What is natural behavior and how does it differ from laboratory-based behavior? The "natural" in natural behavior implies the everyday, complex, ever-changing, yet predictable environment in which children grow up. "Behavior" is motor action and is foundational to psychology, as it includes all things to function in everyday environments. Is behavior demonstrated in the laboratory un-natural? Suppose behavior emerges spontaneously, in a context that is most common to the animal but an observer is there to document it using particular research tools. Is that behavior natural or natural-ish? Methods can powerfully affect conclusions about infant experiences and learning. In the lab, tasks are typically narrowly constrained where infants and children have little opportunity to display the variety of behaviors in their repertoire. Data from naturalistic observations may paint a very different picture of learning and development from those based on structured tasks, exposing striking variability in the environment and behavior and new relations between the organism and its environment. Using motor development as a model system, in this chapter we compare frameworks, methods, and findings originating in the lab and in the field, applied and adapted in different settings. Specifically, we recount our journey of pursuing the study of cultural influences on motor development in Tajikistan, and the challenges, surprises, and lessons learned.

Our objective is to scaffold the natural behaviors that support scientific thinking and STEM learning in children through museum exhibit design and development. Here, we describe a collaborative research-to-practice initiative called "Designing Museum Exhibits to Support the Development Scientific Thinking in Informal Learning Environments: A University-Museum-Community Partnership," in which we document natural behavior in the context of children's informal learning environments and detail our plans to translate our findings into exhibit development. This initiative is part of a long-standing university (UT Austin, Center for Applied Cognitive Science), museum (Thinkery-Austin Children's Museum), and community (Austin's Early Learner Community) partnership called Thinkery Connect. Our first aim here is to review best practices in STEM exhibit design that fosters scientific thinking. We will then describe the design of a study on exhibit signage to promote scientific thinking development. We will also discuss our plans to develop and evaluate exhibit signage in context. Our long-term objective is to deepen engagement in activities that build scientific thinking for visitors at children's museums like Thinkery, at home, and in the community.

Daylong egocentric (i.e., participant-centered) recordings promise an unprecedented view into the experiences that drive early language learning, impacting both assumptions and theories about how learning happens. Thanks to recent advances in technology, collecting long-form audio, photo, and video recordings with child-worn devices is cheaper and more convenient than ever. These recording methods can be similarly deployed across small- and large-scale language communities around the world, opening up enormous possibilities for comparative research on early language development. However, building new high-quality naturalistic corpora is a massive investment of time and money. In this chapter, we provide a practical look into considerations relevant for developing and managing daylong egocentric recording projects: Is it possible to re-use existing data? How much time will manual annotation take? Can automated tools sufficiently tackle the questions at hand? We conclude by outlining two exciting directions for future naturalistic child language research.

Nature is dynamic and interdependent. Yet we typically study and understand it as a hierarchy of independent static things (objects, factors, capacities, traits, attributes) with well-defined boundaries. Hence, since Plato, the dominant research practice has been to 'carve Nature at its joints' (Phaedrus 265e), rooted in the view that the world comes to us pre-divided - into static forms or essences - and that the goal of science is to simply discover (identify and classify) them. This things-based approach dominates developmental science, and especially the study of neurodevelopmental conditions. The goal of this paper is to amplify the marginalised process-based approach: that Nature has no joints. It is a hierarchy of interacting processes from which emerging functions (with fuzzy boundaries) softly assemble, become actively maintained, and dissipate over various timescales. We further argue (with a specific focus on children with Down syndrome) that the prevailing focus on identifying, isolating, and analysing things rather than understanding dynamic interdependent processes is obstructing progress in developmental science and particularly our understanding of neurodiversity. We explain how re-examining the very foundation of traditional Western thought is necessary to progress our research on neurodiversity, and we provide specific recommendations on how to steer developmental science towards the process-based approach.

Several decades of research have revealed consistent signature limits on infants' ability to represent objects. However, these signature representational limits were established with methods that often removed objects from their most common context. In infants' everyday lives, objects are very often social artifacts: they are the targets of agents' goal-directed actions, communications, and beliefs, and may have social content or relevance themselves. In this chapter, we explore the relationship between infants' object representational capacity limits and their processing of the social world. We review evidence that the social content and context of objects can shift infants' object representational limits. We discuss how taking the social world into account can yield more robust and ecologically valid estimates of infants' early representational capacities.

Identifying the origins of moral sensitivities, and their elaboration, within infancy and early childhood is a challenging task, given inherent limitations in infants' behavior. Here, I argue for a multi-pronged, multi-method approach that involves cleaving the moral response at its joints. Specifically, I chart the emergence of infants' moral expectations, evaluations, generalization and enforcement, demonstrating that while many moral sensitivities are present in the second year of life, these sensitivities are closely aligned with, and likely driven by, infants' everyday experience. Moreover, qualitative differences exist between the moral responses that are present in infancy and those of later childhood, particularly in terms of enforcement (i.e., a lack of punishment in infancy). These findings set the stage for addressing outstanding critical questions regarding moral development, that include identifying discrete causal inputs to early moral cognition, identifying whether moral cognition is distinct from social cognition early in life, and explaining gaps that exist between moral cognition and moral behavior in development.

Disabled people are the largest minority group in the world. Like members of many minority groups, they face considerable prejudice and discrimination-known as ableism. Ableism reflects entrenched beliefs about what human bodies and minds should be like and a devaluation of individuals who deviate from that ideal. There is surprisingly little psychological science about ableism, and even less about its development. This chapter considers how social-cognitive biases evident in early childhood could contribute to its development. The chapter is structured around four biases: Prescriptive reasoning, promiscuous teleology, psychological essentialism, and the positivity bias. For each bias, we review foundational research about how it manifests in early childhood, speculate about its connection to ableism, and outline avenues for additional research. Understanding how social-cognitive biases contribute to the development of ableism is an important first step in efforts to equip children (and adults) with the tools to reject it.

Infant behaviors-walking, vocalizing, playing, interacting with others, and so on-offer an unparalleled window into learning and development. The study of infants requires strategic choices about what to observe, where, when, and how. We argue that loosening study constraints-by allowing infants and caregivers to do whatever they choose, wherever they choose, and with whatever materials they choose-promises to reveal a deep understanding of the everyday data on which learning builds. We show that observations of infants' natural behavior yield unique insights into the nature of visual exploration, object play, posture and locomotion, proximity to caregiver, and communication. Furthermore, we show that by situating the study of behavior in ecologically-valid settings, researchers can gain purchase on the contextual regularities that frame learning. We close by underscoring the value of studies at every point on the research continuum-from cleverly controlled lab-based tasks to fully natural observations in everyday environments. Acceleration in the science of behavior rests on leveraging expertise across disciplines, theoretical positions, and methodological approaches.

Decades of research have informed about ways in which infants and young children learn through action in connection with their sensory system. However, this research has not strongly addressed the issues of cultural diversity or taken into account everyday cultural experiences of young learners across different communities. Diversifying the scholarship of early learning calls for paradigm shifts, extending beyond the analysis at the individual level to make close connections with real-world experience while placing culture front and center. On the other hand, cultural research that specifies diversity in caregiver guidance and scaffolding, while providing insights into young learners' cultural experiences, has been conducted separately from the research of action-based cross-modal learning. Taking everyday activities as contexts for learning, in this chapter, we summarize seminal work on cross-modal learning by infants and young children that connects action and perception, review empirical evidence of cultural variations in caregiver guidance for early action-based learning, and make recommendations of research approaches for advancing the scientific understanding about cultural ways of learning across diverse communities.

This chapter provides the most comprehensive review of risk and resilience models for child development thus far, synthesizing these interdisciplinary frameworks for ease of use in research and practice. This review specifically focuses on process models with broader conceptualizations of risk and resilience that have effects across multiple developmental domains. Risk and resilience models alike agree that alleviating risk factors is beneficial for children's development, including risks ranging from proximal issues with households (e.g., instability) and caregivers (e.g., insecure attachment, abuse) to relatively distal influences like structural racism and socioeconomic status. Resilience models further add that children who experience risks are not inherently doomed to poorer outcomes, but can draw upon positive factors in development to combat negative effects from risk, which cannot always be avoided. Major positive factors include loving relationships, educational resources, and cultural assets. Risk and resilience are highly multidisciplinary fields that have contributed much to our understanding of human development, with ample room for continued growth. Understanding of risk and resilience processes, especially during sensitive developmental periods like early childhood, provides valuable insight for prevention and intervention research and practices. Risk and resilience models share an interest in deciphering the developmental processes that hinder and help children across domains so that kids can live their best lives, resulting in a better off society for all.

Our goal in this chapter is to describe young children's experiences with language by examining three domains-people, places, and things-that define and influence their language input. We highlight how features of each of these three domains could provide useful learning opportunities, as well as how differences in infants' and toddlers' experiences may affect their long-term language skills. However, we ultimately suggest that a full understanding of early environments must move beyond a focus on individual experiences and include the broader systems that shape young children's lives, including both tangible aspects of the environment, such as physical resources or locations, and more hidden factors, such as cultural considerations, community health, or economic constraints.

According to the Relational Developmental Systems perspective, the development of individual differences in spatial thinking (e.g., mental rotation, spatial reorientation, and spatial language) are attributed to various psychological (e.g., children's cognitive strategies), biological (e.g., structure and function of hippocampus), and cultural systems (e.g., caregiver spatial language input). Yet, measuring the development of individual differences in spatial thinking in young children, as well as the psychological, biological, and cultural systems that influence the development of these abilities, presents unique challenges. The current paper outlines ways to harness available technology including eye-tracking, eye-blink conditioning, MRI, Zoom, and LENA technology, to study the development of individual differences in young children's spatial thinking. The technologies discussed offer ways to examine children's spatial thinking development from different levels of analyses (i.e., psychological, biological, cultural), thereby allowing us to advance the study of developmental theory. We conclude with a discussion of the use of artificial intelligence.

Twin bonds, likely the most enduring of human relationships, provide both solace and rivalry for twins. Using an evolutionary psychology perspective, this chapter scrutinizes twins' bonds from prenatal stages to childhood to better understand their unique relationships. Twins' interactions, which begin in the womb, establish patterns of cooperation and competition. The initial years pose parenting challenges that shape the twins' experiences of dependency and rivalry. As twins grow, five dimensions-closeness, dependence, conflict, rivalry, and dominance-emerge, evolving distinctly between monozygotic twins (MZ: sharing close to 100% of their genes) and dizygotic twins (DZ: sharing on average 50% of their genetic variance). The chapter notes the closer relationship MZ twins share compared to DZ twins. While the closeness and dependence among DZ twins decline throughout childhood, these elements remain stable in MZ twins. The effect of zygosity on conflict and rivalry is less clear. For both MZ and DZ twins, conflict stays steady, while rivalry intensifies with school entry, probably driven by external comparisons, but lessens as twins develop into late childhood. Unlike singletons, where birth order dictates dominance dynamics, in twins, this dynamic is more variable and becomes more defined by around 6.5 years of age. Several factors are presented as impacting the nature of the twins' relationships: the evolvement of 'twin language', the parenting style and the differential parenting they receive. This exploration into the development of twins' relationships underlines the importance of tailored caregiving and invites further research into the genetic and environmental factors that shape close bonds.

Conceptual understanding involves understanding connections among ideas within a domain. In this chapter, we consider how teachers support students in learning about connections among ideas in mathematics. We review research focusing on teachers' connection making in mathematics classrooms, and we consider several dimensions of variability in that connection making. Across three corpora of lessons that varied in students' grade levels (first grade to college), cultural settings (United States and China), and mathematics content, we found that all teachers produced linking episodes, but the frequency with which they did so varied substantially, raising new questions about the sources and consequences of that variability. Teachers of first-grade students in China routinely engaged their students in co-constructing links; teachers of middle schoolers and college students in the United States typically explained links to students. Linking episodes targeted many different types of connections, including connections between representations, connections between principles and exemplars, connections between procedures and concepts, and connections between concepts and real-world instantiations. Across all three corpora, teachers expressed linked ideas multimodally in a majority of linking episodes. Based on the findings, we present several hypotheses about how teacher behaviors may support students' understanding of connections among ideas, and we suggest directions for future work.

The last 40 years have been marked by a growing appreciation of organized afterschool activities as a developmental context, with evidence that these activities are linked to academic, social, and behavioral outcomes at least in the short term. In this chapter, we focus on research that builds on these earlier advances to extend afterschool research in two areas that are critical to the future of this field. First, we feature research that examines organized activities longitudinally from kindergarten through the end of high school, enabling us to study organized activities in relation to academic, social-emotional, behavioral, and health outcomes in both the short-run and long-run, including into adulthood. We then turn to a second advance: research focused on organized activities that serve minoritized children and adolescents. These studies identify the barriers minoritized youth often face and how activities can be designed to support their positive development, including efforts to provide culturally responsive programming. Promising directions for future research are presented in a third section.

Children's own language production has a role in structuring the language of their conversation partners and influences their own development. Children's active participation in their own language development is most apparent in the rich body of work investigating language in natural environments. The advent of automated measures of vocalizations and movement have made such in situ research increasingly feasible. In this chapter, we review recent research on children's language development in context with a particular focus on research employing automated methods in preschool classrooms for children between ages 2 and 5 years. These automated methods indicate that the speech directed to preschool children from specific peers predicts the child's speech to those peers on a subsequent observation occasion. Similar patterns are seen in the influence of peer and teacher phonemic diversity on the phonemic diversity of children's speech to those partners. In both cases, children's own speech to partners was the best predictor of their language abilities, suggesting their active role in their own development. Finally, new research suggests the potential of machine learning to predict children's speech in group contexts, and to transcribe classroom speech to better understand the content of children's conversations and how they change with development.

Using a structured literature search and meta-regression procedures, this chapter reports a study that sought to determine whether the associations between coordinated attention and language are moderated by operationalizations of coordinated attention, study design, and other participant characteristics. Studies were located using database searches. This resulted in 46 reports or datasets, 464 effect sizes representing 1,482 participants. Meta-regression was used to answer research questions regarding potential moderators of the effects sizes of interest, which were Pearson's r values quantifying the association between coordinated attention and language assessments. In the final models, we observed that overall effect sizes were significantly above zero, suggesting robust effects across variables of interest. Age when coordinated attention was measured was a significant moderator, suggesting that the relations between coordinated attention and language was stronger when coordinated attention was measured at earlier ages. Interestingly, the longitudinal gap duration between coordinated attention measurement and language assessment was a significant moderator suggesting that the relation between coordinated attention and language was stronger when the longitudinal gap duration was longer. We conclude the meta-analysis by suggesting the phenomena of interest-dynamic coordinated visual attention between infant and caregiver-is robust across operationalizations and has predictive value for concurrent and future language abilities.

One of the most important challenges for a developing infant is learning how best to allocate their attention and forage for information in the midst of a great deal of novel stimulation. We propose that infants of altricial species solve this challenge by learning selectively from events that are contingent on their immature behavior, such as babbling. Such a contingency filter would focus attention and learning on the behavior of social partners, because social behavior reliably fits infants' sensitivity to contingency. In this way a contingent response by a caregiver to an immature behavior becomes a source of learnable information - feedback - to the infant. Social interactions with responsive caregivers afford infants opportunities to explore the impacts of their immature behavior on their environment, which facilitates the development of socially guided learning. Furthermore, contingent interactions are opportunities to make and test predictions about the efficacy of their social behaviors and those of others. In this chapter, we will use prelinguistic vocal learning to exemplify how infants use their developing vocal abilities to elicit learnable information about language from their social partners. Specifically, we review how caregivers' contingent responses to babbling create information that facilitates infant vocal learning and drives the development of communication. Infants play an active role in this process, as their developing predictions about the consequences of their actions serve to further refine their allocation of attention and drive increases in the maturity of their vocal behavior.

Infants' interactions with social partners are richly multimodal. Dyads respond to and coordinate their visual attention, gestures, vocalizations, speech, manual actions, and manipulations of objects. Although infants are typically described as active learners, previous experimental research has often focused on how infants learn from stimuli that is well-crafted by researchers. Recent research studying naturalistic, free-flowing interactions has explored the meaningful patterns in dyadic behavior that relate to language learning. Infants' manual engagement and exploration of objects supports their visual attention, creates salient and diverse views of objects, and elicits labeling utterances from parents. In this chapter, we discuss how the cascade of behaviors created by infant multimodal attention plays a fundamental role in shaping their learning environment, supporting real-time word learning and predicting later vocabulary size. We draw from recent at-home and cross-cultural research to test the validity of our mechanistic pathway and discuss why hands matter so much for learning. Our goal is to convey the critical need for developmental scientists to study natural behavior and move beyond our "tried-and-true" paradigms, like screen-based tasks. By studying natural behavior, the role of infants' hands in early language learning was revealed-though it was a behavior that was often uncoded, undiscussed, or not even allowed in decades of previous research. When we study infants in their natural environment, they can show us how they learn about and explore their world. Word learning is hands-on.

In a recent monograph, my students, colleagues, and I reported on a comprehensive set of tests of the theory of Perceptual Access Reasoning (PAR), a new theory of the development of representational theory of mind (ToM). The central tenet of the theory is that young children acquire a hitherto undetected non-representational ToM (i.e., PAR), the use of which allows them to pass standard false belief tasks without understanding false beliefs. Thus, PAR theory capitalizes on an unrecognized flaw in all standard false belief tasks. In what follows, I present an overview of PAR theory, the tests that we have conducted of the theory, and logical arguments for how PAR explains the classic findings in the ToM literature. Next, I evaluate two recent alternate accounts that have been offered by critics, and I discuss some of the issues raised by three invited commentaries on the monograph. Finally, I consider the question, "What is the development of representational ToM the development of?" Insights from philosophy of mind point to the primacy of children's understanding of mental states in themselves, leading to a new concept of self-permanence that can provide the basis for a unified theory of the development of children's understanding of the mental and physical worlds. As a final thought, I consider how PAR was able to hide in plain sight for so long.

We outline two accounts by which executive function (EF) supports children's moral reasoning: an emergence and an expression account. The emergence account postulates that EF supports the development of moral concepts because it relates to how children navigate their early social environments and how well they can internalize moral messages. The expression account postulates that EF supports children's in-the-moment moral reasoning for complex moral situations. We present data from two studies with preschool children to assess each account. In support of the emergence account, EF longitudinally and positively predicted moral reasoning, but only for children who have experienced moderate forms of peer conflict. In support of the expression account, EF was only correlated with judgments that required the coordination of multiple pieces of information (i.e., retaliation and criterion judgments). We conclude that EF is an important cognitive mechanism of moral development and discuss various implications of these findings for both moral development and EF theory.