Do infants really expect agents to act efficiently? A critical test of the rationality principle

Effects of Joint Action Observation on Children's Imitation

Grasping others' intentions from their actions is essential for learning, as it enhances the ability to identify collaborative acts and anticipate others' actions, facilitating effective coordination toward shared goals. From a young age, children seem to recognize when others are working together based on their interactions and use this understanding to inform their own learning. Although much of early learning occurs in joint contexts, little attention has been devoted to understanding how children learn by participating in joint actions and by observing others acting together. Using a puzzle box paradigm, we tested 3-6-year-old children's imitation of an inefficient performance following individual and joint demonstrations in which the inefficient performance did or did not involve bimanual or joint coordination. This allowed us to test whether the tendency to overimitate extends to joint actions and how action coordination modulates imitative behavior. We found that overimitation extends to joint actions, as indicated by similar rates of inefficient copying following individual and joint action demonstrations. Furthermore, our results suggest that action coordination did not play a significant role in modulating children's tendency to overimitate. Taken together, the results of the study advance our understanding of how learning occurs in social interactions.

Young Children's Understanding of Helping as Increasing Another Agent's Utility

Instrumental helping is one of the paradigmatic "prosocial" behaviors featured in developmental research on sociomoral reasoning, but not much is known about how children recognize instances of helping behaviors or understand the term 'help'. Here, we examined whether young children represent helping as a second-order goal and take it to mean increasing the utility of another agent. In Study 1, we tested whether 12-month-old infants would expect an agent who previously helped to perform an action that reduced the Helpee's action cost. We found that while infants expected agents to act individually efficiently (Experiment 1C), they did not expect the agent to choose the action that maximally reduced the Helpee's cost compared to an action that reduced the cost less (Experiment 1A) or not at all (Experiment 1B). In Study 2, we examined whether three-year-old preschoolers (1) maximize a Helpee's cost reduction when prompted to help in a first-person task, and (2) identify in a third-party context which of two agents, performing superficially similar behaviors with varying effects on the Helpee's action options, actually helped. Contrary to our predictions, preschoolers did not help in a way that maximally reduced the Helpee's cost in (1). In (2), however, they indicated that the agent who reduced the Helpee's action cost was the one who helped. Taken together, these results support the proposal that, at least by preschool age, children possess a second-order utility-based concept of helping, but that they may not exhibit efficiency when choosing their own helping actions.

Doing things efficiently: Testing an account of why simple explanations are satisfying

People often find simple explanations more satisfying than complex ones. Across seven preregistered experiments, we provide evidence that this simplicity preference is not specific to explanations and may instead arises from a broader tendency to prefer completing goals in efficient ways. In each experiment, participants (total N=2820) learned of simple and complex methods for producing an outcome, and judged which was more appealing-either as an explanation why the outcome happened, or as a process for producing it. Participants showed similar preferences across judgments. They preferred simple methods as explanations and processes in tasks with no statistical information about the reliability or pervasiveness of causal elements. But when this statistical information was provided, preferences for simple causes often diminished and reversed in both kinds of judgments. Together, these findings suggest that people may assess explanations much in the same ways they assess methods for completing goals, and that both kinds of judgments depend on the same cognitive mechanisms.

The Cognitive Architecture of Infant Attachment

Meta-analytic evidence indicates that the quality of the attachment relationship that infants establish with their primary caregiver has enduring significance for socioemotional and cognitive outcomes. However, the mechanisms by which early attachment experiences contribute to subsequent development remain underspecified. According to attachment theory, early attachment experiences become embodied in the form of cognitive-affective representations, referred to as internal working models (IWMs), that guide future behavior. Little is known, however, about the cognitive architecture of IWMs in infancy. In this article, we discuss significant advances made in the field of infant cognitive development and propose that leveraging insights from this research has the potential to fundamentally shape our understanding of the cognitive architecture of attachment representations in infancy. We also propose that the integration of attachment research into cognitive research can shed light on the role of early experiences, individual differences, and stability and change in infant cognition, as well as open new routes of investigation in cognitive studies, which will further our understanding of human knowledge. We provide recommendations for future research throughout the article and conclude by using our collaborative research as an example.

Better Together: 14-Month-Old Infants Expect Agents to Cooperate

Humans engage in cooperative activities from early on and the breadth of human cooperation is unparalleled. Human preference for cooperation might reflect cognitive and motivational mechanisms that drive engagement in cooperative activities. Here we investigate early indices of humans' cooperative abilities and test whether 14-month-old infants expect agents to prefer cooperative over individual goal achievement. Three groups of infants saw videos of agents facing a choice between two actions that led to identical rewards but differed in the individual costs. Our results show that, in line with prior research, infants expect agents to make instrumentally rational choices and prefer the less costly of two individual action alternatives. In contrast, when one of the action alternatives is cooperative, infants expect agents to choose cooperation over individual action, even though the cooperative action demands more effort from each agent to achieve the same outcome. Finally, we do not find evidence that infants expect agents to choose the less costly alternative when both options entail cooperative action. Combined, these results indicate an ontogenetically early expectation of cooperation, and raise interesting implications and questions regarding the nature of infants' representations of cooperative actions and their utility.

Not just if, but how much: Children and adults use cost and need to make evaluations about generosity across contexts

Evaluations of others' generosity are critical for selecting quality social partners, yet the factors which systematically affect these evaluations and whether they vary across development are still relatively unclear. Here, we establish that two key dimensions adults and children (aged 4 to 7 years) consider are the cost associated with a giving action and the need of the recipient, through six pre-registered experiments with Canadian and U.S. American participants. Experiments 1 and 2 demonstrate that adults' and children's third-party evaluations of generosity are sensitive to variations in each factor, across several operationalizations of cost and need in both comparative and standalone contexts, suggesting cost and need can be spontaneously evoked. However, children's responses were more consistent for need scenarios than cost scenarios. In Experiments 3 and 4, we modified our scenarios to evaluate whether variations in cost and need are considered simultaneously in both generosity evaluations and affiliative preferences. Adults' and older children's (ages 6 to 7) evaluations of generosity and affiliative preferences were sensitive to both factors, but younger children did not utilize this information systematically. Importantly, in Experiments 5 and 6, adults' and older children's generosity evaluations were only sensitive to information about cost and need when the giver's actions conferred utility to a recipient, but not when actions were self-serving. Taken together, we establish robust evidence that cost and need are considered in generosity evaluations by demonstrating that Canadian and U.S. American adults and children utilize this information consistently, spontaneously, and simultaneously.

Commonsense psychology in human infants and machines

Human infants are fascinated by other people. They bring to this fascination a constellation of rich and flexible expectations about the intentions motivating people's actions. Here we test 11-month-old infants and state-of-the-art learning-driven neural-network models on the "Baby Intuitions Benchmark (BIB)," a suite of tasks challenging both infants and machines to make high-level predictions about the underlying causes of agents' actions. Infants expected agents' actions to be directed towards objects, not locations, and infants demonstrated default expectations about agents' rationally efficient actions towards goals. The neural-network models failed to capture infants' knowledge. Our work provides a comprehensive framework in which to characterize infants' commonsense psychology and takes the first step in testing whether human knowledge and human-like artificial intelligence can be built from the foundations cognitive and developmental theories postulate.

Understanding preferences in infancy

A preference is defined as a dispositional state that helps explain why a person chooses one option over another. Preference understanding is a significant part of interpreting and predicting others' behavior, which can also help to guide social encounters, for instance, to initiate interactions and even form relationships based on shared preferences. Cognitive developmental research in the past several decades has revealed that infants have relatively sophisticated understandings about others' preferences, as part of investigations into how young children make sense of others' behavior in terms of mental states such as intentions, dispositions including preferences, and epistemic states. In recent years, research on early psychological knowledge expands to including infant understanding of social situations. As such, infants are also found to use their preference understandings in their social life. They treat favorably others who share their own preferences, and they prefer prosocial and similar others (e.g., those who speak their language). In reviewing these results, we point out future directions for research and conclude with further suggestions and recommendations. This article is categorized under: Cognitive Biology > Cognitive Development Psychology > Development and Aging.

Dangerous Ground: One-Year-Old Infants are Sensitive to Peril in Other Agents' Action Plans

Do infants appreciate that other people's actions may fail, and that these failures endow risky actions with varying degrees of negative utility (i.e., danger)? Three experiments, including a pre-registered replication, addressed this question by presenting 12- to 15-month-old infants (N = 104, 52 female, majority White) with an animated agent who jumped over trenches of varying depth towards its goals. Infants expected the agent to minimize the danger of its actions, and they learned which goal the agent preferred by observing how much danger it risked to reach each goal, even though the agent's actions were physically identical and never failed. When we tested younger, 10-month-old infants (N = 102, 52 female, majority White) in a fourth experiment, they did not succeed consistently on the same tasks. These findings provide evidence that one-year-old infants use the height that other agents could fall from in order to explain and predict those agents' actions.

Infants use emotion to infer intentionality from non-random sampling events

Infants use statistical information in their environment, as well as others' emotional communication, to understand the intentions of social partners. However, rarely do researchers consider these two sources of social information in tandem. This study assessed 2-year-olds' attributions of intentionality from non-random sampling events and subsequent discrete emotion reactions. Infants observed an experimenter remove five objects from either the non-random minority (18%) or random majority (82%) of a sample and express either joy, disgust, or sadness after each selection. Two-year-olds inferred the experimenter's intentionality by giving her the object that she had previously selected when she expressed joy or disgust after non-random sampling events, but not when she expressed sadness or sampled at random. These findings demonstrate that infants use both statistical regularities and discrete emotion communication to infer an agent's intentions. In particular, the present findings show that 2-year-olds infer that an agent can intentionally select a preferred or an undesired object from a sample as a function of the discrete emotion. Implications for the development of inferring intentionality from statistical sampling events and discrete emotion communication are discussed.

People infer communicative action through an expectation for efficient communication

Humans often communicate using body movements like winks, waves, and nods. However, it is unclear how we identify when someone’s physical actions are communicative. Given people’s propensity to interpret each other’s behavior as aimed to produce changes in the world, we hypothesize that people expect communicative actions to efficiently reveal that they lack an external goal. Using computational models of goal inference, we predict that movements that are unlikely to be produced when acting towards the world and, in particular, repetitive ought to be seen as communicative. We find support for our account across a variety of paradigms, including graded acceptability tasks, forced-choice tasks, indirect prompts, and open-ended explanation tasks, in both market-integrated and non-market-integrated communities. Our work shows that the recognition of communicative action is grounded in an inferential process that stems from fundamental computations shared across different forms of action interpretation.

Humans can quickly infer when someone’s body movements are meant to be communicative. Here, the authors show that this capacity is underpinned by an expectation that communicative actions will efficiently reveal that they lack an external goal.

Adopted Utility Calculus: Origins of a Concept of Social Affiliation

To successfully navigate their social world, humans need to understand and map enduring relationships between people: Humans need a concept of social affiliation. Here I propose that the initial concept of social affiliation, available in infancy, is based on the extent to which one individual consistently takes on the goals and needs of another. This proposal grounds affiliation in intuitive psychology, as formalized in the naive-utility-calculus model. A concept of affiliation based on interpersonal utility adoption can account for findings from studies of infants' reasoning about imitation, similarity, helpful and fair individuals, "ritual" behaviors, and social groups without the need for additional innate mechanisms such as a coalitional psychology, moral sense, or general preference for similar others. I identify further tests of this proposal and also discuss how it is likely to be relevant to social reasoning and learning across the life span.

A New Look at Infant Problem-Solving: Using DeepLabCut to Investigate Exploratory Problem-Solving Approaches

When confronted with novel problems, problem-solvers must decide whether to copy a modeled solution or to explore their own unique solutions. While past work has established that infants can learn to solve problems both through their own exploration and through imitation, little work has explored the factors that influence which of these approaches infants select to solve a given problem. Moreover, past work has treated imitation and exploration as qualitatively distinct, although these two possibilities may exist along a continuum. Here, we apply a program novel to developmental psychology (DeepLabCut) to archival data (Lucca et al., 2020) to investigate the influence of the effort and success of an adult's modeled solution, and infants' firsthand experience with failure, on infants' imitative versus exploratory problem-solving approaches. Our results reveal that tendencies toward exploration are relatively immune to the information from the adult model, but that exploration generally increased in response to firsthand experience with failure. In addition, we found that increases in maximum force and decreases in trying time were associated with greater exploration, and that exploration subsequently predicted problem-solving success on a new iteration of the task. Thus, our results demonstrate that infants increase exploration in response to failure and that exploration may operate in a larger motivational framework with force, trying time, and expectations of task success.

A simple definition of 'intentionally'

Cognitive scientists have been debating how the folk concept of intentional action works. We suggest a simple account: people consider that an agent did X intentionally to the extent that X was causally dependent on how much the agent wanted X to happen (or not to happen). Combined with recent models of human causal cognition, this definition provides a good account of the way people use the concept of intentional action, and offers natural explanations for puzzling phenomena such as the side-effect effect. We provide empirical support for our theory, in studies where we show that people's causation and intentionality judgments track each other closely, in everyday situations as well as in scenarios with unusual causal structures. Study 5 additionally shows that the effect of norm violations on intentionality judgments depends on the causal structure of the situation, in a way uniquely predicted by our theory. Taken together, these results suggest that the folk concept of intentional action has been difficult to define because it is made of cognitive building blocks, such as our intuitive concept of causation, whose logic cognitive scientists are just starting to understand.

Five-month-old infants attribute inferences based on general knowledge to agents

To make sense of others' actions, we generally consider what information is available to them. This information may come from different sources, including perception and inference. Like adults, young infants track what information agents can obtain through perception: If an agent directly observes an event, for example, young infants expect the agent to have information about it. However, no investigation has yet examined whether young infants also track what information agents can obtain through inference, by bringing to bear relevant general knowledge. Building on the finding that by 4 months of age most infants have acquired the physical rule that wide objects can fit into wide containers but not narrow containers, we asked whether 5-month-olds would expect an agent who was searching for a wide toy hidden in her absence to reach for a wide box as opposed to a narrow box. Infants looked significantly longer when the agent selected the narrow box, suggesting that they expected her (a) to share the physical knowledge that wide objects can fit only into wide containers and (b) to infer that the wide toy must be hidden in the wide box. Three additional conditions supported this interpretation. Together, these results cast doubt on two-system accounts of early psychological reasoning, which claim that infants' early-developing system is too inflexible and encapsulated to integrate inputs from other cognitive processes, such as physical reasoning. Instead, the results support one-system accounts and provide new evidence that young infants' burgeoning psychological-reasoning system is qualitatively similar to that of older children and adults.

Children's reasoning about the efficiency of others' actions: The development of rational action prediction

The relative efficiency of an action is a central criterion in action control and can be used to predict others' behavior. Yet, it is unclear when the ability to predict on and reason about the efficiency of others' actions develops. In three main and two follow-up studies, 3- to 6-year-old children (n = 242) were confronted with vignettes in which protagonists could take a short (efficient) path or a long path. Children predicted which path the protagonist would take and why the protagonist would take a specific path. The 3-year-olds did not take efficiency into account when making decisions even when there was an explicit goal, the task was simplified and made more salient, and children were questioned after exposure to the agent's action. Four years is a transition age for rational action prediction, and the 5-year-olds reasoned on the efficiency of actions before relying on them to predict others' behavior. Results are discussed within a representational redescription account.

Infants Consider the Distributor's Intentions in Resource Allocation

Recent experimental studies suggest that preverbal infants are able to evaluate agents on the basis of their distributive actions. Here we asked whether such evaluations are based on infants' understanding of the distributors' intentions, or only the outcome of their actions. Ten-month-old infants observed animated movies of unequal resource allocations by distributors who attempted but failed to distribute resources equally or unequally between two individuals. We found that infants attended longer to the test event showing a third agent approaching a distributor who was unable to make an unequal distribution, compared to the test event where the third agent approached a distributor who was unable to make an equal distribution of resources. Our results suggest that infants' ability to encode distributive actions goes beyond an analysis of the outcome of these actions, by including the intentions of the distributors whose actions lead to these outcomes.

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.

Children avoid inefficient but fair partners in a cooperative game

Human adults use a range of social cues to obtain information about potential partners in cooperative contexts: we prefer partners who are competent, wealthy and generous, and those who abide by moral and social rules. One factor that carries particular weight is whether a prospective partner is fair. Here we ask whether children share this preference for fair partners and, if so, whether a prospective partner’s past fair behaviour influences children’s behaviour in a cooperative dilemma. Six- to nine-year-olds chose between partners who accepted or rejected resource allocations that were either strongly advantageously unequal, strongly disadvantageously unequal, or equal. They then played a one-shot Prisoner’s Dilemma Game with their chosen partner. Children overwhelmingly preferred to play with the partner who accepted rather than rejected allocations. Regardless of their partner choice decisions, children tended to defect in the Prisoner’s Dilemma Game, yet expected that their partners would be relatively more cooperative. Finally, children were more likely to cooperate with those they believed would cooperate. Together, these findings shed new light on the links between partner choice, fairness and cooperation in child development.

Children’s Judgments of Epistemic and Moral Agents: From Situations to Intentions

Children’s evaluations of moral and epistemic agents crucially depend on their discerning that an agent’s actions were performed intentionally. Here we argue that children’s epistemic and moral judgments reveal practices of forgiveness and blame, trust and mistrust, and objection or disapproval and that such practices are supported by children’s monitoring of the situational constraints on agents. Inherent in such practices is the understanding that agents are responsible for actions performed under certain conditions but not others. We discuss a range of situational constraints on children’s early epistemic and moral evaluations and clarify how these situational constraints serve to support children’s identification of intentional actions. By monitoring the situation, children distinguish intentional from less intentional action and selectively hold epistemic and moral agents accountable. We argue that these findings inform psychological and philosophical theorizing about attributions of moral and epistemic agency and responsibility.

Perceptual teleology: expectations of action efficiency bias social perception

Primates interpret conspecific behaviour as goal-directed and expect others to achieve goals by the most efficient means possible. While this teleological stance is prominent in evolutionary and developmental theories of social cognition, little is known about the underlying mechanisms. In predictive models of social cognition, a perceptual prediction of an ideal efficient trajectory would be generated from prior knowledge against which the observed action is evaluated, distorting the perception of unexpected inefficient actions. To test this, participants observed an actor reach for an object with a straight or arched trajectory on a touch screen. The actions were made efficient or inefficient by adding or removing an obstructing object. The action disappeared mid-trajectory and participants touched the last seen screen position of the hand. Judgements of inefficient actions were biased towards the efficient prediction (straight trajectories upward to avoid the obstruction, arched trajectories downward towards the target). These corrections increased when the obstruction's presence/absence was explicitly acknowledged, and when the efficient trajectory was explicitly predicted. Additional supplementary experiments demonstrated that these biases occur during ongoing visual perception and/or immediately after motion offset. The teleological stance is at least partly perceptual, providing an ideal reference trajectory against which actual behaviour is evaluated.

How do 3-month-old infants attribute preferences to a human agent?

The current study showed that 3-month-old infants attributed a preference to a human agent, with her face and upper body visible, when she consistently reached for and grasped one of two objects with her bare hand. In contrast, infants did not appear to interpret the agent's same actions of grasping the object as indicative of her preference when it was the only object present or when it hid the other object from her but not from the infants. These results suggest that even from an early age, infants interpret human agents' actions in terms of mental states such as goals and preferences. In light of the current results, mechanisms for early psychological understanding are discussed.

Infants' understanding of the definite/indefinite article in a third-party communicative situation

The present study examines how infants use their emergent perspective-taking and language comprehension abilities to make sense of interactions between two human agents. In the study, one agent (Agent1) could see only one of two identical balls on an apparatus because of a screen obstructing her view while the infant and another agent (Agent2) could see both balls. 19-month-old English-learning monolingual infants seemed to expect Agent2 to grasp the ball visible to Agent1 when she said to Agent2 "Give me the ball" but not when she said "Give me a ball." 14-month-olds appeared to accept that Agent2 could grasp either ball when Agent1 said "Give me the ball." Therefore, by 19 months of age, English-learning infants seem to attend to the specific linguistic units used, e.g., the definite article, to identify the referent of others' speech. Possible reasons in connection with language acquisition processes and/or environmental factors for the two age groups' respective failures with the definite and the indefinite articles are discussed.

Moving higher and higher: imitators' movements are sensitive to observed trajectories regardless of action rationality

Humans sometimes perform actions which, at least superficially, appear suboptimal to the goal they are trying to achieve. Despite being able to identify these irrational actions from an early age, humans display a curious tendency to copy them. The current study recorded participants’ movements during an established imitation task and manipulated the rationality of the observed action in two ways. Participants observed videos of a model point to a series of targets with either a low, high or ‘superhigh’ trajectory either in the presence or absence of obstacles between her targets. The participants’ task was to watch which targets the model pointed to and then point to the same targets on the table in front of them. There were no obstacles between the participants’ targets. Firstly, we found that the peak height of participants’ movements between their targets was sensitive to the height of the model’s movements, even in the ‘superhigh’ condition where the model’s action was rated as irrational. Secondly, participants showed obstacle priming—the peak height of participants’ movements was higher after having observed the model move over obstacles to reach her targets, compared to when there were no obstacles between her targets. This suggests that participants code the environment of co-actors into their own motor programs, even when this compromises the efficiency of their own movements. We discuss the implications of our findings in terms of theories of imitation and obstacle priming.

Learning about and from others' prudence, impatience or laziness: The computational bases of attitude alignment

Peoples' subjective attitude towards costs such as, e.g., risk, delay or effort are key determinants of inter-individual differences in goal-directed behaviour. Thus, the ability to learn about others' prudent, impatient or lazy attitudes is likely to be critical for social interactions. Conversely, how adaptive such attitudes are in a given environment is highly uncertain. Thus, the brain may be tuned to garner information about how such costs ought to be arbitrated. In particular, observing others' attitude may change one's uncertain belief about how to best behave in related difficult decision contexts. In turn, learning from others' attitudes is determined by one's ability to learn about others' attitudes. We first derive, from basic optimality principles, the computational properties of such a learning mechanism. In particular, we predict two apparent cognitive biases that would arise when individuals are learning about others’ attitudes: (i) people should overestimate the degree to which they resemble others (false-consensus bias), and (ii) they should align their own attitudes with others’ (social influence bias). We show how these two biases non-trivially interact with each other. We then validate these predictions experimentally by profiling people's attitudes both before and after guessing a series of cost-benefit arbitrages performed by calibrated artificial agents (which are impersonating human individuals).

What do people learn from observing others' attitudes, such as "prudence", "impatience" or "laziness"? Rather than viewing these attitudes as examples of highly subjective personality traits, we assume that they derive from uncertain (and mostly implicit) beliefs about how to best weigh risks, delays and efforts in ensuing cost-benefit trade-offs. In this view, it is adaptive to update one's belief after having observed others' attitude, which provides valuable information regarding how to best behave in related difficult decision contexts. This is the starting point of our computational model of attitude alignment, which we derive from first optimality principles as well as from recent neuroscientific findings. Critical here is the impact of one's ability to learn about others' covert mental states or attitudes, which is known as "mentalizing" or "Theory of Mind". In particular, this model makes two (otherwise unrelated) predictions that conform to known but puzzling cognitive biases of social cognition in humans, namely: "false consensus" and "social influence". It also shows how attitude alignment may eventually follow from the interaction between these two biases. Using state-of-the-art behavioural and computational methods, we provide experimental evidence that confirm these predictions. Finally, we discuss the relevance and implications of this work, both from a neuroscientific and economic perspective.

What I don't know won't hurt you: The relation between professed ignorance and later knowledge claims

Testimony is a valuable source of information for young learners, in particular if children maintain vigilance against errors while still being open to learning from imperfectly knowledgeable sources. We find support for this idea by examining how children evaluate individual speakers who present very different epistemic risks by being previously ignorant or inaccurate. Results across 2 experiments show that children attribute knowledge to (Experiment 1) and endorse new claims made by speakers (Experiment 2) who previously professed ignorance about familiar object labels, but not to speakers whose labels were previously inaccurate. Study 2 further clarifies that children are not simply relying on links between informational access and knowledge; children rejected testimony from a previously inaccurate speaker even when she had perceptual access to support her claim. These results show that children actively monitor the reliability of a speaker's knowledge claims, distinguish unreliable speakers from those who sometimes admit ignorance, raising new questions about how such admissions factor in to children's appraisal of the scope and limits of a person's knowledge. (PsycINFO Database Record

Preschoolers, adolescents, and adults visually anticipate an agent's efficient action; but only after having observed it frequently

The present study examined the contribution of efficiency reasoning and statistical learning on visual action anticipation in preschool children, adolescents, and adults. To this end, Experiment 1 assessed proactive eye movements of 5-year-old children, 15-year-old adolescents, and adults, who observed an agent stating the intent to reach a goal as quickly as possible. Subsequently the agent could four times either take a short, hence efficient, or long, hence inefficient, path to get to the goal. The results showed that in the first trial participants in none of the age groups predicted above chance level that the agent would produce the efficient action. Instead, we observed an age-dependent increase in action predictions in the subsequent repeated presentation of the same action. Experiment 2 ruled out that participants’ nonconsideration of the efficient path was due to a lack of understanding of the agent's action goal. Moreover, it demonstrated that 5-year-old children do predict that the agent will act efficiently when verbally reasoning about his future action. Overall, the study supports the view that rapid learning from frequency information guides visual action anticipations.

Infants' Understanding of Object-Directed Action: An Interdisciplinary Synthesis

Recognizing that the object-directed actions of others are governed by goals and intentions is a crucial component of human interaction. These actions often occur rapidly and without explanation, yet we learn from and predict the actions of others with remarkable speed and accuracy, even during the first year of life. This review paper will serve as a bridge between several disparate literatures that, we suggest, can each contribute to our understanding of how infants interpret action. Specifically, we provide a review not just of research on infant goal attribution per se, but also incorporate findings from studies on the mirror neuron system and infant object cognition. The integration of these various research approaches allows for a novel construal of the extents and limits of early goal attribution – one in which the importance of the entire action context is considered – and points to specific future research directions.

Perceiving referential intent: Dynamics of reference in natural parent-child interactions

Two studies are presented which examined the temporal dynamics of the social-attentive behaviors that co-occur with referent identification during natural parent-child interactions in the home. Study 1 focused on 6.2 h of videos of 56 parents interacting during everyday activities with their 14-18 month-olds, during which parents uttered common nouns as parts of spontaneously occurring utterances. Trained coders recorded, on a second-by-second basis, parent and child attentional behaviors relevant to reference in the period (40 s) immediately surrounding parental naming. The referential transparency of each interaction was independently assessed by having naïve adult participants guess what word the parent had uttered in these video segments, but with the audio turned off, forcing them to use only non-linguistic evidence available in the ongoing stream of events. We found a great deal of ambiguity in the input along with a few potent moments of word-referent transparency; these transparent moments have a particular temporal signature with respect to parent and child attentive behavior: it was the object's appearance and/or the fact that it captured parent/child attention at the moment the word was uttered, not the presence of the object throughout the video, that predicted observers' accuracy. Study 2 experimentally investigated the precision of the timing relation, and whether it has an effect on observer accuracy, by disrupting the timing between when the word was uttered and the behaviors present in the videos as they were originally recorded. Disrupting timing by only ±1 to 2 s reduced participant confidence and significantly decreased their accuracy in word identification. The results enhance an expanding literature on how dyadic attentional factors can influence early vocabulary growth. By hypothesis, this kind of time-sensitive data-selection process operates as a filter on input, removing many extraneous and ill-supported word-meaning hypotheses from consideration during children's early vocabulary learning.

Infants understand deceptive intentions to implant false beliefs about identity: New evidence for early mentalistic reasoning

Are infants capable of representing false beliefs, as the mentalistic account of early psychological reasoning suggests, or are they incapable of doing so, as the minimalist account suggests? The present research sought to shed light on this debate by testing the minimalist claim that a signature limit of early psychological reasoning is a specific inability to understand false beliefs about identity: because of their limited representational capabilities, infants should be unable to make sense of situations where an agent mistakes one object for another, visually identical object. To evaluate this claim, three experiments examined whether 17-month-olds could reason about the actions of a deceptive agent who sought to implant in another agent a false belief about the identity of an object. In each experiment, a thief attempted to secretly steal a desirable rattling toy during its owner's absence by substituting a less desirable silent toy. Infants realized that this substitution could be effective only if the silent toy was visually identical to the rattling toy (Experiment 1) and the owner did not routinely shake her toy when she returned (Experiment 2). When these conditions were met, infants expected the owner to be deceived and to mistake the silent toy for the rattling toy she had left behind (Experiment 3). Together, these results cast doubt on the minimalist claim that infants cannot represent false beliefs about identity. More generally, these results indicate that infants in the 2nd year of life can reason not only about the actions of agents who hold false beliefs, but also about the actions of agents who seek to implant false beliefs, thus providing new support for the mentalistic claim that an abstract capacity to reason about false beliefs emerges early in human development.

Which way to take? Infants select an efficient path to their goal

In two experiments, we examined the development of the ability to select efficient means in order to attain a goal in 1.5- and 2-year-olds (N = 79) using a setup in which two paths led to a goal. One of the paths was shorter, and thus more efficient, than the other path. Experiment 1 showed a strong tendency in both age groups to choose the shorter path. In Experiment 2, the shorter path was initially blocked and became available only after infants repeatedly took the longer path. Children demonstrated increasing use of the more efficient path over time. The results of both experiments point to some abilities of efficient action selection in infants.

Not So Innocent

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.

13-Month-Olds’ Understanding of Social Interactions

In the present research, we investigated how 13-month-olds use their emergent theory-of-mind understanding (i.e., understanding about other people’s mental states, such as their intentions, perceptions, and beliefs) and social-evaluation skills to make sense of social interactions. The infants watched three puppets (A, B, and C) interact. The results showed that after seeing Agents A and B interact in a positive manner, infants expected them to continue doing so, even after they saw B hit another agent, C, while A was absent. When A was present to witness B’s harmful action, however, infants expected A to change his or her behavior and ignore B. Therefore, infants seemed to consider A’s perspectives when predicting A’s actions. Furthermore, if B accidentally hit C when A was present, infants seemed to accept that A could interact or not interact with B, which suggests that they had taken into account B’s intention in their interpretations of the agents’ interactions.

First-person action experience reveals sensitivity to action efficiency in prereaching infants

Do infants learn to interpret others' actions through their own experience producing goal-directed action, or does some knowledge of others' actions precede first-person experience? Several studies report that motor experience enhances action understanding, but the nature of this effect is not well understood. The present research investigates what is learned during early motoric production, and it tests whether knowledge of goal-directed actions, including an assumption that actors maximize efficiency given environmental constraints, exists before experience producing such actions. Three-month-old infants (who cannot yet effectively reach for and grasp objects) were given novel experience retrieving objects that rested on a surface with no barriers. They were then shown an actor reaching for an object over a barrier and tested for sensitivity to the efficiency of the action. These infants showed heightened attention when the agent reached inefficiently for a goal object; in contrast, infants who lacked successful reaching experience did not differentiate between direct and indirect reaches. Given that the infants could reach directly for objects during training and were given no opportunity to update their actions based on environmental constraints, the training experience itself is unlikely to have provided a basis for learning about action efficiency. We suggest that infants apply a general assumption of efficient action as soon as they have sufficient information (possibly derived from their own action experience) to identify an agent's goal in a given instance.