Toddlers better retain novel object-label mappings from taxonomic categories they have more knowledge of. Separately, words for concepts with more perceptual features are learned earlier than words for concepts with fewer perceptual features. Because these factors have only been examined separately, it is unclear whether the effects of taxonomic density stem from differences in structured taxonomic knowledge or simply reflect lower-level differences in perceptual similarity among concepts. We asked how taxonomic structure and perceptual information jointly contribute to word learning at 24 months old in an ostensive word learning task. We found that semantic category knowledge facilitated word learning. We also found that the availability of perceptual features served as additional supports for word learning by children with smaller expressive vocabularies. This indicates that structured taxonomic knowledge is a better predictor of word learning compared to lower-level perceptual features at 24 months old. However, perceptual cues may provide additional support for vocabulary growth at the start of development. SUMMARY: We explore how semantic category knowledge and perceptual features jointly influence novel word learning at 24 months old in an ostensive word learning context. Novel word learning was facilitated within semantic categories the toddlers knew more about, when controlling for the availability of perceptual information. Toddlers with smaller productive vocabularies used perceptual features as additional supports for word learning, but those with larger vocabularies did not. These findings show that structured taxonomic knowledge is a better predictor of word learning at 24 months old compared to lower-level perceptual information.

Emotion and language are very common in young children's everyday lives. Hour by hour, they play, listen, vocalize, react, and emote. Despite the centrality of emotion and language to toddlers' local environments, the dynamic interplay of these communicative signals is practically unexplored. Here, we investigated how fluctuations in caregiver and child affect are linked to caregiver-child communication and children's emerging knowledge of words. Multiday household audio recordings and densely-sampled ratings of affect revealed that, in a US-based sample, children (24-30 months) were more likely to know words that they heard frequently in moments with more positive valence or higher arousal. These moments were also associated with denser communication, suggesting that moments of higher valence or arousal facilitate word knowledge in part by supporting mutually engaging communication. This investigation underscores the importance of natural affective states for understanding how children learn language. SUMMARY: Multiday audio and affect experience sampling revealed that caregivers and children talked more in moments when they experienced higher arousal or more positive valence. Toddlers were more likely to know words heard more often in moments with higher arousal or more positive valence. Associations between affect, language input, and word knowledge highlight the importance of affect as a key factor of the early learning environment.

Research has shown that infants are curious and actively seek situations from which they can learn. For instance, a recent eye-tracking study demonstrates that babies tend to allocate their attention to stimuli that offer opportunities for learning new information. Interestingly, however, the degree to which attention is guided by information gain varies among individual infants. This longitudinal study provides the first empirical evidence suggesting that these early individual differences in infants' sensitivity to information gain are linked to later cognitive development. Specifically, we found that the extent to which infants' attention was guided by information gain at 8 months was related to their IQ scores at 3.5 years of age (n = 60, 50% female): especially children who displayed the greatest curiosity as infants tended to have a more favourable cognitive development. These findings demonstrate the lasting consequences of early existing differences in curiosity-driven exploration for later childhood cognitive development. SUMMARY: We link individual differences in curiosity, measured as infants' sensitivity to information gain, to later cognitive outcomes. Infants' sensitivity to information gain was related to their IQ scores 3 years later. Curiosity may act as a boost, improving cognitive functioning for those children that were especially curious during infancy.

The last decade has seen an exponential rise in children's digital media use, as well as growing evidence that it is associated with changes in children's vocabulary. However, while high rates of low-quality digital media have been associated with lower amounts of words a child says, little work has examined whether digital media alters the types of words a child knows. Here, we explore whether differences in the amount of digital media exposure are associated with differences in the composition of children's vocabulary. The current study surveyed 388 caregivers of children 17-30 months (M = 23.9 months) on their children's productive vocabulary and technology use. Multiple regression models predicted the proportion of words children knew in different semantic categories based on the time they spent watching videos/TV, controlling for total noun vocabulary size, age, and income. Increased video watching was associated with producing a smaller proportion of body part words and more people and furniture words, but not other semantic categories. Increased video watching was not associated with differences in shape- or material-based nouns. The results suggest that differences in children's video watching are associated with differences in overall vocabulary size, but also with the particular types of words children know. This may have implications for supporting children's future language in a technology-filled world. SUMMARY: Digital media exposure has been associated with changes in children's vocabularies. However, little work examines whether the media alters the types of words a child learns. The current study explores whether differences in the amount of digital media exposure are associated with differences in the composition of children's vocabulary. Increased video watching was associated with producing fewer body part words, more people, and more furniture words, but no difference in shape- or material-based nouns. The results suggest that differences in children's video watching are associated with differences in overall vocabulary size, but also with the types of words children know.

Developmental dyslexia (DD) is a prevalent neurodevelopmental disorder that significantly affects academic learning and social development. Although numerous brain regions have been implicated in DD under both task-based and resting-state conditions, dysfunctions in large-scale functional coordination across brain systems in DD remains poorly understood. Using AES-SDM, we conducted a meta-analysis of seed-based whole-brain functional connectivity (FC) studies, including 12 task-based studies with 226 dyslexics and 232 age-matched controls, and 7 resting-state studies with 120 dyslexics and 145 controls. Results revealed consistently reduced FC between the left inferior frontal gyrus (IFG) and the left fusiform gyrus (FFG) in dyslexics compared with age-matched controls across both task and resting states, suggesting a core neural pathway underlying DD. In addition, task-specific abnormalities were identified, including hypoconnectivity between the left IFG and the right cerebellum, and hyperconnectivity between the left IFG and the bilateral angular gyrus (AG), anterior cingulate cortex (ACC), and left thalamus. By contrast, resting-state analyses identified additional hypoconnectivity between the left FFG and the posterior cingulate cortex (PCC). Together, these findings suggest that DD is associated with widespread disruption in functional integration across the brain, shedding new light on its neural mechanisms of DD and pointing to potential connectivity-based biomarkers for diagnosis. SUMMARY: Dyslexics exhibited consistent hypoconnectivity between the left inferior frontal gyrus and the left fusiform gyrus across both task and resting conditions. Under the task condition, dyslexics showed specific hypoconnectivity between the left inferior frontal gyrus and the right cerebellum, and hyperconnectivity with the bilateral angular gyrus, anterior cingulate cortex, and left thalamus. Under the resting condition, dyslexics showed specific hypoconnectivity between the left fusiform gyrus and the posterior cingulate cortex.

After conflict, intergroup divisions often persist, becoming entrenched and normative. Violating norms of division to help outgroup members may be an effective form of peacebuilding, yet involves social risks, thus requiring prosocial risk-taking. We explore predictors of willingness to help general, ingroup, and outgroup targets across three countries (Switzerland, N = 431; Northern Ireland, N = 256; Colombia, N = 286) with varying experiences of intergroup conflict, and a broad age range of youth (12-26-years, M = 18.36, SD = 4.00, 57.2% female, 40.2% male, 2.6% another gender). Of interest was the extent to which prosocial risk-taking was predicted by individual differences in prosocial behavior, trait risk-taking, or their combination. The moderating role of perceived peer norms of intergroup friendship-a proxy for social risk of non-conformity-was also explored. Prosocial behavior and trait risk-taking differentially predicted prosocial risk-taking by country; we found no evidence in any country that combined traits of higher prosociality and risk-taking were associated with prosocial risk-taking. Findings indicated various motives to participate in prosocial risk-taking. Perceived peer norms moderated the primary paths of interest. Higher prosociality (Study 2) and risk-taking (Study 3) were only positively related to prosocial risk-taking when peer norms were relatively supportive; yet, when peer norms were relatively unsupportive, higher levels of prosociality and risk-taking were not sufficient to motivate higher prosocial risk-taking. Our research situates individual-level cognitive factors linked to potential peacebuilding in an ecological context and center youth as agents with the capacity to disrupt cycles of division and conflict. SUMMARY: We advance prosocial risk-taking (taking a risk to help others) as a form of peacebuilding after intergroup conflict. Prosocial risk-taking was differentially predicted by prosociality and trait risk-taking across three countries with different conflict histories. Perceived peer norms of intergroup friendship moderated the associations between prosociality (Study 2), trait risk-taking (Study 3) and prosocial risk-taking. Prosociality and trait risk-taking converged with age to jointly predict prosocial risk-taking (Study 1) across a broad age span (12-26-years).

Inequalities in access to important resources and opportunities between social groups persist throughout societies worldwide. Social psychological research has shown that adults often use meritocratic beliefs to justify the existence of such inequalities. Yet, the developmental origins of meritocratic beliefs have yet to be fully explored. This study investigated how children and young adults (N = 144; 5- to 6-year-olds, M = 5.83, SD = 0.97; 9- to 11-year-olds, M = 10.74, SD = 0.68; 18- to 22-year-olds, M = 19.92, SD = 1.10) factored information about merit into their moral judgments and reasoning about science education resource inequalities between groups of girls and boys. Confirming our hypotheses, participants overall judged inequalities that disadvantaged high-merit groups more negatively than inequalities that disadvantaged low-merit groups, regardless of which gender group was disadvantaged. Further, exploratory analyses revealed age-related differences in judgments of inequalities that disadvantaged girls, but not boys. Whereas all age groups judged inequalities that disadvantaged boys more negatively when boys were described as high-merit compared to low-merit, only older children judged inequalities that disadvantaged girls more negatively when girls were described as high-merit compared to low-merit. Age-related differences also emerged for participants' reasoning about inequalities, such that older children were more likely to reason about merit, and less likely to reason about equality, compared to both younger children and young adults. These novel findings offer insights into how concerns for merit shape individuals' moral judgments of social inequalities throughout childhood and young adulthood. SUMMARY: Overall, children and young adults judged inequalities of science resources that disadvantaged high-merit groups more negatively than inequalities that disadvantaged low-merit groups. More positive judgments of inequalities were associated with a lower likelihood of reasoning about equality and a higher likelihood of reasoning about merit. Older children were more likely to reason about merit and less likely to reason about equality compared to both younger children and young adults. Exploratory analyses showed age-related differences in the extent to which participants factored merit into their judgments of inequalities that disadvantaged girls, but not boys.

Vision is considered the dominant sense for spatial perception. Yet, how vision contributes to its refinement in other modalities remains unclear. Consequently, we investigated the development of audio-tactile spatial integration using a localization task in which participants had to determine the position of auditory, tactile, and audio-tactile stimuli and the influence of visual experience in this process. We tested sighted and blind children at different ages. We found that in sighted children, tactile spatial perception stabilizes earlier than the auditory one, and optimal audio-tactile integration is achieved only after 12 years-of-age. Conversely, blind children showed higher uni-sensory precisions from a younger age, although multisensory performance exhibited minimal improvement through age. Overall, our findings suggest that optimal audio-tactile spatial integration develops late during childhood and that vision might play a pivotal role in this process, that is, the absence of vision prompts earlier development of other sensory modalities when processing bodily stimuli. SUMMARY: Sighted children achieve optimal audio-tactile spatial integration only after 12 years, aligning bimodal precision with MLE predictions in adolescence. Blind children show superior early uni-modal sensory localization precision compared to sighted peers. Tactile precision stabilizes earlier than auditory in sighted children, whereas blind children show the opposite developmental trajectory for localization.

In the first months or years of life, newborns learn to perceive their environment at a remarkable pace. This capacity is often attributed to heightened neuronal plasticity that diminishes over time. While this decline in plasticity could be seen as constituting a mere biological constraint, we ask whether it might, in fact, serve an adaptive function. A natural consequence of time-limited plasticity is the preservation of sensory processing mechanisms formed early in life. Emerging evidence has supported the "adaptive initial degradation" hypothesis, which posits that early experience with degraded sensory inputs, such as blurred or color-reduced vision, helps instantiate important sensory mechanisms subserving robust perception later in life. Here, we employ deep neural networks as computational models to systematically probe how developmental improvements in visual fidelity interact with diminishing plasticity, modeled via decreasing learning rates. Across both acuity and color domains, we find that time-limited plasticity yields modest performance gains and helps stabilize early-formed representations. However, these improvements remain surprisingly modest. Further analysis of the networks' internal representations also reveals that earlier layers stabilize sooner than deeper layers, loosely paralleling findings from biological development. Overall, our results suggest that while declining plasticity can confer small benefits, it is not the primary force behind the more pronounced advantages of commencing visual experience with degraded inputs. These insights refine the "adaptive initial degradation" hypothesis and, more broadly, underscore how computational modeling can shed light on longstanding questions in developmental neuroscience. SUMMARY: Time-limited neuronal plasticity is often viewed as a mere biological constraint. However, might it provide adaptive advantages by preserving sensory mechanisms learned early in development? Simulations with initially degraded sensory inputs reveal modest performance gains when modeling time-limited plasticity as decreasing learning rates. Despite these gains, plasticity reductions contribute less than the benefits conferred by starting with degraded inputs, refining the "adaptive initial degradation" hypothesis. These results underscore the utility of computational models to illuminate questions in developmental neuroscience and point to interesting future research avenues.

The left-hemisphere language cortex is known to be structurally aberrant in developmental dyslexia (also referred to as reading disability, RD). However, studies have not addressed the neuroanatomical bases of dyslexia in bilinguals, even though bilingualism is common, and the bilingual experience is thought to alter the language cortex. This raises the question of whether current brain-based models of dyslexia are applicable to bilinguals. We employed a factorial analysis with participants from the ABCD Study (total N = 268, aged 9-10 years), comparing Bilinguals with RD, Bilingual Controls, Monolinguals with RD, and Monolingual Controls on gray matter volume (GMV) and cortical thickness (CT). RD was determined for reading in English. We included only cultural early bilinguals of Spanish and English; these are prevalent in the United States and represent a homogeneous group of bilinguals who learned their languages early in their home environment. Both main effects analyses (RD vs. Control; Bilingual vs. Monolingual) yielded results for GMV and, to a lesser extent for CT, and the effects for bilingualism were more pronounced than those for dyslexia. Importantly, the interaction analysis revealed no exponential effect, indicating that the neuroanatomical signature of dyslexia is not compounded by experience-dependent plasticity associated with early bilingualism. Our results suggest that brain-based models of dyslexia derived from monolinguals can be generalized to early bilinguals. They also reveal no differences in left-hemisphere language cortex in dyslexia (main effects analysis of RD vs. Controls), suggesting that prior results of GMV and CT differences in these regions from smaller studies may not have been robust. SUMMARY: Neuroanatomical aberrations in dyslexia have been reported in left-hemisphere language cortex, but this work is based primarily on monolingual participants. We tested for the first time if aberrations of gray matter volume and cortical thickness in reading disability (RD) are magnified by a dual language-experience. An ANOVA of Bilinguals with and without RD and Monolinguals with and without RD resulted in no exponential effect of bilingual experience. The main effect for RD revealed no differences in left language cortex and far fewer regions than those revealed by the main effect of bilingualism.

Prior research has explored children's help-seeking tendencies in relation to the characteristics of help providers with a primary focus on the helper's competencies. In the current study, we propose that acknowledging a child's emotions without judgment, referred to as emotional validation, is another cue that guides children's help-seeking behavior. In Study 1, we surveyed mothers of children aged 3-6 years (N = 200) and found that their tendency to validate their children's emotions was positively associated with the children's help-seeking behavior, particularly among older children (5-6 years). In Study 2, a randomized experiment with children aged 3-6 years (N = 68) tested the causal effect of emotional validation on help-seeking behaviors. When presented with a challenging task, older children (5-6 years) were more likely to seek help from an emotion-validating adult than an emotion-invalidating adult. This pattern was not observed in younger children (3-4 years). These findings underscore the fact that by around the age of 5, children begin to integrate emotional validation into their social evaluations, using it as a critical cue in deciding whom to approach for help. This developmental shift highlights the role of emotional validation in fostering supportive relationships and promoting adaptive help-seeking behaviors. SUMMARY: Preschoolers are selective when choosing whom to seek help from. Children prefer to seek help from an emotionally validating responder. This preference was particularly evident among older preschoolers (ages 5-6), but not among younger ones (ages 3-4).

The cognitive mechanisms and benefits of active learning in early child development are poorly understood. The current study investigated 20-23-month-old infants' curiosity-driven information selection in a novel word learning task, designed to identify any potential advantage for active learning over passive learning. In a gaze-contingent eye-tracking paradigm, infants in one condition were given the opportunity to structure their own information seeking to actively create word learning opportunities for themselves, while infants in two other conditions engaged in learning novel words passively. Infants' learning of word-object associations was compared across active and passive learning paradigms. The results indicate no advantage of active information selection on retention of novel words above and beyond passive learning, with infants across all conditions retaining novel words above chance. This study provides a crucial insight advancing our understanding of early word learning, and of the mechanisms and benefits of active, curiosity-based learning in infants. SUMMARY: We investigated the effect of active, curiosity-driven word learning, as compared to passive word learning, on infants' label recognition. Infants' self-motivated information selection was tested using a novel word learning task in a gaze-contingent eye-tracking paradigm. Self-motivated information selection had no effect on early word learning above and beyond passive learning, with infants across all conditions retaining novel words above chance. This provides novel insights into infants' active and passive learning for language acquisition.

Evidence from rodent studies highlights the mother as a safety cue that regulates fear and biology. However, when infant rats are exposed to rough maternal care (i.e., threat), their brains show atypical patterns of activity in response to maternal cues. In humans, childhood adversity (i.e., international adoption, involvement with Child Protective Services) is also associated with differential neural responses to caregiver cues. However, to date, no studies have tested the hypothesis that childhood adversity characterized by threat (e.g., physical abuse, domestic violence) influences neural responses to caregiver cues in children, as suggested by the rodent literature. This study investigates associations between threat experiences and neural responses to caregiver cues in young children using fMRI. The sample included 148 young children (52.02% Male; M = 6.45 years). Across the entire sample, children demonstrated heightened recruitment in regions associated with salience detection, visual processing, and social cognition in response to caregiver cues (relative to stranger cues). Moreover, threat experiences were associated with greater recruitment of the insula in response to caregiver cues (relative to stranger cues), even when controlling for deprivation experiences. The present findings contribute to a growing field of research linking childhood adversity to brain function, suggesting that experiences of threat may disrupt how children process caregiver cues at the neural level. Moreover, these results are in line with rodent studies that underscore threat as a potential disruptor of dyadic interaction between children and their caregivers. SUMMARY: Children demonstrate widespread brain activation in response to caregiver cues. Threat experiences are linked to heightened activation of the insula, a region implicated in salience detection and primary visceral processing, in response to caregiver cues. These findings suggest that caregiver cue processing might be a mechanism through which threat impacts the caregiver-child relationship, leading to cascading effects on mental health.

A critical aspect of spoken language development is learning to categorize the sounds of the child's language(s). This process was thought to develop early during infancy to set the stage for the later development of higher-level aspects of language (e.g., vocabulary, syntax). However, many recent studies have shown that speech categorization continues to develop through adolescence. This work, which uses more sophisticated forced-choice tasks and stimuli that span speech continua (e.g., /b/ to /p/ in small steps) suggests that children show increasingly sharp category boundaries over development. However, this contrasts with the consensus view in adult speech perception that speech categories are graded and this may help listeners be more flexible. Here, our longitudinal study revisited these results using a new Visual Analogue Scaling (VAS) task, which employs a continuous rating scale to potentially unpack the underlying cause of a shallower or more gradient boundary. We tested 225 school-aged children (in grades 1-3) over 4 years (through grades 4-6). A Bayesian Hierarchical psychometric model was fit to extract the Slope of the categorization function and Response Consistency (the trial-by-trial variance). Results show that as children age, they show shallower (more gradient) slopes. It also highlighted a new variable, suggesting that older children exhibit greater trial-by-trial categorization consistency. These findings suggest that sound categorization continues to develop through early school age. These findings also suggest that children become increasingly sensitive to fine-grained gradient detail in the signal. The dramatic changes in consistency represent a challenge to current theoretical models that focus primarily on underlying category representation. SUMMARY: Speech categorization continues to develop through the school years, refining children's ability to categorize speech sounds more precisely and flexibly. A longitudinal study tested 225 school-aged children using a Visual Analogue Scaling (VAS) task and Bayesian Hierarchical psychometric modeling. With age, children showed shallower (more gradient) categorization slopes and greater trial-by-trial response consistency. Findings challenge theoretical models, revealing continued development of speech categorization and increasing sensitivity to fine-grained gradient detail in the signal.

Questions about early word knowledge pervade the literature on both typical and atypical language trajectories. To determine which words an infant knows, researchers have relied on two types of measures-caregiver-report and eye-gaze behavior. When these measures are compared, however, their results frequently fail to converge, making it difficult to ascertain whether a given infant knows a given set of words. What are the reasons for these misalignments in gold-standard tasks that are designed to investigate the same underlying construct, and can convergent validity be improved? The current study was designed to investigate multiple methodological features of caregiver-report and looking-while-listening (LWL) tasks hypothesized to contribute to their alignment. American English-learning infants (18-20 months; N = 52) completed an LWL task assessing their understanding of eight early-acquired words. Caregivers reported their child's knowledge of the same eight words, as well as their confidence in their responses and the amount of time they spend with their child. Overall, caregivers' reports of word knowledge did not predict infants' eye-gaze behavior. However, the measures were more likely to be aligned when caregivers reported higher confidence in their responses. Caregivers' reports about both the target and the distractor word on each trial were related to infants' eye-gaze behavior, suggesting that LWL tasks capture knowledge about the labels of both objects tested, not just the label of the target object. The results suggest several critical methodological modifications that could be implemented to improve the measurement validity of both caregiver-report and eye-gaze measures of word comprehension. SUMMARY: This study provides novel insights to improve the validity of infant vocabulary measurement by highlighting factors that explain differences between caregivers' reports and eye-gaze behavior. Caregivers' reports of individual word knowledge failed to converge with infants' eye-gaze behavior during a looking-while-listening (LWL) task. Caregivers' reports of individual word knowledge aligned more strongly with their infant's eye-gaze behavior when caregivers reported more confidence in their responses. Caregivers' reports of both the target and the distractor words predicted infants' eye gaze behavior.

Children experience a variety of messages about racial-ethnic socialization from their parents, teachers, and other sources, who might not answer children's questions about race, or might explicitly promote the idea that race does not matter. However, how such messages affect children's reasoning about disparities, including whether children attribute disparities to intrinsic differences between groups, remains unclear. We contrast the effects of hearing common messages, such as no explanation and colorblindness, with the effects of hearing a structural explanation, which highlights a typical cause of such disparities. Here, we examine the impact of these messages by exposing 7- to 10-year-olds (n = 90) to a scripted parent-child conversation about an achievement disparity between novel groups that used one of these messages. After hearing no explanation or colorblindness, children overwhelmingly provided intrinsic explanations and interventions, attributing the underperformance of one group to their intrinsic capacities, and encouraging them to work harder. However, after hearing a structural explanation that the underperforming group lacked sufficient resources, children shifted away from such intrinsic attributions and towards more extrinsic explanations and interventions, such as calling for change in the larger society. Overall, colorblindness and no explanation seem to be ineffective in reducing children's intrinsic reasoning about group disparities. Instead, structural explanations may be a more constructive approach to counter racial stereotyping. SUMMARY: Messages common in racial-ethnic socialization, for example, no explanation and colorblindness, may be ineffective in suppressing children's intrinsic reasoning, which could support stereotypes. We tested whether structural explanations are more effective by embedding each of these messages in a prescripted conversation about an achievement disparity between novel groups. Children who heard no explanation or colorblindness engaged in intrinsic reasoning, while those who heard structural explanations were more likely to engage in structural reasoning. Contrary to many parents' beliefs, no explanation and colorblindness are ineffective; structural explanations could be a more effective strategy for racial-ethnic socialization.

Collaboration, the process by which individuals work together toward mutual benefits, is a core feature of human sociality. Capacities for collaboration emerge early in development and represent an important social competence. Yet, collaborative commitments can conflict with commitments to societal norms such as honesty and rule compliance, and little is known about whether the development of collaborative proclivities can promote dishonesty in young children. In this study, we tested pairs of 6- to 8-year-old Kazakh-speaking and Russian-speaking children in Kazakhstan (N = 192), a Central Asian post-Soviet society characterized by relatively high social interdependence compared to European and North American, post-industrialized samples commonly recruited in developmental research. Children participated in a die-rolling game in which they could misreport the frequency of a specific outcome to win rewards. We found that children were more likely to cheat when they benefited together with a partner (collaboration condition) than when they benefited individually (solo condition). Additionally, across both conditions, children in Kazakh-speaking classes overreported winning outcomes more frequently than children in Russian-speaking classes. These findings demonstrate that collaborative motives and socio-cultural contexts can influence honesty from an early stage in development. SUMMARY: We investigated children's tendency to cheat in a game in which they could benefit together with a partner (collaboration condition) or benefit alone (solo condition). We tested 6- to 8-year-old Kazakh-speaking and Russian-speaking children from Kazakhstan. Children were more likely to cheat when they benefited together, suggesting that collaborative goals can compromise honesty early in development. Russian-speaking children cheated less than Kazakh-speaking children, highlighting the role of sociocultural factors in how children resolve norm conflicts.

Children often say that possible events are impossible, and only gradually come to see these events as possible. For instance, they often deny that people could do unusual things, like own a pet peacock, or immoral things, like stealing or lying. These possibility denials are surprising. For instance, children have first-hand experience with the very moral violations they say are impossible. In two experiments (total N = 220), we provide evidence that children's possibility denials can nonetheless be taken at face value and do not merely arise from quirks in how children understand questions about possibility. We do this by showing that these denials also arise in children's judgments of actuality-their judgments about what has actually happened and about which assertions of actual events could be true. In Experiment 1, children aged 4-7 judged whether ordinary, immoral, and improbable events could happen or had ever happened. With both judgments, children mostly responded affirmatively to ordinary events, often responded negatively for immoral events, and mostly responded negatively to improbable ones. In Experiment 2, children aged 5-7 judged if assertions of the three kinds of events could be true, and the same pattern emerged again. Together, these findings show that children's denials of immoral and conceptually improbable events extend beyond their judgments about what is possible and match their inferences about what is actual. These correspondences across judgments suggest that children drew on a single procedure, or set of procedures, for assessing possibility. SUMMARY: We show that children judge unexpected events as both impossible and nonactual. Four- to seven-year-olds judged if events could happen, if events had ever happened, and if assertions about events could be true. For all judgments, children often responded negatively to immoral events, and mostly responded negatively to conceptually improbable ones. Children's possibility denials can be taken at face value, and do not reflect quirks in how they respond to questions about possibility.

A basic question about bilingual development is how the acquisition of one language affects the acquisition of the other. Previous findings are few and mixed. The present study addressed this question with longitudinal data on the dual-language vocabulary growth of 149 US-born children from Spanish-speaking immigrant families, who were followed from the age of 2.5 to 12 years. Expressive and receptive vocabulary skills in English and Spanish were assessed with standardized tests, and primary caregivers provided estimates of the relative quantity of the children's English and Spanish exposure at home. The relations between English and Spanish skill levels and growth rates were assessed with concurrent correlations at each age and longitudinal bivariate structural equation models. The relations of skill levels in each language to the relative quantity of home exposure were assessed with concurrent correlations at each age. Findings indicated a tradeoff between English and Spanish expressive vocabulary growth through age 4 only and no competitive relation between English and Spanish in receptive vocabulary development at any age. English vocabularies were related to relative exposure quantity at home only through age 6; Spanish vocabularies were related to home exposure through age 12. The findings thus suggest that bilingual development is subtractive only in the first years of development when both languages compete for the same limited resource-home exposure, and that bilingual receptive language development is additive from an earlier age than is expressive language development. SUMMARY: The relation between two simultaneously acquired languages is subtractive only during the first 4 years of development and only in expressive language skill. After age 4 years, simultaneously acquired languages grow independently of each other. Growth in the societal language is unrelated to home exposure after the preschool years, while minority language growth continues to depend on home exposure. The quantity of home language exposure is more of a limiting factor in expressive vocabulary development than in receptive vocabulary development.

Although exploratory play is considered a hallmark of cognitive development and learning, relatively few studies have been able to quantitatively characterize the shifts that may occur in children's approach to exploration. One reason for this gap is due to challenges coding and analyzing children's exploratory play behavior. In our paper, we employ a novel computational modeling approach to understand whether and how children's exploratory play patterns shift in early childhood (3- to 11-years-old). We analyze data from children (N = 432) across five different experiments that varied in the type of exploration task (including novel toys, novel topics, and novel envelopes). Children's behaviors were coded action-by-action according to whether children repeated an action on the same type of target, switched to a novel target, or terminated play. Our computational Markov model searches over the space of possible "stay," "switch," and "end" parameters to quantify child-specific transition probabilities. We find that overall, older children are less likely to perseverate, more likely to switch, and more likely to end the task earlier. Our approach provides a demonstration of how Markov models can be used to map the process of play, providing insight into theories of developmental changes in exploration. SUMMARY: We use Markov models to quantify developmental shifts in children's exploratory play across five naturalistic tasks. Older children showed increased exploratory variability and decreased perseveration during play. Developmental effects were most consistent in novel toy tasks, but varied across contexts. Our findings help reconcile conflicting prior research by highlighting the role of task structure and developmental changes in exploratory strategy.