Infants who are rarely spoken to nevertheless understand many words.

Theories of language development-informed largely by studies of Western, middleclass infants-have highlighted the language that caregivers direct to children as a key driver of language learning. However, some have argued that language development unfolds similarly across environmental contexts, including those in which childdirected language is scarce. This raises the possibility that children are able to learn from other sources of language in their environments, particularly the language directed to others in their environment. We explore this hypothesis with infants in an indigenous Tseltal-speaking community in Southern Mexico who are rarely spoken to, yet have the opportunity to overhear a great deal of other-directed language by virtue of being carried on their mothers' backs. Adapting a previously established gaze-tracking method for detecting early word knowledge to our field setting, we find that Tseltal infants exhibit implicit knowledge of common nouns (Exp. 1), analogous to their US peers who are frequently spoken to. Moreover, they exhibit comprehension of Tseltal honorific terms that are exclusively used to greet adults in the community (Exp. 2), representing language that could only have been learned through overhearing. In so doing, Tseltal infants demonstrate an ability to discriminate words with similar meanings and perceptually similar referents at an earlier age than has been shown among Western children. Together, these results suggest that for some infants, learning from overhearing may be an important path toward developing language.

Disagreement reduces overconfidence and prompts exploration in young children.

Can the experience of disagreement lead young children to reason in more sophisticated ways? Across two preregistered studies, four- to six-year-old US children (N = 136, 50% female, mixed ethnicities, data collected 2020-2022) experienced either a disagreement or an agreement with a confederate about a causal mechanism after being presented with ambiguous evidence. We measured (1) children's confidence in their belief before and after the (dis)agreement, and (2) how long children searched for information about the correct answer. Disagreement, especially with an expert (Experiment 2), reduced overconfidence and prompted children to search longer for information, compared to agreement. Together, our findings suggest possibilities for interventions aimed at fostering humility and learning across the lifespan.

Structural explanations lead young children and adults to rectify resource inequalities.

Decisions about how to divide resources have profound social and practical consequences. Do explanations regarding the source of existing inequalities influence how children and adults allocate new resources? When 3- to 6-year-old children (N = 201) learned that inequalities were caused by structural forces (stable external constraints affecting access to resources) as opposed to internal forces (effort), they rectified inequalities, overriding previously documented tendencies to perpetuate inequality or divide resources equally. Adults (N = 201) were more likely than children to rectify inequality spontaneously; this was further strengthened by a structural explanation but reversed by an effort-based explanation. Allocation behaviors were mirrored in judgments of which allocation choices by others were appropriate. These findings reveal how explanations powerfully guide social reasoning and action from childhood through adulthood.

Developmental psychologists should adopt citizen science to improve generalization and reproducibility.

Widespread failures of replication and generalization are, ironically, a scientific triumph, in that they confirm the fundamental metascientific theory that underlies our field. Generalizable and replicable findings require testing large numbers of subjects from a wide range of demographics with a large, randomly-sampled stimulus set, and using a variety of experimental parameters. Because few studies accomplish any of this, meta-scientists predict that findings will frequently fail to replicate or generalize. We argue that to be more robust and replicable, developmental psychology needs to find a mechanism for collecting data at greater scale and from more diverse populations. Luckily, this mechanism already exists: Citizen science, in which large numbers of uncompensated volunteers provide data. While best-known for its contributions to astronomy and ecology, citizen science has also produced major findings in neuroscience and psychology, and increasingly in developmental psychology. We provide examples, address practical challenges, discuss limitations, and compare to other methods of obtaining large datasets. Ultimately, we argue that the range of studies where it makes sense *not* to use citizen science is steadily dwindling.

Children's use of pragmatic inference to learn about the social world.

Young children often endorse stereotypes-such as "girls are bad at math." We explore one mechanism through which these beliefs may be transmitted: via pragmatic inference. Specifically, we ask whether preschoolers and adults can learn about an unmentioned social group from what is said about another group, and if this inferential process is sensitive to the context of the utterance. Sixty-three- to five-year-old children and fifty-five adults were introduced to two novel social groups-Stripeys and Dotties-and witnessed a speaker praising abilities of one group (e.g., "the Stripeys are good at building chairs"). To examine the effect of context, we compared situations where the speaker was knowledgeable about the abilities of both groups, and had been queried about the performance of both groups (broad context), versus situations where the speaker was only knowledgeable about one group and was only asked about that group (narrow context). Both preschoolers and adults were sensitive to context: they were more likely to infer that the group not mentioned by the speaker was relatively unskilled, and were more confident about it, in the broad context condition. Our work integrates research in language development and social cognitive development and demonstrates that even young children can "read between the lines," utilizing subtle contextual cues to pick up negative evaluative messages about social groups even from statements that ostensibly do not mention them at all. HIGHLIGHTS: After hearing a speaker praise one group's skill, preschoolers and adults infer that an unmentioned group is relatively less skilled across a range of measures. These inferences are context-sensitive and are stronger when the speaker is knowledgeable of and asked about both groups' skill level. These results shed light on how children may indirectly learn negative stereotypes, especially ones that adults are unlikely to state explicitly. This work extends previous research on children's developing pragmatic ability, as well as their ability to learn about the social world from language.

Children's developing ability to adjust their beliefs reasonably in light of disagreement.

Two preregistered experiments (N = 218) investigated children's developing ability to respond reasonably to disagreement. U.S. children aged 4-9, and adults (50% female, mostly white) formed an initial belief, and were confronted with the belief of a disagreeing other, whose evidence was weaker, stronger than, or equal to participants' evidence. With age, participants were increasingly likely to maintain their initial belief when their own evidence was stronger, adopt the other's belief when their evidence was weaker, and suspend judgment when both had equally strong evidence. Interestingly, 4- to 6-year-olds only suspended judgment reliably when this was assessed via the search for additional information (Experiment 2). Together, our experiments suggest that the ability to respond reasonably to disagreement develops over the preschool years.

What causes the word gap? Financial concerns may systematically suppress child-directed speech.

Parents with fewer educational and economic resources (low socioeconomic-status, SES) tend to speak less to their children, with consequences for children's later life outcomes. Despite this well-established and highly popularized link, less research addresses why the SES "word gap" exists. Moreover, while research has assessed individual-level contributors to the word gap-like differences in parenting knowledge-we know little about how structural constraints that vary according to SES might affect caregivers' speech. In two pre-registered studies, we test whether experiencing financial scarcity can suppress caregivers' speech to their children. Study 1 suggests that higher-SES caregivers who are prompted to reflect on scarcity-particularly those who reflect on financial scarcity-speak less to their 3-year-olds in a subsequent play session, relative to a control group. Study 2 suggests that mid- to higher-SES caregivers engage in fewer back-and-forth exchanges with their children at the end of the month-when they are more likely to be experiencing financial hardship-than the rest of the month. These studies provide preliminary evidence that-above and beyond caregivers' individual characteristics-structural constraints may affect how much parents speak to their children.

Preschoolers learn new moral and conventional norms from direct experiences.

By observing others, children can learn about different types of norms, including moral norms rooted in concerns for welfare and rights, and social conventions based on directives from authority figures or social consensus. Two experiments examined how preschoolers and adults constructed and applied knowledge about novel moral and conventional norms from their direct social experiences. Participants watched a video of a novel prohibited action that caused pain to a victim (moral conditions) or a sound from a box (conventional conditions). Next, they saw a transgressor puppet, who had either watched the video alongside participants or not, engage in the prohibited action. Preschoolers and adults rapidly constructed distinct moral and conventional evaluations about the novel actions. These distinctions were evident across several response modalities that have often been studied separately, including judgments, reasoning, and actions. However, children did not reliably track the puppet's knowledge of the novel norms. These studies provide experimental support for the idea that children and adults construct distinct moral and conventional norms from social experiences, which in turn guide judgments, reasoning, and behavior.

Spatial Metaphor Facilitates Word Learning.

Why are spatial metaphors, like the use of "high" to describe a musical pitch, so common? This study tested one hundred and fifty-four 3- to 5-year-old English-learning children on their ability to learn a novel adjective in the domain of space or pitch and to extend this adjective to the untrained dimension. Children were more proficient at learning the word when it described a spatial attribute compared to pitch. However, once children learned the word, they extended it to the untrained dimension without feedback. Thus, children leveraged preexisting associations between space and pitch to spontaneously understand new metaphors. These results suggest that spatial metaphors may be common across languages in part because they scaffold children's acquisition of word meanings that are otherwise difficult to learn.

Algorithms in the historical emergence of word senses.

Human language relies on a finite lexicon to express a potentially infinite set of ideas. A key result of this tension is that words acquire novel senses over time. However, the cognitive processes that underlie the historical emergence of new word senses are poorly understood. Here, we present a computational framework that formalizes competing views of how new senses of a word might emerge by attaching to existing senses of the word. We test the ability of the models to predict the temporal order in which the senses of individual words have emerged, using an historical lexicon of English spanning the past millennium. Our findings suggest that word senses emerge in predictable ways, following an historical path that reflects cognitive efficiency, predominantly through a process of nearest-neighbor chaining. Our work contributes a formal account of the generative processes that underlie lexical evolution.

Indian = Hindu? The Development of Nationalist Attitudes Among Hindu and Muslim Children in India.

Many political movements across the world today define citizenship in exclusionary ethnic or religious terms. This study extends research on ethnic-national associations in adults to children, adding to the relatively sparse literature on the development of national associations in children and in nonwestern contexts. Explicit and implicit religious-national associations were examined in a sample of 160 nine- to sixteen-year-olds (79 Hindu; 81 Muslim) in Gujarat, India. Results suggest that while Hindu children show a strong Indian = Hindu association by age 9, Muslim children appear to be buffered from this association. Furthermore, this association uniquely predicts variance in children's attitudes about social policy and their concept of nationality, above and beyond their age, religion, and intergroup attitudes.

Reasoning About the Scope of Religious Norms: Evidence From Hindu and Muslim Children in India.

Conflicts arise when members of one religion apply their norms to members of another religion. Two studies explored how one hundred 9- to 15-year-old Hindu and Muslim children from India reason about the scope of religious norms. Both Hindus and Muslims from a diverse Hindu-Muslim school (Study 1) and Hindus from a homogeneous Hindu school (Study 2) more often judged it wrong for Hindus to violate Hindu norms, compared to Muslim norms, and said the opposite for Muslims. In contrast, children judged it wrong for both Hindus and Muslims to harm others. Thus, even in a setting marred by religious conflict, children can restrict the scope of a religion's norms to members of that religion, providing a basis for peaceful coexistence.

Evolution of word meanings through metaphorical mapping: Systematicity over the past millennium.

One way that languages are able to communicate a potentially infinite set of ideas through a finite lexicon is by compressing emerging meanings into words, such that over time, individual words come to express multiple, related senses of meaning. We propose that overarching communicative and cognitive pressures have created systematic directionality in how new metaphorical senses have developed from existing word senses over the history of English. Given a large set of pairs of semantic domains, we used computational models to test which domains have been more commonly the starting points (source domains) and which the ending points (target domains) of metaphorical mappings over the past millennium. We found that a compact set of variables, including externality, embodiment, and valence, explain directionality in the majority of about 5000 metaphorical mappings recorded over the past 1100years. These results provide the first large-scale historical evidence that metaphorical mapping is systematic, and driven by measurable communicative and cognitive principles.

Today is tomorrow's yesterday: Children's acquisition of deictic time words.

Deictic time words like "yesterday" and "tomorrow" pose a challenge to children not only because they are abstract, and label periods in time, but also because their denotations vary according to the time at which they are uttered: Monday's "tomorrow" is different than Thursday's. Although children produce these words as early as age 2 or 3, they do not use them in adult-like ways for several subsequent years. Here, we explored whether children have partial but systematic meanings for these words during the long delay before adult-like usage. We asked 3- to 8-year-olds to represent these words on a bidirectional, left-to-right timeline that extended from the past (infancy) to the future (adulthood). This method allowed us to independently probe knowledge of these words' deictic status (e.g., "yesterday" is in the past), relative ordering (e.g., "last week" was before "yesterday"), and remoteness from the present (e.g., "last week" was about 7 times longer ago than "yesterday"). We found that adult-like knowledge of deictic status and order emerge in synchrony, between ages 4 and 6, but that knowledge of remoteness emerges later, after age 7. Our findings suggest that children's early use of deictic time words is not random, but instead reflects the gradual construction of a structured lexical domain.

Do attitudes toward societal structure predict beliefs about free will and achievement? Evidence from the Indian caste system.

Intuitive theories about the malleability of intellectual ability affect our motivation and achievement in life. But how are such theories shaped by the culture in which an individual is raised? We addressed this question by exploring how Indian children's and adults' attitudes toward the Hindu caste system--and its deterministic worldview--are related to differences in their intuitive theories. Strikingly, we found that, beginning at least in middle school and continuing into adulthood, individuals who placed more importance on caste were more likely to adopt deterministic intuitive theories. We also found a developmental change in the scope of this relationship, such that in children, caste attitudes were linked only to abstract beliefs about personal freedom, but that by adulthood, caste attitudes were also linked to beliefs about the potential achievement of members of different castes, personal intellectual ability, and personality attributes. These results are the first to directly relate the societal structure in which a person is raised to the specific intuitive theories they adopt.

Learning Mathematics in a Visuospatial Format: A Randomized, Controlled Trial of Mental Abacus Instruction.

Mental abacus (MA) is a technique of performing fast, accurate arithmetic using a mental image of an abacus; experts exhibit astonishing calculation abilities. Over 3 years, 204 elementary school students (age range at outset: 5-7 years old) participated in a randomized, controlled trial to test whether MA expertise (a) can be acquired in standard classroom settings, (b) improves students' mathematical abilities (beyond standard math curricula), and (c) is related to changes in basic cognitive capacities like working memory. MA students outperformed controls on arithmetic tasks, suggesting that MA expertise can be achieved by children in standard classrooms. MA training did not alter basic cognitive abilities; instead, differences in spatial working memory at the beginning of the study mediated MA learning.

Religion insulates ingroup evaluations: the development of intergroup attitudes in India.

Research on the development of implicit intergroup attitudes has placed heavy emphasis on race, leaving open how social categories that are prominent in other cultures might operate. We investigate two of India's primary means of social distinction, caste and religion, and explore the development of implicit and explicit attitudes towards these groups in minority-status Muslim children and majority-status Hindu children, the latter drawn from various positions in the Hindu caste system. Results from two tests of implicit attitudes find that caste attitudes parallel previous findings for race: higher-caste children as well as lower-caste children have robust high-caste preferences. However, results for religion were strikingly different: both lower-status Muslim children and higher-status Hindu children show strong implicit ingroup preferences. We suggest that religion may play a protective role in insulating children from the internalization of stigma.

The development and diversity of religious cognition and behavior: Protocol for Wave 1 data collection with children and parents by the Developing Belief Network.

The Developing Belief Network is a consortium of researchers studying human development in diverse social-cultural settings, with a focus on the interplay between general cognitive development and culturally specific processes of socialization and cultural transmission in early and middle childhood. The current manuscript describes the study protocol for the network's first wave of data collection, which aims to explore the development and diversity of religious cognition and behavior. This work is guided by three key research questions: (1) How do children represent and reason about religious and supernatural agents? (2) How do children represent and reason about religion as an aspect of social identity? (3) How are religious and supernatural beliefs transmitted within and between generations? The protocol is designed to address these questions via a set of nine tasks for children between the ages of 4 and 10 years, a comprehensive survey completed by their parents/caregivers, and a task designed to elicit conversations between children and caregivers. This study is being conducted in 39 distinct cultural-religious groups (to date), spanning 17 countries and 13 languages. In this manuscript, we provide detailed descriptions of all elements of this study protocol, give a brief overview of the ways in which this protocol has been adapted for use in diverse religious communities, and present the final, English-language study materials for 6 of the 39 cultural-religious groups who are currently being recruited for this study: Protestant Americans, Catholic Americans, American members of the Church of Jesus Christ of Latter-day Saints, Jewish Americans, Muslim Americans, and religiously unaffiliated Americans.

Sortal concepts and pragmatic inference in children's early quantification of objects.

It is typically assumed that count nouns like fork act as logical sortals, specifying whether objects are countable units of a kind (e.g., that a whole fork counts as "one fork") or not (e.g., that a piece of a fork does not count as "one fork"). In four experiments, we provide evidence from linguistic and conceptual development that nouns do not specify units of quantification, but include both whole objects and their arbitrary parts in their denotations. We argue that, to restrict quantification to whole objects, nominal concepts are enriched pragmatically, via contrast with concepts denoted by alternative descriptions: a piece of a fork is not counted as "one fork" because it is "one piece of fork." Experiment 1 replicated previous findings that children count pieces of broken objects as whole objects (e.g., two pieces of fork as "two forks"), and showed that children also accept whole object labels as descriptions of object pieces (e.g., "two forks" to describe two pieces of fork). Experiment 2 showed that although children accept such descriptions in isolation, they prefer measure phrases (e.g., "two pieces of fork") when they are explicitly presented as alternatives. Experiment 3 found that children were better at excluding pieces from their counts of whole objects when measure phrases were primed prior to counting, making them accessible as alternatives to whole object labels. Finally, Experiment 4 taught children names for novel objects, and found that they do not count parts that are given unique labels or that have non-linguistic properties that suggest they are members of distinct object kinds (e.g., unique functions or physical affordances). Together, our results suggest that for children and adults alike, nominal concepts do not provide necessary and sufficient criteria for excluding parts from object kinds. To specify units of quantification--and do the work of sortals--concepts are contrasted with one another and enriched pragmatically.

Crossing religious boundaries: Individual and contextual determinants of who can violate religious norms.

In pluralistic societies, encounters with individuals, contexts, and norms of other religions can prompt conflict. We test a novel framework for explaining how individuals apply religious norms across individuals and contexts. In Studies 1 and 2, adolescents and adults in India and the United States judged events in which religious norms were violated by protagonists of different religions in different religious contexts. Participants often judged that norm violations were wrong even when the norm religion matched only the protagonist or context religion. Study 3 presented dilemmas that pitted religious norms against non-religious concerns. Participants favored following the religious norm yet accepted the protagonist's right to violate it. In each adult sample, more religious participants more often judged that protagonists were obligated to follow the protagonist's own religious norms. These findings reveal individual and contextual determinants of judgments about religious violations with implications for peaceful coexistence in pluralistic societies.