Retrieval Protracts Deferred Imitation by 6‐Month‐Olds

Past research using a deferred imitation task has shown that 6‐month‐olds remember a 3‐part action sequence for only 1 day. The concept of a time window suggests that there is a limited period within which additional information can be integrated with a prior memory. Its width tracks the forgetting function of the memory. This study asked if retrieving the memory of the modeled actions at the end of the time window protracts its retention, if the type of retrieval (active or passive) differentially influences retention, and if the retrieval delay influences its specificity. In Experiment 1, 6‐month‐olds either imitated the modeled actions (active retrieval group) or merely watched them modeled again (passive retrieval group) 1 day after the original demonstration. Both groups showed deferred imitation after 10 days. In Experiment 2, 6‐month‐olds who repeatedly retrieved the memory at or near the end of the time window deferred imitation for 2.5 months. In Experiment 3,6‐month‐olds spontaneously generalized imitation late in the time window after 1 prior retrieval, whether it was active or passive. These studies reveal that the retention benefit of multiple retrievals late in the time window is huge. Because most retrievals are undoubtedly latent, the contribution of repeated events to the growth of the knowledge base early in infancy has been greatly underestimated.     

12‐Month‐Olds Produce Others' Intended but Unfulfilled Acts

Following Meltzoff's (1995) behavioral reenactment paradigm, this study investigated the ability of 12‐month‐olds (N = 44) to reproduce a model's attempted‐but‐failed actions on objects. Testing was conducted using a novel set of objects designed to enable young infants to readily identify the potential outcome of the model's actions. Infants who saw an adult's attempted‐but‐failed actions now produced her intended outcomes at an equivalent rate to infants who saw the model's completed acts, and significantly more so than infants who either observed an adult manipulating the test apparatus using nontarget actions or who did not see any actions demonstrated on the test apparatus. This result shows that, contrary to previous studies, 12‐month‐olds can produce the intended but unconsummated acts of others.     

Sensitivity to Confidence Cues Increases during the Second Year of Life

We investigated the emergence in infancy of a preference to imitate individuals who display confidence over lack of confidence. Eighteen‐ and 24‐month‐olds (N = 70) were presented with an experimenter who demonstrated the use of several objects accompanied by either nonverbal expressions of confidence or lack of confidence. At 24 months, infants were more likely to imitate the actions when demonstrated by a confident experimenter than by an unconfident experimenter; 18‐month‐olds showed no such preference. The experimenter then presented an additional imitation trial and a word‐learning trial while displaying a neutral expression. Twenty‐four‐month‐olds persisted in preferentially imitating a previously confident experimenter, but prior confidence had no effect on their word learning. These findings demonstrate a developmental increase in infants’ use of confidence cues toward the end of the second year of life.     

Role Reversal Imitation and Language in Typically Developing Infants and Children With Autism

Three types of role reversal imitation were investigated in typically developing 12‐ and 18‐month‐old infants and in children with autism and other developmental delays. Many typically developing infants at both ages engaged in each of the 2 types of dyadic, body‐oriented role reversal imitation: self‐self reversals, in which the adult acted on herself and the child then acted on himself, and other‐other reversals, in which the adult acted on the child and the child then acted back on the adult. However, 12‐month‐olds had more difficulty than 18‐month‐olds with triadic, object‐mediated role reversals involving interactions around objects. There was little evidence of any type of role reversal imitation in children with autism. Positive relations were found between role reversal imitation and various measures of language development for 18‐month‐olds and children with autism.     

I Don't Like the Tone of Your Voice: Infants Use Vocal Affect to Socially Evaluate Others

Infants can make social judgments about characters by visually observing their interactions with others (e.g., Hamlin, Wynn & Bloom, Nature, 2007, 450, 557). Here, we ask whether infants can form similar judgments about potential social partners based solely on their tone of voice. In Experiment 1, we presented 10.5‐month‐olds with two visually neutral puppets. One puppet spoke in a positive affect and the other spoke in a negative affect. When the puppets were placed within reach of the infants, infants selected the formerly positive puppet. This preference disappeared when the voices were paired with nonsocial objects (Experiment 2). In Experiment 3, 10.5‐month‐olds were once again exposed to the same emotionally negative and positive voices. However, no visual characters were present. At test, infants’ visual orientation controlled how long they heard the neutral versions of each voice. Here, infants listened longer to the neutral voice of the formerly positive speaker. That is, just as in Experiment 1, infants’ preferences for the emotionally neutral test stimuli were shaped by their earlier exposure to emotionally charged recordings of that voice. Our findings provide convergent evidence to suggest that infants possess sophisticated social evaluation abilities, preferring to interact with prosocial over antisocial others.     

Interacting Socially With Human Hands at 24 Months of Age

This experiment explored whether or not 2‐year‐olds would engage in synchronic imitation with human hands. Sixty‐four 24‐month‐old infants participated. In a test of synchronic imitation, infants were given a toy while a model simultaneously performed novel actions on an identical toy. Infants were randomly assigned to 1 of 4 model conditions: a familiar person, an unfamiliar person, disembodied human hands, and disembodied robotic pincers. Infants were as likely to synchronically imitate disembodied hands as a person. Imitation of the pincers was significantly lower. This pattern suggests that 2‐year‐olds will engage socially with human hands in the absence of the rest of the body.     

Memory for One‐Time Experiences in the Second Year of Life: Implications for the Status of Episodic Memory

Memory based on a one‐time experience is an important element of its definition as “episodic.” Infants' memories for one‐time experiences over long delays are largely unexplored. Using elicited imitation, we tested 20‐ and 16‐month‐olds' (Experiment 1) and 13‐month‐olds' (Experiment 2) memories as a function of number of experiences and delay. Over 1 month, 20‐ and 16‐month‐olds remembered individual actions of one‐time events; 20‐month‐olds also remembered temporal order; with verbal reminders, 16‐month‐olds did as well. Over 3 months, recall depended on multiple experiences. Thirteen‐month‐olds' required multiple experiences, even over 1 month. The findings speak to the gradual emergence of an important element of episodic memory, namely the ability to preserve memories of one‐time experiences over long periods of time.     

Do 8‐Month‐Old Infants Consider Situational Constraints When Interpreting Others’ Gaze as Goal‐Directed Action?

Some actions of agents are ambiguous in terms of goal‐directedness to young infants. If given reasons why an agent performed these ambiguous actions, would infants then be able to perceive the actions as goal‐directed? Prior results show that infants younger than 12 months can not encode the relationship between a human agent’s looking behavior and the target of her gaze as goal‐directed. In the present experiments, 8‐month‐olds responded in ways suggesting that they interpreted an agent’s action of looking at object‐A as opposed to object‐B as evidence for her goal directed toward object‐A, if her looking action was rational given certain situational constraints: a barrier separated her from the objects or her hands were occupied. Therefore, the infants seem to consider situational constraints when attributing goals to agents’ otherwise ambiguous actions; they seem to realize that within such constraints, these actions are efficient ways for agents to achieve goals.     

Eighteen‐Month‐Olds,but not 14‐Month‐Olds,Use Social Context to Bind Action Sequences

We demonstrate that 18‐month‐olds, but not 14‐month‐olds, can anticipate others' actions based on an interpretation of shared goals that bind together individual actions into a collaborative sequence. After viewing a sequence of actions performed by two people who socially interact, 18‐month‐olds bound together the socially engaged actors' actions such that they later expected the actors to share the same final goal. Eighteen‐month‐olds who saw nonsocially engaged actors did not have this expectation and neither did 14‐month‐olds when viewing either socially or nonsocially engaged actors. The results are discussed in light of the possibility that experience in collaborations could be necessary for understanding collaboration from a third‐person perspective.     

The Development of Rational Imitation in 9‐ and 12‐Month‐Old Infants

Studies on rational imitation have provided evidence for the fact that infants as young as 12 months of age engage in rational imitation. However, the developmental onset of this ability is unclear. In this study, we investigated whether 9‐ and 12‐month‐olds detect voluntary and implicit as well as nonvoluntary and explicit constraints in the head touch task. Three groups of infants watched video sequences, which displayed a person illuminating a lamp using the head. The hands of the model were either free, occupied by voluntarily holding a blanket, or nonvoluntarily restrained by being tied to the table. An additional control group of infants watched the model turning on the lamp by using the hand. Given that the majority of infants imitated the head touch when the model's hands were free, there was evidence for rational imitation in comparison to the condition in which the model's hands were tied to the table, but not in comparison to the condition in which the hands were occupied by holding a blanket. Nine‐month‐olds showed no differences in their behavior according to the condition. These findings clarify the onset of rational imitation by showing that 12‐month‐olds (but not 9‐month‐olds) take into account a situational constraint only when the constraint is nonvoluntary and explicit.     

Development of Three‐Dimensional Completion of Complex Objects

Three‐dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. This study examined infants’ 3D object completion when presented with more complex stimuli. Infants (N = 48) were habituated to an “L”‐shaped object shown from a limited viewpoint; then they were tested with volumetrically complete (solid) and incomplete (hollow) versions of the object. Four‐month‐olds and 6‐month‐old girls had no preference for either display. Six‐month‐old boys and both sexes at 9.5 months of age showed a novelty preference for the incomplete object. A control group (N = 48), only shown the test displays, had no spontaneous preference. Perceptual completion of complex 3D objects requires infants to integrate multiple, local object features and thus may tax their nascent attentional skills. Infants might use mental rotation to supplement performance, giving an advantage to young boys. Examining the development of perceptual completion of more complex 3D objects reveals distinct mechanisms for the acquisition and refinement of 3D object completion in infancy.     

Picture Perception in Infants: Do 9‐Month‐Olds Attempt to Grasp Objects Depicted in Photographs?

Two experiments tested the DeLoache, Pierroutsakos, Uttal, Rosengren, and Gottlieb (1998 claim that 9‐month‐old infants attempt to grasp objects depicted in photographs. In Experiment 1, 9‐month‐olds viewed an object, a photograph of the object, and 2 flat, nonpictorial displays. On average, they reached for the photograph and nonpictorial displays with their hands approximately horizontal and close to the display surfaces, but reached for the object with their hands oriented obliquely and at significantly higher heights. The infants also exhibited similar behaviors when touching the photograph and nonpictorial displays. In Experiment 2, 9‐month‐olds exhibited similar behaviors when touching a photograph of an object and a photograph of textured carpet. The results of both experiments suggest that 9‐month‐olds treat photographs of objects as 2‐dimensional surfaces and not as graspable objects.     

Speed of Processing and Face Recognition at 7 and 12 Months

This research examined developmental and individual differences in infants' speed of processing faces and the relation of processing speed to the type of information encoded. To gauge processing speed, 7‐ and 12‐month‐olds were repeatedly presented with the same face (frontal view), each time paired with a new one, until they showed a consistent preference for the new one. Subsequent probe trials assessed recognition of targets that either preserved configural integrity (Study 1: 3/4 profile and full profile poses) or disrupted it while preserving featural information (Study 2: rotations of 160° or 200° and fracturings). There were developmental differences in both speed and in infants' appreciation of information about faces. Older infants took about 60% fewer trials to reach criterion and had more mature patterns of attention (i.e., looks of shorter duration and more shifts of gaze). Whereas infants of both ages recognized the familiar face in a 3/4 pose, the 12‐month‐olds also recognized it in profile and when rotated. Twelve‐month‐olds who were fast processors additionally recognized the fractured faces; otherwise, processing speed was unrelated to the type of information extracted. At 7 months then, infants made use of some configural information in processing faces; at 12 months, they made use of even more of the configural information, along with part‐based or featural information.     

Transfer of Social Learning Across Contexts: Exploring Infants' Attribution of Trait‐Like Emotions to Adults

We explored whether 15‐month‐olds expect another person's emotional disposition to be stable across social situations. In three observation trials, infants watched two adults interact. Half the infants saw one of the adults (“Emoter”) respond negatively to the other adult's actions (Anger group); half saw the Emoter respond neutrally to the same actions (Neutral group). After a change in social context, infants participated in novel tasks with the (now‐neutral) Emoter. Infants in the Anger group were significantly more likely to relinquish desirable toys to the Emoter. We hypothesize that, in the initial observation trials, infants learned that the Emoter was “anger‐prone” and expected her to get angry again in a new social situation. Consequently, infants readily gave the Emoter what she wanted. These findings reveal three key features of infants' affective cognition: (1) infants track adults' emotional history across encounters; (2) infants learn from observing how people interact with others and use this to form expectations about how these people will treat them; and (3) more speculatively, infants use appeasement to cope with social threat. We hypothesize that infants form “trait‐like” attributions about people's emotional dispositions and use this to formulate adaptive responses to adults in novel social contexts.     

Infant Imitation From Televised Peer and Adult Models

Developmental changes in learning from peers and adults during the second year of life were assessed using an imitation paradigm. Independent groups of 15‐ and 24‐month‐old infants watched a prerecorded video of an unfamiliar child or adult model demonstrating a series of actions with objects. When learning was assessed immediately, 15‐month‐old infants imitated the target actions from the adult, but not the peer whereas 24‐month‐old infants imitated the target actions from both models. When infants’ retention was assessed after a 10‐min delay, only 24‐month‐old infants who had observed the peer model exhibited imitation. Across both ages, there was a significant positive correlation between the number of actions imitated from the peer and the length of regular peer exposure reported by caregivers. Length of peer exposure was not related to imitation from the adult model. Taken together, these findings indicate that a peer‐model advantage develops as a function of age and experience during the second year of life.     

Helping and Cooperation at 14 Months of Age

Two experiments investigated the proclivity of 14‐month‐old infants (a) to altruistically help others toward individual goals, and (b) to cooperate toward a shared goal. The infants helped another person by handing over objects the other person was unsuccessfully reaching for, but did not help reliably in situations involving more complex goals. When a programmed adult partner interrupted a joint cooperative activity at specific moments, infants sometimes tried to reengage the adult, perhaps indicating that they understood the interdependency of actions toward a shared goal. However, as compared to 18‐ and 24‐month‐olds, their skills in behaviorally coordinating their actions with a social partner remained rudimentary. Results are integrated into a model of cooperative activities as they develop over the 2nd year of life.     

Infants' Ability to Distinguish Between Intentional and Accidental Actions and Its Relation to Internal State Language

The experiment reported here investigated infants' concept of intention, as well as the relation among intention understanding, general productive vocabulary, and internal state language production during the 2nd year. Results from an imitation task indicated that 18‐month‐olds are better able to differentiate between intentional and accidental actions than 14‐month‐olds. Although there was no relation between infants' performance on the intention task and their general productive vocabulary, internal state language production at 30 months was predicted by infants' ability to differentiate between intentional and accidental actions about a year earlier. These findings shed light on the developmental progression of infants' concept of intention, as well as on the continuity between infants' understanding of intentional action and their ability to use internal state words.     

The Development of Affect Specificity in Infants' Use of Emotion Cues

This study examined the emergence of affect specificity in infancy. In this study, infants received verbal and facial signals of 2 different, negatively valenced emotions (fear and sadness) as well as neutral affect via a television monitor to determine if they could make qualitative distinctions among emotions of the same valence. Twenty 12‐ to 14‐month‐olds and 20 16‐ to 18‐month‐olds were examined. Results suggested that younger infants showed no evidence of referential specificity, as they responded similarly to both the target and distracter toys, and showed no evidence of affect specificity, showing no difference in play between affect conditions. Older infants, in contrast, showed evidence both of referential and affect specificity. With respect to affect specificity, 16‐ to 18‐month‐olds touched the target toy less in the fear condition than in the sad condition and showed a larger proportion of negative facial expressions in the sad condition versus the fear condition. These findings suggest a developmental emergence after 15 months of age for affect specificity in relating emotional messages to objects.     

Encoding Action Roles in Meaningful Social Interaction in the First Year of Life

Previous research has shown that 6‐ to 9‐month‐old infants detect role reversals in dyadic interaction involving 2‐argument relations. These studies extend this line of research to a 3‐argument structure: An agent gives an object to a recipient. We conducted 4 experiments in a novelty‐preference paradigm. Infants were habituated to videotaped sequences of a puppet giving a flower to another puppet. In the test phase, the puppets' spatial positions were switched, and infants alternately saw role‐reversal and direction‐reversal trials. Results indicate that 10.5‐ and 12‐month‐olds but not 9‐month‐olds selectively encoded the change of action role (agent‐recipient) over a change in the spatiotemporal properties of the interaction and that action role encoding was specific to intentional relations in a 3‐argument structure. Thus, infants at the end of their 1st year seem to be sensitive to movement cues that specify intentional relations between an agent and a recipient.     

The Microstructure of Infants' Gaze as They View Adult Shifts in Overt Attention

We presented infants (5, 6, 9, and 12 months old) with movies in which a female model turned toward and fixated 1 of 2 toys placed on a table. Infants' gaze was measured using a Tobii 1750 eye tracker. Six‐, 9‐, and 12‐month‐olds' first gaze shift from the model's face (after the model started turning) was directed to the attended toy. The 5‐month‐olds performed at random. Following this initial response, 5‐, 6‐, and 9‐month‐olds performed more gaze shifts to the attended target; 12‐month‐olds performed at random. Infants at all ages displayed longer looking times to the attended toy. We discuss a number of explanations for 5‐month‐olds' ability to follow a shift in overt attention by an adult after an initially random response, including the possibility that infants' initial gaze response strengthens the representation of the objects in the peripheral visual field.