Actions Seen through Babies' Eyes: A Dissociation between Looking Time and Predictive Gaze

The development of children's and adults' use of kinematic cues for visual anticipation and verbal prediction of action

Expectations about how others' actions unfold in the future are crucial for our everyday social interactions. The current study examined the development of the use of kinematic cues for action anticipation and prediction in 3-year-olds, 4-year-olds, 10-year-olds, and adults in two experiments. Participants observed a hand repeatedly reaching for either a close or far object. The motor kinematics of the hand varied depending on whether the hand reached for the close or far object. We assessed whether participants would use kinematic cues to visually anticipate (Experiment 1; N=98) and verbally predict (Experiment 2; N=80) which object the hand was going to grasp. We found that only adults, but not 3- to 10-year-olds, based their visual anticipations on kinematic cues (Experiment 1). This speaks against claims that action anticipations are based on simulating others' motor processes and instead provides evidence that anticipations are based on perceptual mechanisms. Interestingly, 10-year-olds used kinematic cues to correctly verbally predict the target object, and 4-year-olds learned to do so over the trials (Experiment 2). Thus, kinematic cues are used earlier in life for explicit action predictions than for visual action anticipations. This adds to a recent debate on whether or not an implicit understanding of others' actions precedes their ability to verbally reason about the same actions.

How young children use manifest emotions and dominance cues to understand social rules: a registered report

Given the complexity of human social life, it is astonishing to observe how quickly children adapt to their social environment. To be accepted by the other members, it is crucial to understand and follow the rules and norms shared by the group. How and from whom do young children learn these social rules? In the experiments, based on the crucial role of affective social learning and dominance hierarchies in simple rule understanding, we showed 15-to-23-month-olds and 3-to-5-year-old children videos where the agents' body size and affective cues were manipulated. In the dominant rule-maker condition, when a smaller protagonist puts an object in one location, a bigger agent reacts with a positive reaction; on the contrary, when the smaller protagonist puts an object in another location, the bigger agent displays a negative reaction. In the subordinate rule-maker condition, the roles are shifted but the agents differ. Toddlers expect the protagonist to follow the rules (based on anticipatory looks), independent of the dominant status of the rule-making agent. Three-to-five-year-old pre-schoolers overall perform at the chance level but expect the protagonist to disobey a rule in the first trial, and obey the rule in the second trial if the rule-maker is dominant.

What is in an action? Preschool children predict that agents take previous paths and not previous goals

Developmental science has experienced a vivid debate on whether young children prioritize goals over means in their prediction of others' actions. Influential developmental theories highlight the role of goal objects for action understanding. Yet, recent infant studies report evidence for the opposite. The empirical evidence is therefore inconclusive. The current study advanced this debate by assessing preschool children's verbal predictions of others' actions. In five experiments (N = 302), we investigated whether preschool children and adults predict agents to move towards their previous goal (that is, show goal-related predictions) or predict agents to move along the same movement path that they pursued before. While Experiments 1a, 1b and 1c presented young children and adults with animated agents, Experiments 2a and 2b presented participants with human grasping action. An integrative analysis across experiments revealed that children were more likely to predict the agent to move along the same movement path, Z = -4.574, p ≤ 0.0001 (r = 0.304). That is, preschool children were more likely to predict that agents would move along the same trajectory even though this action would lead to a new goal object. Thus, our findings suggest that young children's action prediction relies on the detection of spatial and movement information. Overall, we discuss our findings in terms of theoretical frameworks that conceive of action understanding as an umbrella term that comprises different forms and facets in which humans understand others' actions. RESEARCH HIGHLIGHTS: We investigated whether preschool children predict agents to move towards their previous goal or to move along the same movement path that they pursued before. Unlike adults, preschool children predicted that agents would move along the same trajectory even though this action would lead to a new goal. Adults' goal-based predictions were affected from contextual details, whereas children systematically made path-based predictions. Young children's action prediction relies on the detection of spatial and movement information.

Do dogs preferentially encode the identity of the target object or the location of others' actions?

The ability to make sense of and predict others' actions is foundational for many socio-cognitive abilities. Dogs (Canis familiaris) constitute interesting comparative models for the study of action perception due to their marked sensitivity to human actions. We tested companion dogs (N = 21) in two screen-based eye-tracking experiments, adopting a task previously used with human infants and apes, to assess which aspects of an agent's action dogs consider relevant to the agent's underlying intentions. An agent was shown repeatedly acting upon the same one of two objects, positioned in the same location. We then presented the objects in swapped locations and the agent approached the objects centrally (Experiment 1) or the old object in the new location or the new object in the old location (Experiment 2). Dogs' anticipatory fixations and looking times did not reflect an expectation that agents should have continued approaching the same object nor the same location as witnessed during the brief familiarization phase; this contrasts with some findings with infants and apes, but aligns with findings in younger infants before they have sufficient motor experience with the observed action. However, dogs' pupil dilation and latency to make an anticipatory fixation suggested that, if anything, dogs expected the agents to keep approaching the same location rather than the same object, and their looking times showed sensitivity to the animacy of the agents. We conclude that dogs, lacking motor experience with the observed actions of grasping or kicking performed by a human or inanimate agent, might interpret such actions as directed toward a specific location rather than a specific object. Future research will need to further probe the suitability of anticipatory looking as measure of dogs' socio-cognitive abilities given differences between the visual systems of dogs and primates.

The use of gaze to study cognition: limitations, solutions, and applications to animal welfare

The study of gaze responses, typically using looking time paradigms, has become a popular approach to improving our understanding of cognitive processes in non-verbal individuals. Our interpretation of data derived from these paradigms, however, is constrained by how we conceptually and methodologically approach these problems. In this perspective paper, we outline the application of gaze studies in comparative cognitive and behavioral research and highlight current limitations in the interpretation of commonly used paradigms. Further, we propose potential solutions, including improvements to current experimental approaches, as well as broad-scale benefits of technology and collaboration. Finally, we outline the potential benefits of studying gaze responses from an animal welfare perspective. We advocate the implementation of these proposals across the field of animal behavior and cognition to aid experimental validity, and further advance our knowledge on a variety of cognitive processes and welfare outcomes.

Beyond Infant's Looking: The Neural Basis for Infant Prediction Errors

Contemporary conceptualizations on infant cognitive development focus on predictive processes; the basic idea is that the brain continuously creates predictions about what is expected and that the divergence between predicted and actual perceived data yields a prediction error. This prediction error updates the model from which the predictions are generated and therefore is a basic mechanism for learning and adaptation to the dynamics of the ever-changing environment. In this article, we review the types of available empirical evidence supporting the idea that predictive processes can be found in infancy, especially emphasizing the contribution of electrophysiology as a potential method for testing the similarity of the brain mechanisms for processing prediction errors in infants to those of adults. In infants, as with older children, adolescents, and adults, predictions involve synchronization bursts of middle-central theta reflecting brain activity in the anterior cingulate cortex. We discuss how early in development such brain mechanisms develop and open questions that still remain to be empirically investigated.

Spelling out some unaddressed conceptual and methodological challenges in empirical lifespan research

The importance of taking a lifespan approach to describe and understand human development has long been acknowledged (e.g., Baltes, 1987). Nevertheless, theoretical or empirical research that actually encompasses the entire lifespan, that is, from early childhood to old age, is rare. This is not surprising given the challenges such an approach entails. Many of these challenges (e.g., establishing measurement invariance between age groups) have been addressed in the previous literature, but others have not yet been sufficiently considered. The main purpose of this article is to present several examples of such largely unaddressed conceptual and methodological challenges and reflect upon possible ways to address them. We discuss the usefulness of a lifespan approach and the generalization of the challenges to other research comparing different groups, such as gender, culture, or species.

Emergent Goal-Anticipatory Gaze in Infants via Event-Predictive Learning and Inference

From about 7 months of age onward, infants start to reliably fixate the goal of an observed action, such as a grasp, before the action is complete. The available research has identified a variety of factors that influence such goal-anticipatory gaze shifts, including the experience with the shown action events and familiarity with the observed agents. However, the underlying cognitive processes are still heavily debated. We propose that our minds (i) tend to structure sensorimotor dynamics into probabilistic, generative event-predictive, and event boundary predictive models, and, meanwhile, (ii) choose actions with the objective to minimize predicted uncertainty. We implement this proposition by means of event-predictive learning and active inference. The implemented learning mechanism induces an inductive, event-predictive bias, thus developing schematic encodings of experienced events and event boundaries. The implemented active inference principle chooses actions by aiming at minimizing expected future uncertainty. We train our system on multiple object-manipulation events. As a result, the generation of goal-anticipatory gaze shifts emerges while learning about object manipulations: the model starts fixating the inferred goal already at the start of an observed event after having sampled some experience with possible events and when a familiar agent (i.e., a hand) is involved. Meanwhile, the model keeps reactively tracking an unfamiliar agent (i.e., a mechanical claw) that is performing the same movement. We qualitatively compare these modeling results to behavioral data of infants and conclude that event-predictive learning combined with active inference may be critical for eliciting goal-anticipatory gaze behavior in infants.

Adults, but not preschoolers or toddlers integrate situational constraints in their action anticipations: a developmental study on the flexibility of anticipatory gaze

Recent theories stress the role of situational information in understanding others' behaviour. For example, the predictive coding framework assumes that people take contextual information into account when anticipating other's actions. Likewise, the teleological stance theory assumes an early developing ability to consider situational constraints in action prediction. The current study investigates, over a wide age range, whether humans flexibly integrate situational constraints in their action anticipations. By means of an eye-tracking experiment, 2-year-olds, 5-year-olds, younger and older adults (together N = 181) observed an agent repeatedly taking one of two paths to reach a goal. Then, this path became blocked, and for test trials only the other path was passable. Results demonstrated that in test trials younger and older adults anticipated that the agent would take the continuous path, indicating that they took the situational constraints into account. In contrast, 2- and 5-year-olds anticipated that the agent would take the blocked path, indicating that they still relied on the agent's previous observed behaviour and-contrary to claims by the teleological stance theory-did not take the situational constraints into account. The results highlight developmental changes in human's ability to include situational constraints in their visual anticipations. Overall, the study contributes to theories on predictive coding and the development of action understanding.

Let's get it together: Infants generate visual predictions based on collaborative goals

Infants engage in social interactions that include multiple partners from very early in development. A growing body of research shows that infants visually predict the outcomes of an individual's intentional actions, such as a person reaching towards an object (e.g., Krogh-Jespersen & Woodward, 2014), and even show sophistication in their predictions regarding failed actions (e.g., Brandone, Horwitz, Aslin, & Wellman, 2014). Less is known about infants' understanding of actions involving more than one individual (e.g., collaborative actions), which require representing each partners' actions in light of the shared goal. Using eye-tracking, Study 1 examined whether 14-month-old infants visually predict the actions of an individual based on her previously shared goal. Infants viewed videos of two women engaged in either a collaborative or noncollaborative interaction. At test, only one woman was present and infants' visual predictions regarding her future actions were measured. Fourteen-month-olds anticipated an individual's future actions based on her past collaborative behavior. Study 2 revealed that 11-month-old infants only visually predict higher-order shared goals after engaging in a collaborative intervention. Together, our results indicate that by the second year after birth, infants perceive others' collaborative actions as structured by shared goals and that active engagement in collaboration strengthens this understanding in young infants.

Six-Month-Old Infants Predict Agents' Goal-Directed Actions on Occluded Objects

Infants can infer agents' goals after observing agents' goal-directed actions on objects and can subsequently make predictions about how agents will act on objects in the future. We investigated the representations supporting these predictions. We familiarized 6-month-old infants to an agent who preferentially reached for one of two featurally distinct objects following a cue. At test, the objects were sequentially occluded from the infant in the agent's presence. We asked whether infants could generate action predictions without visual access to the relevant objects by measuring whether infants shifted their gaze to the location of the agent's hidden goal object following the cue. We also examined what infants represented about the hidden objects by removing one of the occluders to reveal either the original hidden object or the unexpected other object and measuring infants' looking time. We found that, even without visual access to the objects, infants made predictive gazes to the location of the agent's occluded goal object, but failed to represent the features of either hidden object. These results suggest that infants make goal-based action predictions when the relevant objects in the scene are occluded, but doing so may come at the expense of maintaining representations of the objects.

Visual attention and action: How cueing, direct mapping, and social interactions drive orienting

Despite considerable interest in both action perception and social attention over the last 2 decades, there has been surprisingly little investigation concerning how the manual actions of other humans orient visual attention. The present review draws together studies that have measured the orienting of attention, following observation of another's goal-directed action. Our review proposes that, in line with the literature on eye gaze, action is a particularly strong orienting cue for the visual system. However, we additionally suggest that action may orient visual attention using mechanisms, which gaze direction does not (i.e., neural direct mapping and corepresentation). Finally, we review the implications of these gaze-independent mechanisms for the study of attention to action. We suggest that our understanding of attention to action may benefit from being studied in the context of joint action paradigms, where the role of higher level action goals and social factors can be investigated.

Reaching the goal: Active experience facilitates 8-month-old infants' prospective analysis of goal-based actions

From early in development, infants view others' actions as structured by intentions, and this action knowledge may be supported by shared action production/perception systems. Because the motor system is inherently prospective, infants' understanding of goal-directed actions should support predictions of others' future actions, yet little is known about the nature and developmental origins of this ability, specifically whether young infants use the goal-directed nature of an action to rapidly predict future social behaviors and whether their action experience influences this ability. Across three conditions, we varied the level of action experience infants engaged in to determine whether motor priming influenced infants' ability to generate rapid social predictions. Results revealed that young infants accurately generated goal-based visual predictions when they had previously been reaching for objects; however, infants who passively observed a demonstration were less successful. Further analyses showed that engaging the cognitively based prediction system to generate goal-based predictions following motor engagement resulted in slower latencies to predict, suggesting that these smart predictions take more time to deploy. Thus, 8-month-old infants may have motor representations of goal-directed actions, yet this is not sufficient for them to predict others' actions; rather, their own action experience supports the ability to rapidly implement knowledge to predict future behavior.

Action Prediction Allows Hypothesis Testing via Internal Forward Models at 6 Months of Age

We propose that action prediction provides a cornerstone in a learning process known as internal forward models. According to this suggestion infants' predictions (looking to the mouth of someone moving a spoon upward) will moments later be validated or proven false (spoon was in fact directed toward a bowl), information that is directly perceived as the distance between the predicted and actual goal. Using an individual difference approach we demonstrate that action prediction correlates with the tendency to react with surprise when social interactions are not acted out as expected (action evaluation). This association is demonstrated across tasks and in a large sample (n = 118) at 6 months of age. These results provide the first indication that infants might rely on internal forward models to structure their social world. Additional analysis, consistent with prior work and assumptions from embodied cognition, demonstrates that the latency of infants' action predictions correlate with the infant's own manual proficiency.

Statistical learning in social action contexts

Sensitivity to the regularities and structure contained within sequential, goal-directed actions is an important building block for generating expectations about the actions we observe. Until now, research on statistical learning for actions has solely focused on individual action sequences, but many actions in daily life involve multiple actors in various interaction contexts. The current study is the first to investigate the role of statistical learning in tracking regularities between actions performed by different actors, and whether the social context characterizing their interaction influences learning. That is, are observers more likely to track regularities across actors if they are perceived as acting jointly as opposed to in parallel? We tested adults and toddlers to explore whether social context guides statistical learning and-if so-whether it does so from early in development. In a between-subjects eye-tracking experiment, participants were primed with a social context cue between two actors who either shared a goal of playing together ('Joint' condition) or stated the intention to act alone ('Parallel' condition). In subsequent videos, the actors performed sequential actions in which, for certain action pairs, the first actor's action reliably predicted the second actor's action. We analyzed predictive eye movements to upcoming actions as a measure of learning, and found that both adults and toddlers learned the statistical regularities across actors when their actions caused an effect. Further, adults with high statistical learning performance were sensitive to social context: those who observed actors with a shared goal were more likely to correctly predict upcoming actions. In contrast, there was no effect of social context in the toddler group, regardless of learning performance. These findings shed light on how adults and toddlers perceive statistical regularities across actors depending on the nature of the observed social situation and the resulting effects.

Infants' use of movement synchrony to infer social affiliation in others

Infants socially engage with others and observe others' social interactions from early in life. One characteristic found to be important for signaling and establishing affiliative social relationships is physical coordination and synchronization of movements. This study investigated whether synchrony in others' movements signals affiliation to 12- and 15-month-old infants. The infants were shown a scene in which two characters moved either synchronously or non-synchronously with a third character in the center. Next, the center character made an affiliation declaration and subsequently approached and cuddled one of the two characters. Using measures of gaze, we gauged infants' inferences about whom the center character would affiliate with before the cuddling took place. We found that 15-month-olds, but not 12-month-olds, inferred that the center character would affiliate with the previously synchronous character, suggesting that they can make inferences about others' affiliation based on movement synchrony. The findings are discussed in terms of their relevance to the infants' personal preferences and the potential importance of first-person experience in the development of social cognition.

Infants' Looking to Surprising Events: When Eye-Tracking Reveals More than Looking Time

Research on infants' reasoning abilities often rely on looking times, which are longer to surprising and unexpected visual scenes compared to unsurprising and expected ones. Few researchers have examined more precise visual scanning patterns in these scenes, and so, here, we recorded 8- to 11-month-olds' gaze with an eye tracker as we presented a sampling event whose outcome was either surprising, neutral, or unsurprising: A red (or yellow) ball was drawn from one of three visible containers populated 0%, 50%, or 100% with identically colored balls. When measuring looking time to the whole scene, infants were insensitive to the likelihood of the sampling event, replicating failures in similar paradigms. Nevertheless, a new analysis of visual scanning showed that infants did spend more time fixating specific areas-of-interest as a function of the event likelihood. The drawn ball and its associated container attracted more looking than the other containers in the 0% condition, but this pattern was weaker in the 50% condition, and even less strong in the 100% condition. Results suggest that measuring where infants look may be more sensitive than simply how much looking there is to the whole scene. The advantages of eye tracking measures over traditional looking measures are discussed.

Predictive action tracking without motor experience in 8-month-old infants

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Can infants predictively track the kinematics of actions outside their motor repertoire?

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Pre-walking infants predictively tracked upright, but not inverted stepping actions.

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Sensorimotor cortex was activated more when infants observed upright stepping actions.

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Motor experience is not necessary for predictive tracking of action kinematics.

A popular idea in cognitive neuroscience is that to predict others’ actions, observers need to map those actions onto their own motor repertoire. If this is true, infants with a relatively limited motor repertoire should be unable to predict actions with which they have no previous motor experience. We investigated this idea by presenting pre-walking infants with videos of upright and inverted stepping actions that were briefly occluded from view, followed by either a correct (time-coherent) or an incorrect (time-incoherent) continuation of the action (Experiment 1). Pre-walking infants looked significantly longer to the still frame after the incorrect compared to the correct continuations of the upright, but not the inverted stepping actions. This demonstrates that motor experience is not necessary for predictive tracking of action kinematics. In a follow-up study (Experiment 2), we investigated sensorimotor cortex activation as a neural indication of predictive action tracking in another group of pre-walking infants. Infants showed significantly more sensorimotor cortex activation during the occlusion of the upright stepping actions that the infants in Experiment 1 could predictively track, than during the occlusion of the inverted stepping actions that the infants in Experiment 1 could not predictively track. Taken together, these findings are inconsistent with the idea that motor experience is necessary for the predictive tracking of action kinematics, and suggest that infants may be able to use their extensive experience with observing others’ actions to generate real-time action predictions.

Action perception in infancy: the plasticity of 7-month-olds' attention to grasping actions

The present study investigates the plasticity of 7-month-old infants' orienting of attention during their perception of grasping actions. Previous research has shown that when infants observe a grasping hand, they shift their attention in line with the grasping direction, which is indicated by a reliable priming effect in this direction. The mechanisms behind this priming effect are largely unknown, and it is unclear how malleable this priming effect is with respect to a brief exposure to novel action-target contingencies. In a spatial-cueing paradigm, we presented a series of training trials prior to a series of test trials. These training sequences significantly modulated infants' attention. This suggests that action perception, when assessed through shifts of attention, is not solely based on the infants' grasping experience but quickly adapts to context-specific observed regularities.

Measuring action understanding: Relations between goal prediction and imitation

We explored the developmental course of goal prediction and imitation as two commonly used measures of action understanding. In particular, we investigated the relationships between the measures in two complex multistep actions (hammering and pulling action) in children between 12 and 30 months (n = 64) in a between-subjects design. The results showed that the prediction of an action goal was related to the imitation in the hammering action, but not in the pulling action. The results are discussed in the light of current theories on goal prediction and imitation.

Eye Movements During Action Observation

An important element in social interactions is predicting the goals of others, including the goals of others' manual actions. Over a decade ago, Flanagan and Johansson demonstrated that, when observing other people reaching for objects, the observer's gaze arrives at the goal before the action is completed. Moreover, those authors proposed that this behavior was mediated by an embodied process, which takes advantage of the observer's motor knowledge. Here, we scrutinize work that has followed that seminal article. We include studies on adults that have used combined eye tracking and transcranial magnetic stimulation technologies to test causal hypotheses about underlying brain circuits. We also include developmental studies on human infants. We conclude that, although several aspects of the embodied process of predictive eye movements remain to be clarified, current evidence strongly suggests that the motor system plays a causal role in guiding predictive gaze shifts that focus on another person's future goal. The early emergence of the predictive gaze in infant development underlines its importance for social cognition and interaction.

Eighteen-month-olds' memory interference and distraction in a modified A-not-B task is not associated with their anticipatory looking in a false-belief task

Infants’ performance in non-verbal false-belief tasks is often interpreted as if they have understood false beliefs. This view has been questioned by a recent account that explains infants’ performance in non-verbal false-belief tasks as the result of susceptibility to memory interference and distraction. We tested this alternative account by investigating the relationship between infants’ false-belief understanding, susceptibility to memory interference and distraction, and general cognitive development in 18-month-old infants (N = 22). False-belief understanding was tested in an anticipatory looking paradigm of a standard false-belief task. Susceptibility to memory interference and distraction was tested in a modified A-not-B task. Cognitive development was measured via the Mental Scale of the Bayley Scales of Infant Development. We did not find any relationship between infants’ performance in the false-belief task and the A-not-B task, even after controlling for cognitive development. This study shows that there is no ubiquitous relation between susceptibility to memory interference and distraction and performance in a false-belief task in infancy.

The Microstructure of Action Perception in Infancy: Decomposing the Temporal Structure of Social Information Processing

In this article, we review recent evidence of infants' early competence in perceiving and interpreting the actions of others. We present a theoretical model that decomposes the timeline of action perception into a series of distinct processes that occur in a particular order. Once an agent is detected, covert attention can be allocated to the future state of the agent (priming), which may lead to overt gaze shifts that predict goals (prediction). Once these goals are achieved, the consequence of the agents' actions and the manner in which the actions were performed can be evaluated (evaluation). We propose that all of these processes have unique requirements, both in terms of timing and cognitive resources. To understand more fully the rich social world of infants, we need to pay more attention to the temporal structure of social perception and ask what information is available to infants and how this changes over time.

Perception of individual and joint action in infants and adults

Infants and adults frequently observe actions performed jointly by more than one person. Research in action perception, however, has focused largely on actions performed by an individual person. Here, we explore how 9- and 12-month-old infants and adults perceive a block-stacking action performed by either one agent (individual condition) or two agents (joint condition). We used eye tracking to measure the latency of participants' gaze shifts towards action goals. Adults anticipated goals in both conditions significantly faster than infants, and their gaze latencies did not differ between conditions. By contrast, infants showed faster anticipation of goals in the individual condition than in the joint condition. This difference was more pronounced in 9-month-olds. Further analyses of fixations examined the role of visual attention in action perception. These findings are cautiously interpreted in terms of low-level processing in infants and higher-level processing in adults. More precisely, our results suggest that adults are able to infer the overarching joint goal of two agents, whereas infants are not yet able to do so and might rely primarily on visual cues to infer the respective sub-goals. In conclusion, our findings indicate that the perception of joint action in infants develops differentially from that of individual action.

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.

What are you doing? How active and observational experience shape infants' action understanding

From early in life, infants watch other people's actions. How do young infants come to make sense of actions they observe? Here, we review empirical findings on the development of action understanding in infancy. Based on this review, we argue that active action experience is crucial for infants' developing action understanding. When infants execute actions, they form associations between motor acts and the sensory consequences of these acts. When infants subsequently observe these actions in others, they can use their motor system to predict the outcome of the ongoing actions. Also, infants come to an understanding of others' actions through the repeated observation of actions and the effects associated with them. In their daily lives, infants have plenty of opportunities to form associations between observed events and learn about statistical regularities of others' behaviours. We argue that based on these two forms of experience-active action experience and observational experience-infants gradually develop more complex action understanding capabilities.

Belief-based action prediction in preverbal infants

Successful mindreading entails both the ability to think about what others know or believe, and to use this knowledge to generate predictions about how mental states will influence behavior. While previous studies have demonstrated that young infants are sensitive to others' mental states, there continues to be much debate concerning how to characterize early theory of mind abilities. In the current study, we asked whether 6-month-old infants appreciate the causal role that beliefs play in action. Specifically, we tested whether infants generate action predictions that are appropriate given an agent's current belief. We exploited a novel, neural indication of action prediction: motor cortex activation as measured by sensorimotor alpha suppression, to ask whether infants would generate differential predictions depending on an agent's belief. After first verifying our paradigm and measure with a group of adult participants, we found that when an agent had a false belief that a ball was in the box, motor activity indicated that infants predicted she would reach for the box, but when the agent had a false belief that a ball was not in the box, infants did not predict that she would act. In both cases, infants based their predictions on what the agent, rather than the infant, believed to be the case, suggesting that by 6months of age, infants can exploit their sensitivity to other minds for action prediction.

Perception of conversations: the importance of semantics and intonation in children's development

In conversations, adults readily detect and anticipate the end of a speaker's turn. However, little is known about the development of this ability. We addressed two important aspects involved in the perception of conversational turn taking: semantic content and intonational form. The influence of semantics was investigated by testing prelinguistic and linguistic children. The influence of intonation was tested by presenting participants with videos of two dyadic conversations: one with normal intonation and one with flattened (removed) intonation. Children of four different age groups--two prelinguistic groups (6- and 12-month-olds) and two linguistic groups (24- and 36-month-olds)--and an adult group participated. Their eye movements were recorded, and the frequency of anticipated turns was analyzed. Our results show that (a) the anticipation of turns was reliable only in 3-year-olds and adults, with younger children shifting their gaze between speakers regardless of the turn taking, and (b) only 3-year-olds anticipated turns better if intonation was normal. These results indicate that children anticipate turns in conversations in a manner comparable (but not identical) to adults only after they have developed a sophisticated understanding of language. In contrast to adults, 3-year-olds rely more strongly on prosodic information during the perception of conversational turn taking.

Infants use social context to bind actions into a collaborative sequence

Eye tracking was used to show that 18-month-old infants are sensitive to social context as a sign that others' actions are bound together as a collaborative sequence based on a joint goal. Infants observed five identical demonstrations in which Actor 1 moved a block to one location and Actor 2 moved the same block to a new location, creating a sequence of actions that could be considered either individual actions or collaboration. In the test phase, Actor 1 was alone and sitting so that she could reach both locations. The question was whether she would place a new block in the location she had previously (individual goal) or in the location that could be considered the goal of collaboration (joint goal). Importantly, in the Social condition, the actors were socially engaged with each other before and during the demonstration, while in the Non-Social condition, they were not. Results revealed that infants in the Social condition spontaneously anticipated Actor 1 placing her block in the joint goal location more often than those in the Non-Social condition. Thus, the social context seems to allow infants to bind actions into a collaborative sequence and anticipate joint rather than individual goals, giving insight into how actions are perceived using top-down processing early in life.

Examining implicit metacognition in 3.5-year-old children: an eye-tracking and pupillometric study

The current study examined early signs of implicit metacognitive monitoring in 3.5-year-old children. During a learning phase children had to learn paired associates. In the test phase, children performed a recognition task and choose the correct associate for a given target among four possible answers. Subsequently, children's explicit confidence judgments (CJs) and their fixation time allocation at the confidence scale were assessed. Analyses showed that explicit CJs did not differ for remembered compared to non-remembered items. In contrast, children's fixation patterns on the confidence scale were affected by the correctness of their memory, as children looked longer to high confidence ratings when they correctly remembered the associated item. Moreover, analyses of pupil size revealed pupil dilations for correctly remembered, but not incorrectly remembered items. The results converge with recent behavioral findings that reported evidence for implicit metacognitive memory monitoring processes in 3.5-year-old children. The study suggests that implicit metacognitive abilities might precede the development of explicit metacognitive knowledge.

Infants generate goal-based action predictions

Predicting the actions of others is critical to smooth social interactions. Prior work suggests that both understanding and anticipation of goal-directed actions appears early in development. In this study, on-line goal prediction was tested explicitly using an adaptation of Woodward's (1998) paradigm for an eye-tracking task. Twenty 11-month-olds were familiarized to movie clips of a hand reaching to grasp one of two objects. Then object locations were swapped, and the hand made an incomplete reach between the objects. Here, infants reliably made their first look from the hand to the familiarized goal object, now in a new location. A separate control condition of 20 infants familiarized to the same movements of an unfamiliar claw revealed the opposite pattern: reliable prediction to the familiarized location, rather than the familiarized object. This study suggests that by 11 months infants actively use goal analysis to generate on-line predictions of an agent's next action.