Developmental origin of a language-cognition interface in infants: Gateway to advancing core knowledge?

Spelke's sweeping proposal requires greater precision in specifying the place of language in early cognition. We now know by 3 months of age, infants have already begun to forge a link between language and core cognition. This precocious link, which unfolds dynamically over development, may indeed offer an entry point for acquiring higher-order, abstract conceptual and representational capacities.

Navigating accent variability: 24-month-olds recognize known words spoken in an unfamiliar accent but require additional support to learn new words.

As infants learn their native languages, they must also learn to contend with variability across speakers of those languages. Here, we examine 24-month-olds' ability to process speech in an unfamiliar accent. We demonstrate that 24-month-olds successfully identify the referents of known words in unfamiliar-accented speech but cannot use known words alone to infer new word meanings. However, when the novel word occurs in a supportive referential context, with the target referent visually available, 24-month-olds successfully learn new word-referent mappings. Thus, 24-month-olds recognize and learn words in unfamiliar accents, but unfamiliar-accented speech may pose challenges for more sophisticated language processing strategies.

Preschoolers benefit from sentential context in familiar- and unfamiliar-accented speech.

To learn the meaning of a new word, or to recognize the meaning of a known one, both children and adults benefit from surrounding words, or the sentential context. Most of the evidence from children is based on their accuracy and efficiency when listening to speech in their familiar native accent: they successfully use the words they know to identify other words' referents. Here, we assess how accurately and efficiently 4-year-old children use sentential context to identify referents of known and novel nouns in unfamiliar-accented speech, as compared to familiar-accented speech. In a looking-while-listening task, children showed considerable success in processing unfamiliar-accented speech. Children robustly mapped known nouns produced in an unfamiliar accent to their target referents rather than novel competitors, and they used informative surrounding verbs (e.g., "You can eat the dax") to identify the referents of both known and novel nouns-although there was a processing cost for unfamiliar-accented speech in some cases. This demonstrates that 4-year-olds successfully and rapidly process unfamiliar-accented speech by recruiting the same strategies available to them in familiar-accented speech, revealing impressive flexibility in word recognition and word learning across diverse linguistic environments. RESEARCH HIGHLIGHTS: We examined 4-year-old children's accuracy and processing efficiency in comprehending known and novel nouns embedded in sentences produced in familiar-accented or unfamiliar-accented speech. Children showed limited processing costs for unfamiliar-accented speech and mapped known words to their referents even when these were produced in unfamiliar-accented speech. Children used known verbs to predict the referents of upcoming nouns in both familiar- and unfamiliar-accented speech, but processing costs were evident for unfamiliar-accented speech. Thus, the strategies that support children's word comprehension and word learning in familiar-accented speech are available to them in unfamiliar accents as well.

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.

Longer looks for language: Novel labels lengthen fixation duration for 2-year-old children.

The language infants hear guides their visual attention; infants look more to objects when they are labeled. However, it is unclear whether labels also change the way infants attend to and encode those objects-that is, whether hearing an object label changes infants' online visual processing of that object. Here, we examined this question in the context of novel word learning, asking whether nuanced measures of visual attention, specifically fixation durations, change when 2-year-olds hear a label for a novel object (e.g., "Look at the dax") compared with when they hear a non-labeling phrase (e.g., "Look at that"). Results confirmed that children visually process objects differently when they are labeled, using longer fixations to examine labeled objects versus unlabeled objects. Children also showed robust retention of these labels on a subsequent test trial, suggesting that these longer fixations accompanied successful word learning. Moreover, when children were presented with the same objects again in a silent re-exposure phase, children's fixations were again longer when looking at the previously labeled objects. Finally, fixation duration at first exposure and silent re-exposure were correlated, indicating a persistent effect of language on visual processing. These effects of hearing labels on visual attention point to the critical interactions involved in cross-modal learning and emphasize the benefits of looking beyond aggregate measures of attention to identify cognitive learning mechanisms during infancy.

Rhythm May Be Key to Linking Language and Cognition in Young Infants: Evidence From Machine Learning.

Rhythm is key to language acquisition. Across languages, rhythmic features highlight fundamental linguistic elements of the sound stream and structural relations among them. A sensitivity to rhythmic features, which begins in utero, is evident at birth. What is less clear is whether rhythm supports infants' earliest links between language and cognition. Prior evidence has documented that for infants as young as 3 and 4 months, listening to their native language (English) supports the core cognitive capacity of object categorization. This precocious link is initially part of a broader template: listening to a non-native language from the same rhythmic class as (e.g., German, but not Cantonese) and to vocalizations of non-human primates (e.g., lemur, Eulemur macaco flavifrons, but not birds e.g., zebra-finches, Taeniopygia guttata) provide English-acquiring infants the same cognitive advantage as does listening to their native language. Here, we implement a machine-learning (ML) approach to ask whether there are acoustic properties, available on the surface of these vocalizations, that permit infants' to identify which vocalizations are candidate links to cognition. We provided the model with a robust sample of vocalizations that, from the vantage point of English-acquiring 4-month-olds, either support object categorization (English, German, lemur vocalizations) or fail to do so (Cantonese, zebra-finch vocalizations). We assess (a) whether supervised ML classification models can distinguish those vocalizations that support cognition from those that do not, and (b) which class(es) of acoustic features (including rhythmic, spectral envelope, and pitch features) best support that classification. Our analysis reveals that principal components derived from rhythm-relevant acoustic features were among the most robust in supporting the classification. Classifications performed using temporal envelope components were also robust. These new findings provide in principle evidence that infants' earliest links between vocalizations and cognition may be subserved by their perceptual sensitivity to rhythmic and spectral elements available on the surface of these vocalizations, and that these may guide infants' identification of candidate links to cognition.

Sparse labels, no problems: Infant categorization under challenging conditions.

Labeling promotes infants' object categorization even when labels are rare. By 2 years, infants engage in "semi-supervised learning" (SSL), integrating labeled and unlabeled exemplars to learn categories. However, everyday learning contexts pose substantial challenges for infants' SSL. Here, two studies (n = 74, 51% female, 62% non-Hispanic White, 18% multiracial, 8% Asian, 6% Black, Mage  = 27.3 months, collected 2018-2020) implemented a familiarization-novelty preference paradigm assessing 2-year-olds' SSL when (i) exemplars from the target category are interspersed with other objects (Study 1, d = .67) and (ii) multiple categories are learned simultaneously (Study 2, d = .74). The findings indicate 2-year-olds' SSL is robust enough to support object categorization despite substantial challenges posed by everyday learning contexts.

Racial Awareness and Bias Begin Early: Developmental Entry Points, Challenges, and a Call to Action.

Overt expressions of racial intolerance have surged precipitously. The dramatic uptick in hate crimes and hate speech is not lost on young children. But how, and how early, do children become aware of racial bias? And when do their own views of themselves and others become infused with racial bias? This article opens with a brief overview of the existing experimental evidence documenting developmental entry points of racial bias in infants and young children and how it unfolds. The article then goes on to identify gaps in the extant research and outlines three steps to narrow them. By bringing together what we know and what remains unknown, the goal is to provide a springboard, motivating a more comprehensive psychological-science framework that illuminates early steps in the acquisition of racial bias. If we are to interrupt race bias at its inception and diminish its effects, then we must build strong cross-disciplinary bridges that span the psychological and related social sciences to shed light on the pressing issues facing our nation's young children and their families.

An object lesson: Objects, non-objects, and the power of conceptual construal in adjective extension.

Despite the seemingly simple mapping between adjectives and perceptual properties (e.g., color, texture), preschool children have difficulty establishing the appropriate extension of novel adjectives. When children hear a novel adjective applied to an individual object, they successfully extend the adjective to other members of the same object category but have difficulty extending it more broadly to members of different categories. We propose that the source of this difficulty lies at the interface of the linguistic and conceptual systems: children initially limit the extension of an adjective to the category of the object on which it was introduced. To test this hypothesis, we manipulated whether participants construed images as "pictures of things" (objects) or "blobs of stuff" (non-objects). For both 36-month-old children (Experiments 1 and 2) and adults (Experiment 3), the conceptual status of an image influenced how they extended an adjective applied to that image. Children extended novel adjectives more successfully when they construed the images as non-objects than when they construed the same images as objects. Similarly, adults were faster to make adjective extensions when construing the images as non-objects rather than objects. Learners of all ages must navigate this linguistic-conceptual interface in assessing whether and how novel adjectives should be extended to new individuals.

Developmental changes in auditory-evoked neural activity underlie infants' links between language and cognition.

The power and precision with which humans link language to cognition is unique to our species. By 3-4 months of age, infants have already established this link: simply listening to human language facilitates infants' success in fundamental cognitive processes. Initially, this link to cognition is also engaged by a broader set of acoustic stimuli, including non-human primate vocalizations (but not other sounds, like backwards speech). But by 6 months, non-human primate vocalizations no longer confer this cognitive advantage that persists for speech. What remains unknown is the mechanism by which these sounds influence infant cognition, and how this initially broader set of privileged sounds narrows to only human speech between 4 and 6 months. Here, we recorded 4- and 6-month-olds' EEG responses to acoustic stimuli whose behavioral effects on infant object categorization have been previously established: infant-directed speech, backwards speech, and non-human primate vocalizations. We document that by 6 months, infants' 4-9 Hz neural activity is modulated in response to infant-directed speech and non-human primate vocalizations (the two stimuli that initially support categorization), but that 4-9 Hz neural activity is not modulated at either age by backward speech (an acoustic stimulus that doesn't support categorization at either age). These results advance the prior behavioral evidence to suggest that by 6 months, speech and non-human primate vocalizations elicit distinct changes in infants' cognitive state, influencing performance on foundational cognitive tasks such as object categorization.

Birdsong fails to support object categorization in human infants.

Recent evidence reveals a precocious link between language and cognition in human infants: listening to their native language supports infants' core cognitive processes, including object categorization, and does so in a way that other acoustic signals (e.g., time-reversed speech; sine-wave tone sequences) do not. Moreover, language is not the only signal that confers this cognitive advantage: listening to vocalizations of non-human primates also supports object categorization in 3- and 4-month-olds. Here, we move beyond primate vocalizations to clarify the breadth of acoustic signals that promote infant cognition. We ask whether listening to birdsong, another naturally produced animal vocalization, also supports object categorization in 3- and 4-month-old infants. We report that listening to zebra finch song failed to confer a cognitive advantage. This outcome brings us closer to identifying a boundary condition on the range of non-linguistic acoustic signals that initially support infant cognition.

Semantic priming supports infants' ability to learn names of unseen objects.

Human language permits us to call to mind objects, events, and ideas that we cannot witness directly. This capacity rests upon abstract verbal reference: the appreciation that words are linked to mental representations that can be established, retrieved and modified, even when the entities to which a word refers is perceptually unavailable. Although establishing verbal reference is a pivotal achievement, questions concerning its developmental origins remain. To address this gap, we investigate infants' ability to establish a representation of an object, hidden from view, from language input alone. In two experiments, 15-month-olds (N = 72) and 12-month-olds (N = 72) watch as an actor names three familiar, visible objects; she then provides a novel name for a fourth, hidden fully from infants' view. In the Semantic Priming condition, the visible familiar objects all belong to the same semantic neighborhood (e.g., apple, banana, orange). In the No Priming condition, the objects are drawn from different semantic neighborhoods (e.g., apple, shoe, car). At test infants view two objects. If infants can use the naming information alone to identify the likely referent, then infants in the Semantic Priming, but not in the No Priming condition, will successfully infer the referent of the fourth (hidden) object. Brief summary of results here. Implications for the development of abstract verbal reference will be discussed.

Naming guides how 12-month-old infants encode and remember objects.

A foundation of human cognition is the flexibility with which we can represent any object as either a unique individual (my dog Fred) or a member of an object category (dog, animal). This conceptual flexibility is supported by language; the way we name an object is instrumental to our construal of that object as an individual or a category member. Evidence from a new recognition memory task reveals that infants are sensitive to this principled link between naming and object representation by age 12 mo. During training, all infants (n = 77) viewed four distinct objects from the same object category, each introduced in conjunction with either the same novel noun (Consistent Name condition), a distinct novel noun for each object (Distinct Names condition), or the same sine-wave tone sequence (Consistent Tone condition). At test, infants saw each training object again, presented in silence along with a new object from the same category. Infants in the Consistent Name condition showed poor recognition memory at test, suggesting that consistently applied names focused them primarily on commonalities among the named objects at the expense of distinctions among them. Infants in the Distinct Names condition recognized three of the four objects, suggesting that applying distinct names enhanced infants' encoding of the distinctions among the objects. Infants in the control Consistent Tone condition recognized only the object they had most recently seen. Thus, even for infants just beginning to speak their first words, the way in which an object is named guides infants' encoding, representation, and memory for that object.

Early lexical acquisition in the Wichi language.

This research brings new evidence on early lexical acquisition in Wichi, an under-studied indigenous language in which verbs occupy a privileged position in the input and in conjunction with nouns are characterized by a complex and rich morphology. Focusing on infants ranging from one- to three-year-olds, we analyzed the parental report of infants' vocabulary (Study 1) and naturalistic speech samples of children and their caregivers (Study 2). Results reveal that: (1) although verbs predominate in the linguistic input, children's lexicons favor nouns over verbs; (2) children's early noun-advantage decreases, coming into closer alignment with the patterns in the linguistic input at a MLU of 1.5; and (3) this early transition is temporally related to children's increasing productive command over the grammatical categories that characterize the morphology of both nouns and verbs. These findings emphasize the early effects of language-specific properties of the input, broadening the vantage point from which to view the lexical acquisition process.

Crying helps, but being sad doesn't: Infants constrain nominal reference online using known verbs, but not known adjectives.

Speakers can make inferences about the meaning of new words appearing in an utterance based on the lexical semantics of other words that co-occur with them. Previous work has revealed that infants at 19 and 24 months of age can recruit the semantic selectional restrictions of known verbs (e.g., eating) to deduce that a noun appearing in the subject position maps onto an animate referent. We asked whether this ability to capitalize on the semantics of familiar words to identify the referent of a novel noun in subject position extends to adjectives, which also denote properties, and which also have animacy constraints (e.g., hungry). We found that unlike in the previous studies with verbs, neither 24- nor 36-month-olds could successfully recruit known adjectival semantics in an online task to home in on an animate nominal referent. However, 36-month-olds were successful in a more interactive, forced-choice version of the task without such strict time limitations. We discuss multiple non-mutually-exclusive hypotheses for this pattern of results, focusing on the role of the morphosyntactic cues, the (lack of) perceptual cues for the target property in context of the utterance, truth conditions, and cross-linguistic implications. These possibilities raise fundamental questions about the infant's developing lexicon and the linguistic and conceptual mechanisms at play in the process of word learning.

Studying the Real-Time Interpretation of Novel Noun and Verb Meanings in Young Children.

Decades of research show that children rely on the linguistic context in which novel words occur to infer their meanings. However, because learning in these studies was assessed after children had heard numerous occurrences of a novel word in informative linguistic contexts, it is impossible to determine how much exposure would be needed for a child to learn from such information. This study investigated the speed with which French 20-month-olds and 3-to-4-year-olds exploit function words to determine the syntactic category of novel words and therefore infer their meanings. In a real-time preferential looking task, participants saw two videos side-by-side on a TV-screen: one showing a person performing a novel action, and the other a person passively holding a novel object. At the same time, participants heard only three occurrences of a novel word preceded either by a determiner (e.g., "Regarde! Une dase! - "Look! A dase!") or a pronoun (e.g., "Regarde! Elle dase!" - "Look! She's dasing!"). 3-to-4-year-olds exploited function words to categorize novel words and infer their meanings: they looked more to the novel action in the verb condition, while participants in the noun condition looked more to the novel object. 20-month-olds, however, did not show this difference. We discuss possible reasons for why 20-month-olds may have found it difficult to infer novel word meanings in our task. Given that 20-month-olds can use function words to learn word meanings in experiments providing many repetitions, we suspect that more repetitions might be needed to observe positive effects of learning in this age range in our task. Our study establishes nevertheless that before age 4, young children become able to exploit function words to infer the meanings of unknown words as soon as they occur. This ability to interpret speech in real-time and build interpretations about novel word meanings might be extremely useful for young children to map words to their possible referents and to boost their acquisition of word meanings.

Infants' advances in speech perception shape their earliest links between language and cognition.

The power of human language derives not only from the precision of its signal or the complexity of its grammar, but also from its links to cognition. Infants as young as 3 months have begun to link language and core cognitive capacities. At 3 and 4 months, this link is not exclusive to human language: listening to vocalizations of nonhuman primates also supports infant cognition. By 6 months, infants have tuned this link to human speech alone. Here we provide evidence that infants' increasing precision in speech perception shapes which signals they will link to cognition. Infants listening to German, a nonnative language that shares key rhythmic and prosodic properties with their own native language (English), successfully formed object categories. In contrast, those listening to Cantonese, a language that differs considerably in these suprasegmental properties, failed. This provides the first evidence that infants' increasingly precise perceptual tuning to the sounds of their native language sets constraints on the range of human languages they will link to cognition: infants begin to specify which human languages they will link to core cognitive capacities even before they sever the link between nonhuman primate vocalizations and cognition.

Defining the Role Of Language in Infants' Object Categorization with Eye-tracking Paradigms.

Assessing infant category learning is a challenging but vital aspect of studying infant cognition. By employing a familiarization-test paradigm, we straightforwardly measure infants' success in learning a novel category while relying only on their looking behavior. Moreover, the paradigm can directly measure the impact of different auditory signals on the infant categorization across a range of ages. For instance, we assessed how 2-year-olds learn categories in a variety of labeling environments: in our task, 2-year-olds successfully learned categories when all exemplars were labeled or the first two exemplars were labeled, but they failed to categorize when no exemplars were labeled or only the final two exemplars were labeled. To determine infants' success in such tasks, researchers can examine both the overall preference displayed by infants in each condition and infants' pattern of looking over the course of the test phase, using an eye-tracker to provide fine-grained time-course data. Thus, we present a powerful paradigm for identifying the role of language, or any auditory signal, in infants' object category learning.

Bias at the intersection of race and gender: Evidence from preschool-aged children.

There is ample evidence of racial and gender bias in young children, but thus far this evidence comes almost exclusively from children's responses to a single social category (either race or gender). Yet we are each simultaneously members of many social categories (including our race and gender). Among adults, racial and gender biases intersect: negative racial biases are expressed more strongly against males than females. Here, we consider the developmental origin of bias at the intersection of race and gender. Relying on both implicit and explicit measures, we assessed 4-year-old children's responses to target images of children who varied systematically in both race (Black and White) and gender (male and female). Children revealed a strong and consistent pro-White bias. This racial bias was expressed more strongly for males than females: children's responses to Black boys were less positive than to Black girls, White boys or White girls. This outcome, which constitutes the earliest evidence of bias at the intersection of race and gender, underscores the importance of addressing bias in the first years of life.

A little labeling goes a long way: Semi-supervised learning in infancy.

There is considerable evidence that labeling supports infants' object categorization. Yet in daily life, most of the category exemplars that infants encounter will remain unlabeled. Inspired by recent evidence from machine learning, we propose that infants successfully exploit this sparsely labeled input through "semi-supervised learning." Providing only a few labeled exemplars leads infants to initiate the process of categorization, after which they can integrate all subsequent exemplars, labeled or unlabeled, into their evolving category representations. Using a classic novelty preference task, we introduced 2-year-old infants (n = 96) to a novel object category, varying whether and when its exemplars were labeled. Infants were equally successful whether all exemplars were labeled (fully supervised condition) or only the first two exemplars were labeled (semi-supervised condition), but they failed when no exemplars were labeled (unsupervised condition). Furthermore, the timing of the labeling mattered: when the labeled exemplars were provided at the end, rather than the beginning, of familiarization (reversed semi-supervised condition), infants failed to learn the category. This provides the first evidence of semi-supervised learning in infancy, revealing that infants excel at learning from exactly the kind of input that they typically receive in acquiring real-world categories and their names.