Validation of an open source, remote web-based eye-tracking method (WebGazer) for research in early childhood.

Measuring eye movements remotely via the participant's webcam promises to be an attractive methodological addition to in-person eye-tracking in the lab. However, there is a lack of systematic research comparing remote web-based eye-tracking with in-lab eye-tracking in young children. We report a multi-lab study that compared these two measures in an anticipatory looking task with toddlers using WebGazer.js and jsPsych. Results of our remotely tested sample of 18-27-month-old toddlers (N = 125) revealed that web-based eye-tracking successfully captured goal-based action predictions, although the proportion of the goal-directed anticipatory looking was lower compared to the in-lab sample (N = 70). As expected, attrition rate was substantially higher in the web-based (42%) than the in-lab sample (10%). Excluding trials based on visual inspection of the match of time-locked gaze coordinates and the participant's webcam video overlayed on the stimuli was an important preprocessing step to reduce noise in the data. We discuss the use of this remote web-based method in comparison with other current methodological innovations. Our study demonstrates that remote web-based eye-tracking can be a useful tool for testing toddlers, facilitating recruitment of larger and more diverse samples; a caveat to consider is the larger drop-out rate.

The influence of sibship composition on language development at 2 years of age in the ELFE birth cohort study.

The number of older siblings a child has is negatively correlated with the child's verbal skills, an effect that is well known in the literature. However, few studies have examined the effect of older siblings' sex, of the age gap between siblings, of having foreign-speaking parents, as well as the mediating role of parental interaction. Using data from 12,296 children (49.3% female) from the French ELFE birth cohort, we analyzed the effect of these characteristics of the siblings and their family on children's expressive vocabulary measured using the French MacArthur-Bates Communicative Development Inventory. Children's vocabulary at age 2 years was negatively associated with the number of older siblings (-0.08 SD per additional sibling), and this effect was partly mediated by parental interactions. In analyses restricted to children with one older sibling, the vocabulary score was negatively correlated with the age gap between the target child and their older sibling. The vocabulary score was not correlated to their sibling's sex, contrary to the result of a previous study. In addition, the effect of the number of siblings was less negative in foreign speaking families that in French speaking families, suggesting that older siblings might partly compensate for the effect of having foreign-speaking parents. Overall, our results are consistent with the resource dilution (stating that parents have limited resources to distribute among their children) and inconsistent with the confluence model (stating that a child's cognitive ability is correlated to the mean cognitive ability of the family). RESEARCH HIGHLIGHTS: Our results are consistent with the resource dilution model and inconsistent with the confluence model The negative effect of the number of siblings on expressive vocabulary is partly mediated by parental interactions Larger age gaps between a child and their older sibling are associated with lower expressive vocabulary score.

There might be more to syntactic bootstrapping than being pragmatic: A look at grammatical person and prosody in naturalistic child-directed speech.

In 'Being pragmatic about syntactic bootstrapping', Hacquard (2022) argues that abstract syntax is useful for word learning, but that an additional cue, pragmatics, is both necessary and available for young children during the first steps of language acquisition. She focuses on modals and attitude verbs, where the physical context seems particularly impoverished as the sole basis for deriving meanings, and thus where linguistic cues may be particularly helpful. She convincingly shows how pragmatic and syntactic cues could be combined to help young language learners learn and infer the possible meanings of attitude verbs such as "think", "know" or "want". She also argues that, in some circumstances, syntax and pragmatics would need to be supplemented by semantic information from context - for instance, in the case of modals such as "might", "can", or "must". We agree with Hacquard on the importance of the synergies between these different cues to meaning, and wish to add two other aspects of the input that might also be used by young children in these contexts. The aspects we describe can only be noticed when one analyzes concrete examples of what children hear in their everyday lives, something which Hacquard does very often in her work (e.g., Dieuleveut, van Dooren, Cournane & Hacquard, 2022; Huang, White, Liao, Hacquard & Lidz, 2022; Yang, 2022). Taking into account different cues for meaning would help the field go beyond current models of syntactic bootstrapping, and create an integrated picture of the synergies between different levels of linguistic information.

Socioeconomic status correlates with measures of Language Environment Analysis (LENA) system: a meta-analysis.

Using a meta-analytic approach, we evaluate the association between socioeconomic status (SES) and children's experiences measured with the Language Environment Analysis (LENA) system. Our final analysis included 22 independent samples, representing data from 1583 children. A model controlling for LENATM measures, age and publication type revealed an effect size of r z = .186, indicating a small effect of SES on children's language experiences. The type of LENA metric measured emerged as a significant moderator, indicating stronger effects for adult word counts than child vocalization counts. These results provide important evidence for the strength of association between SES and children's everyday language experiences as measured with an unobtrusive recording analyzed automatically in a standardized fashion.

18-month-olds fail to use recent experience to infer the syntactic category of novel words.

Infants are able to use the contexts in which familiar words appear to guide their inferences about the syntactic category of novel words (e.g. 'This is a' + 'dax' -> dax = object). The current study examined whether 18-month-old infants can rapidly adapt these expectations by tracking the distribution of syntactic structures in their input. In French, la petite can be followed by both nouns (la petite balle, 'the little ball') and verbs (la petite mange, 'the little one is eating'). Infants were habituated to a novel word, as well as to familiar nouns or verbs (depending on the experimental group), all appearing after la petite. The familiar words served to create an expectation that la petite would be followed by either nouns or verbs. If infants can utilize their knowledge of a few frequent words to adjust their expectations, then they could use this information to infer the syntactic category of a novel word - and be surprised when the novel word is used in a context that is incongruent with their expectations. However, infants in both groups did not show a difference between noun and verb test trials. Thus, no evidence for adaptation-based learning was found. We propose that infants have to entertain strong expectations about syntactic contexts before they can adapt these expectations based on recent input.

Starting Big: The Effect of Unit Size on Language Learning in Children and Adults.

Multiword units play an important role in language learning and use. It was proposed that learning from such units can facilitate mastery of certain grammatical relations, and that children and adults differ in their use of multiword units during learning, contributing to their varying language-learning trajectories. Accordingly, adults learn gender agreement better when encouraged to learn from multiword units. Previous work has not examined two core predictions of this proposal: (1) that children also benefit from initial exposure to multiword units, and (2) that their learning patterns reflect a greater reliance on multiword units compared to adults. We test both predictions using an artificial-language. As predicted, both children and adults benefit from early exposure to multiword units. In addition, when exposed to unsegmented input - adults show better learning of nouns compared to article-noun pairings, but children do not, a pattern consistent with adults' predicted tendency to focus less on multiword units.

Child-directed and overheard input from different speakers in two distinct cultures.

Despite the fact that in most communities interaction occurs between the child and multiple speakers, most previous research on input to children focused on input from mothers. We annotated recordings of Sesotho-learning toddlers living in non-industrial Lesotho in South Africa, and French-learning toddlers living in urban regions in France. We examined who produced the input (mothers, other children, adults), how much input was child directed, and whether and how it varied across speakers. As expected, mothers contributed most of the input in the French recordings. However, in the Sesotho recordings, input from other children was more common than input from mothers or other adults. Child-directed speech from all speakers in both cultural groups showed similar qualitative modifications. Our findings suggest that input from other children is prevalent and has similar features as child-directed from adults described in previous work, inviting cross-cultural research into the effects of input from other children.

Four- and 5-year-old children adapt to the reliability of conflicting sources of information to learn novel words.

A central challenge in language acquisition is the integration of multiple sources of information, potentially in conflict, to acquire new knowledge and adjust current linguistic representations. One way to accomplish this is to assign more weight to more reliable sources of information in context. We tested the hypothesis that children adjust the weight of different sources of information during learning, considering two specific sources of information: their knowledge of the meaning of familiar words (semantics) and their familiarity with syntax. We varied the reliability of these sources of information through an induction phase (reliable syntax or reliable semantics). At test, French 4- and 5-year-old children and adults listened to sentences where information provided by these two cues conflicted and were asked to choose between two videos that illustrate the sentence. One video presented the reasonable choice if the sentence is assumed to be syntactically correct, but familiar words refer to novel things (e.g., une mange-"an eats" describes a novel object). The other video was the reasonable choice if the sentence is assumed to be syntactically incorrect and familiar words' meaning is preserved (e.g., "an eats" describes a girl eating and actually should have been "she eats"). As predicted, the proportion of syntactic choices (e.g., interpreting mange-"eats" as a novel noun) was found to be higher in the reliable syntax condition than in the reliable semantics condition, showing that children and adults can adapt their expectations to the reliability of sources of information.

Preregistration in infant research-A primer.

Preregistration, the act of specifying a research plan in advance, is becoming more common in scientific research. Infant researchers contend with unique problems that might make preregistration particularly challenging. Infants are a hard-to-reach population, usually yielding small sample sizes, they can only complete a limited number of trials, and they can be excluded based on hard-to-predict complications (e.g., parental interference, fussiness). In addition, as effects themselves potentially change with age and population, it is hard to calculate an a priori effect size. At the same time, these very factors make preregistration in infant studies a valuable tool. A priori examination of the planned study, including the hypotheses, sample size, and resulting statistical power, increases the credibility of single studies and adds value to the field. Preregistration might also improve explicit decision making to create better studies. We present an in-depth discussion of the issues uniquely relevant to infant researchers, and ways to contend with them in preregistration and study planning. We provide recommendations to researchers interested in following current best practices.

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.

Minding the gaps: literacy enhances lexical segmentation in children learning to read.

Can emergent literacy impact the size of the linguistic units children attend to? We examined children's ability to segment multiword sequences before and after they learned to read, in order to disentangle the effect of literacy and age on segmentation. We found that early readers were better at segmenting multiword units (after controlling for age, cognitive, and linguistic variables), and that improvement in literacy skills between the two sessions predicted improvement in segmentation abilities. Together, these findings suggest that literacy acquisition, rather than age, enhanced segmentation. We discuss implications for models of language learning.

Correction: Infant-directed input and literacy effects on phonological processing: Non-word repetition scores among the Tsimane'.

[This corrects the article DOI: 10.1371/journal.pone.0237702.].

The effect of older sibling, postnatal maternal stress, and household factors on language development in two- to four-year-old children.

Previous literature has shown that family structure affects language development. Here, factors relating to older siblings (their presence in the house, sex, and age gap), mothers (maternal stress), and household size and residential crowding were assessed to systematically examine the different roles of these factors. Data from mother-child dyads in a Singaporean birth cohort, (677-855 dyads; 52% males; 58% to 61% Chinese, 20% to 24% Malay, 17% to 19% Indian) collected when children were 24, 48, and 54 months old, were analyzed. There was a negative effect of having an older sibling, moderated by the siblings' age gap, but not by the older sibling's sex, nor household size or residential crowding. Maternal stress affected language outcomes in some analyses but not others. Implications for understanding the possible effects of family structure on language development are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Young children's screen time during the first COVID-19 lockdown in 12 countries.

Older children with online schooling requirements, unsurprisingly, were reported to have increased screen time during the first COVID-19 lockdown in many countries. Here, we ask whether younger children with no similar online schooling requirements also had increased screen time during lockdown. We examined children's screen time during the first COVID-19 lockdown in a large cohort (n = 2209) of 8-to-36-month-olds sampled from 15 labs across 12 countries. Caregivers reported that toddlers with no online schooling requirements were exposed to more screen time during lockdown than before lockdown. While this was exacerbated for countries with longer lockdowns, there was no evidence that the increase in screen time during lockdown was associated with socio-demographic variables, such as child age and socio-economic status (SES). However, screen time during lockdown was negatively associated with SES and positively associated with child age, caregiver screen time, and attitudes towards children's screen time. The results highlight the impact of the COVID-19 lockdown on young children's screen time.

"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.

Infant-directed input and literacy effects on phonological processing: Non-word repetition scores among the Tsimane'.

Language input in childhood and literacy (and/or schooling) have been described as two key experiences impacting phonological processing. In this study, we assess phonological processing via a non-word repetition (NWR) group game, in adults and children living in two villages of an ethnic group where infants are rarely spoken to, and where literacy is variable. We found lower NWR scores than in previous work for both children (N = 17; aged 1-12 years) and adults (N = 13; aged 18-60 years), which is consistent with the hypothesis that there would be long-term effects on phonological processing of experiencing low levels of directed input in infancy. Additionally, we found some evidence that literacy and/or schooling increases NWR scores, although results should be interpreted with caution given the small sample size. These findings invite further investigations in similar communities, as current results are most compatible with phonological processing being influenced by aspects of language experience that vary greatly between and within populations.