Fourteen-month-olds know what others experience only in joint engagement

We investigated how 14‐month‐old infants know what others know. In two studies, an infant played with each of two objects in turn while an experimenter was present. Then the experimenter left the room, and the infant played with a third object with an assistant. The experimenter returned, faced all three objects, and said excitedly ‘Look! Can you give it to me?’ In Study 1, the experimenter experienced each of the first two toys in episodes of joint visual engagement (without manipulation) with the infant. In response to her excited request infants gave the experimenter the object she did not know, thus demonstrating that they knew which ones she knew. In Study 2, infants witnessed the experimenter jointly engage around each of the experienced toys with the assistant, from a third‐person perspective. In response to her request, infants did not give the experimenter the object she had not experienced. In combination with other studies, these results suggest that to know what others have experienced 14‐month‐old infants must do more than just perceive others perceiving something; they must engage with them actively in joint engagement.     

Social referencing in 10-month-old infants

In Experiment 1, forty 10-month-old infants participated together with an experimenter and a parent in a social referencing encounter. The experimenter or the parent presented an ambiguous toy. Neither of the adults provided information about the toy in order to examine infant spontaneous looking behaviour. The infants looked more at both adults when the experimenter presented the toy. In Experiment 2, forty-four 10-month-old infants participated. The experimenter or the parent provided positive information about an ambiguous toy. The infants played more with the toy when the experimenter provided information than when the parent did. The results are discussed in terms of seeking information from knowledgeable others in ambiguous situations.     

Does contingency in adults’ responding influence 12-month-old infants’ social referencing?

In two experiments we examined the influence of contingent versus non-contingent responding on infant social referencing behavior. EXPERIMENT 1: Forty 12-month-old infants were exposed to an ambiguous toy in a social referencing situation. In one condition an unfamiliar adult who in a previous play situation had responded contingently to the infant’s looks gave the infant positive information about the toy. In the other condition an unfamiliar adult who previously had not responded contingently delivered the positive information. EXPERIMENT 2: Forty-eight 12-month-old infants participated in Experiment 2. In this experiment it was examined whether the familiarity of the adult influences infants’ reactions to contingency in responding. In one condition a parent who previously had responded contingently to the infant’s looks provided positive information about the ambiguous toy, and in the other condition a parent who previously had not responded contingently provided the positive information. The infants looked more at the contingent experimenter in Experimenter 1, and also played more with the toy after receiving positive information from the contingent experimenter. No differences in looking at the parent and in playing with the toy were found in Experiment 2. The results indicate that contingency in responding, as well as the familiarity of the adult, influence infants’ social referencing behavior.     

The control of social attention from 1 to 4 months

The control of social attention during early infancy was investigated in two studies. In both studies, an adult turned towards one of two targets within the infant's immediate visual field. We tested: (a) whether infants were able to follow the direction of the adult's head turn; and (b) whether following a head turn was accompanied by further gaze shifts between experimenter and target. In the first study, 1‐month‐olds did not demonstrate attention following at the group level. In addition, those infants who turned towards the same target remained fixed on it and did not shift attention again. In Study 2, we tested infants longitudinally at 2–4 months. At the group level, infants followed the adult's head turn at 3 and 4 months but not at 2 months. Those infants who turned towards the same target at 3 and 4 months also shifted gaze back and forth between experimenter and target. By 3 months, infants seem able to capitalize on the social environment to disengage and distribute attention more flexibly. The results support the claim that the control of social attention begins in early infancy, and are consistent with the hypothesis that following the attention of other people is dependent on the development of disengagement skills.     

Does contingency in adults’ responding influence 12-month-old infants’ social referencing?

In two experiments we examined the influence of contingent versus non-contingent responding on infant social referencing behavior. EXPERIMENT 1: Forty 12-month-old infants were exposed to an ambiguous toy in a social referencing situation. In one condition an unfamiliar adult who in a previous play situation had responded contingently to the infant’s looks gave the infant positive information about the toy. In the other condition an unfamiliar adult who previously had not responded contingently delivered the positive information. EXPERIMENT 2: Forty-eight 12-month-old infants participated in Experiment 2. In this experiment it was examined whether the familiarity of the adult influences infants’ reactions to contingency in responding. In one condition a parent who previously had responded contingently to the infant’s looks provided positive information about the ambiguous toy, and in the other condition a parent who previously had not responded contingently provided the positive information. The infants looked more at the contingent experimenter in Experimenter 1, and also played more with the toy after receiving positive information from the contingent experimenter. No differences in looking at the parent and in playing with the toy were found in Experiment 2. The results indicate that contingency in responding, as well as the familiarity of the adult, influence infants’ social referencing behavior.     

Infant’s gaze in a teasing task with an experimenter or parent: A naturalistic approach

We assessed infant’s gaze in a teasing task in New York City public spaces. The task was administered to two different groups of 5- to 13-month-old infants. We used a between participants design across two studies. In Study 1 an experimenter administered the task to these infants (n = 79), whereas a parent did so in Study 2 (n = 79). The adult engaged the infant with a toy and then pulled it away to one side by counting to 7. A second trial to the other side was repeated. Infants passed the teasing task if they looked to the adult’s face within the first 5 seconds after removing the toy in at least one trial. In Study 1, we found that infants looked to the experimenter’s face after teasing by 7 months of age. In Study 2, infants did not show any significant gazes to the parent’s face after teasing at any age. Most trained parents successfully administered the teasing task to their infant. A teasing game played by an adult stranger (e.g., experimenter) may be optimal to elicit infant’s gaze in a naturalistic setting. Implications for developing cost-effective social-cognitive milestone measures in non-laboratory settings are discussed.     

Effects of adults’ contingent responding on infants’ behavior in ambiguous situations

We examined the effect of adults’ contingency in responding to infants’ behavior in an ambiguous situation in two experiments. In Experiment 1, forty-four 12-month-old infants were exposed to an ambiguous toy. An unfamiliar adult responded either contingently or non-contingently to the infant’s bids and then presented the toy and provided positive information. During toy presentation, infants in the non-contingent condition looked less at the experimenter than infants in the contingent condition. In a concluding free-play situation infants in the non-contingent condition played less and tended to touch the toy less. In Experiment 2 (forty-four 12-month-old infants), the parent either responded promptly or with a delay each time the infant made contact initiatives and then presented an ambiguous toy and delivered the positive information. The infants in the non-contingent condition tended to look less at the parent during toy presentation and also tended to play less with the toy during the concluding free-play situation. The findings show that adults’ contingency in responding influences infants’ behavior in ambiguous situations.     

Interpretation bias and social anxiety: does interpretation bias mediate the relationship between trait social anxiety and state anxiety responses?

Two studies aimed to examine whether high socially anxious individuals are more likely to negatively interpret ambiguous social scenarios and facial expressions compared to low socially anxious individuals. We also examined whether interpretation bias serves as a mediator of the relationship between trait social anxiety and state anxiety responses, in particular current state anxiety, bodily sensations, and perceived probability and cost of negative evaluation pertaining to a speech task. Study 1 used ambiguous social scenarios and Study 2 used ambiguous facial expressions as stimuli to objectively assess interpretation bias. Undergraduate students with high and low social anxiety completed measures of state anxiety responses at three time points: baseline, after the interpretation bias task, and after the preparation for an impromptu speech. Results showed that high socially anxious individuals were more likely to endorse threat interpretations for ambiguous social scenarios and to interpret ambiguous faces as negative than low socially anxious individuals. Furthermore, negative interpretations mediated the relationship between trait social anxiety and perceived probability of negative evaluation pertaining to the speech task in Study 1 but not Study 2. The present studies provide new insight into the role of interpretation bias in social anxiety.     

DO INFANTS SHOW GENERALIZED IMITATION OF GESTURES?

Two experiments were conducted to investigate generalized imitation of manual gestures in 1- to 2-year-old infants. In Experiment 1, 6 infants were first trained four baseline matching relations (e.g., when instructed "Do this", to raise their arms after they saw the experimenter do so). Next, four novel gestures that the infants did not match in probe trials were selected as target behaviors during generalized imitation Test 1; models of these gestures were presented on unreinforced matching trials interspersed with intermittently reinforced baseline matching trials. None of the infants matched the target behaviors. To ensure that these behaviors were in the infants' motor skills repertoires, the infants were next trained to produce them, at least once, under stimulus control that did not include an antecedent model of the target behavior. In repeat generalized imitation trials (Test 2), the infants again failed to match the target behaviors. Five infants (3 from Experiment 1) participated in Experiment 2, which was identical to Experiment 1 except that, following generalized imitation Test 1, the motor-skills training was implemented to a higher criterion (21 responses per target behavior), and in a multiple-baseline, across-target-behaviors procedure. In the final generalized imitation test, 1 infant matched one, and another infant matched two target behaviors; the remaining 17 target behaviors still were not matched. The results did not provide convincing evidence of generalized imitation, even though baseline matching was well maintained and the target behaviors were in the infants' motor skills repertoires, raising the question of what are the conditions that reliably give rise to generalized imitation.     

Nine-month-old infants learn about a physical event in a single session: Implications for infants' understanding of physical phenomena

Infants' ability to learn about physical phenomena after only brief training was observed. During training, infants first observed and handled a weighted ball or an identical-looking empty ball, then watched an experimenter place a ball in the bottom of a tube connected to a paddle. When infants pressed the paddle, the empty ball ascended the tube while the weighted ball stayed down. During test trials infants experienced trials that were consistent and inconsistent (i.e., heavy ball ascended and empty ball did not) with training trials. Infants pressed and looked longer at the inconsistent events. A second experiment replicated the findings and ensured that infants were not using prior knowledge about gravity and weight. Infants formed a representation of what was inside the balls, remembered what each ball did during training, and detected a violation of expectations about the ball's movement.     

Infant's perception of goal-directed actions performed by a mechanical device

The present work investigated whether by the end of the first year, infants interpret actions performed by a mechanical device as goal-directed and why they would do so. Using a modified version of the Woodward (1998) habituation paradigm, 9- and 12-month-old infants were tested in a condition in which they saw a mechanical claw performing an action (Study 1). When infants viewed the claw grasping and transporting objects to the back of a stage, 12-month-old but not 9-month-old infants interpreted the action as goal-directed. In Study 2, 9-month-olds received prior to habituation an information phase showing infants how a human held and operated the claw. This enrichment of infants’ knowledge enabled 9-month-old infants to interpret the action display as goal-directed. The role of the developing means-end understanding and tool-use for infants’ interpretation of actions performed by a mechanical device is discussed.     

Behavioral cues that great apes use to forage for hidden food

We conducted three studies to examine whether the four great ape species (chimpanzees, bonobos, gorillas, and orangutans) are able to use behavioral experimenter-given cues in an object-choice task. In the subsequent experimental conditions subjects were presented with two eggs, one of which contained food and the other did not. In Study 1 the experimenter examined both eggs by smelling or shaking them, but only made a failed attempt to open (via biting) the egg containing food. In a control condition, the experimenter examined and attempted to open both eggs, but in reverse order to control for stimulus enhancement. The apes significantly preferred the egg that was first examined and then bitten, but had no preference in a baseline condition in which there were no cues. In Study 2, we investigated whether the apes could extend this ability to cues not observed in apes so far (i.e., attempting to pull apart the egg), as well as whether they made this discrimination based on the function of the action the experimenter performed. Subjects significantly preferred eggs presented with this novel cue, but did not prefer eggs presented with a novel but functionally irrelevant action. In Study 3, apes did not interpret human actions as cues to food-location when they already knew that the eggs were empty. Thus, great apes were able to use a variety of experimenter-given cues associated with foraging actions to locate hidden food and thereby were partially sensitive to the general purpose underlying these actions.     

Effects of maternal inattentiveness on infant social referencing

The aim of the study was to clarify the meaning of infant looking behaviour when the infant is confronted with an ambiguous situation in order to disentangle the two processes social referencing and attachment. Ninety‐six 12‐month‐olds, presented with an ambiguous or an unambiguous toy, were assigned to one of four conditions; mother inattentive, mother conveyed positive information, and mother conveyed negative information about the ambiguous toy. In the fourth condition (control condition), an unambiguous toy was presented (mother inattentive). The ambiguous situation elicited more referencing looks than the unambiguous situation. During the presentation of the ambiguous toy, infants with inattentive mothers referenced the experimenter more than infants whose mothers provided guidance. In the following free‐play situation, infants in the inattentive group referenced mother to a higher degree than did the other infants. They played less with the toy than infants who had received positive information and infants in the control group, and were less eager to explore the surroundings than infants in the other three groups. When mother turned attentive the infants ceased referencing her and showed an interest in exploring. Copyright © 2003 John Wiley & Sons, Ltd.     

How 7-month-olds interpret ambiguous motion events: Category-based reasoning in infancy

This paper investigates the role of static and dynamic attributes for the animate-inanimate distinction in category-based reasoning of 7-month-olds. Three experiments tested infants’ responses to movement events involving an unfamiliar animal and a ball. When either the animal or the ball showed self-initiated irregular movements (Experiment 1), infants expected the previously active object to start moving again. When both objects were moving together in an ambiguous motion event (Experiment 2), infants expected only the animal to start moving again. Initial looking preferences for each object did not influence results. When either the facial features of the animal were removed, or its furry body was replaced by a plastic spiral in an ambiguous motion event (Experiment 3), infants formed no clear expectation regarding future movements. Based on this set of findings we conclude that 7-month-olds flexibly combine information about the static and dynamic properties of objects in order to reason about motion events.     

Object individuation in young infants: Further evidence with an event-monitoring paradigm

Recent results indicate that, when tested with an event-monitoring task, 7.5- and 9.5-month-olds give evidence that they can individuate objects in different-objects occlusion events – events in which two distinct objects appear successively on either side of an occluder (Wilcox and Baillargeon, in press). The present research sought to confirm and extend these findings. The experiments examined 7.5- and 4.5-month-olds’ ability to correctly interpret a different-objects (ball-box condition) and a same-object (ball-ball condition) occlusion event. The infants in the ball-box condition saw a test event in which a ball disappeared behind the left edge of a screen; after a pause, a box emerged from behind the screen's right edge. For half of the infants (wide-screen event), the screen was wide and could occlude the ball and box simultaneously; for the other infants (narrow-screen event), the screen was narrow and should not have been able to occlude the ball and box at the same time. The infants in the ball-ball condition saw identical wide- and narrow-screen events except that the ball appeared on both sides of the screen. The infants in the ball-box condition looked reliably longer at the narrow- than at the wide-screen event, whereas those in the ball-ball condition tended to look equally at the events. These results suggest that the ball-box infants (a) were led by the featural differences between the ball and box to view them as distinct objects; (b) judged that the ball and box could both be occluded by the wide but not the narrow screen; and (c) were surprised in the narrow-screen event when this judgment was violated. In contrast, the ball-ball infants (a) assumed, based on the featural similarities of the balls that appeared on either side of the screen, that they were one and the same ball, and (b) realized that the ball could be occluded by either the wide or the narrow screen. These results indicate that, by 4.5 months of age, infants are able to use featural information to correctly interpret different-objects and same-object occlusion events. These findings are discussed in the context of the newly-drawn distinction between event-monitoring and event-mapping paradigms (Wilcox and Baillargeon, in press).     

Do infants have a sense of fairness?

Two experiments examined infants' expectations about how an experimenter should distribute resources and rewards to other individuals. In Experiment 1, 19-month-olds expected an experimenter to divide two items equally, as opposed to unequally, between two individuals. The infants held no particular expectation when the individuals were replaced with inanimate objects, or when the experimenter simply removed covers in front of the individuals to reveal the items (instead of distributing them). In Experiment 2, 21-month-olds expected an experimenter to give a reward to each of two individuals when both had worked to complete an assigned chore, but not when one of the individuals had done all the work while the other played. The infants held this expectation only when the experimenter could determine through visual inspection who had worked and who had not. Together, these results provide converging evidence that infants in the 2nd year of life already possess context-sensitive expectations relevant to fairness.     

Can we talk to robots? Ten-month-old infants expected interactive humanoid robots to be talked to by persons

As technology advances, many human-like robots are being developed. Although these humanoid robots should be classified as objects, they share many properties with human beings. This raises the question of how infants classify them. Based on the looking-time paradigm used by [Legerstee, M., Barna, J., & DiAdamo, C., (2000). Precursors to the development of intention at 6 months: understanding people and their actions. Developmental Psychology, 36, 5, 627-634.], we investigated whether 10-month-old infants expected people to talk to a humanoid robot. In a familiarization period, each infant observed an actor and an interactive robot behaving like a human, a non-interactive robot remaining stationary, and a non-interactive robot behaving like a human. In subsequent test trials, the infants were shown another actor talking to the robot and to the actor. We found that infants who had previously observed the interactive robot showed no difference in looking-time between the two types of test events. Infants in the other conditions, however, looked longer at the test event where the second experimenter talked to the robot rather than where the second experimenter talked to the person. These results suggest that infants interpret the interactive robot as a communicative agent and the non-interactive robot as an object. Our findings imply that infants categorize interactive humanoid robots as a kind of human being.     

The principles of conventionality and contrast in word learning: an empirical examination

In Study 1, 4-year-olds avoided 2 names for an object when exposed to a common or a proper noun in a puppet's presence or to a common noun in a puppet's absence, but not when exposed to a proper noun in a puppet's absence. In Study 2, 3-year-olds avoided 2 names for an object when the requester for the referent of a second label in a different language was bilingual and present during naming, but not when the speaker was bilingual but absent or monolingual. Study 3 followed up on the results of the first 2 studies. When children could assume that the puppet knew the name the experimenter used, they inferred that the puppet's use of a different name implied a different referential intent.     

Fourteen-month-old infants copy an action style accompanied by social-emotional cues

Human adults exaggerate their actions and facial expressions when interacting with infants. These infant-directed modifications highlight certain aspects of action sequences and attract infants’ attention. This study investigated whether social-emotional aspects of infant-directed modifications, such as smiling, eye contact, and onomatopoeic vocalization, influence infants’ copying of another's action, especially action style, during the process of achieving an outcome. In Study 1, 14-month-old infants (n = 22) saw an experimenter demonstrate goal-directed actions in an exaggerated manner. Either the style or the end state of the actions was accompanied by social-emotional cues from the experimenter. Infants copied the style of the action more often when social-emotional cues accompanied the style than when they accompanied the end state. In Study 2, a different group of 14-month-old infants (n = 22) watched the same exaggerated actions as in Study 1, except that either the style or the end state was accompanied by a physical sound instead of social-emotional cues. The infants copied the end state consistently more often than the style. Taken together, these two studies showed that accompanying social-emotional cues provided by a demonstrator, but not accompanying physical sound, increased infants’ copying of action style. These findings suggest that social-emotional cues facilitate efficient social learning through the adult–infant interaction.     

Untrained speakers' use of prosody in syntactic disambiguation and listeners' interpretations

We investigated how naively produced prosody affects listeners' end interpretations of ambiguous utterances. Non-professional speakers who were unaware of any ambiguity produced ambiguous sentences couched in short, unambiguous passages. In a forced-choice task, listeners could not tell which context the isolated ambiguous sentences came from (Exp. 1). However, listeners were able to correctly paraphrase the least ambiguous subset of these utterances, showing that prosody can be used to resolve ambiguity (Exp. 2). Nonetheless, in everyday language use, both prosody and context are available to interpret speech. When the least ambiguous sentences were cross-spliced into contexts biasing towards their original interpretations or into contexts biasing towards their alternative interpretations, answers to content questions about the ambiguous sentence, confidence ratings, and ratings of naturalness all indicated that prosody is ignored when context is available (Exp. 3). Although listeners can use prosody to interpret ambiguous sentences, they generally do not, and this makes sense in light of the frequent lack of reliable prosodic cues in everyday speech. Received: 3 April 1998 / Accepted: 21 October 1998