The role of systematicity in early referent selection.

Previous studies showed that word learning is affected by children's existing knowledge. For instance, knowledge of semantic category aids word learning, whereas a dense phonological neighbourhood impedes learning of similar-sounding words. Here, we examined to what extent children associate similar-sounding words (e.g., rat and cat) with objects of the same semantic category (e.g., both are animals), that is, to what extent children assume meaning overlap given form overlap between two words. We tested this by first presenting children (N = 93, Mage = 22.4 months) with novel word-object associations. Then, we examined the extent to which children assume that a similar sounding novel label, that is, a phonological neighbour, refers to a similar looking object, that is, a likely semantic neighbour, as opposed to a dissimilar looking object. Were children to preferentially fixate the similar-looking novel object, it would suggest that systematic word form-meaning relations aid referent selection in young children. While we did not find any evidence for such word form-meaning systematicity, we demonstrated that children showed robust learning for the trained novel word-object associations, and were able to discriminate between similar-sounding labels and also similar-looking objects. Thus, we argue that unlike iconicity which appears early in vocabulary development, we find no evidence for systematicity in early referent selection.

Limited evidence of test-retest reliability in infant-directed speech preference in a large preregistered infant experiment.

Test-retest reliability-establishing that measurements remain consistent across multiple testing sessions-is critical to measuring, understanding, and predicting individual differences in infant language development. However, previous attempts to establish measurement reliability in infant speech perception tasks are limited, and reliability of frequently used infant measures is largely unknown. The current study investigated the test-retest reliability of infants' preference for infant-directed speech over adult-directed speech in a large sample (N = 158) in the context of the ManyBabies1 collaborative research project. Labs were asked to bring in participating infants for a second appointment retesting infants on their preference for infant-directed speech. This approach allowed us to estimate test-retest reliability across three different methods used to investigate preferential listening in infancy: the head-turn preference procedure, central fixation, and eye-tracking. Overall, we found no consistent evidence of test-retest reliability in measures of infants' speech preference (overall r = 0.09, 95% CI [-0.06,0.25]). While increasing the number of trials that infants needed to contribute for inclusion in the analysis revealed a numeric growth in test-retest reliability, it also considerably reduced the study's effective sample size. Therefore, future research on infant development should take into account that not all experimental measures may be appropriate for assessing individual differences between infants. RESEARCH HIGHLIGHTS: We assessed test-retest reliability of infants' preference for infant-directed over adult-directed speech in a large pre-registered sample (N = 158). There was no consistent evidence of test-retest reliability in measures of infants' speech preference. Applying stricter criteria for the inclusion of participants may lead to higher test-retest reliability, but at the cost of substantial decreases in sample size. Developmental research relying on stable individual differences should consider the underlying reliability of its measures.

The cognitive underpinnings and early development of children's selective trust.

Young children learn selectively from reliable over unreliable sources. However, the cognitive underpinnings of their selectivity (attentional biases or trait ascriptions) and its early ontogeny are unclear. Thus, across three studies (N = 139, monolingual German speakers, 67 female), selective-trust tasks were adapted to test both preschoolers (5-year-olds) and toddlers (24-month-olds), using eye-tracking and interactive measures. These data show that preschoolers' selectivity is not based on attentional biases, but on person-specific trait ascriptions. In contrast, toddlers showed no selective trust, even in the eye-tracking tasks. They succeeded, however, in eye-tracking tasks with the same word-learning demands, if no ascriptions of reliability were required. Thus, these findings suggest that preschoolers, but not toddlers, use trait-like ascriptions of reliability to guide their selective learning.

The impact of goal saliency and verbal information on selective imitation in 16- to 18-month-olds.

This study aimed to assess which action component (movement or goal) infants prioritize in their imitation behavior when they get information about its relevance from two important sources: perceptual goal saliency and experimenter's verbal information. 16- to 18-month-olds (N = 72) observed how the experimenter moved a toy mouse with a hopping or sliding movement onto one of two empty spaces (low goal saliency) or 2D circles (medium saliency), or inside one of two 3D houses (high saliency). Before the demonstration, the experimenter verbally announced the movement style or the goal. Results showed that verbal action descriptions did not influence infants' imitation. However, matching previous findings, infants imitated the goal more often than the movement in the high-saliency condition, and the movement more often than the goal in the low-saliency condition. Moreover, in the novel medium-saliency condition, infants imitated both components equally often. Thus, selective imitation varied as a function of perceptual goal saliency, but not of verbal cues. This suggests that perceptual features can enhance infants' bottom-up processing and imitation of action components, while the impact of top-down processes based on verbal cues may vary depending on task characteristics and infants' verbal abilities, inducing a need for further research.

Better in sync: Temporal dynamics explain multisensory word-action-object learning in early development.

We investigated the temporal impact of multisensory settings on children's learning of word-object and action-object associations at 1- and 2-years of age. Specifically, we examined whether the temporal alignment of words and actions influenced the acquisition of novel word-action-object associations. We used a preferential looking and violation of expectation task in which infants and young children were first presented with two distinct word-object and action-object pairings either in a synchronous (overlapping in time) or sequential manner (one after the other). Findings revealed that 2-year-olds recognized both, action-object and word-object associations when they first saw the word-action-object combinations synchronously, but not sequentially, as evidenced by looking behavior. 1-year-olds did not show evidence for recognition for either of the word-object and action-object pairs, regardless of the initial temporal alignment of these cues. To control for individual differences, we explored factors that might influence associative learning based on parental reports of 1- and 2-year-olds development, however, developmental measures did not explain word-action-object associative learning in either group. We discuss that while young children may benefit from the temporal alignment of multisensory cues as it enables them to actively engage with the multisensory content in real-time, infants may have been overwhelmed by the complexity of this input.

Even young children make multiple predictions in the complex visual world.

Children can anticipate upcoming input in sentences with semantically constraining verbs. In the visual world, the sentence context is used to anticipatorily fixate the only object matching potential sentence continuations. Adults can process even multiple visual objects in parallel when predicting language. This study examined whether young children can also maintain multiple prediction options in parallel during language processing. In addition, we aimed at replicating the finding that children's receptive vocabulary size modulates their prediction. German children (5-6 years, n = 26) and adults (19-40 years, n = 37) listened to 32 subject-verb-object sentences with semantically constraining verbs (e.g., "The father eats the waffle") while looking at visual scenes of four objects. The number of objects being consistent with the verb constraints (e.g., being edible) varied among 0, 1, 3, and 4. A linear mixed effects model on the proportion of target fixations with the effect coded factors condition (i.e., the number of consistent objects), time window, and age group revealed that upon hearing the verb, children and adults anticipatorily fixated the single visual object, or even multiple visual objects, being consistent with the verb constraints, whereas inconsistent objects were fixated less. This provides first evidence that, comparable to adults, young children maintain multiple prediction options in parallel. Moreover, children with larger receptive vocabulary sizes (Peabody Picture Vocabulary Test) anticipatorily fixated potential targets more often than those with smaller ones, showing that verbal abilities affect children's prediction in the complex visual world.

e-Babylab: An open-source browser-based tool for unmoderated online developmental studies.

The COVID-19 pandemic massively changed the context and feasibility of developmental research. This new reality, as well as considerations about sample diversity and naturalistic settings for developmental research, highlights the need for solutions for online studies. In this article, we present e-Babylab, an open-source browser-based tool for unmoderated online studies targeted for young children and babies. e-Babylab offers an intuitive graphical user interface for study creation and management of studies, users, participant data, and stimulus material, with no programming skills required. Various kinds of audiovisual media can be presented as stimuli, and possible measures include webcam recordings, audio recordings, key presses, mouse-click/touch coordinates, and reaction times. An additional feature of e-Babylab is the possibility to administer short adaptive versions of MacArthur-Bates Communicative Development Inventories (Chai et al. Journal of Speech, Language, and Hearing Research, 63, 3488-3500, 2020). Information pages, consent forms, and participant forms are customizable. e-Babylab has been used with a variety of measures and paradigms in over 12 studies with children aged 12 months to 8 years (n = 1516). We briefly summarize some results of these studies to demonstrate that data quality, participant engagement, and overall results are comparable between laboratory and online settings. Finally, we discuss helpful tips for using e-Babylab and present plans for upgrades.

Sequential Bayes Factor designs in developmental research: Studies on early word learning.

Developmental research, like many fields, is plagued by low sample sizes and inconclusive findings. The problem is amplified by the difficulties associated with recruiting infant participants for research as well as the increased variability in infant responses. With sequential testing designs providing a viable alternative to paradigms facing such issues, the current study implemented a Sequential Bayes Factor (SBF) design on three findings in the developmental literature. In particular, using the framework described by Schönbrödt and colleagues (2017), we examined infants' sensitivity to mispronunciations of familiar words, their learning of novel word-object associations from cross-situational learning paradigms, and their assumption of mutual exclusivity in assigning novel labels to novel objects. We tested an initial sample of 20 participants in each study, incrementally increasing sample size by one and computing a Bayes Factor with each additional participant. In one study, we were able to obtain moderate evidence for the alternate hypotheses despite testing less than half the number of participants as in the original study. We did not replicate the findings of the cross-situational learning study. Indeed, the data were five times more likely under the null hypothesis, allowing us to conclude that infants did not recognize the trained word-object associations presented in the task. We discuss these findings in light of the advantages and disadvantages of using a SBF design in developmental research while also providing researchers with an account of how we implemented this design across multiple studies.

A longitudinal study of the role of vocabulary size in priming effects in early childhood.

Studies on lexical development in young children often suggest that the organization of the early lexicon may vary with age and increasing vocabulary size. In the current study, we explicitly examined this suggestion in further detail using a longitudinal study of the development of phonological and semantic priming effects in the same group of toddlers at three different ages. In particular, our longitudinal design allows us to disentangle effects of increasing age and vocabulary size on priming and the extent to which vocabulary size may predict later priming effects. We tested phonological and semantic priming effects in monolingual German infants at 18, 21, and 24 months of age. We used the intermodal preferential looking paradigm combined with eye tracking to measure the influence of phonologically and semantic related/unrelated primes on target recognition. We found that phonological priming effects were predicted by participants' current vocabulary size even after controlling for participants' age and participants' early vocabulary size. Semantic priming effects were, in contrast, not predicted by vocabulary size. Finally, we also found a relationship between early phonological priming effects and later semantic priming effects as well as between early semantic priming effects and later phonological priming effects, potentially suggesting (limited) consistency in lexical structure across development. Taken together, these results highlight the important role of vocabulary size in the development of priming effects in early childhood.

Children learn words easier when they are interested in the category to which the word belongs.

The overall pattern of vocabulary development is relatively similar across children learning different languages. However, there are considerable differences in the words known to individual children. Historically, this variability has been explained in terms of differences in the input. Here, we examine the alternate possibility that children's individual interest in specific natural categories shapes the words they are likely to learn - a child who is more interested in animals will learn a new animal name easier relative to a new vehicle name. Two-year-old German-learning children (N = 39) were exposed to four novel word-object associations for objects from four different categories. Prior to the word learning task, we measured their interest in the categories that the objects belonged to. Our measure was pupillary change following exposure to familiar objects from these four categories, with increased pupillary change interpreted as increased interest in that category. Children showed more robust learning of word-object associations from categories they were more interested in relative to categories they were less interested in. We further found that interest in the novel objects themselves influenced learning, with distinct influences of both category interest and object interest on learning. These results suggest that children's interest in different natural categories shapes their word learning. This provides evidence for the strikingly intuitive possibility that a child who is more interested in animals will learn novel animal names easier than a child who is more interested in vehicles.

Maternal input and infants' response to infant-directed speech.

Caregivers typically use an exaggerated speech register known as infant-directed speech (IDS) in communication with infants. Infants prefer IDS over adult-directed speech (ADS) and IDS is functionally relevant in infant-directed communication. We examined interactions among maternal IDS quality, infants' preference for IDS over ADS, and the functional relevance of IDS at 6 and 13 months. While 6-month-olds showed a preference for IDS over ADS, 13-month-olds did not. Differences in gaze following behavior triggered by speech register (IDS vs. ADS) were found in both age groups. The degree of infants' preference for IDS (relative to ADS) was linked to the quality of maternal IDS infants were exposed to. No such relationship was found between gaze following behavior and maternal IDS quality and infants' IDS preference. The results speak to a dynamic interaction between infants' preference for different kinds of social signals and the social cues available to them.

A short version of the MacArthur-Bates Communicative Development Inventories with high validity.

The MacArthur-Bates Communicative Development Inventories (CDIs) are among the most widely used evaluation tools for early language development. CDIs are filled in by the parents or caregivers of young children by indicating which of a prespecified list of words and/or sentences their child understands and/or produces. Despite the success of these instruments, their administration is time-consuming and can be of limited use in clinical settings, multilingual environments, or when parents possess low literacy skills. We present a new method through which an estimation of the full-CDI score can be obtained, by combining parental responses on a limited set of words sampled randomly from the full CDI with vocabulary information extracted from the WordBank database, sampled from age-, gender-, and language-matched participants. Real-data simulations using versions of the CDI-WS for American English, German, and Norwegian as examples revealed the high validity and reliability of the instrument, even for tests having just 25 words, effectively cutting administration time to a couple of minutes. Empirical validations with new German-speaking participants confirmed the robustness of the test.

Predicting visual information during sentence processing: Toddlers activate an object's shape before it is mentioned.

We examined the contents of language-mediated prediction in toddlers by investigating the extent to which toddlers are sensitive to visual shape representations of upcoming words. Previous studies with adults suggest limits to the degree to which information about the visual form of a referent is predicted during language comprehension in low constraint sentences. Toddlers (30-month-olds) heard either contextually constraining sentences or contextually neutral sentences as they viewed images that were either identical or shape-related to the heard target label. We observed that toddlers activate shape information of upcoming linguistic input in contextually constraining semantic contexts; hearing a sentence context that was predictive of the target word activated perceptual information that subsequently influenced visual attention toward shape-related targets. Our findings suggest that visual shape is central to predictive language processing in toddlers.

Word reading skill predicts anticipation of upcoming spoken language input: a study of children developing proficiency in reading.

Despite the efficiency with which language users typically process spoken language, a growing body of research finds substantial individual differences in both the speed and accuracy of spoken language processing potentially attributable to participants' literacy skills. Against this background, the current study took a look at the role of word reading skill in listeners' anticipation of upcoming spoken language input in children at the cusp of learning to read; if reading skills affect predictive language processing, then children at this stage of literacy acquisition should be most susceptible to the effects of reading skills on spoken language processing. We tested 8-year-olds on their prediction of upcoming spoken language input in an eye-tracking task. Although children, like in previous studies to date, were successfully able to anticipate upcoming spoken language input, there was a strong positive correlation between children's word reading skills (but not their pseudo-word reading and meta-phonological awareness or their spoken word recognition skills) and their prediction skills. We suggest that these findings are most compatible with the notion that the process of learning orthographic representations during reading acquisition sharpens pre-existing lexical representations, which in turn also supports anticipation of upcoming spoken words.

The quality of caregiver-child interaction is predicted by (caregivers' perception of) their child's interests.

This current study examines the extent to which children's interests and caregivers' sensitivity to their children's interests are associated with the quality of caregiver-child interaction, and subsequent learning. Eighty-one caregiver-child dyads (24-30-month old children) completed an online shared book-reading task where caregivers and children read two e-books with pictures and descriptions of objects from different categories-one previously determined to be of low and one of high interest to the child (with one novel word-object mapping introduced in each book). We also obtained separate behavioural indices of children's interests and children's later recognition of newly introduced word-object mappings. Our findings highlight that the quality of caregiver-child interaction is predicted by children's interests and caregivers' perception of children's interests, although we find only limited overlap between our behavioural indices of children's interests and caregiver perception of children's interests. Neither of these factors predicted later novel word recognition. Thus, while the dynamics between higher quality of caregiver-child interaction, children's interests and learning remain inconclusive, caregivers and children appear to be more attentive, enthusiastic and engaged in reading about topics that (caregivers believe) interest the child. Furthermore, learning in itself seems to be successful, regardless of factors involved, through the mere task of shared book reading.

Words and arbitrary actions in early object categorization: weak evidence for a word advantage.

Both words and gestures have been shown to influence object categorization, often even overriding perceptual similarities to cue category membership. However, gestures are often meaningful to infants while words are arbitrarily related to an object they refer to, more similar to arbitrary actions that can be performed on objects. In this study, we examine how words and arbitrary actions shape category formation. Across three conditions (word cue, action cue, word-action cue), we presented infants (N = 90) with eight videos of single-category objects which vary in colour and other perceptual features. The objects were either accompanied by a word and/or an action that is being performed on the object. Infants in the word and action condition showed a decrease in looking over the course of the familiarization phase indicating habituation to the category, but infants in the word-action condition did not. At test, infants saw a novel object of the just-learned category and a novel object from another category side-by-side on the screen. There was some evidence for an advantage for words in shaping early object categorization, although we note that this was not robust across analyses.

Children's subjective uncertainty-driven sampling behaviour.

Are children and adults sensitive to gaps in their knowledge, and do they actively elicit information to resolve such knowledge gaps? In a cross-situational word learning task, we asked 5-year-olds, 6- to 9-year-olds and adults to estimate their knowledge of newly learned word-object associations. We then examined whether participants preferentially sampled objects they reported not knowing the label in order to hear their labels again. We also examined whether such uncertainty-driven sampling behaviour led to improved learning. We found that all age groups were sensitive to gaps in their knowledge of the word-object associations, i.e. were more likely to say they had correctly indicated the label of an object when they were correct, relative to when they were incorrect. Furthermore, 6- to 9-year-olds and adults-but not 5-year-olds-were more likely to sample objects whose labels they reported not knowing. In other words, older children and adults displayed sampling behaviour directed at reducing knowledge gaps and uncertainty, while younger children did not. However, participants who displayed more uncertainty-driven sampling behaviour were not more accurate at test. Our findings underscore the role of uncertainty in driving 6- to 9-year-olds' and adults' sampling behaviour and speak to the mechanisms underlying previously reported performance boosts in active learning.

An examination of measures of young children's interest in natural object categories.

Developmental research utilizes various different methodologies and measures to study the cognitive development of young children; however, the reliability and validity of such measures have been a critical issue in all areas of research practices. To address this problem, particularly in the area of research on infants' interests, we examined the convergent validity of previously reported measures of children's interests in natural object categories, as indexed by (1) parents' estimation of their child's interest in the categories, (2) extrinsic (overt choices in a task), (3) intrinsic (looking time toward objects), and (4) physiological (pupil dilation) responses to objects of different categories. Additionally, we also examined the discriminant validity of all the aforementioned measures against the well-established and validated measure of parents' estimations of children's vocabulary knowledge. Children completed two tasks: (a) an eye-tracking task, where they were presented with images from a range of defined categories, which collected indices of looking time and pupillary activity; (b) a sticker-choice task, where they were asked to choose between two sticker-images from two different categories belonging to the range of categories assessed in the previous task. Parents completed two questionnaires to estimate (i) their child's interests and (ii) vocabulary knowledge in the categories presented. We first analyzed the discriminant validity between the two parent measures, and found a significant positive association between them. Our successive analyses showed no strong or significant associations between any of our measures, apart from a significant positive association between children's looking time and parents' estimations of children's vocabulary knowledge. From our findings, we conclude that measures of infants' interests thus far may not have sufficient reliability to adequately capture any potential relationship between these measures, or index different components of interest in young children. We suggest next steps for further validation studies in infant research.

Word-form familiarity bootstraps infant speech segmentation.

At about 7 months of age, infants listen longer to sentences containing familiar words - but not deviant pronunciations of familiar words (Jusczyk & Aslin, 1995). This finding suggests that infants are able to segment familiar words from fluent speech and that they store words in sufficient phonological detail to recognize deviations from a familiar word. This finding does not examine whether it is, nevertheless, easier for infants to segment words from sentences when these words sound similar to familiar words. Across three experiments, the present study investigates whether familiarity with a word helps infants segment similar-sounding words from fluent speech and if they are able to discriminate these similar-sounding words from other words later on. Results suggest that word-form familiarity may be a powerful tool bootstrapping further lexical acquisition.

Toddlers' processing of phonological alternations: early compensation for assimilation in English and French.

Using a picture pointing task, this study examines toddlers' processing of phonological alternations that trigger sound changes in connected speech. Three experiments investigate whether 2;5- to 3-year-old children take into account assimilations--processes by which phonological features of one sound spread to adjacent sounds--for the purpose of word recognition (e.g., in English, ten pounds can be produced as te[mp]ounds). English toddlers (n = 18) show sensitivity to native place assimilations during lexical access in Experiment 1. Likewise, French toddlers (n = 27) compensate for French voicing assimilations in Experiment 2. However, French toddlers (n = 27) do not take into account a hypothetical non-native place assimilation rule in Experiment 3, suggesting that compensation for assimilation is already language specific.