Birdsong fails to support object categorization in human infants

The link between non-human primate vocalizations and cognition is not constrained by maturation alone: Evidence from healthy preterm infants

To acquire language, infants must not only identify the signals of their language(s), but also discover how these signals are connected to meaning. By 3 months of age, infants' native language, non-native languages, and vocalizations of non-human primates support infants' formation of object categories-a building block of cognition. But by 6 months, only the native language exerts this cognitive advantage. Prior work with preterm infants indicates that maturation constrains this developing link between the native language and cognition. Here, we assess whether maturation exerts similar constraints on the influence of non-human primate vocalizations on infant categorization. Cross-sectional growth curve analyses of new data from preterm infants and extant data from fullterm infants indicate that developmental tuning of this signal's influence on categorization is best predicted by infants' chronological age, and not gestational status. This evidence, together with prior work, suggests that as infants tune the initially broad set of signals that support early cognition, they are guided by two independent processes: maturation constrains the expression of a link between their native language and cognition, while the influence of non-linguistic signals are guided by other factors, such as postnatal age and experience.

The sound of silence: Reconsidering infants' object categorization in silence, with labels, and with nonlinguistic sounds

A large body of research based on a specific stimulus set (dinosaur/fish) has argued that auditory labels and novel communicative signals (such as beeps used in a communicative context) facilitate category formation in infants, that such effects can be attributed to the auditory signals' communicative nature, and that other auditory stimuli have no effect on categorization. A contrasting view, the auditory overshadowing hypothesis, maintains that auditory signals disrupt processing of visual information and, therefore, interfere with categorization, with more unfamiliar sounds having a more disruptive effect than familiar ones. Here, we used the dinosaur/fish stimulus set to test these contrasting theories in two experiments. In Experiment 1 (N = 17), we found that 6-month-old infants were able to form categories of these stimuli in silence, weakening the claim that labels facilitated their categorization in infants. These results imply that prior findings of no categorization of these stimuli in the presence of nonlinguistic sounds must be due to disruptive effects of such sounds. In Experiment 2 (N = 17), we showed that familiarity modulated the disruptive effect of nonlinguistic sounds on infants' categorization of these stimuli. Together, these results support the auditory overshadowing hypothesis and provide new insights into the interaction between visual and auditory information in infants' category formation.

From social contingency to verbal reference: A constructivist hypothesis

In the first year of life, infants' word learning is slow, laborious, and requires repeated exposure to word-referent co-occurrences. In contrast, by 14-18 months, infants learn words from just a few labeling events, use joint attention and eye gaze to decipher word meaning, and begin to use speech to communicate about absent things. We propose that this remarkable advancement in word learning results from attaining a referential understanding of words-that words are linked to mental representations and used intentionally to communicate about real-world entities. We suggest that verbal reference is supported by codeveloping conceptual, social, representational, and statistical learning capacities. We also propose that infants' recognition of this tri-directional link between words, referents, and mental representations is enabled by their experience participating in and observing socially contingent interactions. Understanding verbal reference signals a qualitative shift in infants' word learning. This shift enables infants to bootstrap word meanings from syntax and semantics, learn novel words and facts from nonostensive communication, and make inferences about speakers' epistemic competence based on their language production. In this paper, we review empirical findings across multiple facets of infant cognition and propose a novel developmental theory of verbal reference. Finally, we suggest new directions of empirical research that may provide stronger and more direct evidence for our theory and contribute to our understanding of the development of verbal reference and language-mediated learning in infancy and beyond. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

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.

Sign language, like spoken language, promotes object categorization in young hearing infants

The link between language and cognition is unique to our species and emerges early in infancy. Here, we provide the first evidence that this precocious language-cognition link is not limited to spoken language, but is instead sufficiently broad to include sign language, a language presented in the visual modality. Four- to six-month-old hearing infants, never before exposed to sign language, were familiarized to a series of category exemplars, each presented by a woman who either signed in American Sign Language (ASL) while pointing and gazing toward the objects, or pointed and gazed without language (control). At test, infants viewed two images: one, a new member of the now-familiar category; and the other, a member of an entirely new category. Four-month-old infants who observed ASL distinguished between the two test objects, indicating that they had successfully formed the object category; they were as successful as age-mates who listened to their native (spoken) language. Moreover, it was specifically the linguistic elements of sign language that drove this facilitative effect: infants in the control condition, who observed the woman only pointing and gazing failed to form object categories. Finally, the cognitive advantages of observing ASL quickly narrow in hearing infants: by 5- to 6-months, watching ASL no longer supports categorization, although listening to their native spoken language continues to do so. Together, these findings illuminate the breadth of infants' early link between language and cognition and offer insight into how it unfolds.