Rapid infant learning of syntactic-semantic links.

In the second year of life, infants begin to rapidly acquire the lexicon of their native language. A key learning mechanism underlying this acceleration is syntactic bootstrapping: the use of hidden cues in grammar to facilitate vocabulary learning. How infants forge the syntactic-semantic links that underlie this mechanism, however, remains speculative. A hurdle for theories is identifying computationally light strategies that have high precision within the complexity of the linguistic signal. Here, we presented 20-mo-old infants with novel grammatical elements in a complex natural language environment and measured their resultant vocabulary expansion. We found that infants can learn and exploit a natural language syntactic-semantic link in less than 30 min. The rapid speed of acquisition of a new syntactic bootstrap indicates that even emergent syntactic-semantic links can accelerate language learning. The results suggest that infants employ a cognitive network of efficient learning strategies to self-supervise language development.

Toddler word learning from contingent screens with and without human presence.

While previous studies have documented that toddlers learn less well from passive screens than from live interaction, the rise of interactive, digital screen media opens new perspectives, since some work has shown that toddlers can learn similarly well from a human present via video chat as from live exposure. The present study aimed to disentangle the role of human presence from other aspects of social interactions on learning advantages in contingent screen settings. We assessed 16-month-old toddlers' fast mapping of novel words from screen in three conditions: in-person, video chat, and virtual agent. All conditions built on the same controlled and scripted interaction. In the in-person condition, toddlers learned two novel word-object associations from an experimenter present in the same room and reacting contingently to infants' gaze direction. In the video chat condition, the toddler saw the experimenter in real time on screen, while the experimenter only had access to the toddler's real-time gaze position as captured by an eyetracker. This setup allowed contingent reactivity to the toddler's gaze while controlling for any cues beyond these instructions. The virtual agent condition was programmed to follow the infant's gaze, to smile, and to name the object with the same parameters as the experimenter in the other conditions. After the learning phase, all toddlers were tested on their word recognition in a looking-while-listening paradigm. Comparisons against chance revealed that toddlers showed above-chance word learning in the in-person group only. Toddlers in the virtual agent group showed significantly worse performance than those in the in-person group, while performance in the video chat group overlapped with the other two groups. These results confirm that in-person interaction leads to best learning outcomes even in the absence of rich social cues. They also elucidate that contingency is not sufficient either, and that in order for toddlers to learn from interactive digital media, more cues to social agency are required.

"The tiger is hitting! the duck too!" 3-year-olds can use prosodic information to constrain their interpretation of ellipsis.

This work aims to investigate French children's ability to use phrasal boundaries for disambiguation of a type of ambiguity not yet studied, namely stripping sentences versus simple transitive sentences. We used stripping sentences such as "[Le tigre tape]! [Le canard aussi]!" ("[The tiger is hitting]! [The duck too]!", in which both the tiger and the duck are hitting), which, without the prosodic information, would be ambiguous with a transitive sentence such as "[Le tigre] [tape le canard aussi]!" ("[The tiger] [is hitting the duck too]!", in which the tiger is hitting the duck). We presented 3-to-4-year-olds and 28-month-olds with one of the two types of sentence above, while they watched two videos side-by-side on a screen: one depicting the transitive interpretation of the sentences, and another depicting the stripping interpretation. The stripping interpretation video showed the two characters as agents of the named action (e.g. a duck and a tiger hitting a bunny), and the transitive interpretation video showed only the first character as an agent, and the second character as a patient of the action (e.g. the tiger hitting the duck and the bunny). The results showed that 3-to-4-year-olds use prosodic information to correctly distinguish stripping sentences from transitive sentences, as they looked significantly more at the appropriate video, while 28-month-olds show only a trend in the same direction. While recent studies demonstrated that from 18 months of age, infants are able to use phrasal prosody to guide the syntactic analysis of ambiguous sentences, our results show that only 3-to-4-year-olds were able to reliably use phrasal prosody to constrain the parsing of stripping sentences. We discuss several factors that can explain this delay, such as differences in the frequency of these structures in child-directed speech, as well as in the complexity of the sentences and of the experimental task. Our findings add to the growing body of evidence on the role of prosody in constraining parsing in young children.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech.

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

Toddlers exploit referential and syntactic cues to flexibly adapt their interpretation of novel verb meanings.

Because linguistic communication is often noisy and uncertain, adults flexibly rely on different information sources during sentence processing. We tested whether toddlers engage in a similar process and how that process interacts with verb learning. Across two experiments, we presented French 28-month-olds with right-dislocated sentences featuring a novel verb ("Hei is VERBing, the boyi"), where a clear prosodic boundary after the verb indicates that the sentence is intransitive (such that the NP "the boy" is coreferential with the pronoun "he" and the sentence means "The boy is VERBing"). By default, toddlers incorrectly interpreted the sentence based on the number of NPs (assuming, e.g., that someone is VERBing the boy). Yet, when children were provided with additional information about the syntactic contexts (Experiment 1, N = 81) or the referential/semantic content (Experiment 2, N = 72) of the novel verb, they successfully used the prosodic information as a cue to reach the correct syntactic structure of the sentence and infer the probable meaning of the novel verb. These results suggest that toddlers can flexibly adjust their interpretations of sentences depending on the reliability of the linguistic cues available. Thus, failure to parse a sentence in an adult-like fashion might not necessarily reflect the immaturity of children's parsing system but rather might be indicative of what cues children consider reliable in that context.

Three- to Four-Year-Old Children Rapidly Adapt Their Predictions and Use Them to Learn Novel Word Meanings.

Adults create and update predictions about what speakers will say next. This study asks whether prediction can drive language acquisition, by testing whether 3- to 4-year-old children (n = 45) adapt to recent information when learning novel words. The study used a syntactic context which can precede both nouns and verbs to manipulate children's predictions about what syntactic category will follow. Children for whom the syntactic context predicted verbs were more likely to infer that a novel word appearing in this context referred to an action, than children for whom it predicted nouns. This suggests that children make rapid changes to their predictions, and use this information to learn novel information, supporting the role of prediction in language acquisition.

Learning homophones in context: Easy cases are favored in the lexicon of natural languages.

Even though ambiguous words are common in languages, children find it hard to learn homophones, where a single label applies to several distinct meanings (e.g., Mazzocco, 1997). The present work addresses this apparent discrepancy between learning abilities and typological pattern, with respect to homophony in the lexicon. In a series of five experiments, 20-month-old French children easily learnt a pair of homophones if the two meanings associated with the phonological form belonged to different syntactic categories, or to different semantic categories. However, toddlers failed to learn homophones when the two meanings were distinguished only by different grammatical genders. In parallel, we analyzed the lexicon of four languages, Dutch, English, French and German, and observed that homophones are distributed non-arbitrarily in the lexicon, such that easily learnable homophones are more frequent than hard-to-learn ones: pairs of homophones are preferentially distributed across syntactic and semantic categories, but not across grammatical gender. We show that learning homophones is easier than previously thought, at least when the meanings of the same phonological form are made sufficiently distinct by their syntactic or semantic context. Following this, we propose that this learnability advantage translates into the overall structure of the lexicon, i.e., the kinds of homophones present in languages exhibit the properties that make them learnable by toddlers, thus allowing them to remain in languages.

Ambiguous function words do not prevent 18-month-olds from building accurate syntactic category expectations: An ERP study.

To comprehend language, listeners need to encode the relationship between words within sentences. This entails categorizing words into their appropriate word classes. Function words, consistently preceding words from specific categories (e.g., the ballNOUN, I speakVERB), provide invaluable information for this task, and children's sensitivity to such adjacent relationships develops early on in life. However, neighboring words are not the sole source of information regarding an item's word class. Here we examine whether young children also take into account preceding sentence context online during syntactic categorization. To address this question, we use the ambiguous French function word la which, depending on sentence context, can either be used as determiner (the, preceding nouns) or as object clitic (it, preceding verbs). French-learning 18-month-olds' evoked potentials (ERPs) were recorded while they listened to sentences featuring this ambiguous function word followed by either a noun or a verb (thus yielding a locally felicitous co-occurrence of la + noun or la + verb). Crucially, preceding sentence context rendered the sentence either grammatical or ungrammatical. Ungrammatical sentences elicited a late positivity (resembling a P600) that was not observed for grammatical sentences. Toddlers' analysis of the unfolding sentence was thus not limited to local co-occurrences, but rather took into account non-adjacent sentence context. These findings suggest that by 18 months of age, online word categorization is already surprisingly robust. This could be greatly beneficial for the acquisition of novel words.

Neural dynamics of prediction and surprise in infants.

Prior expectations shape neural responses in sensory regions of the brain, consistent with a Bayesian predictive coding account of perception. Yet, it remains unclear whether such a mechanism is already functional during early stages of development. To address this issue, we study how the infant brain responds to prediction violations using a cross-modal cueing paradigm. We record electroencephalographic responses to expected and unexpected visual events preceded by auditory cues in 12-month-old infants. We find an increased response for unexpected events. However, this effect of prediction error is only observed during late processing stages associated with conscious access mechanisms. In contrast, early perceptual components reveal an amplification of neural responses for predicted relative to surprising events, suggesting that selective attention enhances perceptual processing for expected events. Taken together, these results demonstrate that cross-modal statistical regularities are used to generate predictions that differentially influence early and late neural responses in infants.