Lexicon structure and the disambiguation of novel words: evidence from bilingual infants

Comparing apples to manzanas and oranges to naranjas: A new measure of English-Spanish vocabulary for dual language learners

The valid assessment of vocabulary development in dual-language-learning infants is critical to developmental science. We developed the Dual Language Learners English-Spanish (DLL-ES) Inventories to measure vocabularies of U.S. English-Spanish DLLs. The inventories provide translation equivalents for all Spanish and English items on Communicative Development Inventory (CDI) short forms; extended inventories based on CDI long forms; and Spanish language-variety options. Item-Response Theory analyses applied to Wordbank and Web-CDI data (n = 2603, 12-18 months; n = 6722, 16-36 months; half female; 1% Asian, 3% Black, 2% Hispanic, 30% White, 64% unknown) showed near-perfect associations between DLL-ES and CDI long-form scores. Interviews with 10 Hispanic mothers of 18- to 24-month-olds (2 White, 1 Black, 7 multi-racial; 6 female) provide a proof of concept for the value of the DLL-ES for assessing the vocabularies of DLLs.

The scope and role of deduction in infant cognition

The origins of the human capacity for logically structured thought are still a mystery. Studies on young humans, which can be particularly informative, present conflicting results. Infants seem able to generate competing hypotheses1,2,3 and monitor the certainty or probability of one-shot outcomes,4,5,6,7,8 suggesting the existence of an articulated language of thought.9 However, sometimes toddlers10 and even children younger than 411,12,13,14 fail tasks seemingly requiring the same representational abilities. One fundamental test for the presence of logical abilities is the concept of disjunction as a way into the conception of alternative possibilities, and of disjunctive elimination as a way to prune them. Here, we document their widespread presence in 19-month-old infants. In a word-referent association task, both bilingual and monolingual infants display a pattern of oculomotor inspection previously found to be a hallmark of disjunctive reasoning in adults and children,15,16 showing that the onset of logical reasoning is not crucially dependent on language experience. The pattern appears when targets are novel, but also when both objects and words are known, though likely not yet sedimented into a mature lexicon. Disjunctive reasoning also surfaces in a non-linguistic location search task, not prompted by violated expectations, showing that infants reason by elimination spontaneously. Together, these results help answer long-standing empirical and philosophical puzzles about the role of logic in early knowledge development, suggesting that by increasing confidence in some options while eliminating alternatives, logic provides scaffolding for the organization of knowledge about the world, language, and language-world relations.

A principled link between object naming and representation is available to infants by seven months of age

By their first birthdays, infants represent objects flexibly as a function of not only whether but how the objects are named. Applying the same name to a set of different objects from the same category supports object categorization, with infants encoding commonalities among objects at the expense of individuating details. In contrast, applying a distinct name to each object supports individuation, with infants encoding distinct features at the expense of categorical information. Here, we consider the development of this nuanced link between naming and representation in infants' first year. Infants at 12 months (Study 1; N = 55) and 7 months (Study 2; N = 96) participated in an online recognition memory task. All infants saw the same objects, but their recognition of these objects at test varied as a function of how they had been named. At both ages, infants successfully recognized objects that had been named with distinct labels but failed to recognize these objects when they had all been named with the same, consistent label. This new evidence demonstrates that a principled link between object naming and representation is available by 7 months, early enough to support infants as they begin mapping words to meaning.

Polish-German preschoolers develop and use heritage Polish differently depending on whether they heard German from birth or not

This study assessed the language proficiency and use of a hitherto under-investigated group, viz., 3.5-year-olds growing up with Polish as a heritage language and German as societal language. All children (N = 28) heard Polish from birth in the home but half the children also heard German from birth (Bilingual First Language Acquisition, BFLA) while the other half added German through preschool (Early Second Language Acquisition, ESLA). All children attended German preschools. Data collection relied on an online survey filled out by 28 mothers and 20 fathers. There were large discrepancies between parental answers to general versus detailed questions regarding language use (choice) amongst parents and children. This has important repercussions for much of questionnaire based bilingualism research. Children were developing productive language as expected but BFLA preschoolers spoke German better or spoke both languages equally well whereas ESLA preschoolers spoke Polish better. Apart from BFLA children’s much longer and daily exposure to German from birth, these BFLA-ESLA differences in relative Polish proficiency may relate to different current patterns of language choice, with (1) Polish less present in parent–child interactions involving BFLA than ESLA preschoolers, and with (2) BFLA but not ESLA preschoolers mostly hearing Polish from just a single parent. The BFLA-ESLA difference thus made a difference to children’s heritage Polish development and use already at age 3.5.

Language-Fair Fast Mapping and Mutual Exclusivity Tasks for Mono- and Bilingual Preschoolers

PURPOSE

Both monolingual and bilingual children use learning constraints and heuristics to acquire new words from their environment. Overall, fast mapping abilities seem to be similar in both populations, but monolinguals rely more than bilinguals on the mutual exclusivity strategy. Our study probes the robustness of these results in a large group of children learning different language combinations, with a newly devised language-fair task that relies as little as possible on previous linguistic knowledge, in order to avoid disadvantaging bilingual children.

METHOD

We tested 138 3- to 5-year-old mono- and bilingual children in their dominant language (German, French, Italian, or Turkish) in a computerized task starting with a fast mapping phase, followed by a mutual exclusivity phase, using only invented nonobjects and nonwords.

RESULTS

As hypothesized, monolingual and bilingual children showed similar results during the initial fast mapping stage, but monolinguals relied significantly more on the mutual exclusivity strategy than their bilingual peers.

CONCLUSIONS

The language-fair design of our task supports the idea that differences in mutual exclusivity strategy use between mono- and bilingual children really stem from their specific linguistic background, and not from potential familiarity differences with respect to the test words. We discuss the implications of our results for bilingual language assessment in clinical or educational contexts.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20669214.

The role of syntactic cues in monolingual and bilingual two-year-olds’ novel word disambiguation

Although linguistic and nonlinguistic cues help young children infer meaning when presented with unfamiliar words, little is known about how syntactic information and early bilingual experience shape word learning. This study examined how monolingual and bilingual 24- to 30-month-olds' disambiguation of novel words during a mutual exclusivity task differs as a function of syntactic cues, age, and productive vocabulary. English monolinguals and Spanish-English bilinguals were presented with familiar and novel objects within a syntactic context (e.g., "Give me the blick!") or in isolation (e.g., "Blick!"). Results showed that monolinguals and bilinguals adhered to mutual exclusivity more often when provided with syntactic cues than when those cues were absent. Furthermore, bilinguals' mutually exclusive disambiguation of novel words increased with age, but only when syntactic cues were available. These results provide insight into factors that influence children's disambiguation of novel words. The theoretical implications of these findings are discussed.

Testing the Bilingual Cognitive Advantage in Toddlers Using the Early Executive Functions Questionnaire

The present study aims to assess differences in executive functioning between monolingual and multilingual 23-month-old toddlers, both when dichotomizing multilingualism and assessing it on a continuum. It is hypothesized that multilinguals, individuals with greater non-dominant language exposure, and individuals with more translation equivalents, would perform better in the following domains: response inhibition, attentional flexibility, and regulation. No differences are expected for working memory. The Early Executive Functions Questionnaire, a newly developed parental report, is used to measure the four executive functions of interest. Multilinguals and individuals with greater non-dominant language exposure have significantly higher response inhibition; however, no differences are noted for any other executive function. Additionally, no associations between translation equivalents and executive functioning are found. Post-hoc analyses reveal that non-dominant language production had a positive correlation with working memory. The present findings support the notion of a domain-specific cognitive advantage for multilingual toddlers.

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.

Vocabulary production in toddlers from low-income immigrant families: evidence from children exposed to Romanian-Italian and Nigerian English-Italian

The relationship between first and second language in early vocabulary acquisition in bilingual children is still debated in the literature. This study compared the expressive vocabulary of 39 equivalently low-SES two-year-old bilingual children from immigrant families with different heritage languages (Romanian vs. Nigerian English) and the same majority language (Italian). Vocabulary size, vocabulary composition and translation equivalents (TEs) were assessed using the Italian/L1 versions of the CDI. Higher vocabulary in Italian than in the heritage language emerged in both groups. Moreover, Romanian-Italian-speaking children produced higher proportions of TEs than Nigerian English-Italian-speaking children, suggesting that L1-L2 phonological similarity facilitates the acquisition of cross-linguistic synonyms.

Learning Through Processing: Toward an Integrated Approach to Early Word Learning

Children's linguistic knowledge and the learning mechanisms by which they acquire it grow substantially in infancy and toddlerhood, yet theories of word learning largely fail to incorporate these shifts. Moreover, researchers' often-siloed focus on either familiar word recognition or novel word learning limits the critical consideration of how these two relate. As a step toward a mechanistic theory of language acquisition, we present a framework of "learning through processing" and relate it to the prevailing methods used to assess children's early knowledge of words. Incorporating recent empirical work, we posit a specific, testable timeline of qualitative changes in the learning process in this interval. We conclude with several challenges and avenues for building a comprehensive theory of early word learning: better characterization of the input, reconciling results across approaches, and treating lexical knowledge in the nascent grammar with sufficient sophistication to ensure generalizability across languages and development.

Patterns of mutual exclusivity and retention: A study of monolingual and bilingual 2-year-olds

When children learn their native language, they tend to treat objects as if they only have one label-a principle known as mutual exclusivity. However, bilingual children are faced with a different cognitive challenge-they need to learn to associate two labels with one object. In the present study, we compared bilingual and monolingual 24-month-olds' performance on a challenging and semi-naturalistic forced-choice referent selection task and retention test. Overall, both language groups performed similarly on referent selection but differed on retention. Specifically, while monolingual infants showed some retention, bilingual infants performed at chance and significantly worse than their monolingual peers.

Putting Mutual Exclusivity in Context: Speaker Race Influences Monolingual and Bilingual Infants' Word-Learning Assumptions

Previous work indicates mutual exclusivity in word learning in monolingual, but not bilingual toddlers. We asked whether this difference indicates distinct conceptual biases, or instead reflects best-guess heuristic use in the absence of context. We altered word-learning contexts by manipulating whether a familiar- or unfamiliar-race speaker introduced a novel word for an object with a known category label painted in a new color. Both monolingual and bilingual infants showed mutual exclusivity for a familiar-race speaker, and relaxed mutual exclusivity and treated the novel word as a category label for an unfamiliar-race speaker. Thus, monolingual and bilingual infants have access to similar word-learning heuristics, and both use nonlinguistic social context to guide their use of the most appropriate heuristic.

Twelve-month-olds disambiguate new words using mutual-exclusivity inferences

Representing objects in terms of their kinds enables inferences based on the long-term knowledge made available through kind concepts. For example, children readily use lexical knowledge linked to familiar kind concepts to disambiguate new words (e.g., "find the toma"): they exclude members of familiar kinds falling under familiar kind labels (e.g., a ball) as potential referents and link new labels to available unfamiliar objects (e.g., a funnel), a phenomenon dubbed as 'mutual exclusivity'. Younger infants' failure in mutual exclusivity tasks has been commonly interpreted as a limitation of early word-learning or inferential abilities. Here, we investigated an alternative explanation, according to which infants do not spontaneously represent familiar objects under kind concepts, hence lacking access to the information necessary for rejecting them as referents of novel labels. Building on findings about conceptual development and communication, we hypothesized that nonverbal communication could prompt infants to set up kind-based representations which, in turn, would promote mutual exclusivity inferences. This hypothesis was tested in a looking-while-listening task involving novel word disambiguation. Twelve-month-olds saw pairs of objects, one familiar and one unfamiliar, and heard familiar kind labels or novel words. Across two experiments providing a cross-lab replication in two different languages, infants successfully disambiguated novel words when the familiar object had been pointed at before labeling, but not when it had been highlighted in a non-communicative manner (Experiment 1) or not highlighted at all (Experiment 2). Nonverbal communication induced infants to recruit kind-based representations of familiar objects that they failed to recruit in its absence and that, once activated, supported mutual-exclusivity inferences. Developmental changes in children's appreciation of communicative contexts may modulate the expression of early inferential and word learning competences.

The Role of Audiovisual Speech in Fast-Mapping and Novel Word Retention in Monolingual and Bilingual 24-Month-Olds

Three experiments examined the role of audiovisual speech on 24-month-old monolingual and bilinguals’ performance in a fast-mapping task. In all three experiments, toddlers were exposed to familiar trials which tested their knowledge of known word–referent pairs, disambiguation trials in which novel word–referent pairs were indirectly learned, and retention trials which probed their recognition of the newly-learned word–referent pairs. In Experiment 1 (n = 48), lip movements were present during familiar and disambiguation trials, but not retention trials. In Experiment 2 (n = 48), lip movements were present during all three trial types. In Experiment 3 (bilinguals only, n = 24), a still face with no lip movements was present in all three trial types. While toddlers succeeded in the familiar and disambiguation trials of every experiment, success in the retention trials was only found in Experiment 2. This work suggests that the extra-linguistic support provided by lip movements improved the learning and recognition of the novel words.

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.

Lexical-Semantic Development in Bilingual Toddlers at 18 and 24 Months

An important question in early bilingual first language acquisition concerns the development of lexical-semantic associations within and across two languages. The present study investigates the earliest emergence of lexical-semantic priming at 18 and 24 months in Spanish-English bilinguals (N = 32) and its relation to vocabulary knowledge within and across languages. Results indicate a remarkably similar pattern of development between monolingual and bilingual children, such that lexical-semantic development begins at 18 months and strengthens by 24 months. Further, measures of cross-language lexical knowledge are stronger predictors of children's lexical-semantic processing skill than measures that capture single-language knowledge only. This suggests that children make use of both languages when processing semantic information. Together these findings inform the understanding of the relation between lexical-semantic breadth and organization in the context of dual language learners in early development.

The role of developmental change and linguistic experience in the mutual exclusivity effect

Given a novel word and a familiar and a novel referent, children have a bias to assume the novel word refers to the novel referent. This bias - often referred to as "Mutual Exclusivity" (ME) - is thought to be a potentially powerful route through which children might learn new word meanings, and, consequently, has been the focus of a large amount of empirical study and theorizing. Here, we focus on two aspects of the bias that have received relatively little attention in the literature: Development and experience. A successful theory of ME will need to provide an account for why the strength of the effect changes with the age of the child. We provide a quantitative description of the change in the strength of the bias across development, and investigate the role that linguistic experience plays in this developmental change. We first summarize the current body of empirical findings via a meta-analysis, and then present two experiments that examine the relationship between a child's amount of linguistic experience and the strength of the ME bias. We conclude that the strength of the bias varies dramatically across development and that linguistic experience is likely one causal factor contributing to this change. In the General Discussion, we describe how existing theories of ME can account for our findings, and highlight the value of computational modeling for future theorizing.

Novel word learning deficits in infants at family risk for dyslexia

Children of reading age diagnosed with dyslexia show deficits in reading and spelling skills, but early markers of later dyslexia are already present in infancy in auditory processing and phonological domains. Deficits in lexical development are not typically associated with dyslexia. Nevertheless, it is possible that early auditory/phonological deficits would have detrimental effects on the encoding and storage of novel lexical items. Word-learning difficulties have been demonstrated in school-aged dyslexic children using paired associate learning tasks, but earlier manifestations in infants who are at family risk for dyslexia have not been investigated. This study assessed novel word learning in 19-month-old infants at risk for dyslexia (by virtue of having one dyslexic parent) and infants not at risk for any developmental disorder. Infants completed a word-learning task that required them to map two novel words to their corresponding novel referents. Not at-risk infants showed increased looking time to the novel referents at test compared with at-risk infants. These findings demonstrate, for the first time, that at-risk infants show differences in novel word-learning (fast-mapping) tasks compared with not at-risk infants. Our findings have implications for the development and consolidation of early lexical and phonological skills in infants at family risk of later dyslexia.

Sometimes it is better to know less: How known words influence referent selection and retention in 18- to 24-month-old children

Young children are surprisingly good word learners. Despite their relative lack of world knowledge and limited vocabularies, they consistently map novel words to novel referents and, at later ages, show retention of these new word-referent pairs. Prior work has implicated the use of mutual exclusivity constraints and novelty biases, which require that children use knowledge of well-known words to disambiguate uncertain naming situations. The current study, however, presents evidence that weaker vocabulary knowledge during the initial exposure to a new word may be better for retention of new mappings. Children aged 18-24 months selected referents for novel words in the context of foil stimuli that varied in their lexical strength and novelty: well-known items (e.g., shoe), just-learned weakly known items (e.g., wif), and completely novel items. Referent selection performance was significantly reduced on trials with weakly known foil items. Surprisingly, however, children subsequently showed above-chance retention for novel words mapped in the context of weakly known competitors compared with those mapped with strongly known competitors or with completely novel competitors. We discuss implications for our understanding of word learning constraints and how children use known words and novelty during word learning.

When knowing only one word for "car" leads to weak application of mutual exclusivity

From a very young age, monolingual children assume their language has no synonyms, or use the principle of mutual exclusivity (only one label per object). In contrast, bilingual children often accept more novel synonyms than monolinguals. One possible explanation for this difference is the lexicon structure hypothesis: having synonyms (across languages) in the lexicon reduces adherence to mutual exclusivity. The purpose of this study is to test the lexicon structure hypothesis by comparing three- to five-year-old children who speak either Canadian French or English. Canadian French allows more synonyms than English. French-speaking children should therefore accept more novel synonyms than English-speaking children. The children did a disambiguation task, choosing whether a familiar or an unfamiliar object was the referent of a novel word (e.g., moli). Surprisingly, the French-speaking children accepted significantly fewer novel synonyms than English-speaking children. However, they accepted the most synonyms for objects that had synonyms in French but they did not know both synonyms. These results support a modified version of the lexicon structure hypothesis, one that accounts for children's weak access to synonyms.

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 .

Familiar Object Salience Affects Novel Word Learning

Children use the presence of familiar objects with known names to identify the correct referents of novel words. In natural environments, objects vary widely in salience. The presence of familiar objects may sometimes hinder rather than help word learning. To test this hypothesis, 3-year-olds (N = 36) were shown novel objects paired with familiar objects that varied in their visual salience. When the novel objects were labeled, children were slower and less accurate at fixating them in the presence of highly salient familiar objects than in the presence of less salient familiar objects. They were also less successful in retaining these word-referent pairings. While familiar objects may facilitate novel word learning in ambiguous situations, the properties of familiar objects matter.

Direct and indirect effects of multilingualism on novel language learning: An integrative review

Accumulated recent research suggests that prior knowledge of multiple languages leads to advantages in learning additional languages. In the current article, we review studies examining potential differences between monolingual and multilingual speakers in novel language learning in an effort to uncover the cognitive mechanisms that underlie such differences. We examine the multilingual advantage in children and adults, across a wide array of languages and learner populations. The majority of this literature focused on vocabulary learning, but studies that address phonology, grammar, and literacy learning are also discussed to provide a comprehensive picture of the way in which multilingualism affects novel language learning. Our synthesis indicates two avenues to the multilingual advantage including direct transfer of prior knowledge and prior skills as well as indirect influences that result from multilingual background and include more general changes to the cognitive-linguistic system. Finally, we highlight topics that are in need of future systematic research.

Bilingual and Monolingual First Language Acquisition Experience Differentially Shapes Children's Property Term Learning: Evidence from Behavioral and Neurophysiological Measures

Studies of novel noun learning show bilingual children rely less on the Mutual Exclusivity Constraint (MEC) for word learning than monolinguals. Shifting the focus to learning novel property terms (adjectives), the present study compared 3.5- and five-year-old bilingual and monolingual preschoolers' adherence to the MEC. We found no bilingual-monolingual differences on a behavioral forced-choice task for the 3.5-year-olds, but five-year-old monolinguals adhered more to the MEC than bilinguals did. Older bilinguals adhered less to the MEC than younger ones, while there was no difference in MEC adherence between the younger and older monolinguals. In the 5-year-olds, we additionally acquired neurophysiological data using functional near-infrared spectroscopy (fNIRS) to allow for a first explorative look at potential neuronal underpinnings. The data show that, compared to bilinguals, monolinguals reveal higher activation over three brain regions (right frontal, left temporo-parietal, and left prefrontal) that may be involved in exploiting the MEC, building on conflict detection, inhibition, solution of a disjunction, and working memory processes. Taken together, our behavioral and neurophysiological findings reveal different paths towards novel property term learning depending on children's language acquisition context.

Translation Equivalents Facilitate Lexical Access in Very Young Bilinguals

The present study investigated the impact of translation equivalents (TE) on lexical processing in a sample of 36 French-English bilingual toddlers at 22-months of age. Children were administered the Computerized Comprehension Task (CCT; Friend & Keplinger, 2003) in each language and parents completed the MacArthur Bates Communicative Development Inventory (CDI) in both English and French across two visits (one language per visit). Correct trials on the CCT were identified and classified into one of two categories: words with a known TE as reported on the CDI and words without a known TE on the CDI. Reaction times for correct trials were then averaged in each category and compared for each of the bilinguals' languages. Interestingly, children were faster to retrieve words with a known TE on the CDI than words with no known TE. The present findings suggest that the translation facilitation effects reported in adult bilinguals are also present in very young bilinguals.

Differences in Neural Correlates of Speech Perception in 3 Month Olds at High and Low Risk for Autism Spectrum Disorder

In this study, we investigated neural precursors of language acquisition as potential endophenotypes of autism spectrum disorder (ASD) in 3-month-old infants at high and low familial ASD risk. Infants were imaged using functional near-infrared spectroscopy while they listened to auditory stimuli containing syllable repetitions; their neural responses were analyzed over left and right temporal regions. While female low risk infants showed initial neural activation that decreased over exposure to repetition-based stimuli, potentially indicating a habituation response to repetition in speech, female high risk infants showed no changes in neural activity over exposure. This finding may indicate a potential neural endophenotype of language development or ASD specific to females at risk for the disorder.

The development of fast-mapping and novel word retention strategies in monolingual and bilingual infants

The mutual exclusivity (ME) assumption is proposed to facilitate early word learning by guiding infants to map novel words to novel referents. This study assessed the emergence and use of ME to both disambiguate and retain the meanings of novel words across development in 18-month-old monolingual and bilingual children (Experiment 1; N = 58), and in a sub-group of these children again at 24 months of age (Experiment 2: N = 32). Both monolinguals and bilinguals employed ME to select the referent of a novel label to a similar extent at 18 and 24 months. At 18 months, there were also no differences in novel word retention between the two language-background groups. However, at 24 months, only monolinguals showed the ability to retain these label-object mappings. These findings indicate that the development of the ME assumption as a reliable word-learning strategy is shaped by children's individual language exposure and experience with language use.

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.

Bayesian Word Learning in Multiple Language Environments

Infant language learners are faced with the difficult inductive problem of determining how new words map to novel or known objects in their environment. Bayesian inference models have been successful at using the sparse information available in natural child-directed speech to build candidate lexicons and infer speakers' referential intentions. We begin by asking how a Bayesian model optimized for monolingual input (the Intentional Model; Frank et al., 2009) generalizes to new monolingual or bilingual corpora and find that, especially in the case of the bilingual input, the model shows a significant decrease in performance. In the next experiment, we propose the ME Model, a modified Bayesian model, which approximates infants' mutual exclusivity bias to support the differential demands of monolingual and bilingual learning situations. The extended model is assessed using the same corpora of real child-directed speech, showing that its performance is more robust against varying input and less dependent than the Intentional Model on optimization of its parsimony parameter. We argue that both monolingual and bilingual demands on word learning are important considerations for a computational model, as they can yield significantly different results than when only one such context is considered.

Tracking Multiple Statistics: Simultaneous Learning of Object Names and Categories in English and Mandarin Speakers

Two experiments were conducted to examine adult learners' ability to extract multiple statistics in simultaneously presented visual and auditory input. Experiment 1 used a cross-situational learning paradigm to test whether English speakers were able to use co-occurrences to learn word-to-object mappings and concurrently form object categories based on the commonalities across training stimuli. Experiment 2 replicated the first experiment and further examined whether speakers of Mandarin, a language in which final syllables of object names are more predictive of category membership than English, were able to learn words and form object categories when trained with the same type of structures. The results indicate that both groups of learners successfully extracted multiple levels of co-occurrence and used them to learn words and object categories simultaneously. However, marked individual differences in performance were also found, suggesting possible interference and competition in processing the two concurrent streams of regularities.

Dog or chien? Translation equivalents in the receptive and expressive vocabularies of young French-English bilinguals

In order to address gaps in the literature surrounding the acquisition of translation equivalents (TEs) in young bilinguals, two experiments were conducted. In Experiment 1, TEs were measured in the expressive vocabularies of thirty-four French-English bilinguals at 1;4, 1;10, and 2;6 using the MacArthur Bates CDI. Children's acquisition of TEs occurred gradually, with more balanced ratios of exposure and vocabulary associated with larger proportions of TEs at each wave. Experiment 2 compared a direct measure of TE comprehension with parent report of the same set of words. Results showed that parents may over-report children's TE comprehension, as our sample of two-year-old French-English bilinguals (n = 20) comprehended fewer TEs on a direct measure of receptive vocabulary than parents reported on the vocabulary checklist. The present study provides an original contribution to the literature on bilingual vocabulary development by employing both a longitudinal design and a direct measure of TE comprehension.

Competition between multiple words for a referent in cross-situational word learning

Three experiments investigated competition between word-object pairings in a cross-situational word-learning paradigm. Adults were presented with One-Word pairings, where a single word labeled a single object, and Two-Word pairings, where two words labeled a single object. In addition to measuring learning of these two pairing types, we measured competition between words that refer to the same object. When the word-object co-occurrences were presented intermixed in training (Experiment 1), we found evidence for direct competition between words that label the same referent. Separating the two words for an object in time eliminated any evidence for this competition (Experiment 2). Experiment 3 demonstrated that adding a linguistic cue to the second label for a referent led to different competition effects between adults who self-reported different language learning histories, suggesting both distinctiveness and language learning history affect competition. Finally, in all experiments, competition effects were unrelated to participants' explicit judgments of learning, suggesting that competition reflects the operating characteristics of implicit learning processes. Together, these results demonstrate that the role of competition between overlapping associations in statistical word-referent learning depends on time, the distinctiveness of word-object pairings, and language learning history.

Vocabulary size, translation equivalents, and efficiency in word recognition in very young bilinguals

The present study examined early vocabulary development in fifty-nine French monolingual and fifty French-English bilingual infants (1;4-1;6). Vocabulary comprehension was assessed using both parental report (MacArthur-Bates Communicative Development Inventory; CDI) and the Computerized Comprehension Task (CCT). When assessing receptive vocabulary development using parental report, the bilinguals knew more words in their L1 versus their L2. However, young bilinguals were as accurate in L1 as they were in L2 on the CCT, and exhibited no difference in speed of word comprehension across languages. The proportion of translation equivalents in comprehension varied widely within this sample of young bilinguals and was linked to both measures of vocabulary size but not to speed of word retrieval or exposure to L2. Interestingly, the monolinguals outperformed the bilinguals with respect to accuracy but not reaction time in their L1 and L2. These results highlight the importance of using multiple measures to assess early vocabulary development.

Finding patterns and learning words: Infant phonotactic knowledge is associated with vocabulary size

Native language statistical regularities about allowable phoneme combinations (i.e., phonotactic patterns) may provide learners with cues to support word learning. The current research investigated the association between infants' native language phonotactic knowledge and their word learning progress, as measured by vocabulary size. In the experiment, 19-month-old infants listened to a corpus of nonce words that contained novel phonotactic patterns. All words began with "illegal" consonant clusters that cannot occur in native (English) words. The rationale for the task was that infants with fragile phonotactic knowledge should exhibit stronger learning of the novel illegal phonotactic patterns than infants with robust phonotactic knowledge. We found that infants with smaller vocabularies showed stronger phonotactic learning than infants with larger vocabularies even after accounting for general cognition. We propose that learning about native language structure may promote vocabulary development by providing a foundation for word learning; infants with smaller vocabularies may have weaker support from phonotactics than infants with larger vocabularies. Furthermore, stored vocabulary knowledge may promote the detection of phonotactic patterns even during infancy.

Lexical processing and organization in bilingual first language acquisition: Guiding future research

A rich body of work in adult bilinguals documents an interconnected lexical network across languages, such that early word retrieval is language independent. This literature has yielded a number of influential models of bilingual semantic memory. However, extant models provide limited predictions about the emergence of lexical organization in bilingual first language acquisition (BFLA). Empirical evidence from monolingual infants suggests that lexical networks emerge early in development as children integrate phonological and semantic information. These findings tell us little about the interaction between 2 languages in early bilingual memory. To date, an understanding of when and how languages interact in early bilingual development is lacking. In this literature review, we present research documenting lexical-semantic development across monolingual and bilingual infants. This is followed by a discussion of current models of bilingual language representation and organization and their ability to account for the available empirical evidence. Together, these theoretical and empirical accounts inform and highlight unexplored areas of research and guide future work on early bilingual memory. (PsycINFO Database Record

Second label learning in bilingual and monolingual infants

Mutual exclusivity is the assumption that each object has only one category label. Prior research suggests that bilingual infants, unlike monolingual infants, fail to adhere to this assumption to guide word learning. Yet previous work has not addressed whether bilingual infants systematically interpret a novel word for a familiar object (i.e. an object with a known category label) as a second category label. We addressed this question by exploring bilingual and monolingual infants' use of mutual exclusivity in a task in which they heard a novel label for a familiar object with a salient color (e.g. an aqua-colored dog). They were subsequently tested with two trials that probed whether they interpreted the word as a second category label for the object (e.g. another word meaning dog) or as a label for one of the object's salient properties, namely its color (e.g. a word meaning aqua). Bilingual infants failed to adhere to mutual exclusivity and interpreted the novel word systematically as a second object category label for the familiar object. In contrast, consistent with their use of mutual exclusivity, monolingual infants rejected the novel word as a second category label, and instead showed some evidence of interpreting it as a property (color) term for the familiar object. The findings suggest that both bilingual and monolingual infants are systematic in their interpretation of a novel label for a familiar object, but that they show different interpretations of that label. We thus argue that theoretical accounts of early word learning must consider the crucial role of linguistic experience.

Effects of contextual support on preschoolers' accented speech comprehension

Young children often hear speech in unfamiliar accents, but relatively little research characterizes their comprehension capacity. The current study tested preschoolers' comprehension of familiar-accented versus unfamiliar-accented speech with varying levels of contextual support from sentence frames (full sentences vs. isolated words) and from visual context (four salient pictured alternatives vs. the absence of salient visual referents). The familiar accent advantage was more robust when visual context was absent, suggesting that previous findings of good accent comprehension in infants and young children may result from ceiling effects in easier tasks (e.g., picture fixation, picture selection) relative to the more difficult tasks often used with older children and adults. In contrast to prior work on mispronunciations, where most errors were novel object responses, children in the current study did not select novel object referents above chance levels. This suggests that some property of accented speech may dissuade children from inferring that an unrecognized familiar-but-accented word has a novel referent. Finally, children showed detectable accent processing difficulty despite presumed incidental community exposure. Results suggest that preschoolers' accented speech comprehension is still developing, consistent with theories of protracted development of speech processing.

Cognitive adaptations induced by a multi-language input in early development

Children around the world successfully adapt to the specific requirements of their physical and social environment, and they readily acquire any language they are exposed to. Still, learning simultaneously two languages has been a continuous concern of parents, educators and scientists. While the focus has shifted from the possible costs to the possible advantages of bilingualism, the worries still linger that early bilingualism may cause delays and confusion. Here we adopt a less dichotomist view, by asking what specific adaptations might result from simultaneously learning two languages. We will discuss findings that point to a surprising plasticity of the cognitive system allowing young infants to cope with the bilingual input and reaching linguistic milestones at the same time as monolinguals.

How does the bilingual experience sculpt the brain?

The ability to speak two languages often marvels monolinguals, although bilinguals report no difficulties in achieving this feat. Here, we examine how learning and using two languages affect language acquisition and processing as well as various aspects of cognition. We do so by addressing three main questions. First, how do infants who are exposed to two languages acquire them without apparent difficulty? Second, how does language processing differ between monolingual and bilingual adults? Last, what are the collateral effects of bilingualism on the executive control system across the lifespan? Research in all three areas has not only provided some fascinating insights into bilingualism but also revealed new issues related to brain plasticity and language learning.

The development of infants' use of novel verbal information when reasoning about others' actions

How sophisticated are infants at using novel verbal information when reasoning about which of two objects an agent is likely to select? The present research examined the development of infants' ability to interpret a change from one novel word to another as signaling a possible change in which object the agent would choose next. In three experiments, 7- and 12-month-olds were familiarized to an event in which they heard a novel word ("A dax!") and then saw an agent reach for one of two distinct objects. During test, the infants heard a different novel word ("A pilk!") and then saw the agent grasp the same object or the other object. At 7 months, infants ignored the change in word and expected the agent to continue reaching for the same object. At 12 months, however, infants attended to the change in word: They realized that it signaled a possible change in the agent's upcoming actions, though they were unable to form a specific expectation about what these new actions might be, most likely due to their limited mutual-exclusivity assumption. Control conditions supported these interpretations. Together, these results suggest that by 12 months of age, infants understand not only that words are selected for communicative purposes, but also that a change from one novel word to another may signal a change in an agent's upcoming actions.