Inferring the size of a goal object from an actor's grasping movement in 6‐ and 9‐month‐old infants

The present study applied a preferential looking paradigm to test whether 6‐ and 9‐month old infants are able to infer the size of a goal object from an actor's grasping movement. The target object was a cup with the handle rotated either towards or away from the actor. In two experiments, infants saw the video of an actor's grasping movement towards an occluded target object. The aperture size of the actor's hand was varied as between‐subjects factor. Subsequently, two final states of the grasping movement were presented simultaneously with the occluder being removed. In Experiment 1, the expected final state showed the actor's hand holding a cup in a way that would be expected after the performed grasping movement. In the unexpected final state, the actor's hand held the cup at the side which would be unexpected after the performed grasping movement. Results show that 6‐ as well as 9‐month‐olds looked longer at the unexpected than at the expected final state. Experiment 2 excluded an alternative explanation of these findings, namely that the discrimination of the final states was due to geometrical familiarity or novelty of the final states. These findings provide evidence that infants are able to infer the size of a goal object from the aperture size of the actor's hand during the grasp.     

The effects of adults' affective expression and direction of visual gaze on 12‐month‐olds' visual preferences for an object following a 5‐minute, 1‐day,or 1‐month delay

Between 12‐ and 14 months of age infants begin to use another's direction of gaze and affective expression in learning about various objects and events. What is not well understood is how long infants' behaviour towards a previously unfamiliar object continues to be influenced following their participation in circumstances of social referencing. In this experiment, we examined infants' sensitivity to an adult's direction of gaze and their visual preference for one of two objects following a 5‐min, 1‐day, or 1‐month delay. Ninety‐six 12‐month‐olds participated. For half of the infants during habituation (i.e., familiarization), the adults' direction of gaze was directed towards an unfamiliar object (look condition). For the remaining half of the infants during habituation, the adults' direction of gaze was directed away from the unfamiliar object (look‐away condition). All infants were habituated to two events. One event consisted of an adult looking towards (look condition) or away from (look‐away condition) an object while facially and vocally conveying a positive affective expression. The second event consisted of the same adult looking towards or away from a different object while conveying a disgusted affective expression. Following the habituation phase and a 5‐min, 1‐day, or 1‐month delay, infants' visual preference was assessed. During the visual preference phase, infants saw the two objects side by side where the adult conveying the affective expression was not visible. Results of the visual preference phase indicate that infants in the look condition showed a significant preference for object previously paired with the positive affect following a 5‐min and 1‐day delay. No significant visual preference was found in the look condition following a 1‐month delay. No significant preferences were found at any retention interval in the look‐away condition. Results are discussed in terms of early learning, social referencing, and early memory.     

The distribution of infant attention during object examination

The distribution of attention during toy play was studied in 6‐, 9‐ and 12‐month‐old infants. Heart rate and behavior measures of attention were collected as the infants interacted with objects. There was a large deceleration of heart rate at the beginning of behaviorally defined focused attention, but little heart rate change for looks that only had behaviorally defined casual attention. Heart‐rate‐defined sustained attention occurred more frequently at the transition from the first instance of casual attention within a look to focused attention and during the cycling between subsequent epochs of casual and focused attention. These results show that heart rate and behavioral measures of attention are closely related in young infants at the beginning and end of object interaction but are inconsistently related within a single look at an object.     

Joint attention and object learning in 5‐ and 7‐month‐old infants

We examined the effects of joint attention for object learning in 5‐ and 7‐month‐old infants. Infants interacted with an adult social partner who taught them about a novel toy in two conditions. In the Joint Attention condition, the adult spoke about the toy while alternating gaze between the infant and the toy, while in the Object Only condition, the adult looked to the toy and to a spot on the ceiling, but never at the infant. In the test trials following each social interaction, we presented infants with the ‘familiarization’ toy and a novel toy, and monitored looking times to each object. We found that 7‐month‐olds looked significantly longer to the novel toy following the Joint Attention relative to the Object Only condition, while 5‐month‐old infants did not show a significant difference across conditions. We interpret these results to suggest that joint attention facilitated 7‐month‐old infants' encoding of information about the familiarization object. Implications for the ontogeny of infant learning in joint attention contexts are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

See and be seen: Infant–caregiver social looking during locomotor free play

Face‐to‐face interaction between infants and their caregivers is a mainstay of developmental research. However, common laboratory paradigms for studying dyadic interaction oversimplify the act of looking at the partner's face by seating infants and caregivers face to face in stationary positions. In less constrained conditions when both partners are freely mobile, infants and caregivers must move their heads and bodies to look at each other. We hypothesized that face looking and mutual gaze for each member of the dyad would decrease with increased motor costs of looking. To test this hypothesis, 12‐month‐old crawling and walking infants and their parents wore head‐mounted eye trackers to record eye movements of each member of the dyad during locomotor free play in a large toy‐filled playroom. Findings revealed that increased motor costs decreased face looking and mutual gaze: Each partner looked less at the other's face when their own posture or the other's posture required more motor effort to gain visual access to the other's face. Caregivers mirrored infants' posture by spending more time down on the ground when infants were prone, perhaps to facilitate face looking. Infants looked more at toys than at their caregiver's face, but caregivers looked at their infant's face and at toys in equal amounts. Furthermore, infants looked less at toys and faces compared to studies that used stationary tasks, suggesting that the attentional demands differ in an unconstrained locomotor task. Taken together, findings indicate that ever‐changing motor constraints affect real‐life social looking.     

Action experience alters 3-month-old infants' perception of others' actions

An intervention facilitated 3-month-old infants' apprehension of objects either prior to (reach first), or after (watch first) viewing another person grasp similar objects in a visual habituation procedure. Action experience facilitated action perception: reach-first infants focused on the relation between the actor and her goal, but watch-first infants did not. Infants' sensitivity to the actor's goal was correlated with their engagement in object-directed contact with the toys. These findings indicate that infants can rapidly form goal-based action representations and suggest a developmental link between infants' goal directed actions and their ability to detect goals in the actions of others.     

10‐month‐old infants’ inference of invisible agent: Distinction in causality between object motion and human action1

Abstract: Two habituation experiments investigated 10‐month‐old infants’ interpretation of events where a stationary object began to move without any visible causes. During habituation, infants saw that an object partly hidden by an occluder began to move away from the occluder. Then, they were tested with three test events without the occluder: the ?rst event showed a hand pushing the object, the second event showed a hand failing to touch the object, and the last event had no agent. The objects were a ball in Experiment 1, and a person in Experiment 2. The test event that the infants looked at for the shortest duration in Experiment 1 was where the hand pushed the ball, whereas they looked at the three test events almost equal amounts of time in Experiment 2. These results indicate that 10‐month‐old infants responded to the events in terms of causality and could infer the presence of the agent behind the occluder only when they saw the habituation event featuring the ball.     

Two rooms,two representations? Episodic‐like memory in toddlers and preschoolers

Episodic memory involves binding together what‐where‐when associations. In three experiments, we tested the development of memory for such contextual associations in a naturalistic setting. Children searched for toys in two rooms with two different experimenters; each room contained two identical sets of four containers, but arranged differently. A distinct toy was hidden in a distinct container in each room. In Experiment 1, which involved children between 15 and 26 months who were prompted with a very explicit cue (a part of the hidden toy), we found a marked shift in performance with age: while 15‐ to 20‐month‐olds concentrated their searches on the two containers that sometimes contained toys, they did not distinguish between them according to context, but 21–26‐month‐olds did. However, surprisingly, without toy cues, even the youngest children showed a fragile ability to disambiguate the two containers by room context. In Experiment 2, we tested 34‐ to 40‐month‐olds and 64‐ to 72‐month‐olds without toy cues. The 5‐year‐olds were nearly perfect, and the 3‐year‐olds showed a significant preference for the correct container given only the context. In Experiment 3, we filled in the age range, and also investigated the effects of the use of labels (i.e. names of experimenters and rooms) and of familiarization time, in groups of 34‐ to 40‐month‐olds, 42‐ to 48‐month‐olds, and 50‐ to 56‐month‐olds. Neither labels nor familiarization time had an effect. Across experiments, there was regular age‐related improvement in context‐based memory. Overall, the results suggest that children's episodic memory may undergo an early qualitative change, yet to be precisely characterized, and that continuing increments in the use of contextual cues occur throughout the preschool period. A video abstract of this article can be viewed at https://www.youtube.com/watch?v=DkwEFw0UEz4&list=PLwxXcOKHPC0llAPVcJyW4EtzlA934A2Rz&index=1     

To see or not to see: infants prefer to follow the gaze of a reliable looker

In two experiments, we examined whether 14‐month‐olds understand the subjective nature of gaze. In the first experiment, infants first observed an experimenter express happiness as she looked inside a container that either contained a toy (reliable looker condition) or was empty (unreliable looker condition). Then, infants had to follow the same experimenter's gaze to a target object located either behind or in front of a barrier. Infants in the reliable looker condition followed the experimenter's gaze behind the barrier more often than infants in the unreliable looker condition, whereas both groups followed the experimenter's gaze to the target object located in front of the barrier equally often. In the second experiment, infants did not generalize their knowledge about the unreliability of a looker to a second ‘naïve’ looker. These findings suggest that 14‐month‐old infants adapt their gaze following as a function of their past experience with the looker.     

Nine- and twelve-month-old infants relate emotions to people's actions

Under investigation was whether 9- to 12-month-olds appreciate that a person's expression of pleasure when gazing toward an object is consistent with that person's subsequent handling of the object. Infants were randomly assigned to an experimental and control group. In the experimental group infants during the pretrials saw a Happy or an Unhappy person saying either “Oh I like objects” or, “I don't like objects”, respectively, while looking at an abstract object. In the habituation phase, infants saw an actor holding the abstract object, but the emotional expression of the actor was obscured. In the posttrial, infants were alternately presented with either the Happy or the Unhappy actor holding the object. In the control group, infants received the same three phase procedure, except that no object was present during the pre- and habituation trials. Analyses comparing the between-subjects variables revealed that infants in the Experimental group looked significantly longer at the Unhappy actor than infants in the Control group but less long at the Happy actor. This study is the first to compare positive and negative emotions and to show that infants as young as 9 months use these emotions to make inferences about people's subsequent actions on objects.     

Sound induces perceptual reorganization of an ambiguous motion display in human infants

Adults who watch an ambiguous visual event consisting of two identical objects moving toward, through, and away from each other and hear a brief sound when the objects overlap report seeing visual bouncing. We conducted three experiments in which we used the habituation/test method to determine whether these illusory effects might emerge early in development. In Experiments 1 and 3 we tested 4‐, 6‐ and 8‐month‐old infants’ discrimination between an ambiguous visual display presented together with a sound synchronized with the objects’ spatial coincidence and the identical visual display presented together with a sound no longer synchronized with coincidence. Consistent with illusory perception, the 6‐ and 8‐month‐old, but not the 4‐month‐old, infants responded to these events as different. In Experiment 2 infants were habituated to the ambiguous visual display together with a sound synchronized with the objects’ coincidence and tested with a physically bouncing object accompanied by the sound at the bounce. Consistent with illusory perception again, infants treated these two events as equivalent by not exhibiting response recovery. The developmental emergence of this intersensory illusion at 6 months of age is hypothesized to reflect developmental changes in object knowledge and attentional mechanisms.     

Infants can infer the presence of hidden objects from referential gaze information

Infants' apparent failure in gaze‐following tasks is often interpreted as a sign of lack of understanding the referential nature of looking. In the present study, 8‐ and 12‐month‐old infants followed the gaze of a model to one of two locations hidden from their view by occluders. When the occluders were removed, an object was revealed either at the location where the model had looked or at the other side. Infants at both ages looked longer at the empty location when it had been indicated by the model's looking behaviour, and this effect held up even when their first look after gaze following was discounted. This result demonstrates that even young infants hold referential expectations when they follow others' gaze and infer the location of hidden objects accordingly.     

Head and eye movements affect object processing in 4‐month‐old infants more than an artificial orientation cue

This study investigates the effects of attention‐guiding stimuli on 4‐month‐old infants' object processing. In the human head condition, infants saw a person turning her head and eye gaze towards or away from objects. When presented with the objects again, infants showed increased attention in terms of longer looking time measured by eye tracking and an increased Nc amplitude measured by event‐related potentials (ERP) for the previously uncued objects versus the cued objects. This suggests that the uncued objects were previously processed less effectively and appeared more novel to the infants. In a second condition, a car instead of a human head turned towards or away from objects. Eye‐tracking results did not reveal any significant difference in infants' looking time. ERPs indicated only a marginally significant effect in late slow‐wave activity associated with memory encoding for the uncued objects. We conclude that human head orientation and gaze direction affect infants' object‐directed attention, whereas movement and orientation of a car have only limited influence on infants' object processing.     

The Animate-Inanimate Distinction in Infancy: Developing Sensitivity to Constraints on Human Actions

Infants aged 4 and 6 months were presented with events in which a person acted so as to set another person, or an inanimate object, in motion. In one condition, the actor spoke to the person (natural) or inanimate object (unnatural); in the other condition, the actor grasped and manipulated the person (unnatural) or object (natural). Six-month-old infants looked reliably longer at the natural actions than at the unnatural actions. A follow-up experiment revealed that their preference depended on the naturalness of the human actions themselves, not on the features or motions of the person or object that was acted upon. Looking preferences at 4 months were equivocal, consistent with the thesis that sensitivity to the natural actions develops over the first 6 months of age. We discuss these findings in relation to the development of social understanding, social gaze, and visual exploration.     

It's the journey,not the destination: Locomotor exploration in infants

What incites infant locomotion? Recent research suggests that locomotor exploration is not primarily directed toward distant people, places, or things. However, this question has not been addressed experimentally. In the current study, we asked whether a room filled with toys designed to encourage locomotion (stroller, ball, etc.) elicits different quantities or patterns of exploration than a room with no toys. Caregivers were present but did not interact with infants. Although most walking bouts in the toy‐filled room involved toys, to our surprise, 15‐month‐olds in both rooms produced the same quantity of locomotion. This finding suggests that mere space to move is sufficient to elicit locomotion. However, infants' patterns of locomotor exploration differed: Infants in the toy‐filled room spent a smaller percent of the session within arms' reach of their caregiver and explored more locations in the room. Real‐time analyses show that infants in the toy‐filled room took an increasing number of steps per bout and covered more area as the session continued, whereas infants in the no‐toy room took fewer and fewer steps per bout and traveled repeatedly over the same ground. Although not required to elicit locomotion, moving with toys encouraged infants to travel farther from their caregivers and to explore new areas.     

How do 8‐month‐old infants recognize causality in object motion and that in human action?1

Abstract: In Experiment 1, 8‐month‐old infants were first habituated to the event in which a moving object collided with another behind an occluder, then they were shown the two test events with no occluder: the contact event, in which the two objects actually collided, and the non‐contact event, in which the second object started to move without contact with the first. The infants looked at both events for an equal amount of time. In Experiment 2, in which the first object was a human actor, however, infants looked at the non‐contact event reliably longer than the contact event. In Experiment 3, in which both objects were human actors stood face‐to‐back, infants looked at the non‐contact event longer, whereas in Experiment 4, in which human actors faced toward each other, infants looked at both events equally. In Experiment 5, in which the first actor told the second to go, 10‐month‐old infants looked at both events for an equal amount of time. These results suggest that 8‐ and 10‐month‐old infants appreciate different causal principles between objects and humans, and that, in doing this, they may acknowledge the possibility of communication between humans.     

Shared musical knowledge in 11‐month‐old infants

Five‐month‐old infants selectively attend to novel people who sing melodies originally learned from a parent, but not melodies learned from a musical toy or from an unfamiliar singing adult, suggesting that music conveys social information to infant listeners. Here, we test this interpretation further in older infants with a more direct measure of social preferences. We randomly assigned 64 11‐month‐old infants to 1–2 weeks’ exposure to one of two novel play songs that a parent either sang or produced by activating a recording inside a toy. Infants then viewed videos of two new people, each singing one song. When the people, now silent, each presented the infant with an object, infants in both conditions preferentially chose the object endorsed by the singer of the familiar song. Nevertheless, infants’ visual attention to that object was predicted by the degree of song exposure only for infants who learned from the singing of a parent. Eleven‐month‐olds thus garner social information from songs, whether learned from singing people or from social play with musical toys, but parental singing has distinctive effects on infants’ responses to new singers. Both findings support the hypothesis that infants endow music with social meaning. These findings raise questions concerning the types of music and behavioral contexts that elicit infants’ social responses to those who share music with them, and they support suggestions concerning the psychological functions of music both in contemporary environments and in the environments in which humans evolved.     

Social Cognition and Social Responsiveness in 10-month-old Infants

In this study, we investigated relations between infants' understanding of intentional actions and measures of social responsiveness during a transitional period, 9- to 11-months. Infants (N = 52) were tested in visual habituation paradigms tapping their understanding of the relation between a person and the object of her attention. Measures of social responsiveness included orienting to the target of another's attention, point production, and supported joint attention in parent---child play. Infants' responses to the habituation events were related to their social responsiveness. Distinct factors for understanding actions and social responsiveness as relational were revealed. Infants who produced object-directed points were more likely to understand pointing as relational, and infants who engaged in high amounts of shared attention were more likely to understand gaze. Infants' tendency to orient in response to an adult's gaze shifts and points was unrelated to their understanding of gaze and pointing. These findings elucidate the ways in which social cognition and social responsiveness, although distinct, are related in development.     

Observation of another's action but not eye gaze triggers allocentric visual perspective

In the present paper, we investigated whether observation of bodily cues—that is, hand action and eye gaze—can modulate the onlooker's visual perspective taking. Participants were presented with scenes of an actor gazing at an object (or straight ahead) and grasping an object (or not) in a 2?×?2 factorial design and a control condition with no actor in the scene. In Experiment 1, two groups of subjects were explicitly required to judge the left/right location of the target from their own (egocentric group) or the actor's (allocentric group) point of view, whereas in Experiment 2 participants did not receive any instruction on the point of view to assume. In both experiments, allocentric coding (i.e., the actor's point of view) was triggered when the actor grasped the target, but not when he gazed towards it, or when he adopted a neutral posture. In Experiment 3, we demonstrate that the actor's gaze but not action affected participants' attention orienting. The different effects of others' grasping and eye gaze on observers' behaviour demonstrated that specific bodily cues convey distinctive information about other people's intentions.     

Marked referential communicative behaviours,but no differentiation of the “knowledge state” of humans in untrained pet dogs versus 1-year-old infants

The study examines whether untrained dogs and infants take their caregiver’s visual experience into account when communicating with them. Fifteen adult dogs and 15 one-year-old infants were brought into play with their caregivers with one of their own toys. The caregiver gave the toy to the experimenter, who, in different conditions, placed it either above or under one of two containers, with both the infant or dog and the caregiver witnessing the positioning; in a third condition, the caregiver left the room before the toy was placed under one of the two containers and later returned. Afterwards, for each condition, the caregiver asked the participant to indicate the location of the toy. Neither dogs nor infants—untrained to the use of the partner’s knowledge state—showed much difference of behaviour between the three conditions. However, dogs showed more persistence for most behaviours (gaze at the owner, gaze at the toy and gaze alternation) and conditions, suggesting that the situation made more demands on dogs’ communicative behaviours than on those of infants. When all deictic behaviours of infants (arm points towards the toy and gaze at the toy) were taken into account, dogs and infants did not differ. Phylogeny, early experience and ontogeny may all play a role in the ways that both species communicate with adult humans.