Human competencies in object recognition and category generalization implicate representations of the 3D geometry of objects. There is no accepted account of how such object-centric representations are formed. Toddlers' manual and visual exploration of objects is strongly associated with their emerging abilities in object recognition and category generalization, although there is limited understanding of the processes that underlie this association. Building on Marr and Nishihara's seminal theory of shape, we proposed (1) that toddlers actively select views that optimize fundamental visual sensitivities for long extents and for edges oriented horizontally and vertically and (2) that these biased views result in the axis of the object's maximum elongation, the major axis, being stably present in the variable 2D shapes projected from the object to the eye. We analyzed the visual properties of toddlers' (n = 90, 12-38 months) egocentric views as they manipulated objects. We observed a highly biased sampling of object views in which the major axis of the physical object is near maximal extension and oriented near horizontal or vertical, two properties that make the major axis stably determinable in the variable 2D shapes projected to the eye. The findings show how fundamental low-level visual sensitivities may play a critical developmental role in biasing behaviors that bias the input in ways that make hard computational problems tractable. The findings also provide an empirical agenda for research focused on the development of object-centric representations of 3D shape. SUMMARY: We examined the visual properties of toddlers' egocentric views of objects. We found that the generated views were a selective sampling of possible views that optimized foundational low-level visual properties for shape perception. The findings implicate strong intrinsic constraints on toddlers' visual experiences of object views. The biases in the toddler generated views are consistent with class theories of object-centric representations of 3-dimensional geometry.

Children living in conditions of severe socioeconomic (SES) hardship are at elevated risk for neurocognitive delays, yet most developmental neuroscience research has focused on children in high-income, Western populations, limiting our understanding of diverse developmental contexts. This study examined maternal perceived social support as a potential buffer against the stressors associated with SES hardship on child neurocognitive development in a longitudinal sample of Indigenous families in the rural Ecuadorian Amazon. Twenty-eight children (M age = 28.02 months at T1; 57.6 months at T2) participated in the study completing an assessment of early cognitive ability at T1 and an inhibition task while functional near-infrared spectroscopy (fNIRS) measured cortical activation at T2. A three-level linear mixed model revealed a significant interaction between early cognitive ability and maternal perceived social support on functional activation. Specifically, children of mothers with high social support showed no association between early cognitive ability and cortical activation, while those with low support exhibited atypical patterns (hyper- or hypoactivation), suggesting that increased maternal perceived social support may help buffer the risk exposure of chronic stressors associated with SES hardship. These findings underscore the importance of culturally embedded social resources in promoting resilience among children facing cumulative risk. Supporting maternal social networks may be a promising pathway for improving child neurodevelopment in underrepresented, low-resource communities and contributes to more inclusive global models of brain development.

Children learn language from their social partners, and differences in the behavior of these social partners can influence language learning outcomes. The literature largely focuses on adult caregivers; however, there is less clarity regarding the extent to which the social behavior of peers might also impact children's language learning. Children spend a large proportion of their time with peers once they enter preschool; peers are thus an important source of input for learning. Moreover, preschoolers are not just interacting with individual peers but also with groups of peers. To explore the impact of peers' social behavior on preschoolers' word learning, the present study manipulated peer behavior at two levels: individual peers and the peer group context. Forty-four preschoolers (36-60 months) completed a tablet task in which they watched a series of animated videos of a classroom. Participants were exposed to (1) either a positive or negative social group (manipulated between-subjects) and (2) a positive and negative individual (manipulated within-subjects). Participants were then taught four novel object-label pairings by the children in the video. We measured preschoolers' accuracy in learning these novel object-label pairs. Overall, preschoolers learned the words above chance and there was no difference in learning from the positive and negative individual peers. However, participants learned words significantly better in the positive group than in the negative group. This pattern of results suggests that peer groups, and the overall affective context of children's learning environments, may play important roles in boosting preschoolers' language learning trajectories.

In this study, the developmental trajectory of children's finger-based strategies for addition is described for the first time using a longitudinal design involving 207 children aged 4 ½ at the first testing point. Children were observed individually twice a year over a three-year period. The trajectory typically followed by children corresponds to the one theoretically described in the literature as supporting the gradual internalization of finger strategies and leading to the complete mentalization of the solving process. More precisely, children progressed from a modeling strategy in which each operand of an addition is represented on the fingers of each hand, through a concrete counting-on strategy, in which both operands are still represented but enumerated in a single continuous process, to a counting-on strategy, in which only one operand is kept in mind while the other is tracked on fingers. The frequent use of the concrete counting-on strategy between modeling and counting-on strategies supports Baroody's proposition that it serves as a transitional step between concrete and more abstract forms of numerical representation. However, the concrete counting-on strategy was associated with poor addition performance, suggesting that it corresponds to a reconstructive stage in which children gain new insights about numbers but lack the cognitive resources to fully capitalize on them. Overall, this study provides the first detailed description of the evolution of finger-based strategies toward the internalization of the addition solving process.

A growing body of research has aimed to map the characteristics of extraordinary altruists-such as those who have donated a kidney to a stranger. However, this research has primarily focused on adults, and we know little about the development of extraordinary altruism. While children cannot donate their organs to strangers nor large portions of their income to charity, they can choose not to eat animals. In this study we examine independent vegetarians (i.e., children who become vegetarian while being raised in meat eating families) as a potential case-study of extraordinarily altruistic motivation. In retrospective adult (Study 1) and developmental samples (Study 2) of American participants, we compare independently vegetarian children to family vegetarians and non-vegetarians on measures of empathy/compassion, disgust sensitivity, cognitive reflection, fearful facial recognition, social dominance orientation, and speciesism. We find that both independent and family vegetarians were lower in speciesism and SDO, and higher in disgust sensitivity and empathy/compassion, with these differences emerging almost exclusively in the retrospective adult sample. Crucially, and contrary to our hypotheses, we find no differences between independent and family vegetarians, and discuss potential interpretations of this null result. These data offer new insight into a small body of literature about independent vegetarians and show that similar traits are associated with both family and independent vegetarianism.

Metacognition-the capacity to represent and reflect upon our knowledge and its sources-is fundamental for higher cognition and learning. Developmental research suggests that the ability to make explicit metacognitive judgments emerges surprisingly late, not before school age. However, this research has assumed that metacognition is optimized for private reflection and therefore tested children's metacognitive judgments in individual settings. In contrast, recent theoretical approaches propose that explicit metacognition may have a primarily social function and should therefore become most evident in socio-communicative contexts. We tested this proposal across four pre-registered studies (N = 195). First, we conducted two studies in which 3- and 5-year-old children participated in a social version of a well-established metacognition task (partial ignorance task). Children had to communicate their uncertainty towards a cooperative partner who relied on their advice. Even 3-year-olds provided accurate metacognitive judgments under these conditions: They spontaneously and explicitly reported uncertainty when they were partially ignorant, but not when they were knowledgeable. Two control studies yielded mixed evidence regarding the question whether the enhanced metacognitive performance in the first two studies was indeed mainly due to the socio-communicative context rather than other factors. Overall, the current findings suggest that explicit metacognition manifests earlier in development than previously assumed and may be boosted in some-particularly socio-communicative-contexts.

Infants often exhibit goal-directed behaviors, such as reaching for a sensory stimulus, even when no external reward criterion is provided. These intrinsically motivated behaviors facilitate spontaneous exploration and learning of the body and environment during early developmental stages. Although computational modeling can offer insight into the mechanisms underlying such behaviors, many existing studies on intrinsic motivation focus primarily on how exploration contributes to acquiring external rewards. In this paper, we propose a novel density model for an agent's own multimodal sensory experiences, called the "self-prior," and investigate whether it can autonomously induce goal-directed behavior. Integrated within an active inference framework based on the free energy principle, the self-prior generates behavioral references purely from an intrinsic process that minimizes mismatches between average past sensory experiences and current observations. This mechanism is also analogous to the acquisition and utilization of a body schema through continuous interaction with the environment. We examine this approach in a simulated environment and confirm that the agent spontaneously reaches toward a tactile stimulus. Our study implements intrinsically motivated behavior shaped by the agent's own sensory experiences, demonstrating the spontaneous emergence of intentional behavior during early development. SUMMARY: Suggests a computational model for early intentional behavior, integrating body-schema formation and goal-directed actions under the free energy principle. Introduces a self-prior as an internal density model that drives the emergence of goal-directed behaviors without external rewards. Demonstrates spontaneous reaching for a sticker by minimizing mismatches between observed multimodal sensory inputs and the empirically acquired self-prior.

Research increasingly links neighborhood environments to children's cognition; however, whether residential greenspace and built-up exposure show different associations across executive function (EF) components in middle childhood remains unclear. Using a cross-sectional design, we examined these associations in 1446 Chinese children aged 8-11 years. Residential greenspace and built-up exposure were quantified within 300-m residential buffers using land-cover data. EF was assessed using tasks indexing working memory (span and updating), response inhibition, conflict inhibition, and cognitive flexibility. Linear mixed-effects models and complementary network analyses, both accounting for measured covariates, were used to characterize exposure-EF associations. Greenspace exposure showed the clearest and most consistent positive associations with working memory measures and was also associated with better cognitive flexibility; associations with inhibition were less consistent. Built-up exposure showed a more limited pattern of inverse associations, concentrated primarily in working memory. Across both analytical approaches, working memory emerged as the EF component most consistently associated with residential environmental exposure. This cross-method convergence highlights the importance of considering domain-specific patterns in environment-cognition associations and suggests that child-focused neighborhood planning may benefit from considering greenspace and built-up exposure jointly.

The ability to learn and apply rules lies at the heart of cognition. In a seminal study, Marcus et al. (1999) reported that 7-month-old infants learned abstract rules over syllable sequences and were able to generalize those rules to novel syllable sequences. Dozens of studies have since replicated that finding and extended it using different rules, modalities, stimuli, participants (human adults and non-human animals) and experimental procedures. Yet questions remain about the generalizability of the core findings in Marcus et al., and sources of variation across these findings. In the current study, we address this issue by testing 839 infants (650 after exclusions) of a wide age range (5;0-12;0 months) in a multi-laboratory (30 laboratories, [31 samples]) conceptual replication of the Marcus et al. study. This study and the analysis plan were submitted as a registered report. A mixed-model analysis of the looking times at consistent versus inconsistent test trials indicated no significant effect. The current study therefore finds no evidence for rule-learning; to the contrary, a Bayesian analysis of the data indicated strong evidence for a null effect. This was similarly the case for the moderating factors that were part of the design: mono- versus multilingualism, age, and experimental paradigm; none of these factors showed significant effects. Robustness analyses indicated that the results were not different in the case of different choices in the (pre-)processing of the data. A follow-up analysis for single labs indicated that there was no evidence of rule-learning in 30 of the 31 contributed samples. The current finding raises fundamental issues about rule-learning that are presented in the Discussion section.

Peer interactions take on increasing importance for youth in middle childhood and adolescence. Autistic youth face particular challenges interacting with non-autistic peers; thus, it is critical to understand factors that predict interaction enjoyment for autistic and non-autistic youth. One candidate predictor is interpersonal motion synchrony. Experimentally induced motion synchrony leads to interpersonal liking and closeness, but these outcomes from experimental synchrony may not generalize to synchrony that naturally occurs in interpersonal interactions. Computer vision approaches allow for non-invasive quantification of synchrony in developmental populations, and thus provide an opportunity to investigate the role of naturalistic motion synchrony in peer interactions between autistic and non-autistic youth. Autistic and non-autistic youth were paired into three dyad types (autistic with autistic, autistic with non-autistic, and non-autistic with non-autistic) and completed a brief video-recorded "getting-to-know-you" interaction. Head position was extracted frame-by-frame from video recordings using OpenPose. Cross-wavelet coherence was computed to quantify head motion synchrony. We found significant head motion synchrony in interacting (compared to time-scrambled) dyads, but levels of synchrony did not differ by dyad type. Across dyad types, we found evidence that head motion synchrony negatively predicts youth-reported enjoyment and positively predicts youth-reported discomfort in the interaction. Unlike prior findings of relations between synchrony and positive outcomes, here, synchrony predicted negative conversational outcomes. Thus, these findings add nuance to our understanding of the role of synchrony in naturalistic interactions. They also demonstrate the application of non-invasively quantifying synchrony in minimally structured peer interactions including autistic youth using computer vision.

Poverty is a chronic social issue with profound implications for human development. Although scarcity theory provides a new framework for how poverty depletes mental resources, the specific cognitive pathways through which this process of depletion occurs and subsequently impairs cognition remain unclear. This study explored the integrative effect of attention and self-control resources on executive function through eye tracking among children in poverty. A total of 181 Chinese children (mean age 10.73 years; 48.62% boys) participated, 94 of whom lived in poor families. Children who experienced poverty and those who were not in poverty were first randomly assigned to one of three priming conditions (attention depletion, self-control depletion, or non-depletion), followed by executive function tasks. The results revealed that children in poverty showed poorer executive function in the condition of self-control depletion (the active purchasing task) than in the attention depletion (the passive viewing task) or non-depletion conditions. For children experiencing poverty, their attention to price did not differ between the self-control and attention depletion; however, in self-control depletion, they paid more attention to prices than children who were not in poverty did. In addition, more price viewing predicted a decrease in executive function in the poverty group only. Thus, attention scarcity is unique to impoverished children, and self-control results in a major depletion of executive function in the integrative mental process. This study extends the findings of previous research on economic scarcity in younger Asian populations and clarifies the mental process that integrates attention and self-control resources between poverty and executive function.

Infant-caregiver joint exploration is a dynamic process in which dyads coordinate their behaviors. Facing novelty is a critical moment in joint exploration, sparking learning by allowing infants to expand their knowledge and enabling caregivers to support it. However, little research has examined the impacts of novelty on infants' and caregivers' joint exploration. To address this gap, we investigated changes in their real-time contingent dynamics during exploration of novel versus familiar toys. Thirty-nine caregivers and their infants (Mage = 16 months) participated in a 10-min play session at home, consisting of two 5-min phases: a Familiarity Phase and a Novelty Phase, where a novel toy was introduced. A perceptually matched familiar toy was selected for systematic comparison in the Familiarity Phase. Infant exploration and caregiver exploration-promoting strategies (Verbal Promoting, Nonverbal Promoting, Monitoring) were coded at 1-s intervals. Infants were more likely to explore the novel toy following caregivers' exploration-promoting behaviors, particularly when multiple strategies were provided within a short time window. Caregivers maintained similar levels of contingent responsiveness but adopted more observational strategies in response to infants' novel toy exploration, potentially fostering infant-led, autonomous learning. Together, these results underscore the role of novelty in shaping how infant-caregiver dyads coordinate their contingent interactions, and suggest that such moment-to-moment adjustment may foster early learning.

Integrating auditory and visual cues is a hallmark of human speech perception, yet adults from East Asian backgrounds show less reliance on visual speech than their Western counterparts. The origins of this cultural difference, however, remain unknown. To investigate whether this divergence is established early in infancy, we examined audiovisual integration in 6- to 12-month-old White Canadian (n = 111) and Chinese (n = 115) infants using a novel paradigm measuring their perception of the McGurk effect. Across four experiments, we found a clear developmental divergence: Canadian infants showed a stable McGurk effect from 6 months onward, whereas Chinese infants showed a more protracted developmental trajectory, a cultural pattern that was further highlighted when their integration was challenged by other-race faces. These findings provide the first direct evidence that cultural differences in multisensory speech perception are established within the first year of life, suggesting that the brain's strategy for binding sight and sound is shaped by early experience, with broad implications for theories of language acquisition and developmental science.

How do children and adolescents reason about the consequences of institutional reward systems? We examined developmental differences in reasoning about inclusive versus selective awards in a youth sports context. Participants in two age groups (43 in the 7- to 9-year-old age group and 44 in the 15- to 18-year-old age group; 46% female, 49% male, 5% other or preferred not to say; majority Asian/White; USA, 2024-2025) read scenarios in which trophies were awarded either to all participants or only to top performers in a running race and predicted motivational, emotional, and behavioral outcomes. Across age groups, participants expected selective awards to increase effort and pride, suggesting that by 7 years of age children recognize links between incentive structures and task engagement. By adolescence, systematic reasoning expanded to include the possibility that selective incentives could motivate behavior that conflicts with social norms or personal safety, including cheating and risk-taking. In addition, adolescents', but not children's, preferences for reward systems were systematically related to their own perceived running ability, suggesting that evaluations of incentive systems increasingly align with self-interest across development. Together, these findings reveal both continuity and change in how young people reason about incentive systems: children as young as 7 linked reward systems to effort and pride, whereas adolescents additionally made inferences about self-interest and norm-conflicting behavior.