Do 12.5-month-old infants consider what objects others can see when interpreting their actions?

Do monkeys have a theory of mind? How to answer the question?

Since Premack and Woodruf (1978), the study of mindreading abilities in nonhumans, especially primates, has been thoroughly investigated. But attempts to understand the evolution of this aspect of human intelligence have mainly focused on comparisons between apes and human infants, while relatively little is known about the abilities of monkeys. This lack of data on monkeys seems mainly due to the hypothesis of a cognitive "gap" between apes and monkeys. However, in recent years monkeys have been featuring more prominently in the landscape of social cognition research, and some of these systematic studies appear promising. This paper reviews i) current knowledge about monkeys' socio-cognitive abilities, especially regarding gaze processing, attention and intention reading, and perspective-taking, ii) alternative hypotheses regarding the underlying mechanisms of such complex behaviors, and iii) potential new perspectives and future directions for studying ToM in monkeys.

Logistic Mixed Models to Investigate Implicit and Explicit Belief Tracking

We investigated the proposition of a two-systems Theory of Mind in adults' belief tracking. A sample of N = 45 participants predicted the choice of one of two opponent players after observing several rounds in an animated card game. Three matches of this card game were played and initial gaze direction on target and subsequent choice predictions were recorded for each belief task and participant. We conducted logistic regressions with mixed effects on the binary data and developed Bayesian logistic mixed models to infer implicit and explicit mentalizing in true belief and false belief tasks. Although logistic regressions with mixed effects predicted the data well a Bayesian logistic mixed model with latent task- and subject-specific parameters gave a better account of the data. As expected explicit choice predictions suggested a clear understanding of true and false beliefs (TB/FB). Surprisingly, however, model parameters for initial gaze direction also indicated belief tracking. We discuss why task-specific parameters for initial gaze directions are different from choice predictions yet reflect second-order perspective taking.

Young children infer preferences from a single action, but not if it is constrained

Inferring others' preferences is socially important and useful. We investigated whether children infer preferences from the minimal information provided by an agent's single action, and whether they avoid inferring preference when the action is constrained. In three experiments, children saw vignettes in which an agent took a worse toy instead of a better one. Experiment 1 shows that this single action influences how young children infer preferences. Children aged three and four were more likely to infer the agent preferred the worse toy when the agent took this toy, compared with when the agent did not take either toy. Experiment 2 then shows that children consider constraints when inferring preferences from a single action. From age 5, children were less likely to avoid inferring a preference for the worse toy when the agent's action was physically constrained. Finally, Experiment 3 provides evidence that children's and adults' sensitivity to constraints, when inferring preferences, is not based on a general notion of constraints, and instead depends on several specific notions. Whereas 5-6-year-olds in this experiment considered physical and socio-moral constraints when inferring preferences, they had difficulty grasping the relevance of epistemic constraints. Adults considered physical and epistemic constraints, but were not influenced by the socio-moral constraint of ownership. Together these findings contribute to a picture of cognitive development in which children are able to infer non-obvious properties on the basis of minimal concrete information, and are also sensitive to subtle changes in this information.

Unintentional perspective-taking calculates whether something is seen, but not how it is seen

A long established distinction exists in developmental psychology between young children's ability to judge whether objects are seen by another, known as "level-1" perspective-taking, and judging how the other sees those objects, known as "level-2" perspective-taking (Flavell, Everett, Croft, & Flavell, 1981a; Flavell, Flavell, Green, & Wilcox, 1981b). Samson, Apperly, Braithwaite, Andrews, and Bodley Scott (2010) provided evidence that there are two routes available to adults for level-1 perspective-taking: one which is triggered relatively automatically and the other requiring cognitive control. We tested whether both these routes were available for adults' level-2 perspective-taking. Explicit judgements of both level-1 and level-2 perspectives were subject to egocentric interference, suggesting a need for cognitive control. Evidence of unintentional perspective-taking was limited to level-1 judgements.

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.

Human temporal-parietal junction spontaneously tracks others' beliefs: A functional near-infrared spectroscopy study

Humans have the unique capacity to actively reflect on the thoughts, beliefs, and knowledge of others, but do we also track mental states spontaneously when observing other people? We asked this question by monitoring brain activity in belief-sensitive cortex using functional near-infrared spectroscopy (fNIRS) during free-viewing of social videos. More specifically, we identified a portion of the right temporal-parietal junction (rTPJ) selective for mental state processing using an established, explicit theory of mind task, and then analyzed the brain response in that region of interest (ROI) during free-viewing of video clips involving people producing goal-directed actions. We found a significant increase in oxygenated hemoglobin concentration in our rTPJ ROI during free-viewing for all of our test videos. Activity in this region was further modulated by the extent to which the knowledge state, or beliefs, of the protagonist regarding the location of an object contrasted with the reality of where the object was hidden. Open-ended questioning suggested our participants were not explicitly focusing on belief states of the characters during free-viewing. Further analyses ruled out lower-level details of the video clips or general attentional differences between conditions as likely explanations for the results. As such, these results call into question the traditional characterization of theory of mind as a resource intensive, deliberate process, and, instead, support an emerging view of theory of mind as a foundation for, rather than the pinnacle of, human social cognition.

Think fast! The relationship between goal prediction speed and social competence in infants

Skilled social interactions require knowledge about others' intentions and the ability to implement this knowledge in real-time to generate appropriate responses to one's partner. Young infants demonstrate an understanding of other people's intentions (e.g. Woodward, Sommerville, Gerson, Henderson & Buresh, 2009), yet it is not until the second year that infants seem to master the real-time implementation of their knowledge during social interactions (e.g. Warneken & Tomasello, 2007). The current study investigates the possibility that developments in social competence during the second year are related to increases in the speed with which infants can employ their understanding of others' intentions. Twenty- to 22-month-old infants (N = 23) viewed videos of goal-directed actions on a Tobii eye-tracker and then engaged in an interactive perspective-taking task. Infants who quickly and accurately anticipated another person's future behavior in the eye-tracking task were more successful at taking their partner's perspective in the social interaction. Success on the perspective-taking task was specifically related to the ability to correctly predict another person's intentions. These findings highlight the importance of not only being a 'smart' social partner but also a 'fast' social thinker.

Goal attributions and instrumental helping at 14 and 24 months of age

Infants reason about goals and helping as early as 3 months of age, but toddlers fail to help others appropriately until well into the second year. Five experiments explored the reasons for this discrepancy. First, we verified that 14-month-old toddlers encode the goal of an actor's reaching action, in a situation in which a social agent selectively reaches for one of two objects. Then, four further experiments presented toddlers with a social agent who manifested her goal in this manner when the two objects were accessible, and then requested help in obtaining her goal object when the two objects were out of reach. In all the experiments, toddlers responded to the actor's request for help by handing her an out-of-reach object, showing that they understood that a prosocial action was called for and were motivated to perform it. When the two objects had moved out of the social agent's sight so that she could not indicate the goal object directly, 24-month-old children used her prior goal-directed action to select the appropriate goal object, but 14-month-old toddlers did not. The 14-month-olds toddlers helped appropriately only when no attribution of enduring goals was necessary, because the social agent could see the out-of-reach object and both looked at and reached toward it while making her request. These findings suggest striking limits to 14-month-old toddlers' understanding of helping.

Developing intuitions about free will between ages four and six

Our folk psychology includes intuitions about free will; we believe that our intentional acts are choices and that, when such actions are not constrained, we are free to act otherwise. In a series of five experiments, we ask children about their own and others' freedom of choice and about the physical and mental circumstances that place limitations on that freedom. We begin with three experiments establishing a basis for this understanding at age four. We find that 4-year-olds endorse their own and others' ability to "do otherwise" only when they or others are free to choose a course of action, but not when others' actions are physically impossible (Experiment 1), their own actions are physically constrained (Experiment 2), and their own actions are epistemically constrained (Experiment 3). We then examine developmental changes in children's understanding of actions and alternatives that lead to more adult-like free will intuitions. Across two experiments, 6-year-olds, but not 4-year-olds, endorse another person's (Experiment 4) or their own (Experiment 5) freedom to act against stated desires. These age-related changes suggest relationships between a belief in free will and other cognitive and conceptual developments in theory of mind, self-control and self-awareness that take place in early childhood.

My mother is sensitive, but I am too tired to know: infant sleep as a moderator of prospective relations between maternal sensitivity and infant outcomes

This study investigated the moderating role of infant sleep in the connections between maternal sensitivity and three indicators of infant functioning: attachment security, theory of mind, and executive functioning (EF). Maternal sensitivity was assessed when infants (27 girls and 36 boys) were 1 year of age. Infant sleep was assessed with actigraphy at age 2; attachment security, theory of mind, and EF were also assessed at age 2. Results indicated that maternal sensitivity was positively related to attachment security only among infants who got more sleep at night, and to conflict-EF and theory of mind only for infants who got greater proportions of their sleep during the night. These results suggest that sleep may enhance the benefits of maternal sensitivity for some aspects of infants' functioning, providing further support for the importance of sleep maturation as a salient developmental task of infancy.

Making smart social judgments takes time: infants' recruitment of goal information when generating action predictions

Previous research has shown that young infants perceive others' actions as structured by goals. One open question is whether the recruitment of this understanding when predicting others' actions imposes a cognitive challenge for young infants. The current study explored infants' ability to utilize their knowledge of others' goals to rapidly predict future behavior in complex social environments and distinguish goal-directed actions from other kinds of movements. Fifteen-month-olds (N = 40) viewed videos of an actor engaged in either a goal-directed (grasping) or an ambiguous (brushing the back of her hand) action on a Tobii eye-tracker. At test, critical elements of the scene were changed and infants' predictive fixations were examined to determine whether they relied on goal information to anticipate the actor's future behavior. Results revealed that infants reliably generated goal-based visual predictions for the grasping action, but not for the back-of-hand behavior. Moreover, response latencies were longer for goal-based predictions than for location-based predictions, suggesting that goal-based predictions are cognitively taxing. Analyses of areas of interest indicated that heightened attention to the overall scene, as opposed to specific patterns of attention, was the critical indicator of successful judgments regarding an actor's future goal-directed behavior. These findings shed light on the processes that support “smart” social behavior in infants, as it may be a challenge for young infants to use information about others' intentions to inform rapid predictions.

Goal representation in the infant brain

It is well established that, from an early age, human infants interpret the movements of others as actions directed towards goals. However, the cognitive and neural mechanisms which underlie this ability are hotly debated. The current study was designed to identify brain regions involved in the representation of others' goals early in development. Studies with adults have demonstrated that the anterior intraparietal sulcus (aIPS) exhibits repetition suppression for repeated goals and a release from suppression for new goals, implicating this specific region in goal representation in adults. In the current study, we used a modified paired repetition suppression design with 9-month-old infants to identify which cortical regions are suppressed when the infant observes a repeated goal versus a new goal. We find a strikingly similar response pattern and location of activity as had been reported in adults; the only brain region displaying significant repetition suppression for repeated goals and a release from suppression for new goals was the left anterior parietal region. Not only does our data suggest that the left anterior parietal region is specialized for representing the goals of others' actions from early in life, this demonstration presents an opportunity to use this method and design to elucidate the debate over the mechanisms and cues which contribute to early action understanding.

Can infants make transitive inferences?

Researchers have long been interested in the emergence of transitive reasoning abilities (e.g., if A>B and B>C, then A>C). Preschool-aged children are found to make transitive inferences. Additionally, nonhuman animals demonstrate parallel abilities, pointing to evolutionary roots of transitive reasoning. The present research examines whether 16-month-old infants can make transitive inferences about other people's preferences. If an agent prefers object-A over B (A>B) and B over C (B>C), infants seem to reason that she also prefers A over C (A>C) (Experiment 1). Experiment 2 provides indirect evidence that a one-directional linear ordering of the three items (A>B>C) may have helped infants to succeed in the task. These and control results present the first piece of evidence that precursors of transitive reasoning cognitive abilities exist in infancy.

Theory of mind in the wild: toward tackling the challenges of everyday mental state reasoning

A complete understanding of the cognitive systems underwriting theory of mind (ToM) abilities requires articulating how mental state representations are generated and processed in everyday situations. Individuals rarely announce their intentions prior to acting, and actions are often consistent with multiple mental states. In order for ToM to operate effectively in such situations, mental state representations should be generated in response to certain actions, even when those actions occur in the presence of mental state content derived from other aspects of the situation. Results from three experiments with preschool children and adults demonstrate that mental state information is indeed generated based on an approach action cue in situations that contain competing mental state information. Further, the frequency with which participants produced or endorsed explanations that include mental states about an approached object decreased when the competing mental state information about a different object was made explicit. This set of experiments provides some of the first steps toward identifying the observable action cues that are used to generate mental state representations in everyday situations and offers insight into how both young children and adults processes multiple mental state representations.

The primacy of social over visual perspective-taking

In this article, we argue for the developmental primacy of social over visual perspective-taking. In our terminology, social perspective-taking involves some understanding of another person's preferences, goals, intentions etc. which can be discerned from temporally extended interactions, including dialog. As is evidenced by their successful performance on various reference disambiguation tasks, infants in their second year of life first begin to develop such skills. They can, for example, determine which of two or more objects another is referring to based on previously expressed preferences or the distinct quality with which these objects were jointly explored. The pattern of findings from developmental research further indicates that this ability emerges sooner than analogous forms of visual perspective-taking. Our explanatory account of this developmental sequence highlights the primary importance of joint attention and the formation of common ground with others. Before children can develop an awareness of what exactly is seen or how an object appears from a particular viewpoint, they must learn to share attention and build common "experiential" ground. Learning about others' as well as one's own "snapshot" perspectives in a literal, i.e., optical sense of the term, is a secondary step that affords an abstraction from all (prior) pragmatic involvement with objects.

Do infants provide evidence that the mirror system is involved in action understanding?

The mirror neuron theory of action understanding makes predictions concerning how the limited motor repertoire of young infants should impact on their ability to interpret others' actions. In line with this theory, an increasing body of research has identified a correlation between infants' abilities to perform an action, and their ability to interpret that action as goal-directed when performed by others. In this paper, I will argue that the infant data does by no means unequivocally support the mirror neuron theory of action understanding and that alternative interpretations of the data should be considered. Furthermore, some of this data can be better interpreted in terms of an alternative view, which holds that the role of the motor system in action perception is more likely to be one of enabling the observer to predict, after a goal has been identified, how that goal will be attained.

Reasoning about instrumental and communicative agency in human infancy

Theoretical rationality and practical rationality are, respectively, properties of an individual's belief system and decision system. While reasoning about instrumental actions complies with practical rationality, understanding communicative actions complies with the principle of relevance. Section 2 reviews the evidence showing that young infants can reason about an agent's instrumental action by representing her subjective motivations and the episodic contents of her epistemic states (including false beliefs). Section 3 reviews the evidence showing special sensitivity in young human infants to some ostensive behavioral signals encoding an agent's communicative intention. We also address the puzzle of imitative learning of novel means actions by 1-year olds and argue that it can be resolved only by assuming that the infant construes the model's demonstration as a communicative, not an instrumental, action. Section 4 reviews the evidence for natural pedagogy, a species-unique social communicative learning mechanism that exploits human infants' receptivity to ostensive-communicative signals and enables infants to acquire kind-wide generalizations from the nonverbal demonstrations of communicative agents. We argue that the essentialist bias that has been shown to be involved in children's concepts of natural kinds also applies to infants' concepts of artifacts. We further examine how natural pedagogy may also boost inductive learning in human infancy.

The nature of goal-directed action representations in infancy

A critical question for developmental psychologists concerns how representations in infancy are best characterized. Past and current research provides paradoxical evidence regarding the nature of early representations: in some ways, infants appear to build concrete and specific representations that guide their online perception and understanding of different events; in other ways, infants appear to possess abstract representations that support inferences regarding unseen event outcomes. Characterizing the nature of early representations across domains is a central charge for developmentalists because this task can provide important information regarding the underlying learning process or processes that drive development. Yet, little existing work has attempted to resolve this paradox by characterizing the ways in which infants' representations may have both abstract and concrete elements. The goal of this chapter is to take a close look at infants' early representations of goal-directed action in order to describe the nature of these representations. We first discuss the nature of representations of action that infants build through acting on the world and argue that these representations possess both concrete and abstract elements. On the one hand, infants appear to build representations of action that stress goal-relevant features of actions in an action- or event-specific fashion, suggesting specificity or concreteness. On the other hand, these representations are sufficiently abstract to not only drive action but also support infants' perception of others actions and to support inferences regarding unseen action outcomes. We next discuss evidence to suggest that by the end of the first year of life, infants possess increasingly abstract representations of the actions of others and use contextual cues, including linguistic statements accompanying action, to flexibly specify the level of representational specificity. We further consider the possibility that language may play a role in infants' ability to build more abstract representations of goal-directed action.

Insights into the origins of knowledge from the cognitive neuroscience of blindness

Children learn about the world through senses such as touch, smell, vision, and audition, but they conceive of the world in terms of objects, events, agents, and their mental states. A fundamental question in cognitive science is how nature and nurture contribute to the development of such conceptual categories. What innate mechanisms do children bring to the learning problem? How does experience contribute to development? In this article we discuss insights into these longstanding questions from cognitive neuroscience studies of blindness. Despite drastically different sensory experiences, behavioural and neuroscientific work suggests that blind children acquire typical concepts of objects, actions, and mental states. Blind people think and talk about these categories in ways that are similar to sighted people. Neuroimaging reveals that blind people make such judgements relying on the same neural mechanisms as sighted people. One way to interpret these findings is that neurocognitive development is largely hardwired, and so differences in experience have little consequence. Contrary to this interpretation, neuroimaging studies also show that blindness profoundly reorganizes the visual system. Most strikingly, developmental blindness enables "visual" circuits to participate in high-level cognitive functions, including language processing. Thus, blindness qualitatively changes sensory representations, but leaves conceptual representations largely unchanged. The effect of sensory experience on concepts is modest, despite the brain's potential for neuroplasticity.

The mentalistic basis of core social cognition: experiments in preverbal infants and a computational model

Evaluating individuals based on their pro- and anti-social behaviors is fundamental to successful human interaction. Recent research suggests that even preverbal infants engage in social evaluation; however, it remains an open question whether infants' judgments are driven uniquely by an analysis of the mental states that motivate others' helpful and unhelpful actions, or whether non-mentalistic inferences are at play. Here we present evidence from 10-month-olds, motivated and supported by a Bayesian computational model, for mentalistic social evaluation in the first year of life.A video abstract of this article can be viewed at http://youtu.be/rD_Ry5oqCYE.

Twelve-month-olds' understanding of intention transfer through communication

Do infants understand that intention can be transferred through communication? We answered this question by examining 12-month-olds' looking times in a violation-of-expectation paradigm with two human agents. In familiarization, the non-acting agent spoke, clapped her hands, read aloud a book, or remained silent before the acting agent grasped one (the target) of two objects. During test only the non-actor remained, grasping either the target or distractor. The infants looked longer in the distractor than target condition, suggesting violation of expectation, only if the non-actor had spoken or clapped in familiarization. Because the non-actor never had grasped any of the objects in familiarization, the infants' expectation on her behavior could have developed from the understanding that her intention was transferred to the actor, who executed it by grasping the target in familiarization, via speaking and clapping as acts of communication (but not reading aloud and remaining silent).

Nine-month-old infants generalize object labels, but not object preferences across individuals

As with all culturally relevant human behaviours, words are meaningful because they are shared by the members of a community. This research investigates whether 9-month-old infants understand this fundamental fact about language. Experiment 1 examined whether infants who are trained on, and subsequently habituated to, a new word-referent link expect the link to be consistent across a second speaker. Experiment 2 examined whether 9-month-old infants distinguish between behaviours that are shared across individuals (i.e. words) from those that are not (i.e. object preferences). The present findings indicate that infants as young as 9 months of age expect new word-referent links, but not object preferences, to be consistent across individuals. Thus, by 9 months, infants have identified at least one of the aspects of human behaviour that is shared across individuals within a community. The implications for children's acquisition of language and culture are discussed.

Nine-months-old infants do not need to know what the agent prefers in order to reason about its goals: on the role of preference and persistence in infants' goal-attribution

Human infants readily interpret others' actions as goal-directed and their understanding of previous goals shapes their expectations about an agent's future goal-directed behavior in a changed situation. According to a recent proposal (Luo & Baillargeon, 2005), infants' goal-attributions are not sufficient to support such expectations if the situational change involves broadening the set of choice-options available to the agent, and the agent's preferences among this broadened set are not known. The present study falsifies this claim by showing that 9-month-olds expect the agent to continue acting towards the previous goal even if additional choice-options become available for which there is no preference-related evidence. We conclude that infants do not need to know about the agent's preferences in order to form expectations about its goal-directed actions. Implications for the role of action persistency and action selectivity are discussed.

Twelve-month-old infants recognize that speech can communicate unobservable intentions

Much of our knowledge is acquired not from direct experience but through the speech of others. Speech allows rapid and efficient transfer of information that is otherwise not directly observable. Do infants recognize that speech, even if unfamiliar, can communicate about an important aspect of the world that cannot be directly observed: a person's intentions? Twelve-month-olds saw a person (the Communicator) attempt but fail to achieve a target action (stacking a ring on a funnel). The Communicator subsequently directed either speech or a nonspeech vocalization to another person (the Recipient) who had not observed the attempts. The Recipient either successfully stacked the ring (Intended outcome), attempted but failed to stack the ring (Observable outcome), or performed a different stacking action (Related outcome). Infants recognized that speech could communicate about unobservable intentions, looking longer at Observable and Related outcomes than the Intended outcome when the Communicator used speech. However, when the Communicator used nonspeech, infants looked equally at the three outcomes. Thus, for 12-month-olds, speech can transfer information about unobservable aspects of the world such as internal mental states, which provides preverbal infants with a tool for acquiring information beyond their immediate experience.

On the spatial foundations of the conceptual system and its enrichment

A theory of how concept formation begins is presented that accounts for conceptual activity in the first year of life, shows how increasing conceptual complexity comes about, and predicts the order in which new types of information accrue to the conceptual system. In a compromise between nativist and empiricist views, it offers a single domain-general mechanism that redescribes attended spatiotemporal information into an iconic form. The outputs of this mechanism consist of types of spatial information that we know infants attend to in the first months of life. These primitives form the initial basis of concept formation, allow explicit preverbal thought, such as recall, inferences, and simple mental problem solving, and support early language learning. The theory details how spatial concepts become associated with bodily feelings of force and trying. It also explains why concepts of emotions, sensory concepts such as color, and theory of mind concepts are necessarily later acquisitions because they lack contact with spatial descriptions to interpret unstructured internal experiences. Finally, commonalities between the concepts of preverbal infants and nonhuman primates are discussed.

Emerging perception of causality in action-and-reaction sequences from 4 to 6 months of age: is it domain-specific?

Two experiments (N=136) studied how 4- to 6-month-olds perceive a simple schematic event, seen as goal-directed action and reaction from 3 years of age. In our causal reaction event, a red square moved toward a blue square, stopping prior to contact. Blue began to move away before red stopped, so that both briefly moved simultaneously at a distance. Primarily, our study sought to determine from what age infants see the causal structure of this reaction event. In addition, we looked at whether this causal percept depends on an animate style of motion and whether it correlates with tasks assessing goal perception and goal-directed action. Infants saw either causal reactions or noncausal delayed control events in which blue started some time after red stopped. These events involved squares that moved either rigidly or nonrigidly in an apparently animate manner. After habituation to one of the four events, infants were tested on reversal of the habituation event. Spatiotemporal features reversed for all events, but causal roles changed only in reversed reactions. The 6-month-olds dishabituated significantly more to reversal of causal reaction events than to noncausal delay events, whereas younger infants reacted similarly to reversal of both. Thus, perceptual causality for reaction events emerges by 6 months of age, a younger age than previously reported but, crucially, the same age at which perceptual causality for launch events has emerged in prior research. On our second question, animate/inanimate motion had no effect at any age, nor did significant correlations emerge with our additional tasks assessing goal perception or goal-directed object retrieval. Available evidence, here and elsewhere, is as compatible with a view that infants initially see A affecting B, without differentiation into physical or psychological causality, as with the standard assumption of distinct physical/psychological causal perception.

Direct and indirect measures of Level-2 perspective-taking in children and adults

Studies with infants show divergence between performance on theory of mind tasks depending on whether direct or indirect measures are used. It has been suggested that direct measures assess a flexible but cognitively demanding ability to reason about the minds of others, whereas indirect measures assess distinct processes which afford more efficient but less flexible theory of mind abilities (Apperly & Butterfill, 2009). This leads to the prediction that performance on indirect measures should be subject to signature limits. The current study tested whether the Level-1/Level-2 distinction might constitute one such limit. The study adapted a task that has shown evidence of Level-1 perspective-taking on both direct and indirect measures (Samson, Apperly, Braithwaite, Andrews, & Bodley-Scott, 2010). The aim was to test Level-2 perspective-taking in a sample of 6- to 11-year-olds (N = 80) and adults (N = 20). Participants were able to make Level-2 judgements on the direct measure. In contrast with the findings from Level-1 perspective-taking, there was no evidence of automatic processing of Level-2 perspectives on the indirect measure. This finding is consistent with the view that theory of mind abilities assessed by indirect measures are subject to signature limits. The Level-1/Level-2 distinction, suitably refined, marks one way in which efficient but inflexible theory of mind abilities are limited.

Do 10-month-old infants understand others' false beliefs?

As adults, we know that others' mental states, such as beliefs, guide their behavior and that these mental states can deviate from reality. Researchers have examined whether young children possess adult-like theory of mind by focusing on their understanding about others' false beliefs. The present research revealed that 10-month-old infants seemed to interpret a person's choice of toys based on her true or false beliefs about which toys were present. These results indicate that like adults, even preverbal infants act as if they can consider others' mental states when making inferences about others' actions.