Children selectively endorse speculative conjectures.

Young children are epistemically vigilant, attending to the reliability, expertise, and confidence of their informants and the prior probability and verifiability of their claims. But the pre-eminent requirement of any hypothesis is that it provides a potential solution to the question at hand. Given questions with no known answer, the ability to selectively adopt new, unverified, speculative proposals may be critical to learning. This study explores when people might reasonably reject known facts in favor of unverified conjectures. Across four experiments, when conjectures answer questions that available facts do not, both adults (n = 48) and children (4.0-7.9 years, n = 241, of diverse race and ethnicity) prefer the conjectures, even when the conjectures are preceded by uncertainty markers or explicitly violate prior expectations.

The Naïve Utility Calculus as a unified, quantitative framework for action understanding.

The human ability to reason about the causes behind other people' behavior is critical for navigating the social world. Recent empirical research with both children and adults suggests that this ability is structured around an assumption that other agents act to maximize some notion of subjective utility. In this paper, we present a formal theory of this Naïve Utility Calculus as a probabilistic generative model, which highlights the role of cost and reward tradeoffs in a Bayesian framework for action-understanding. Our model predicts with quantitative accuracy how people infer agents' subjective costs and rewards based on their observable actions. By distinguishing between desires, goals, and intentions, the model extends to complex action scenarios unfolding over space and time in scenes with multiple objects and multiple action episodes. We contrast our account with simpler model variants and a set of special-case heuristics across a wide range of action-understanding tasks: inferring costs and rewards, making confidence judgments about relative costs and rewards, combining inferences from multiple events, predicting future behavior, inferring knowledge or ignorance, and reasoning about social goals. Our work sheds light on the basic representations and computations that structure our everyday ability to make sense of and navigate the social world.

Understanding Social Display Rules: Using One Person's Emotional Expressions to Infer the Desires of Another.

In social contexts, people's emotional expressions may disguise their true feelings but still be revealing about the probable desires of their intended audience. This study investigates whether children can use emotional expressions in social contexts to recover the desires of the person observing, rather than displaying the emotion. Children (7.0-10.9 years, N = 211 across five experiments) saw a protagonist express one emotional expression in front of her social partner, and a different expression behind her partner's back. Although the protagonist expressed contradictory emotions (and the partner expressed none), even 7-year-olds inferred both the protagonist's and social partner's desires. These results suggest that children can recover not only the desire of the person displaying emotion but also of the person observing it.

How Adults' Actions, Outcomes, and Testimony Affect Preschoolers' Persistence.

Across four experiments, we looked at how 4- and 5-year-olds' (n = 520) task persistence was affected by observations of adult actions (high or low effort), outcomes (success or failure), and testimony (setting expectations-"This will be hard," pep talks-"You can do this," value statements-"Trying hard is important," and baseline). Across experiments, outcomes had the biggest impact: preschoolers consistently tried harder after seeing the adult succeed than fail. Additionally, adult effort affected children's persistence, but only when the adult succeeded. Finally, children's persistence was highest when the adult both succeeded and practiced what she preached: exerting effort while testifying to its value.

Social Pragmatics: Preschoolers Rely on Commonsense Psychology to Resolve Referential Underspecification.

Four experiments show that 4- and 5-year-olds (total N = 112) can identify the referent of underdetermined utterances through their Naïve Utility Calculus-an intuitive theory of people's behavior structured around an assumption that agents maximize utilities. In Experiments 1-2, a puppet asked for help without specifying to whom she was talking ("Can you help me?"). In Experiments 3-4, a puppet asked the child to pass an object without specifying what she wanted ("Can you pass me that one?"). Children's responses suggest that they considered cost trade-offs between the members in the interaction. These findings add to a body of work showing that reference resolution is informed by commonsense psychology from early in childhood.

One- to four-year-olds connect diverse positive emotional vocalizations to their probable causes.

The ability to understand why others feel the way they do is critical to human relationships. Here, we show that emotion understanding in early childhood is more sophisticated than previously believed, extending well beyond the ability to distinguish basic emotions or draw different inferences from positively and negatively valenced emotions. In a forced-choice task, 2- to 4-year-olds successfully identified probable causes of five distinct positive emotional vocalizations elicited by what adults would consider funny, delicious, exciting, sympathetic, and adorable stimuli (Experiment 1). Similar results were obtained in a preferential looking paradigm with 12- to 23-month-olds, a direct replication with 18- to 23-month-olds (Experiment 2), and a simplified design with 12- to 17-month-olds (Experiment 3; preregistered). Moreover, 12- to 17-month-olds selectively explored, given improbable causes of different positive emotional reactions (Experiments 4 and 5; preregistered). The results suggest that by the second year of life, children make sophisticated and subtle distinctions among a wide range of positive emotions and reason about the probable causes of others' emotional reactions. These abilities may play a critical role in developing theory of mind, social cognition, and early relationships.

Changing minds: Children's inferences about third party belief revision.

By the age of 5, children explicitly represent that agents can have both true and false beliefs based on epistemic access to information (e.g., Wellman, Cross, & Watson, 2001). Children also begin to understand that agents can view identical evidence and draw different inferences from it (e.g., Carpendale & Chandler, 1996). However, much less is known about when, and under what conditions, children expect other agents to change their minds. Here, inspired by formal ideal observer models of learning, we investigate children's expectations of the dynamics that underlie third parties' belief revision. We introduce an agent who has prior beliefs about the location of a population of toys and then observes evidence that, from an ideal observer perspective, either does, or does not justify revising those beliefs. We show that children's inferences on behalf of third parties are consistent with the ideal observer perspective, but not with a number of alternative possibilities, including that children expect other agents to be influenced only by their prior beliefs, only by the sampling process, or only by the observed data. Rather, children integrate all three factors in determining how and when agents will update their beliefs from evidence.

Inferring Beliefs and Desires From Emotional Reactions to Anticipated and Observed Events.

Researchers have long been interested in the relation between emotion understanding and theory of mind. This study investigates a cue to mental states that has rarely been investigated: the dynamics of valenced emotional expressions. When the valence of a character's facial expression was stable between an expected and observed outcome, children (N = 122; M = 5.0 years) recovered the character's desires but did not consistently recover her beliefs. When the valence changed, older but not younger children recovered both the characters' beliefs and desires. In contrast, adults jointly recovered agents' beliefs and desires in all conditions. These results suggest that the ability to infer mental states from the dynamics of emotional expressions develops gradually through early and middle childhood.

Learning From Others and Spontaneous Exploration: A Cross-Cultural Investigation.

How does early social experience affect children's inferences and exploration? Following prior work on children's reasoning in pedagogical contexts, this study examined U.S. children with less experience in formal schooling and Yucatec Mayan children whose early social input is predominantly observational. In Experiment 1, U.S. 2-year-olds (n = 77) showed more restricted exploration of a toy following a pedagogical demonstration than an interrupted, accidental, or no demonstration (baseline). In Experiment 2, Yucatec Mayan and U.S. 2-year-olds (n = 66) showed more restricted exploration following a pedagogical than an observational demonstration, while only Mayan children showed more restriction with age. These results suggest that although schooling is not a necessary precursor for sensitivity to pedagogy, early social experience may influence children's inferences and exploration in pedagogical contexts.

Not so innocent: toddlers' inferences about costs and culpability.

Adults' social evaluations are influenced by their perception of other people's competence and motivation: Helping when it is difficult to help is praiseworthy, and not helping when it is easy to help is reprehensible. Here, we look at whether children's social evaluations are affected by the costs that agents incur. We found that toddlers can use the time and effort associated with goal-directed actions to distinguish agents, and that children prefer agents who incur fewer costs in completing a goal. When two agents refuse to help, children retain a preference for the more competent agent but infer that the less competent agent is nicer. These results suggest that children value agents who incur fewer costs, but understand that failure to engage in a low-cost action implies a lack of motivation. We propose that a naive utility calculus underlies inferences from the costs and rewards of goal-directed action and thereby supports social cognition.

In praise of folly: flexible goals and human cognition.

Humans often pursue idiosyncratic goals that appear remote from functional ends, including information gain. We suggest that this is valuable because goals (even prima facie foolish or unachievable ones) contain structured information that scaffolds thinking and planning. By evaluating hypotheses and plans with respect to their goals, humans can discover new ideas that go beyond prior knowledge and observable evidence. These hypotheses and plans can be transmitted independently of their original motivations, adapted across generations, and serve as an engine of cultural evolution. Here, we review recent empirical and computational research underlying goal generation and planning and discuss the ways that the flexibility of our motivational system supports cognitive gains for both individuals and societies.

Infants consider both the sample and the sampling process in inductive generalization.

The ability to make inductive inferences from sparse data is a critical aspect of human learning. However, the properties observed in a sample of evidence depend not only on the true extension of those properties but also on the process by which evidence is sampled. Because neither the property extension nor the sampling process is directly observable, the learner's ability to make accurate generalizations depends on what is known or can be inferred about both variables. In particular, different inferences are licensed if samples are drawn randomly from the whole population (weak sampling) than if they are drawn only from the property's extension (strong sampling). Given a few positive examples of a concept, only strong sampling supports flexible inferences about how far to generalize as a function of the size and composition of the sample. Here we present a Bayesian model of the joint dependence between observed evidence, the sampling process, and the property extension and test the model behaviorally with human infants (mean age: 15 months). Across five experiments, we show that in the absence of behavioral cues to the sampling process, infants make inferences consistent with the use of strong sampling; given explicit cues to weak or strong sampling, they constrain their inferences accordingly. Finally, consistent with quantitative predictions of the model, we provide suggestive evidence that infants' inferences are graded with respect to the strength of the evidence they observe.

Not Playing by the Rules: Exploratory Play, Rational Action, and Efficient Search.

Recent studies suggest children's exploratory play is consistent with formal accounts of rational learning. Here we focus on the tension between this view and a nearly ubiquitous feature of human play: In play, people subvert normal utility functions, incurring seemingly unnecessary costs to achieve arbitrary rewards. We show that four-and-five-year-old children not only infer playful behavior from observed violations of rational action (Experiment 1), but themselves take on unnecessary costs during both retrieval (Experiment 2) and search (Experiments 3A-B) tasks, despite acting efficiently in non-playful, instrumental contexts. We discuss the value of such apparently utility-violating behavior and why it might serve learning in the long run.

Foundations of intuitive power analyses in children and adults.

Decades of research indicate that some of the epistemic practices that support scientific enquiry emerge as part of intuitive reasoning in early childhood. Here, we ask whether adults and young children can use intuitive statistical reasoning and metacognitive strategies to estimate how much information they might need to solve different discrimination problems, suggesting that they have some of the foundations for 'intuitive power analyses'. Across five experiments, both adults (N = 290) and children (N = 48, 6-8 years) were able to precisely represent the relative difficulty of discriminating populations and recognized that larger samples were required for populations with greater overlap. Participants were sensitive to the cost of sampling, as well as the perceptual nature of the stimuli. These findings indicate that both young children and adults metacognitively represent their own ability to make discriminations even in the absence of data, and can use this to guide efficient and effective exploration.

Children's exploratory play tracks the discriminability of hypotheses.

Effective curiosity-driven learning requires recognizing that the value of evidence for testing hypotheses depends on what other hypotheses are under consideration. Do we intuitively represent the discriminability of hypotheses? Here we show children alternative hypotheses for the contents of a box and then shake the box (or allow children to shake it themselves) so they can hear the sound of the contents. We find that children are able to compare the evidence they hear with imagined evidence they do not hear but might have heard under alternative hypotheses. Children (N = 160; mean: 5 years and 4 months) prefer easier discriminations (Experiments 1-3) and explore longer given harder ones (Experiments 4-7). Across 16 contrasts, children's exploration time quantitatively tracks the discriminability of heard evidence from an unheard alternative. The results are consistent with the idea that children have an "intuitive psychophysics": children represent their own perceptual abilities and explore longer when hypotheses are harder to distinguish.

Leveraging cognitive science to foster children's persistence.

Persistence is crucial for overcoming academic and interpersonal challenges. However, there has been little progress in developing effective interventions to improve persistence in childhood. Here we outline how recent insights from cognitive science can be leveraged to promote young children's persistence and highlight future directions to bridge research with practice.

Word, thought, and deed: the role of object categories in children's inductive inferences and exploratory play.

Previous research (e.g., S. A. Gelman & E. M. Markman, 1986; A. Gopnik & D. M. Sobel, 2000) suggests that children can use category labels to make inductive inferences about nonobvious causal properties of objects. However, such inductive generalizations can fail to predict objects' causal properties when (a) the property being projected varies within the category, (b) the category is arbitrary (e.g., things smaller than a bread box), or (c) the property being projected is due to an exogenous intervention rather than intrinsic to the object kind. In 4 studies, the authors showed that preschoolers (M = 48 months; range = 42-57 months) were sensitive to these constraints on induction and selectively engaged in exploration when evidence about objects' causal properties conflicted with inductive generalizations from the objects' kind to their causal powers. This suggests that the exploratory actions children generate in free play could support causal learning.

Rational Inference of Beliefs and Desires From Emotional Expressions.

We investigated people's ability to infer others' mental states from their emotional reactions, manipulating whether agents wanted, expected, and caused an outcome. Participants recovered agents' desires throughout. When the agent observed, but did not cause the outcome, participants' ability to recover the agent's beliefs depended on the evidence they got (i.e., her reaction only to the actual outcome or to both the expected and actual outcomes; Experiments 1 and 2). When the agent caused the event, participants' judgments also depended on the probability of the action (Experiments 3 and 4); when actions were improbable given the mental states, people failed to recover the agent's beliefs even when they saw her react to both the anticipated and actual outcomes. A Bayesian model captured human performance throughout (rs ≥ .95), consistent with the proposal that people rationally integrate information about others' actions and emotional reactions to infer their unobservable mental states.

Serious fun: preschoolers engage in more exploratory play when evidence is confounded.

Researchers, educators, and parents have long believed that children learn cause and effect relationships through exploratory play. However, previous research suggests that children are poor at designing informative experiments; children fail to control relevant variables and tend to alter multiple variables simultaneously. Thus, little is known about how children's spontaneous exploration might support accurate causal inferences. Here the authors suggest that children's exploratory play is affected by the quality of the evidence they observe. Using a novel free-play paradigm, the authors show that preschoolers (mean age: 57 months) distinguish confounded and unconfounded evidence, preferentially explore causally confounded (but not matched unconfounded) toys rather than novel toys, and spontaneously disambiguate confounded variables in the course of free play.

Can being scared cause tummy aches? Naive theories, ambiguous evidence, and preschoolers' causal inferences.

Causal learning requires integrating constraints provided by domain-specific theories with domain-general statistical learning. In order to investigate the interaction between these factors, the authors presented preschoolers with stories pitting their existing theories against statistical evidence. Each child heard 2 stories in which 2 candidate causes co-occurred with an effect. Evidence was presented in the form: AB?E; CA?E; AD?E; and so forth. In 1 story, all variables came from the same domain; in the other, the recurring candidate cause, A, came from a different domain (A was a psychological cause of a biological effect). After receiving this statistical evidence, children were asked to identify the cause of the effect on a new trial. Consistent with the predictions of a Bayesian model, all children were more likely to identify A as the cause within domains than across domains. Whereas 3.5-year-olds learned only from the within-domain evidence, 4- and 5-year-olds learned from the cross-domain evidence and were able to transfer their new expectations about psychosomatic causality to a novel task.