Acoustic variability in the speech input has been shown, in certain contexts, to be beneficial during infants' acquisition of sound contrasts. One approach attributes this result to the potential of variability to make the stability of individual cues visible. Another approach suggests that, instead of highlighting individual cues, variability uncovers stable relations between cues that signal a sound contrast. Here, we investigate the relation between Voice Onset Time and the onset of F1 formant frequency, two cues that subserve the voicing contrast in German. First, we verified that German-speaking adults' use of VOT to categorize voiced and voiceless stops is dependent on the value of the F1 onset frequency, in the specific form of a so-called trading relation. Next, we tested whether 6-month-old German learning infants exhibit differential sensitivity to stimulus continua in which the cues varied to an equal extent, but either adhered to the trading relation established in the adult experiment or adhered to a reversed relation. Our results present evidence that infants prefer listening to speech in which phonetic cues conform to certain cue trading relations over cue relations that are reversed.

This study investigated the association between Sensory processing (SP) (i.e., hyporesponsiveness, Sensory Seeking (SS) and hyperresponsiveness) at 10 months (M) and language/social-communicative difficulties at 24M, mediated through object play at 14M in young children at elevated likelihood for autism (EL). Parent-report instruments were used to measure all variables in younger siblings of children with autism (siblings, n = 74) and children born before 30 gestational weeks (preterms, n = 38). Higher scores of object play fully mediated the association between more SS and better language/less social-communicative difficulties. Hypo- and hyperresponsiveness at 10M did not seem to predict language heterogeneity at 24M, but more hypo- and less hyperresponsiveness at 10M were associated with more social-communicative difficulties at 24M. The explained variance in social-communicative difficulties and language was limited (15.25%-16.39%). Similar associations were found for siblings and preterms. This highlights that high frequency of SP behaviors does not necessarily negatively affect communication in young EL-children as is commonly assumed. Early object play skills play a role in the association between early SS and later language/social communicative difficulties. This implies that some criteria of the two core domains of characteristics of autism are interrelated in EL-children, and this may have implications for early intervention programs.

Parent-infant interactions highlight the role of parental input, considering both the quality, infant-directed speech, and quantity of interactions, adult words and communicative turns, in these interactions. However, communication is bidirectional, yet little is known about the infant's role in these interactions. This study (n = 35 4-month-old infants) explores how infant-directed speech, the number of adult words and turn-taking (both measured by the LENA system) are correlated with infants' temperament. Our findings reveal that, while mothers use the typical characteristics of infant-directed speech, they are not correlated with the infant's temperament. However, we observe more adult-infant turn-taking in both introverted infants (with lower Surgency scores) and infants with lower attention regulation (with lower Regulatory/Orienting scores). The number of adult words was not correlated with infants' temperament. We suggest that infants with an introverted temperament prefer quieter exchanges that may lead to more turns and that infants with lower attention regulation might create more opportunities for interactions due to their lower level of self-regulation. These findings suggest that infants' temperament is associated with how adults talk with infants (communicative turns) rather than how adults talk to infants (infant-directed speech, number of adult words). Our results underscore the infant's role in parent-infant communication.

In the current study we identified salient parental factors for child anxiety symptoms by considering the role of stressful life events, maternal anxiety symptoms, maternal depressive symptoms, and maternal neuroticism. Families (N = 399) in an urban area in the United States were participants in a longitudinal study beginning in infancy. Mothers completed measures of stressful life events (Revised Life Events Questionnaire at all visits), maternal anxiety and depressive symptoms (State-Trait Anxiety Inventory and Beck Depression Inventory, respectively, at infancy between 5 and 12 months, at 2 years, and at 3 years), maternal neuroticism (NEO Five-Factor Inventory at infancy), and child anxiety symptoms (Child Behavior Checklist 1.5-5 at 5 years). Linear mixed models (LMMs) were used in analyses. Maternal depressive symptoms from infancy through 3 years were associated with child anxiety symptoms; other main effects modeled (stressful life events, maternal anxiety symptoms, maternal neuroticism) were not associated with child anxiety symptoms. There was a significant interaction effect between stressful life events and maternal depression. Stressful events from infancy through 5 years of age increased risk for child anxiety symptoms at 5 years if the child's mother had a mild mood disturbance or depression, but not for children with non-depressed mothers.

Many in-lab studies have demonstrated that the distribution of word learning moments affects the strength and quality of word representations. How are words distributed in speech to children in their daily lives, and how is distribution related to other input characteristics? The present study analyzes transcripts of language input to English-learning infants from three longitudinal, naturalistic corpora captured between 6 and 39 months of age. To describe how word frequency varies across time, we calculated dispersion scores for all word types for each child. Dispersion quantifies the deviation of observed frequencies in each recording session from expected (uniform across sessions) word frequency, providing a measure of how evenly word utterances were spread across sessions. Dispersion is strongly correlated with frequency and moderately correlated with concreteness across all corpora, such that high frequency and low concreteness words are more evenly dispersed. Correlations with measures of age of acquisition (AoA) varied across corpora, and dispersion did not reliably predict AoA above and beyond frequency and concreteness. The contradiction between the current results and results from in-lab experiments is discussed. This study provides a foundation to explore how word learning unfolds across time and contexts in the real world.

The current study examined the extent to which labels shape visuocortical processing during the first year of life during a brief (~6-min) associative learning task. Images of computer-generated artificial objects were paired with either individual-level (e.g., Jimmy, Boris) or category-level labels (e.g., Hitchel) while event-related potentials were recorded in response to the onset of the visual stimulus in 6- (n = 41), 9- (n = 27), and 12-month-old (n = 28) infants. Analyses examined experience-dependent visuocortical changes within and across trials, label conditions, and ages. Overall, results demonstrate that infants deploy greater visuocortical resources during the first half of associative learning trials and to stimuli paired with category-level relative to individual-level labels. Waveform morphologies also differed between stimuli paired with individual- and category-level labels and across the age groups, with more complex deflections and amplitude differences between label type at 9- and 12-month-olds, but not 6-month-old infants. The present results highlight the importance of associative learning during infancy and suggest that category- versus individual-level labels differentially direct infant attention and visuocortical processing.

There is robust evidence that infants' gestures and vocalisations and caregivers' contingent responses predict later child vocabulary. Recent studies suggest that dyadic combinations of infants' behaviors and caregivers' responses are more robust predictors of children's vocabularies than these behaviors separately. Previous studies have not yet systematically compared different types of dyadic combinations. This study aimed to compare the predictive value of (a) frequencies of infants' behaviors (vocalisations, points, and shows + gives) regardless of caregivers' responses, (b) frequencies of infants' behaviors that elicited verbal responses, (c) frequencies of infants' behaviors that elicited multimodal responses, and (d) frequencies of infants' behaviors that did not elicit any responses from caregivers. We examined 114 caregiver-infant dyads at 9-11 months and children's concurrent and longitudinal vocabulary outcomes at 2-4 years. We found that infants' points elicited a large proportion of verbal responses from caregivers which were related to children's later receptive vocabularies. We also found that only shows + gives that elicited caregivers' responses related to infants' concurrent gesture repertoires. In contrast, infants' behaviors that did not elicit responses negatively related to child vocabulary. The results highlight the importance of examining dyadic combinations of infants' behaviors and caregivers' responses during interactions when examining relations to children's vocabulary development.

Object play is a ubiquitous context for learning. Existing knowledge on infant object interaction has relied on Euro-American samples and observations confined to laboratory playrooms or families' homes, where object play is typically observed indoors and in rooms brimming with toys. Here we examined infants' everyday object play in Tajikistan, where spaces are uniquely laid out and homes are not child-centered and toy-abundant. The restrictive gahvora cradling practice in Tajikistan may indirectly shape how infants access and engage with objects. We documented how much time infants spent in object play, the types and diversity of objects they contacted, and the locations of play-indoors or outside. We observed 59 infants (12-24 months) during a 45-min naturalistic observation when infants were out of the gahvora. Infants engaged with objects 50% of the time. Despite a lack of object diversity, object interactions were frequent and dispersed throughout observations. Walkers tended to divide their object interactions between time spent indoors and outside, but pre-walkers mostly interacted with objects indoors. Caregivers inadvertently shape infants' opportunities for exploration and play through culturally guided childrearing practices. And infants make due: they take it upon themselves to move, explore, and engage-gleaning culturally relevant routines.

Developmental plasticity refers to conditions and circumstances that increase phenotypic variability. In infancy, plasticity expands and contracts depending on domains of functioning, developmental history, and timing. In terms of language processing, infants attend to and discriminate both native and non-native phonetic contrasts, but selectively attune to their native phonemes by the end of the first postnatal year. However, relevant studies have excluded factors regarded as promoters of attention such as infant-directed (ID) speech, synchronous multimodal presentations, and female speakers. Here we investigated whether English-learning 11-month-olds would discriminate a non-native phonetic contrast while manipulating these factors. Results showed significant discrimination of the non-native contrast, regardless of speech register, provided that they were presented by a dynamic female speaker. Interestingly, when a static object or a dynamic male ID speaker replaced the female, no significant discrimination was found. These results show infants to be capable of discriminating non-native phonetic contrasts in an enhanced context at an age when they have been characterized as not being able to do so. Synchronized, multimodal information from female speakers allowed infants to perceive difficult non-native phonemes, highlighting the importance of an ecologically valid context for studying speech perception and language learning in early development.

What environmental regularities support infant communicative learning from social interactions? We propose that infants allocate their attention toward and learn from external events that are contingent on their own behaviors. We tested the robustness of the influence of contingency on communicative learning by using a non-biological stimulus, a remote-controlled car, as the social partner. The car approached infants and produced a speech sound either contingently to infants' vocalizations or on a yoked schedule. Two additional groups had an unfamiliar human experimenter as their social partner in contingent and yoked control conditions. We assessed whether infants formed expectations about their partner's responsiveness to their vocalizations. Expectations made based on contingent responsiveness would support the role of contingency in promoting plasticity in early communicative learning. Infants across all conditions increased their vocalization rates when their partner paused in responding, suggesting that they expected their vocalizations to influence their partners' behavior. Infants vocalized significantly more to the social partner than their caregiver if they received contingent rather than yoked responses from the social partner, regardless of if the partner was a human or non-biological agent. Contingent responses to prelinguistic vocalizations facilitated the formation of expectations for interactivity of social partners.

High-quality early care and education (ECE) programs are associated with positive outcomes, especially for children from low-income families. During the initial COVID-19 pandemic lockdown many of these families faced an abrupt halt to ECE. Here, we examined how toddlers from economically disadvantaged backgrounds enrolled in high-quality ECE programs in the United States during the 2020 pandemic (n = 48) fared on cognitive and socioemotional outcomes compared to a 2019 pre-pandemic cohort (n = 94) and a pandemic 2021 cohort (n = 132). Toddlers in the 2020 cohort scored significantly lower on executive function compared to toddlers in 2019 and 2021 cohorts. Toddlers in the 2020 cohort had higher ratings self-regulation compared to the pre-pandemic cohort, but not 2021 cohort. There were no differences on attachment ratings between cohorts. Findings suggest that the abrupt halt to ECE programs due to the COVID-19 pandemic impacted US toddlers' cognitive and socioemotional abilities. This underscores the importance of continued high-quality ECE for infants and toddlers from low-income families during disruptive times. Further work is needed to investigate the long-term impacts of experiencing an abrupt halt to ECE due to COVID-19.

During early development, increases in vocabulary are related to gains in motor ability, above and beyond the effects of maturation alone. However, little is known about the association between motor development and children's early acquisition of different types of words. We examined whether motor development is differentially associated with concurrent verb and noun vocabulary in 83 infants aged 6- to 24-months-old. We asked caregivers to complete parent-report measures of vocabulary acquisition and motor development. Analyses revealed that the association between word comprehension and motor development significantly differed for verb and nouns. Infants' verb comprehension was more strongly associated with motor development than noun comprehension. We discuss how infants' own motor actions may provide cues that are especially important for narrowing down the meaning of novel verbs.

Young infants' face perception capabilities quickly tune to the features of their primary caregiver. The current study examines whether infants distinguish faces in a more conceptual manner using a manual-search, violation of expectation task that has previously been used to test kind-based individuation. We tested how well infants between 11 and 27 months of age individuated faces that varied by superordinate category (human vs. non-human in Experiment 1) subordinate category (individual identity in Experiment 2) or by race (White vs. Black, Experiments 1 & 2). We assessed individuation by quantifying the difference in infants' duration of reaching within an empty box between trials when the box was unexpectedly empty and expectedly empty. We found evidence of individuation across all ages and conditions, but with within-infant variation. On average, infants individuated face from non-face stimuli (Experiment 1), individual face identities (Experiment 2), and White versus Black faces (Experiments 1 & 2). These findings suggest that 1- to 2-year-old infants use distinct human face features to represent individuals across time and space. We discuss this evidence for race-based individuation and related complexities of face identity in terms of implications for conceptual development for faces in the first years of life.

The developmental importance of infant gesture use is well established, yet few investigations examine what adults can do to facilitate infant gestures. We used an event lag with pauses sequential analysis to generate an index of association between each adult interactional strategy and deictic infant gesture during ten-minute play interactions with 27 typically developing infants (11-25 months) and trained interventionists. We ran correlations to examine potential relationships between the sequential associations, child age, and language scores. Results indicated modeling gestures with a short phrase increased the momentary likelihood of infant gestures overall and points specifically, whereas modeling short phrases without gestures decreased the momentary likelihood of any infant gesture.

This article reviews empirical methods and findings on early language discrimination, questioning rhythm-class based hypotheses on language discrimination in infancy, as well as the assumption that early language discrimination is driven primarily (or solely) by temporal prosodic cues. The present work argues that within-rhythm class discrimination which - according to the rhythmic hypothesis - is not applicable very early in life, has not been sufficiently tested with infants under 4 months of age, that familiarity with a language is not a prerequisite for its discrimination from another rhythmically similar language, and that the temporal rhythm properties may not universally be the primary cues to language discrimination. Although rhythm taxonomy is now by many understood as outdated, some developmental literature still draws on the assumption that rhythm classification determines infants' language discrimination; other studies consider rhythm along a continuous scale and only a few account for cues to language discrimination other than temporal ones. It is proposed that studies on early language discrimination systematically test the contribution of other than temporal rhythm cues, similarly to recent work on multidimensional psychoacoustic salience in the acquisition of segmental categories.

Exposure to early life stress shapes further development, affects later stress reactivity, and mental health outcomes. Despite the central role of early experiences, there is little understanding of how these rapidly forgotten events gain their influence. An infant's ability to cope with everyday stressors is founded on successful co-regulation through mother-infant interaction. A significant disruption of this interaction through the Face-to-Face Still-Face paradigm elicits a well-documented behavioral and physiological stress response in infants. What has yet to be explored is whether infants show regulatory adaptions when encountering the situation over again. To fill this gap, 80 mother-infant dyads were observed in the lab on two consecutive days. Infants in the experimental condition (n = 40) were exposed to a double Still-Face paradigm on day one. Infants in the control group (n = 40) completed time-matched episodes of typical play during their first visit. Mother-infant dyads from both groups returned to the lab 24 h later and participated in the double Still-Face paradigm. Changes in behavior (positive and negative affect), physiology (heart rate), and salivary cortisol, compared to day one and between groups, were evaluated and used to infer adaption to the previous experienced laboratory visit. Infants in the experimental condition showed a significant decrease in positive affect (p = 0.016) and an increase in heart rate (p < 0.001) on day two, compared to controls, even during baseline measures and a neutral first play episode. Infants in the control condition showed a significant decrease in affect (p = 0.05) and non-significant increase in heart rate on day two when first encountering the Still-Face paradigm. Infants in the experimental condition showed significant higher heart rate on day two compared to the control group (p = 0.046). Infants in the experimental condition also exhibited a marginally significant increase in salivary cortisol on day two, compared to day one (p = 0.054). The change in infant heart rate was independent of maternal heart rate which did not differ between day one and day two, or between groups. Findings suggest that a previous stressful experience may elicit a behavioral and physiological adaption in infants 24 h later. Our results suggest that even a short, acute stressful event can elicit a lasting stress response in infants 24 h later. The effect we observed was specific to the context of the stressful event, not just the stressor. More precisely, the effect "spilled over" from the stressful experience on day one into the baseline measure of day two, usually a neutral experience. The results could have implications for further research on how stressful experiences may shape the stress response.

Previous work has found that shy children show chance-level disambiguation and retention of novel word meanings in a typical lab-based word learning task. This effect could be explained in terms of shy children's aversion to unfamiliarity disrupting the requisite attentional processes, because the task is marked by a high degree of unfamiliarity. To test this argument, we examined whether increasing the familiarity of the task facilitates shy children's ability to form and retain word meanings. Two-year-old children (N = 23) took part in a word learning task in which their caregiver acted as the experimenter. On referent selection trials, children were presented with sets of three objects, one novel and two familiar, and were asked for either a familiar object using its known label, or a novel object using a novel word. Children were then tested on their retention of the previously formed novel word-object mappings. In this context of increased familiarity, shyness was unrelated to performance on referent selection trials. However, shyness was positively related to children's retention of the word-object mappings, meaning that shyer children outperformed less-shy children on this measure of word learning. These findings show that context-based familiarity interacts with intrinsic individual differences to affect word learning performance.

From early in development, infants process faces in their environment differentially from other items. By around 6 months of age, they are able to orient toward faces in the presence of distractor items. This paper aimed to assess whether this preferential looking toward faces was observable prior to 6 months of age, and whether there were developmental trends. We assessed this using the face pop-out task, a free viewing eye-tracking experiment in which infants viewed arrays containing an image of a face, alongside four distractor items. We assessed whether infants at 4, 5, 6 and 7 months (n = 1585 participants) differed in the proportion of first looks, total dwell time, and frequency of fixations to faces compared to other items. All three outcome variables were significantly higher toward faces than toward any of the other items in all the age groups. Moreover, there were age-related differences across all measures-the older the infants were, the more pronounced their face preferences were. These age-related differences could not be attributed to differences in data quality, and thus suggest that face preference is observable at 4 months of age but shows a strong development until 6 months.

The acquisition of social-emotional competence (SEC) in early childhood has implications for critical child and adult outcomes, such as school readiness, educational and occupational attainment, and mental health. To elucidate this developmental process, normative trajectories of social-emotional competence in infants and toddlers were modeled using longitudinal mixed effects modeling, including the evaluation of child and family characteristics as moderators. The SEC of 12-36-month-old children (N = 256, 83% White, 51% female) was assessed in a cohort-sequential design using the Infant Toddler Social-Emotional Assessment Competence scale. Trajectories were modeled using linear, quadratic, exponential, and logistic mean forms. Following base model selection, child sex, maternal education, parental occupation, family income, and number of siblings were separately added to the model to assess their effect on trajectories. Results show that infants and toddlers SEC follows a quadratic pattern of growth. Additionally, girls had higher scores than boys at 12 months with similar slopes. Number of siblings was also significant at 12 months such that children with fewer siblings had higher scores than those with more with similar slopes. This suggests a female advantage in early SEC acquisition exists even before 12 months and that sibling number may moderate SEC in infancy and toddlerhood.

Maternal mind-mindedness refers to a caregiver's tendency to respond to their infants as individuals with their own thoughts, feelings, desires, and beliefs. Although previous studies have focused on maternal speech in quantifying mind-mindedness, maternal mind-mindedness should manifest not only as mind-related comments but also through non-verbal behaviors during infant-mother interactions. In this study, we investigated the relationship between maternal gaze at the infant's face and typical verbal measurement of mind-mindedness in free-flowing interactions. Forty 11- to 13-month-old infants and their mothers participated in the study; the mothers were asked to wear a head-mounted eye tracker to measure their gaze during infant-mother free-play interactions. We measured the proportion of time mothers looked at the infant's face when it was present in the mother's field of view and examined the relationship between the face-looking proportion and verbal measurement of mothers' mind-mindedness. Mothers who displayed appropriate mind-related comments looked at the faces of their infants more frequently. Moreover, their looking was coordinated in a timely manner with appropriate mind-related comments compared with other comments. Our findings suggest that mothers looking at infants' faces supports comments regarding infants' mental states and shed new light on real-time behaviors underlying mothers' mentalization processes.

The Face-to-Face Still-Face (FF-SF) procedure has been a popular paradigm to understand infant behavior. The current study examines the validity of mothers' behavior during the Still-Face phase of the FF-SF, especially the quality of her neutral face and its impact on infant arousal (N = 358 ethnically-diverse mother-infant dyads, Mean infant age = 223 days, SD = 27 days). Results showed that more than half of the mothers in the sample breached one or more Still-Face phase instructions; however, mothers' breaches of the Still-Face instructions were unrelated to infant arousal (Skin Conductance Responses) during the FF-SF. Additionally, facial analysis revealed that along with a neutral quality to the Still-Face, mothers also displayed significant levels of facial emotion during the Still-Face phase. Higher levels of scared and/or sad expressions during the Still-Face were associated with higher infant arousal during the Still-Face phase. The current study helps us to understand the real-life implementation of the Still-Face during the Face-to-Face Still-Face paradigm. Results indicate that mothers show considerable non-compliance with Still-Face phase instructions, and the infant arousal levels are associated with emotional expressions contaminating the quality of mothers' neutral faces.

Daylong recordings provide an ecologically valid option for analyzing language input, and have become a central method for studying child language development. However, the vast majority of this work has been conducted in North America. We harnessed a unique collection of daylong recordings from Slovenian infants (age: 16-30 months, N = 40, 18 girls), and focus our attention on manually annotated measures of parentese (infant-directed speech with a higher pitch, slower tempo, and exaggerated intonation), conversational turns, infant words, and word combinations. Measures from daylong recordings showed large variation, but were comparable to previous studies with North American samples. Infants heard almost twice as much speech and parentese from mothers compared to fathers, but there were no differences in language input to boys and girls. Positive associations were found between the social-interactional features of language input (parentese, turn-taking) and infants' concurrent language production. Measures of child speech from daylong recordings were positively correlated with measures obtained through the Slovenian MacArthur-Bates Communicative Development Inventory. These results support the notion that the social-interactional features of parental language input are the foundation of infants' language skills, even in an environment where infants spend much of their waking hours in childcare settings, as they do in Slovenia.

During the COVID-19 pandemic, children were repeatedly confronted with people wearing facial masks. Little is known, however, about how this affected young children's interactions with their caregivers. This preregistered experimental within-participants study explored whether facial masks influence young children's initiation and response to joint attention. Using two structured tasks and one free-play task, we measured joint attention episodes in interactions of 12- to 15-month-old Swiss infants with one of their caregivers during the pandemic. In one experimental condition, the caregivers wore a facial mask; in the other, they did not. The results show no significant differences in infants' joint attention between the two conditions. Infants may have interacted with their caregivers wearing facial masks enough previously not to be influenced by masks; alternatively, even with a partially covered face, a person provides enough information via eyes and other body parts that help infants to guide their attention.

Children's ability to identify relevant object features, such as shape, plays a key role in learning object names. However, successful attention to shape (shape bias) is dependent on other factors, including children's vocabulary size as well as opportunities for object exploration. The current study explored the combined impact of both vocabulary and object exploration on attention to shape and their cascading impact on retention of object labels. Here, 336 17-to-30-month-old children completed a Novel Noun Generalization (NNG) task and were tested on retention of exemplar name-object pairings. Children in a pre-familiarization condition physically explored objects before every trial; children in a no-familiarization condition did not. Vocabulary (via MacArthur-Bates Communicative Development Inventory) significantly predicted attention to shape, and higher rates of shape-match exploration yielded a stronger shape bias. However, object exploration did not impact NNG performance or retention, and children struggled to retain word-referent mappings. Though attention to shape is thought to support learning, exploratory analyses revealed that children's NNG performance did not predict retention. The results suggest that vocabulary significantly influences word learning processes but object exploration may not offer support. Future research should consider how task demands and other cognitive abilities impact word learning.

This study investigates attention modulation as a function of infant directed (ID) versus adult directed (AD) speech in seven-month-old infants using electroencephalographic measures. In three experiments, infants were presented with either ID speech or AD speech as stimuli, followed by highly variable images of inanimate objects as targets. In Experiment 1 (N = 18), images were preceded by ID or AD speech with semantic content ("Look here"). Contrary to hypothesis, targets preceded by AD speech elicited increased amplitude of the Negative central (Nc) component compared to targets preceded by ID speech, indicating increased attention. Experiment 2 (N = 23) explored whether ID versus AD speech influences attention allocation also without semantic content. The same targets were either preceded by human voice sounds without semantic content ("Uh-Ah") following the prosody of either ID or AD speech register. No differences in attention allocation or object processing were observed. Experiment 3 (N = 18) contrasted ID speech with and without semantic content and found enhanced attention allocation following stimuli without semantic content, but increased object processing following stimuli with semantic content. Overall, the effects observed here are consistent with the idea that less familiar speech stimuli increase attention for subsequent objects. Semantic content of stimuli increased the depth of object processing in 7-month-olds.

Infants are sensitive to distortions to the global configurations of bodies by 3.5 months of age, suggesting an early onset of body knowledge. It is unclear, however, whether such sensitivity indicates knowledge of the location of specific body parts or solely reflects sensitivity to the overall gestalt of bodies. This study addressed this issue by examining whether, like adults, infants attend to specific locations where body parts have been reorganized. Results show that adults and 5-month-olds, but not 3.5-month-olds, allocated more attention to the body joint areas (e.g., where the arm connects to the shoulder) that were reorganized versus ones that were typical. To examine whether this kind of processing is driven by low-level features, 5-month-olds were tested on images in which the head was removed. Infants no longer exhibited differential scanning of typical versus reorganized bodies. Results suggest that 5-month-olds are sensitive to the location of body parts, thereby demonstrating adult-like response patterns consistent with early expertise in body processing. The contrasting failure of 3.5-month-olds to exhibit sensitivity to the reorganization suggests a developmental change between these ages.

The COVID-19 pandemic created an unprecedented situation for families worldwide, with its potential impact on child development remaining uncertain, particularly within Latin American communities. This study aimed to analyze child development in children from Costa Rica and Mexico who grew up during COVID-19 pandemic. A cross-sectional study was conducted using a convenience sample of 183 children; a historical control group of Costa Rican children (n = 171) was also included. Child development was assessed using the EDIN-II in Costa Rica and the EDI in Mexico, along with a parental questionnaire. Descriptive statistics, chi-square tests, and logistic regression analysis were performed, with a significance level of 0.05. Significant differences were found when comparing the risk of development delay, particularly in the overall score and the fine motor domain score. The probability of overall delay was associated with the child's sex, age, maternal education level and whether the primary caregiver role was shared by both parents or fulfilled by a single parent. In Costa Rica, the development of children assessed post-pandemic was lower than that of children assessed pre-pandemic. The probability of these delays was associated with growing up during the pandemic, child's sex, and families' Socioeconomic Development Index. These results contribute to understanding child development during the COVID-19 context and provide a foundation for future research.

Infants prefer infant-directed (ID) speech. Concerning talking faces, previous research showed that 3- and 5-month-olds prefer faces that produce native ID than native adult-directed (AD) speech, regardless of background speech being ID, AD or silent. Here, we explored whether infants also show a preference for non-native ID speech. We presented 3- and 6-month-old infants with pairs of talking faces, one producing non-native ID speech and the other non-native AD speech, either in silence (Experiment 1) or accompanied by non-native ID or AD background speech (Experiment 2). Results from Experiment 1 showed an overall preference for the silent ID talking faces across both age groups, suggesting a reliance on cross-linguistic, potentially universal cues for this preference. However, Experiment 2 showed that preference for ID faces was disrupted at 3 months when auditory speech was present (ID or AD). At 6 months, infants maintained a preference for ID talking faces, but only when accompanied by ID speech. These findings show that auditory non-native speech interferes with infants' processing of ID talking faces. They also suggest that by 6 months, infants start associating ID features from faces and voices irrespective of language familiarity, suggesting that infants' ID preference may be universal and amodal.

Caregivers may perceive pointing as an indication of infants' readiness to learn, thereby increasing their tendency to label objects regardless of the infant's gesture type and context. This was investigated in this study by tracking 35 infants at home at the ages of 11 and 13 months and observing their interactions with their mothers during object manipulation. We focused on four types of communicative gestures: typical giving gestures, gestures contingent on exploration, gestures contingent on play, and pointing. We analyzed maternal response tendencies, including affirmation, naming, discourse, and pretense. The results revealed that when infants reached the age of 13 months, they tripled their pointing production; in turn, the maternal response changed entirely, with naming becoming the preferred response to all types of gestures. Furthermore, when infants were 13 months old and offered an object contingent on play acts, mothers increased their pretense acts sevenfold. Based on the most informative responses to infants among those examined, we argue that an increase in the number of pointing gestures may gradually be associated with the establishment of the maternal perception that an infant is ready to learn and a subsequent increase in naming and pretense production by the mother.

Human infants seem to make positive social inferences about individuals who imitate others. In three preregistered experiments we test if these inferences include an expectation that imitators will be helpful, and also ask if the inferences infants make are about imitators' dispositions or primarily about their relationships. In each experiment 8- to 9-month-old infants saw one individual imitate, and another individual not imitate, the same target social partner. When the imitator and non-imitator had the opportunity to help the target individual they had previously interacted with, infants looked longer when the non-imitator helped than when the imitator helped. However, when the potential recipient of help was a new social partner, infants' looking did not differ when the imitator or non-imitator helped. Overall, these results support the hypothesis that infants perceive imitation as prosocial or affiliative and thus expect imitators to be helpful. However, these expectations are limited to inferences about a specific prosocial relationship between the imitator and their target.