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 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.     

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.     

Rational Imitation in 12‐Month‐Old Infants Christiane Schwier,Catharine van Maanen,Malinda Carpenter

Gergely, Bekkering, and Király (2002) demonstrated that 14‐month‐old infants engage in “rational imitation.” To investigate the development and flexibility of this skill, we tested 12‐month‐olds on a different but analogous task. Infants watched as an adult made a toy animal use a particular action to get to an endpoint. In 1 condition there was a barrier that prevented a more straightforward action and so gave the actor no choice but to use the demonstrated action. In the other condition there was no barrier, so the actor had a free choice to use the demonstrated action or not. Twelve‐month‐olds showed the same pattern of results as in Gergely and colleagues' study: They copied the particular action demonstrated more often when the adult freely chose to use the action than when she was forced to use it. Twelve‐month‐olds, too, thus show an understanding of others' intentions as rational choices and can use this understanding in cultural learning contexts.     

The Role of Verbal Repetition in the Development of Infant Speech Preferences From 4 to 14 Months of Age

Four experiments investigated infants' preferences for age‐appropriate and age‐inappropriate infant‐directed speech (IDS) over adult‐directed speech (ADS). Two initial experiments showed that 6‐, 10‐, and 14‐month‐olds preferred IDS directed toward younger infants, and 4‐, 8‐, 10‐, and 14‐month‐olds, but not 6‐month‐olds, preferred IDS directed toward older infants. In Experiment 3. 6‐month‐olds preferred IDS directed toward older infants when the frequency of repeated utterances matched IDS to younger infants. In Experiment 4, 6‐month‐olds preferred repeated IDS utterances over the same IDS utterances organized without repetition. Attention to repeated utterances precedes word segmentation and sensitivity to statistical cues in continuous speech, and might play a role in the discovery of these and other aspects of linguistic structure.     

Infants’ Use of Shared Experience in Declarative Pointing

In this study, we asked whether 14‐ and 18‐month‐old infants use the experiences they have previously shared with others when deciding what to point to for them declaratively. After sharing a particular type of referent with an adult in an excited manner, 18‐month‐olds subsequently found a picture of that type of referent more worthy of declarative pointing than some other picture—but only for that adult, not for a different adult. Mixed results were found with 14‐month‐olds. We thus show that by 18 months, infants accurately track their shared experiences with specific individuals and use this to make communicative decisions. These results also demonstrate that infants sometimes use declarative pointing to indicate not totally “new” things, as in the classic formulation, but things which are “old” in the sense that “we” should recognize them as similar to something we have previously shared.     

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.     

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.     

Toddlers’ Responses to Infants’ Negative Emotions

Early developments in toddlers’ responses to adults’ distress have been extensively examined, but less work has been directed to young children's responses to other children in distress. In the current study, we examined 12‐, 18‐, and 24‐month‐old children's (N = 71) behavioral and affective responses to a crying infant (doll) present in the room with the child. A comparison condition included a contented, neutral infant to contrast with the crying infant so as to disambiguate social interest from distress‐specific responding. Results showed that 12‐month‐olds were neither particularly interested in nor concerned about the infant, although they did discriminate between conditions. In contrast, 18‐ and 24‐month‐olds were socially interested and attentive to the infant, but 24‐month‐olds exhibited greater affective concern to the crying infant than did 18‐month‐olds. Children at all three ages were also mildly distressed themselves by the infant's crying, and this did not decline over the second year. Both girls and children without siblings were more interested in the infant; no effects were found for gender, daycare experience, or siblings on affective concern.     

Maternal input and infants’ response to infant‐directed speech

Caregivers typically use an exaggerated speech register known as infant‐directed speech (IDS) in communication with infants. Infants prefer IDS over adult‐directed speech (ADS) and IDS is functionally relevant in infant‐directed communication. We examined interactions among maternal IDS quality, infants’ preference for IDS over ADS, and the functional relevance of IDS at 6 and 13 months. While 6‐month‐olds showed a preference for IDS over ADS, 13‐month‐olds did not. Differences in gaze following behavior triggered by speech register (IDS vs. ADS) were found in both age groups. The degree of infants’ preference for IDS (relative to ADS) was linked to the quality of maternal IDS infants were exposed to. No such relationship was found between gaze following behavior and maternal IDS quality and infants’ IDS preference. The results speak to a dynamic interaction between infants’ preference for different kinds of social signals and the social cues available to them.     

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.     

Integration of Thought and Action: Arm Weights Facilitate Search Accuracy in 24‐Month‐Old Children

Search errors are common in cognitive tasks with infants and toddlers, and these errors reveal important insights to the development of competence and performance. Rivière and Lécuyer (2008, Journal of Experimental Child Psychology, 100, 1) demonstrated that 29‐month‐olds typically make an error during a search task involving invisible displacement. However, performance improves significantly when children wear weighted wrist bands while doing the task. To investigate this phenomenon further, we tested 24‐month‐old children in an identical search task (N = 35). Half the children wore weighted wrist bands, and the rest were in a no‐weight condition. To test how far this phenomenon generalizes, we also tested the same children in a second search task where they needed to find a ball that had rolled behind one of four doors. The results showed that children in the no‐weight condition replicated previous findings of poor performance on both search tasks. Unlike 29‐month‐olds, the 24‐month‐olds in the weighted condition did not immediately show improvement on the search tasks. However, after an initial search attempt, children wearing weights performed significantly better than chance. The findings shed new light on the interplay between thought and action.     

Language Experience Shapes the Development of the Mutual Exclusivity Bias

Halberda (2003) demonstrated that 17‐month‐old infants, but not 14‐ or 16‐month‐olds, use a strategy known as mutual exclusivity (ME) to identify the meanings of new words. When 17‐month‐olds were presented with a novel word in an intermodal preferential looking task, they preferentially fixated a novel object over an object for which they already had a name. We explored whether the development of this word‐learning strategy is driven by children’s experience of hearing only one name for each referent in their environment by comparing the behavior of infants from monolingual and bilingual homes. Monolingual infants aged 17–22 months showed clear evidence of using an ME strategy, in that they preferentially fixated the novel object when they were asked to “look at the dax.” Bilingual infants of the same age and vocabulary size failed to show a similar pattern of behavior. We suggest that children who are raised with more than one language fail to develop an ME strategy in parallel with monolingual infants because development of the bias is a consequence of the monolingual child’s everyday experiences with words.     

18‐Month‐Olds Predict Specific Action Mistakes Through Attribution of False Belief,Not Ignorance,and Intervene Accordingly

This study employed a new “anticipatory intervening” paradigm to tease apart false belief and ignorance‐based interpretations of 18‐month‐olds’ helpful informing. We investigated in three experiments whether 18‐month‐old infants inform an adult selectively about one of the two locations depending on the adult’s belief about which of the two locations held her toy. In experiments 1 and 2, the adult falsely believed that one of the locations held her toy. In experiment 3, the adult was ignorant about which of the two locations held her toy. In all cases, however, the toy had been removed from the locations and the locations contained instead materials which the adult wanted to avoid. In experiments 1 and 2, infants spontaneously and selectively informed the adult about the aversive material in the location the adult falsely believed to hold her toy. In contrast, in experiment 3, infants informed the ignorant adult about both locations equally. Results reveal that infants expected the adult to commit a specific action mistake when she held a false belief, but not when she was ignorant. Further, infants were motivated to intervene proactively. Findings reveal a predictive action‐based usage of “theory‐of‐mind” skills at 18 months of age.     

Latent Learning and Deferred Imitation at 3 Months

Young infants spend most of their waking time looking around, but whether they learn anything about what they see is unknown. We used a sensory preconditioning paradigm and a deferred imitation task to assess if 3‐month‐olds formed a latent association between 2 objects (S₁, S₂) that they merely saw together. Because infants cannot perform the imitation task until 6 months, we maintained the latent memory with periodic reminders until then, when we modeled the target actions on S₁ and tested them with S₂ 24 hr later. At 6 months of age, infants who had seen S₁ and S₂ paired (but not unpaired) deferred imitation on S₂, confirming that they had associated the objects 3 months earlier. In addition, 3‐month‐olds who saw the objects paired and then saw the target actions modeled on S₁ for 60 sec also recalled and imitated them on S₂ 3 months later, at 6 months of age. These data reveal that latent learning by very young infants is both extensive and enduring and document that the knowledge base begins to form early in life, long before infants are able to express what they know.     

Changes in the Ability to Detect Ordinal Numerical Relationships Between 9 and 11 Months of Age

When are the precursors of ordinal numerical knowledge first evident in infancy? Brannon (2002) argued that by 11 months of age, infants possess the ability to appreciate the greater than and less than relations between numerical values but that this ability experiences a sudden onset between 9 and 11 months of age. Here we present 5 experiments that explore the changes that take place between 9 and 11 months of age in infants' ability to detect reversals in the ordinal direction of a sequence of arrays. In Experiment 1, we replicate the finding that 11‐ but not 9‐month‐old infants detect a numerical ordinal reversal. In Experiment 2 we rule out an alternative hypothesis that 11‐month‐old infants attended to changes in the absolute numerosity of the first stimulus in the sequence rather than a reversal in ordinal direction. In Experiment 3, we demonstrate that 9‐month‐old infants are not aided by additional exposure to each numerosity stimulus in a sequence. In Experiment 4 we find that 11‐month‐old but not 9‐month‐old infants succeed at detecting the reversal in a nonnumerical size or area‐based rule, casting doubt on Brannon's prior claim that what develops between 9 and 11 months of age is a specifically numerical ability. In Experiment 5 we demonstrate that 9‐month‐old infants are capable of detecting a reversal in ordinal direction but only when there are multiple converging cues to ordinality. Collectively these data indicate that at 11 months of age infants can represent ordinal relations that are based on number, size, or cumulative area, whereas at 9 months of age infants are unable to use any of these dimensions in isolation but instead require a confluence of cues.     

Getting into the Groove: The Development of Tempo‐Flexibility Between 10 and 18 Months of Age

Despite good early rhythm processing abilities, and clear enjoyment of music, infants appear not to be able to spontaneously synchronize their movement to the beat of a song (Zentner and Eerola, Proceedings of the National Academy of Sciences, 107, 2010, 5768). We present a new social bell‐ringing task designed to facilitate synchronous movement to music in infants. Ten‐month‐olds, 18‐month‐olds, and adults were played musical tracks of various tempos and given handheld bells to ring, in the presence of either a live experimenter or an animated nonsocial stimulus. Surface electromyography (EMG) was used to measure the timing of arm movements during periods of bell ringing. Infants showed no evidence of synchronous bell ringing at any tempo. However, while the 10‐month‐olds did not modulate their ringing to the music tempo, the 18‐month‐olds showed tempo‐flexibility. Moreover, 18‐month‐olds displayed more associated behaviors such as bouncing and rocking in the absence (rather than presence) of a social partner, whereas the behavior of the 10‐month‐olds was not modulated by the presence or absence of a social partner. The results suggest a distinction between “moving together” and “moving to the beat,” which may have separate underlying mechanisms and developmental trajectories.     

Differences in How 12‐ and 24‐Month‐Olds Interpret the Gaze of Adults

This study examined the hypothesis that toddlers interpret an adult's head turn as evidence that the adult was looking at something, whereas younger infants interpret gaze based on an expectancy that an interesting object will be present on the side to which the adult has turned. Infants of 12 months and toddlers of 24 months were first shown that an adult head turn to the side predicted the activation of a remote‐controlled toy on that side of the room. After this connection had been demonstrated, participants were assigned to 2 conditions. In the head turn condition the toys were removed but the adult continued to produce head turns to the side. In the toy condition the adult stopped turning but the toys continued to be activated when the participant turned toward them. Results showed that, compared to 12‐month‐olds, 24‐month‐olds were more likely to continue to turn to the side when the adult continued to turn even though there was no longer anything of interest to see. In contrast, compared to 24‐month‐olds, 12‐month‐olds were, if anything, more likely to continue to turn to the side in the condition in which the adult stopped turning. The latter result was replicated in a condition in which the activation of the toy was not contingent on the child's own head turn. These results imply that the meaning of gaze following may change significantly over the 2nd year of life. For 12‐month‐olds, gaze is a useful predictor of where interesting sights may occur. In contrast, for 24‐month‐olds, gaze may be a signal that the adult is looking at something.     

The Development of Gaze Following in a Third‐Party Context

Infants follow the gaze of an individual with whom they are directly interacting by the end of the first year. By 18 months infants are capable of learning novel words in observational (or third‐party) contexts (Floor & Akhtar, 2006). To examine third‐party gaze following in 12‐ and 18‐month‐olds, the parent and experimenter engaged in a conversation while the infant was present. For 8 trials approximately every 30 sec the experimenter would turn her head to the right or left to fixate on a toy placed on either side of the room with the parent following suit. In the first experiment, the parent was seated next to the infant and the experimenter opposite, whereas in the second experiment the positions of the adults were switched. In Experiment 1, 18‐month‐olds but not 12‐month‐olds followed gaze. In Experiment 2, 12‐month‐olds acquired a tendency to follow gaze during the experimental session. These results suggest that an incipient ability to follow third‐party gaze is present by 12 months and that infants acquire a more reliable and general ability to follow the gaze of noninteractive others between 12 and 18 months.     

Infants Discriminate the Affective Expressions of their Peers: The Roles of Age and Familiarization Time

Research examining infants’ discrimination of affect often uses unfamiliar faces and voices of adults. Recently, research has examined infant discrimination of affect in familiar faces and voices. In much of this research, infants were habituated to the affective expressions using a “standard” 50% habituation criterion. We extend this line of research by examining infants’ discrimination of unfamiliar peers’, that is, 4‐month‐olds, dynamic, facial, and vocal affective expressions and assessing how discrimination is affected by changing the habituation criterion. In two experiments, using an infant‐controlled habituation design, we explored 3‐ and 5‐month‐olds’ discrimination of their peers’ dynamic audiovisual displays of positive and negative expressions of affect. Results of Experiment 1, using a 50% habituation criterion, revealed that 5‐month‐olds, but not 3‐month‐olds discriminated the affective expressions of their peers. In Experiment 2, we examined whether 3‐month‐olds’ lack of discrimination in Experiment 1 was a result of insufficient habituation (i.e., familiarization). Specifically, 3‐month‐olds were habituated using a 70% habituation criterion, providing them with longer familiarization time. Results revealed that using the more stringent habituation criterion, 3‐month‐olds showed longer habituation times, that is increased familiarization, and discriminated their peers’ affective expressions. Results are discussed in terms of infants’ discrimination of affect, the role of familiarization time, and limitations of the 50% habituation criterion.