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

Wordform variability in infants' language environment and its effects on early word learning

Most research regarding early word learning in English tends to make the simplifying assumption that there exists a one-to-one mapping between concrete objects and their labels. In the current work, we provide evidence that runs counter to this assumption, aligning English with more morphologically-rich languages. We suggest that even in a morphologically-poor language like English, real world language input to infants does not provide tidy 1-to-1 mappings. Instead, infants encounter many variant wordforms for familiar nouns (e.g. dog∼doggy∼dogs). We explore this wordform variability in 44 English-learning infants' naturalistic environments using a longitudinal corpus of infant-available speech. We look at both the frequency and composition of wordform variability. We find two broad categories of variability: referent-changing alterations, where words were pluralized or compounded (e.g. coat∼raincoats); and wordplay, where words changed form without a notable change in referent (e.g. bird∼birdie). We further find that wordplay occurs with a limited number of lemmas that are usually early-learned, high-frequency, and shorter. When looking at all wordform variability, we find that individual words with higher levels of wordform variability are learned earlier than words with fewer wordforms, over and above the effect of frequency.

Four- and six-year-old children track a single meaning with both familiar and unfamiliar referents when the referent is clear: More evidence for propose-but-verify

In word learning, learners need to identify the referent of words by leveraging the fact that the same word may co-occur with different sets of objects. This raises the question, what do children remember from "in the moment" that they can use for cross-situational learning? Furthermore, do children represent pictures of familiar animals versus drawings of non-existent novel objects as potential referents differently? This study examined these questions by creating learning scenarios with only two potential referents, requiring the least amount of memory to represent all co-present objects. Across three experiments (n > 250) with 4- and 6-year-old children, children reliably selected the intended referent from learning at test, though the learning of novel objects was better than familiar objects. When asked for a co-present object, children of all ages in the study performed at chance in all of the conditions. We discuss the developmental differences in cross-situational word learning capabilities with regard to representing different stimuli as potential referents. Importantly, all children used a propose-but-verify procedure for learning novel words even in the simplest of the learning scenarios given repeated exposure.

Object labeling and disambiguation in 4-month-old infants

The account that word learning starts in earnest during the second year of life, when infants have mastered the disambiguation skills, has recently been challenged by evidence that infants during the first year already know many common words. The preliminary ability to rapidly map and disambiguate linguistic labels was tested in Italian-speaking infants (N = 96, 47 boys; age = 4 and 6 months, eye tracking). Infants can rapidly map linguistic labels to objects and movements, and disambiguate the intended referents to novel words, but they fail with sinewave analogs. In hearing infants, mapping and disambiguation emerge early in development, and are flexible as to which visual referents infants are willing to map to linguistic labels, but may be constrained to linguistic sounds.

The role of translation equivalents in bilingual word learning

Bilingual environments present an important context for word learning. One feature of bilingual environments is the existence of translation equivalents (TEs)-words in different languages that share similar meanings. Documenting TE learning over development may give us insight into the mechanisms underlying word learning in young bilingual children. Prior studies of TE learning have often been confounded by the fact that increases in overall vocabulary size with age lead to greater opportunities for learning TEs. To address this confound, we employed an item-level analysis, which controls for the age trajectory of each item independently. We used Communicative Development Inventory data from four bilingual datasets (two English-Spanish and two English-French; total N = 419) for modeling. Results indicated that knowing a word's TE increased the likelihood of knowing that word for younger children and for TEs that are more similar phonologically. These effects were consistent across datasets, but varied across lexical categories. Thus, TEs may allow bilingual children to bootstrap their early word learning in one language using their knowledge of the other language. RESEARCH HIGHLIGHTS: Bilingual children must learn words that share a common meaning across both languages, that is, translation equivalents, like dog in English and perro in Spanish. Item-level models explored how translation equivalents affect word learning, in addition to child-level (e.g., exposure) and item-level (e.g., phonological similarity) factors. Knowing a word increased the probability of knowing its corresponding translation equivalent, particularly for younger children and for more phonologically-similar translation equivalents. These findings suggest that young bilingual children use their word knowledge in one language to bootstrap their learning of words in the other language.

Holding multiple category representations: The role of age, theory of mind, and rule switching in children's developing cross-classification abilities

Cross-classification, the ability to categorize multifaceted entities in many ways, is a remarkable cognitive milestone for children. Past work has focused primarily on documenting the timeline for when children reach cross-classification competence. However, it is not well understood what cognitive factors underpin children's improvements. The current study aimed to examine the contributions of age, theory of mind, and rule switching to children's cross-classification development. We tested 3- to 5-year-old children (N = 75) using a cross-classification task, the Theory of Mind Task Battery, and the Three-Dimensional Change Card Sort test. The results revealed that age and theory of mind predict children's cross-classification over and above the effects of rule switching. The results also revealed that advanced-level theory of mind reasoning is a particularly strong predictor of cross-classification development. These findings increase understanding of cross-classification within children's broader cognitive development.

Combining Languages in Bilingual Input: Using Experimental Evidence to Formulate Bilingual Exposure Strategies

PURPOSE

Traditional approaches to studying bilingual language development through bilingual-monolingual comparisons are deeply flawed. They are also insufficient as the evidence base for informing advice to bilingual parents regarding the optimal bilingual exposure strategy and for supporting the formulation of bilingual intervention approaches. The purpose of this review article is to provide an overview of empirical studies that have queried the question of how different types of dual-language input shape learning and language outcomes in bilingual children.

METHOD

We rely on tightly controlled experimental studies of word learning in Spanish-English bilingual children, where we contrast children's learning in dual-language conditions (defined as distributed exposure and code-switched input) to a single-language condition in a within-subjects design.

RESULTS

Word-learning studies querying the role of distributed exposure indicated that distribution of exposures across Spanish and English reduced children's performance in comparison to English-only exposure. However, this effect was rooted in the abrupt switch from Spanish to English rather than distributed exposure itself. In contrast, an experiment designed to test the role of code-switched context on children's word learning revealed that code-switched context where switches resembled naturalistic code-switching behaviors enhanced learning in Spanish-English bilingual children. Notably, across different studies, children with weaker language skills (developmental language disorder) were no more affected by dual-language input than children with typical language skills.

CONCLUSIONS

Together, experimental studies of word learning indicate that bilingual children can effectively learn from dual-language input but that different ways of combining languages in the input to bilingual children can have distinct consequences for learning. Ultimately, word-learning experiments, beyond answering critical questions regarding bilingual learning, can serve as an effective bridge between laboratory-based work and intervention studies whose goal it is to discover the optimal way of combining languages in the input to bilingual children with communication impairments.

PRESENTATION VIDEO

https://doi.org/10.23641/asha.23929515.

An individual differences perspective on pragmatic abilities in the preschool years

Pragmatic abilities are fundamental to successful language use and learning. Individual differences studies contribute to understanding the psychological processes involved in pragmatic reasoning. Small sample sizes, insufficient measurement tools, and a lack of theoretical precision have hindered progress, however. Three studies addressed these challenges in three- to 5-year-old German-speaking children (N = 228, 121 female). Studies 1 and 2 assessed the psychometric properties of six pragmatics tasks. Study 3 investigated relations among pragmatics tasks and between pragmatics and other cognitive abilities. The tasks were found to measure stable variation between individuals. Via a computational cognitive model, individual differences were traced back to a latent pragmatics construct. This presents the basis for understanding the relations between pragmatics and other cognitive abilities. RESEARCH HIGHLIGHTS: Individual differences in pragmatic abilities are important to understanding variation in language development. Research in this domain lacks a precise theoretical framework and psychometrically high-quality measures. We present six tasks capturing a wide range of pragmatic abilities with excellent re-test reliability. We use a computational cognitive model to provide a substantive theory of individual differences in pragmatic abilities.

Pragmatics aid referent disambiguation and word learning in young children and adults

How do children succeed in learning a word? Research has shown robustly that, in ambiguous labeling situations, young children assume novel labels to refer to unfamiliar rather than familiar objects. However, ongoing debates center on the underlying mechanism: Is this behavior based on lexical constraints, guided by pragmatic reasoning, or simply driven by children's attraction to novelty? Additionally, recent research has questioned whether children's disambiguation leads to long-term learning or rather indicates an attentional shift in the moment of the conversation. Thus, we conducted a pre-registered online study with 2- and 3-year-olds and adults. Participants were presented with unknown objects as potential referents for a novel word. Across conditions, we manipulated whether the only difference between both objects was their relative novelty to the participant or whether, in addition, participants were provided with pragmatic information that indicated which object the speaker referred to. We tested participants' immediate referent selection and their retention after 5 min. Results revealed that when given common ground information both age groups inferred the correct referent with high success and enhanced behavioral certainty. Without this information, object novelty alone did not guide their selection. After 5 min, adults remembered their previous selections above chance in both conditions, while children only showed reliable learning in the pragmatic condition. The pattern of results indicates how pragmatics may aid referent disambiguation and learning in both adults and young children. From early ontogeny on, children's social-cognitive understanding may guide their communicative interactions and support their language acquisition. RESEARCH HIGHLIGHTS: We tested how 2-3-year-olds and adults resolve referential ambiguity without any lexical cues. In the pragmatic context both age groups disambiguated novel word-object-mappings, while object novelty alone did not guide their referent selection. In the pragmatic context, children also showed increased certainty in disambiguation and retained new word-object-mappings over time. These findings contribute to the ongoing debate on whether children learn words on the basis of domain-specific constraints, lower-level associative mechanisms, or pragmatic inferences.

Understanding preschoolers' word learning success in different scenarios: disambiguation meets statistical learning and eBook reading

Children's ability to learn new words during their preschool years is crucial for further academic success. Previous research suggests that children rely on different learning mechanisms to acquire new words depending on the available context and linguistic information. To date, there is limited research integrating different paradigms to provide a cohesive view of the mechanisms and processes involved in preschool children's word learning. We presented 4 year-old children (n = 47) with one of three different novel word-learning scenarios to test their ability to connect novel words to their correspondent referents without explicit instruction to do so. The scenarios were tested with three exposure conditions of different nature: (i) mutual exclusivity-target novel word-referent pair presented with a familiar referent, prompting fast-mapping via disambiguation, (ii) cross-situational-target novel word-referent pair presented next to an unfamiliar referent prompting statistically tracking the target pairs across trials, and (iii) eBook - target word-referent pairs presented within an audio-visual electronic storybook (eBook), prompting inferring meaning incidentally. Results show children succeed at learning the new words above chance in all three scenarios, with higher performance in eBook and mutual exclusivity than in cross-situational word learning. This illustrates children's astounding ability to learn while coping with uncertainty and varying degrees of ambiguity, which are common in real-world situations. Findings extend our understanding of how preschoolers learn new words more or less successfully depending on specific word learning scenarios, which should be taken into account when working on vocabulary development for school readiness in the preschool years.

Learning with certainty in childhood

Learners use certainty to guide learning. They maintain existing beliefs when certain, but seek further information when they feel uninformed. Here, we review developmental evidence that this metacognitive strategy does not require reportable processing. Uncertainty prompts nonverbal human infants and nonhuman animals to engage in strategies like seeking help, searching for additional information, or opting out. Certainty directs children's attention and active learning strategies and provides a common metric for comparing and integrating conflicting beliefs across people. We conclude that certainty is a continuous, domain-general signal of belief quality even early in life.

What Children with Developmental Language Disorder Teach Us About Cross-Situational Word Learning

Children with developmental language disorder (DLD) served as a test case for determining the role of extant vocabulary knowledge, endogenous attention, and phonological working memory abilities in cross‐situational word learning. First‐graders (M_age = 7 years; 3 months), 44 with typical development (TD) and 28 with DLD, completed a cross‐situational word‐learning task comprised six cycles, followed by retention tests and independent assessments of attention, memory, and vocabulary. Children with DLD scored lower than those with TD on all measures of learning and retention, a performance gap that emerged in the first cycle of the cross‐situational protocol and that we attribute to weaknesses in initial encoding. Over cycles, children with DLD learned words at a similar rate as their TD peers but they were less flexible in their strategy use, demonstrating a propose‐but‐verify approach but never a statistical aggregation approach. Also, they drew upon different mechanisms to support their learning. Attention played a greater role for the children with DLD, whereas extant vocabulary size played a greater role for the children with TD. Children navigate the problem space of cross‐situational learning via varied routes. This conclusion is offered as motivation for theorists to capture all learners, not just the most typical ones.

Mutual Exclusivity in Pragmatic Agents

One of the great challenges in word learning is that words are typically uttered in a context with many potential referents. Children's tendency to associate novel words with novel referents, which is taken to reflect a mutual exclusivity (ME) bias, forms a useful disambiguation mechanism. We study semantic learning in pragmatic agents-combining the Rational Speech Act model with gradient-based learning-and explore the conditions under which such agents show an ME bias. This approach provides a framework for investigating a pragmatic account of the ME bias in humans but also for building artificial agents that display an ME bias. A series of analyses demonstrates striking parallels between our model and human word learning regarding several aspects relevant to the ME bias phenomenon: online inference, long-term learning, and developmental effects. By testing different implementations, we find that two components, pragmatic online inference and incremental collection of evidence for one-to-one correspondences between words and referents, play an important role in modeling the developmental trajectory of the ME bias. Finally, we outline an extension of our model to a deep neural network architecture that can process more naturalistic visual and linguistic input. Until now, in contrast to children, deep neural networks have needed indirect access to (supposed to be novel) test inputs during training to display an ME bias. Our model is the first one to do so without using this manipulation.

Logical word learning: The case of kinship

We examine the conceptual development of kinship through the lens of program induction. We present a computational model for the acquisition of kinship term concepts, resulting in the first computational model of kinship learning that is closely tied to developmental phenomena. We demonstrate that our model can learn several kinship systems of varying complexity using cross-linguistic data from English, Pukapuka, Turkish, and Yanomamö. More importantly, the behavioral patterns observed in children learning kinship terms, under-extension and over-generalization, fall out naturally from our learning model. We then conducted interviews to simulate realistic learning environments and demonstrate that the characteristic-to-defining shift is a consequence of our learning model in naturalistic contexts containing abstract and concrete features. We use model simulations to understand the influence of logical simplicity and children’s learning environment on the order of acquisition of kinship terms, providing novel predictions for the learning trajectories of these words. We conclude with a discussion of how this model framework generalizes beyond kinship terms, as well as a discussion of its limitations.

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.

Quantifying the syntactic bootstrapping effect in verb learning: A meta-analytic synthesis

How do children infer the meaning of a novel verb? One prominent proposal is that children rely on syntactic information in the linguistic context, a phenomenon known as "syntactic bootstrapping". For example, given the sentence "The bunny is gorping the duck," a child could use knowledge of English syntactic roles to infer that "gorping" refers to an action where the bunny is acting in some way on a duck. Here, we examine the strength of the syntactic bootstrapping effect, its developmental trajectory and generalizability using meta-analytic methods. Across 60 experiments in the literature (N = 849 participants), we find a reliable syntactic bootstrapping effect (d = 0.24). Yet, despite its theoretical prominence, the syntactic bootstrapping effect is relatively small, comparable in size to cross-situational learning and sound symbolism, but smaller than mutual-exclusivity and gaze-following. Further, we find that the effect does not strengthen over development, and is present only for studies that use transitive sentences. An examination of a range of methodological factors suggests that the effect is not strongly influenced by methodological implementation. In the General Discussion, we consider implications of our findings for theories of verb learning and make recommendations for future research.

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.

How young children integrate information sources to infer the meaning of words

Before formal education begins, children typically acquire a vocabulary of thousands of words. This learning process requires the use of many different information sources in their social environment, including their current state of knowledge and the context in which they hear words used. How is this information integrated? We specify a developmental model according to which children consider information sources in an age-specific way and integrate them via Bayesian inference. This model accurately predicted 2-5-year-old children's word learning across a range of experimental conditions in which they had to integrate three information sources. Model comparison suggests that the central locus of development is an increased sensitivity to individual information sources, rather than changes in integration ability. This work presents a developmental theory of information integration during language learning and illustrates how formal models can be used to make a quantitative test of the predictive and explanatory power of competing theories.

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.

Sampling to learn words: Adults and children sample words that reduce referential ambiguity

How do learners gather new information during word learning? One possibility is that learners selectively sample items that help them reduce uncertainty about new word meanings. In a series of cross-situational word learning tasks with adults and children, we manipulated the referential ambiguity of label-object pairs experienced during training and subsequently investigated which words participants chose to sample additional information about. In the first experiment, adult learners chose to receive additional training on object-label associations that reduce referential ambiguity during cross-situational word learning. This ambiguity-reduction strategy was related to improved test performance. In two subsequent experiments, we found that, at least in some contexts, children (3-8 years of age) show a similar preference to seek information about words experienced in ambiguous word learning situations. In Experiment 2, children did not preferentially select object-label associations that remained ambiguous during cross-situational word learning. However, in a third experiment that increased the relative ambiguity of two sets of novel object-label associations, we found evidence that children preferentially make selections that reduce ambiguity about novel word meanings. These results carry implications for understanding how children actively contribute to their own language development by seeking information that supports learning.

When slowing down processing helps learning: Lexico-semantic structure supports retention, but interferes with disambiguation of novel object-label mappings

This project explores how children disambiguate and retain novel object-label mappings in the face of semantic similarity. Burgeoning evidence suggests that semantic structure in the developing lexicon promotes word learning in ostensive contexts, whereas other findings indicate that semantic similarity interferes with and temporarily slows familiar word recognition. This project explores how these distinct processes interact when mapping and retaining labels for novel objects (i.e., low-frequency objects that are unfamiliar to toddlers) via disambiguation from a semantically similar familiar referent in 24-month-olds (N = 65). Toddlers' log-adjusted looking to labeled target objects (relative to distractor objects) was measured in three conditions: Familiar trials (familiar label spoken while viewing semantically related familiar and novel objects), Disambiguation trials (unfamiliar label spoken while viewing semantically similar familiar and unfamiliar object), and Retention trials (unfamiliar label spoken while viewing novel object pairs). Toddlers' individual vocabulary structure was then compared to performance on each condition. Vocabulary structure was measured at two levels: category-level structure (semantic density) for experimental items, and lexicon-level structure (global clustering coefficient). The findings suggest, consistent with prior results, that semantic density interfered with known word recognition, and facilitated unfamiliar word retention. Children did not show a significant novel word preference during disambiguation, and disambiguation behavior was not impacted by semantic structure. These findings connect seemingly disparate mechanisms of semantic interference in processing and semantic leveraging in word learning. Semantic interference momentarily slows word recognition and resolution of referential uncertainty for novel label-object mappings. Nevertheless, this slowing might support retention by enabling comparison between related objects.