Object play and problem solving in infancy: Insights into tool use.

Tool use is primarily, but not exclusively, present in species with otherwise advanced cognitive traits. However, the interaction between such traits and conspecific inter-individual variation in the presence, complexity, or intensity of tool use is far from being established. We addressed this matter among human infants, seeking factors that relate to differences in tool use. We examined, both correlationally and experimentally, whether the propensity to engage in object combinations predicts performance in means-end problem-solving tasks involving or not involving the use of a tool. We tested 71 infants aged 15, 18, 21, and 24 months, dividing them into two subgroups: one exposed to an adult demonstrating object-object combinations (i.e., "prompting" infants to combine objects together) and another with comparable social exposure but where the adult demonstrated single-object manipulations. We found a correlation between the combined level of spontaneous and prompted object combinations and problem-solving performance regardless of the involvement of tools in the problem. However, we did not find differences in tool-use performance between the two demonstration subgroups. The correlational analysis suggests that complexity of play, as measured by the frequency of combining objects, is linked to infants' problem-solving skills rather than being specifically associated with tool use, as previously suggested in the literature.

Prime saliency in semantic priming with 18-month-olds.

This study investigated semantic priming in 18-month-old infants using the inter-modal priming technique, focusing on the effects of prime repetition on saliency. Our findings showed that prime repetition led to longer looking times at target referents for related primes compared to unrelated primes, supporting the existence of a structured semantic system in infants as young as 18 months. The results are consistent with both Spreading Activation and Distributed models of semantic priming. Additionally, our findings highlighted the impact of prime-target stimulus onset asynchronies (SOAs) on priming effects, revealing positive, negative, or no priming effects depending on the chosen SOA. A post-hoc explanation of this finding points to negative priming as a possible mechanism. The study also demonstrated the utility of the inter-modal priming task in studying lexical-semantic structure in younger infants with its diverse measures of infant behaviour.

Double it up: Vocabulary size comparisons between UK bilingual and monolingual toddlers.

We compared vocabulary sizes in comprehension and production between bilingual toddlers growing up in the United Kingdom (UK) and age-matched UK English monolinguals (12-36 months old) using parent-report vocabulary questionnaires. We found that bilingual toddlers' vocabulary sizes in English were smaller than the vocabulary sizes of their monolingual peers. Notably, this vocabulary gap was not found when groups were compared on conceptual vocabulary in comprehension. Conceptual scoring also reduced the vocabulary gap in production but group differences were still significant. Bilingual toddlers knew more words than monolinguals when words across their two languages were added together, for both comprehension and production. This large total vocabulary size could be attributed to a high proportion of doublets (cross-linguistic word pairs with the same meaning) in bilinguals' vocabularies. These findings are discussed in relation to language exposure, facilitation from cross-linguistic overlap and maturation constraints on vocabulary size.

A network model of referent identification by toddlers in a visual world task.

We present a neural network model of referent identification in a visual world task. Inputs are visual representations of item pairs unfolding with sequences of phonemes identifying the target item. The model is trained to output the semantic representation of the target and to suppress the distractor. The training set uses a 200-word lexicon typically known by toddlers. The phonological, visual, and semantic representations are derived from real corpora. Successful performance requires correct association between labels and visual and semantic representations, as well as correct location identification. The model reproduces experimental evidence that phonological, perceptual, and categorical relationships modulate item preferences. The model provides an account of how language can drive visual attention in the inter-modal preferential looking task.

Colour perception changes with basic colour word comprehension.

Recent work has investigated the origin of infant colour categories, showing pre-linguistic infants categorise colour even in the absence of colour words. These infant categories are similar but not identical to adult categories, giving rise to an important question about how infant colour perception changes with the learning of colour words. Here we present two novel paradigms in which 12- and 19-month-old participants learning English as their first language were assessed on their perception of colour, while data on their colour word comprehension were also collected. Results indicate that participants' perception of colours close to the colour category boundaries dramatically change after colour word learning. The results highlight the shift made from infant colour categories to adult-like linguistically mediated colour categories that accompanies colour word learning. RESEARCH HIGHLIGHTS: We aimed to test whether colour perception is linguistically mediated in infants. We used novel eye-tracking and pupillometry paradigms to test infant colour perception either side of learning colour words. Infants' discrimination of colour changes after learning colour words, suggesting a shift due to colour word learning. A shift from pre-linguistic colour representation to linguistically mediated colour representation is discussed.

Tracking the associative boost in infancy.

Do words that are both associatively and taxonomically related prime each other in the infant mental lexicon? We explore the impact of these semantic relations in the emerging lexicon. Using the head-turn preference procedure, we show that 18-month-old infants have begun to construct a semantic network of associatively and taxonomically related words, such as dog-cat or apple-cheese. We demonstrate that priming between words is longer-lasting when the relationship is both taxonomic and associative, as opposed to purely taxonomic, reflecting the associative boost reported in the adult priming literature. Our results demonstrate that 18-month-old infants are able to construct a lexical-semantic network based on associative and taxonomic relations between words in the network, and that lexical-semantic links are more robust when they are both associative and taxonomic in character. Furthermore, the manner in which activation is propagated through the emerging lexical-semantic network appears to depend upon the type of semantic relation between words. We argue that 18-month-old infants have a mental lexicon that shares important structural and processing properties with that of the adult system.

Bottom-up processes dominate early word recognition in toddlers.

This study set out to investigate whether the 'phonological onset preference effect' often reported in adult studies using the visual world task (i.e., increased attention to an object that is phonologically-related to a spoken-target word, such as boat-bear) is also contingent upon toddler participants having sufficient preview time to inspect the picture stimuli. Picture preview is thought to support the activation of phonological codes which can then be matched to the phonological representations extracted from incoming speech signals and the picture stimuli, supporting the 'phonological mapping hypothesis'. We found that both toddlers and adults were able to show an early phonological onset preference in short preview conditions, though, adults' early phonological onset preferences in the short preview condition was extinguished by the presence of a semantic competitor, replicating previous adult findings (Huettig & McQueen, 2007). Removal of a semantic competitor reinstated the phonological onset preference effect under short preview conditions for adults. Our findings indicate that toddlers are driven more by bottom-up, phonological information when selecting a referent in a visual world task, as compared to adults who are more inclined to exploit top-down, semantic information when directing their attention to a visual object, especially when there is insufficient preview time. We propose that, when implicit naming is improbable in short-preview conditions, a phonological onset preference effect is driven by mapping on the visual-semantic levels, which is more susceptible to top-down influences.

Discovering category boundaries: The role of comparison in infants' novel category learning.

A key question in categorization is how infants extract regularities from the exemplars they encounter. Detecting similarities and dissimilarities across items is vital in order to determine category-relevant features. Previous research found evidence that infants acquire a single category more easily with paired presentations in comparison with single presentations (Oakes & Ribar, 2005, Infancy, 7, 85; Oakes & Kovack-Lesh, 2007, Cogniție, Creier, Comportament / Cognition, Brain, Behavior, XI, 661). Here, we focus on infants' acquisition of a category contrast, that is, when they are exposed to two categories. In an eye-tracking study, we examined 10-month-old infants' ability to learn two novel visual categories when presented with one item at a time and with items in pairs. Infants were familiarized with pairs of items from the same category or with pairs of items from different categories (cross-category pairs). Using a linear model with a priori contrasts, we show that infants' learning is directly related to the opportunity for category comparison: There is no evidence of category learning in the single-item condition, improved performance when familiarized with same-category pairs, and finally robust category learning when familiarized with cross-category pairs. We conclude that comparison which involves items from different categories promotes category formation, by highlighting differences and promoting a discovery of category boundaries.

A Neural Network Model of Lexical-Semantic Competition During Spoken Word Recognition.

Visual world studies show that upon hearing a word in a target-absent visual context containing related and unrelated items, toddlers and adults briefly direct their gaze toward phonologically related items, before shifting toward semantically and visually related ones. We present a neural network model that processes dynamic unfolding phonological representations of words and maps them to static internal lexical, semantic, and visual representations. The model, trained on representations derived from real corpora, simulates this early phonological over semantic/visual preference. Our results support the hypothesis that incremental unfolding of a spoken word is in itself sufficient to account for the transient preference for phonological competitors over both unrelated and semantically and visually related ones. Phonological representations mapped dynamically in a bottom-up fashion to semantic-visual representations capture the early phonological preference effects reported in visual world tasks. The semantic visual preference typically observed later in such a task does not require top-down feedback from a semantic or visual system.

The development of contour processing abilities in the second year.

Recent years have seen a rise in the popularity of eye-tracking methods to evaluate infant and toddler interpretation of visual stimuli. The application of these methods makes it increasingly important to understand the development of infant sensitivity to the perceptual properties implicated in such methods. In light of recent studies that demonstrate the use of pseudoisochromatic plates in testing infants for color vision, we investigated the perceptual contouring abilities required to pass a color-vision test of this type. A total of 115 (51 female) 16- and 19-month-old U.K.-based participants from the Oxfordshire region participated in this study. The evidence collected in this study indicated their ability to systematically fixate a contoured target, but the speed at which they did so was much slower in the younger age group. These findings suggest that the perceptual contouring abilities implicated in this study are still under development in the second year of life, and as such, the results suggest a lower age limit for color-vision tests displayed in this format. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The role of labels and motions in infant category learning.

We investigated the impact of two highly salient transient features, labels and motions, on novel visual category learning in 10-month-old infants. In three eye-tracking experiments, infants were presented with exemplars from two novel categories either accompanied by category-specific labels, accompanied by category-specific motions, or in silence. Labels (Experiment 1) and motions (Experiment 2) were presented using a gaze-contingent design in which these transient features were triggered by infants' fixations. Gaze-contingent transient features, despite being redundant, had a strong impact on categorization. The results revealed that both labels and motions support infants' category formation. Furthermore, both labels and motions promoted similarity-focused exploration, whereas no such pattern was found when infants learned the categories in silence. Analyses of visual exploration patterns revealed that infants readily form expectations about motion properties of categories and that these expectations drive their looking behavior.

Infant categorization as a dynamic process linked to memory.

Recency effects are well documented in the adult and infant literature: recognition and recall memory are better for recently occurring events. We explore recency effects in infant categorization, which does not merely involve memory for individual items, but the formation of abstract category representations. We present a computational model of infant categorization that simulates category learning in 10-month-olds. The model predicts that recency effects outweigh previously reported order effects for the same stimuli. According to the model, infant behaviour at test should depend mainly on the identity of the most recent training item. We evaluate these predictions in a series of experiments with 10-month-old infants. Our results show that infant behaviour confirms the model's prediction. In particular, at test infants exhibited a preference for a category outlier over the category average only if the final training item had been close to the average, rather than distant from it. Our results are consistent with a view of categorization as a highly dynamic process where the end result of category learning is not the overall average of all stimuli encountered, but rather a fluid representation that moves depending on moment-to-moment novelty. We argue that this is a desirable property of a flexible cognitive system that adapts rapidly to different contexts.

Linguistic and Cultural Variation in Early Color Word Learning.

When and how do infants learn color words? It is generally supposed that color words are learned late and with a great deal of difficulty. By examining infant language surveys in British English and 11 other languages, this study shows that color word learning occurs earlier than has been previously suggested and that the order of acquisition of color words is similar in related languages. This study also demonstrates that frequency and syllabic complexity can be used to predict variability in infant color word learning across languages. In light of recent evidence indicating that color categories have universal biological foundations, these findings suggest that infants' experience and linguistic exposure drive their shift to culturally and linguistically mediated adult-like understandings of color words.

Sleep is atypical across neurodevelopmental disorders in infants and toddlers: A cross-syndrome study.

This cross-syndrome study focuses on sleep and its relationship with language development. Children with neurodevelopmental disorders present with language delay. Typical language development is constrained by numerous factors including sleep. Sleep is often disrupted in adolescents/adults with neurodevelopmental disorders. We therefore hypothesised that sleep may be disrupted, and correlate with language development, in infants/toddlers with neurodevelopmental disorders. To test our hypothesis, we obtained sleep and vocabulary size data from 75 infants/toddlers with one of three neurodevelopmental disorders (Down syndrome [DS], fragile X syndrome [FXS], Williams syndrome [WS]). Sleep was indeed disrupted in these children. It was also positively associated with receptive vocabulary size in the infants/toddlers with DS and WS (we could not test the relationship between sleep and language in FXS due to lack of power). We argue that disrupted sleep may be a common occurrence in very young children with neurodevelopmental disorders, and it may relate to their ability to acquire their first language.

The role of colour labels in mediating toddler visual attention.

Toddlers, children and adults will spontaneously attend to a semantically- or perceptually-related object when a named target is absent from the visual scene: Upon hearing "strawberry", they will orient to a red plate rather than a yellow one. We examine the role that knowledge of feature labels plays in mediating visual attention to unnamed features. For example, does knowing the word "red", facilitate attending to red objects, though the label is not uttered? We show that toddlers systematically fixate a colour-related object, if and only if they know the name of the colour associated with the named object and the perceptually-related object. These findings suggest that knowledge of perceptual feature labels can play a central role in highlighting salient similarities between objects, both present and absent in the toddler's visual field. We discuss the implications and limitations of these findings beyond the realm of recognition of colour similarities between objects.

Infants show early comprehension of basic color words.

Previous research has highlighted the difficulty that infants have in learning to use color words. Even after acquiring the words themselves, infants are reported to use them incorrectly, or overextend their usage. We tested 146 infants from 5 different age groups on their knowledge of 6 basic color words, red, green, yellow, blue, black, and white, using an intermodal preferential looking task. The results showed that infants show reliable comprehension of color words as early as 19 months of age. No order of acquisition effects were observed. In addition, infants' behavior in the task was facilitated by the provision of redundant noun information, "Look at the red car," and even general referential noun phrases, "Look at the red one," with greater looking to the target than when the color label was not presented in adjective position, "Look, red." The findings indicate that color words may be learned with greater ease than previously thought, verifying recent parental reports showing similar findings. The findings also suggest that 19 month olds have already developed an expectation that color labels should occur in adjectival position. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The vocabulary spurt predicts the emergence of backward semantic inhibition in 18-month-old toddlers.

The current study examines the relationship between 18-month-old toddlers' vocabulary size and their ability to inhibit attention to no-longer relevant information using the backward semantic inhibition paradigm. When adults switch attention from one semantic category to another, the former and no-longer-relevant semantic category becomes inhibited, and subsequent attention to an item that belongs to the inhibited semantic category is impaired. Here we demonstrate that 18-month-olds can inhibit attention to no-longer relevant semantic categories, but only if they have a relatively large vocabulary. These findings suggest that an increased number of items (word knowledge) in the toddler lexical-semantic system during the "vocabulary spurt" at 18-months may be an important driving force behind the emergence of a semantic inhibitory mechanism. Possessing more words in the mental lexicon likely results in the formation of inhibitory links between words, which allow toddlers to select and deselect words and concepts more efficiently. Our findings highlight the role of vocabulary growth in the development of inhibitory processes in the emerging lexical-semantic system.

Spotlight on daytime napping during early childhood.

Daytime napping undergoes a remarkable change in early childhood, and research regarding its relationship to cognitive development has recently accelerated. In this review, we summarize our current understanding of this relationship focusing on children aged <5 years. First, we evaluate different studies on the basis of the experimental design used and the specific cognitive processes they investigate. Second, we analyze how the napping status of children may modulate the relationship between learning and napping. Third, the possible role of sleep spindles, ie, specific electroencephalographic components during sleep, in cognitive development is explored. We conclude that daytime napping is crucial in early memory development.