. In Experiment 2, we examined verbal and non-verbal parental labeling behaviors. First, we found that both groups were similarly able to learn a novel label using social cues alone, and to generalize this label to other representations of the object. Children who utilized social cues for word learning had higher language levels. Second, we found that parental cues used to introduce object labels were strikingly similar across groups. Moreover, parents in both groups adapted labeling behavior to their child's language level, though this surfaced in different ways across groups.