Infants' Object Search: Effects of Variable Object Visibility Under Constant Means-End Demands

Why do infants have difficulty searching for objects hidden by occluders before 8 months when other evidence has indicated they are sensitive to hidden objects months earlier? One explanation suggests that infants know hidden objects exist but lack the means-end skill to retrieve them from occluders. However, this experiment explores the unique contribution of object visibility by presenting 6- and 10-month-old infants with visible and hidden objects that could be retrieved with little to no means-end skill. Results indicate that 6-month-old infants searched significantly less for hidden objects than visible objects, although both conditions were equated for means-end demands. In contrast, there were no differences among 10-month-old infants. These results highlight the effect of object visibility on search and indicate that a means-end deficit cannot be the only cause of search problems. Explanations for the effect of object visibility are discussed.     

Rich interpretation vs. deflationary accounts in cognitive development: the case of means-end skills in 7-month-old infants

Seven-month-old infants appear to learn means-end skills, such as pushing a button to retrieve a distant toy (Psychological Review 104 (1997) 686). The present studies tested whether such apparent means-end behaviors are genuine, or simply the repetition of trained behaviors under conditions of greatest arousal, as suggested by a dynamic systems reinterpretation. When infants were trained to repeat behaviors that did not serve as means to retrieving toys (pushing a button to light a set of distant lights), their button-pushing differed significantly from infants for whom button-pushing served as a means for retrieving toys. Further, infants demonstrated means-end skills with behaviors that they had not been trained to repeat. Implications for early means-end abilities and for debates surrounding the interpretation of infant behavior are discussed.     

Pulling out the intentional structure of action: the relation between action processing and action production in infancy

Adults and children readily construct action representations organized with respect to an ultimate goal. These representations allow one to predict the consequences of action, interpret and describe actions, and categorize action sequences. In this paper, we explore the ontogeny of hierarchically organized action representations, and its relation to infants' ability to produce similar sequences. To do so, we examine infants' perception and performance of a means-end sequence: pulling a cloth to retrieve a toy. Using a visual habituation paradigm, we demonstrate that 12-month-old infants understand that the initial step of the cloth-pulling sequence is directed toward the ultimate goal of attaining the toy, and use their knowledge of the causal constraints of the sequence to make this goal attribution. Ten-month-olds, however, appear transitional with respect to this understanding: their ability to identify the goal of the cloth-pulling sequence is related to their own ability to planfully solve a similar sequence. These findings are consistent with a burgeoning body of literature suggesting an intimate link between action production and perception, and suggest that this link is in place by at least 10 months of age.     

Why do young infants fail to search for hidden objects?

Recent evidence indicates that infants as young as 3.5 months of age understand that objects continue to exist when hidden (Baillargeon, 1987a; Baillargeon & DeVos, 1990). Why, then, do infants fail to search for hidden objects until 7 to 8 months of age? The present experiments tested whether 5.5-month-old infants could distinguish between correct and incorrect search actions performed by an experimenter. In Experiment 1, a toy was placed in front of (possible event) or under (impossible event) a clear cover. Next, a screen was slid in front of the objects, hiding them from view. A hand then reached behind the screen and reappeared holding the toy. The infants looked reliably longer at the impossible than at the possible event, suggesting that they understood that the hand's direct reaching action was sufficient to retrieve the toy when it stood in front of but not under the clear cover. The same results were obtained in a second condition in which a toy was placed in front of (possible event) or behind (impossible event) a barrier. In Experiment 2, a toy was placed under the right (possible event) or the left (impossible event) of two covers. After a screen hid the objects, a hand reached behind the screen's right edge and reappeared first with the right cover and then with the toy. The infants looked reliably longer at the impossible than at the possible event, suggesting that they realized that the hand's sequence of action was sufficient to retrieve the toy when it stood under the right but not the left cover. A control condition supported this interpretation. Together, the results of Experiments 1 and 2 indicate that by 5.5 months of age, infants not only represent hidden objects, but are able to identify the actions necessary to retrieve these objects. The implications of these findings for a problem solving explanation of young infants' failure to retrieve hidden objects are considered.     

Perceptual Sensitivity and Motoric Competence in 5- and 6-Month-Old Infants

The authors explored whether 5- to 6-month-old infants were sensitive to perceptual information and how they used perception as a recognition cue to search for a hidden object. In addition, the authors categorized and examined infant grasp by developmental effectiveness to determine any impact on infant search behaviors. In a within-participants design, 20 infants were presented with a toy in 2 occluder conditions. The toy was hidden under either a thick, camouflaging cloth or a thin, semitransparent cloth. The data revealed significant effects of perceptual sensitivity, age, and motor sophistication on search tasks. The results suggest that motor competence might be a limiting factor in infants' abilities to link motoric responses to notions about an object.     

Perceptual sensitivity and motoric competence in 5- and 6-month-old infants

The authors explored whether 5- to 6-month-old infants were sensitive to perceptual information and how they used perception as a recognition cue to search for a hidden object. In addition, the authors categorized and examined infant grasp by developmental effectiveness to determine any impact on infant search behaviors. In a within-participants design, 20 infants were presented with a toy in 2 occluder conditions. The toy was hidden under either a thick, camouflaging cloth or a thin, semitransparent cloth. The data revealed significant effects of perceptual sensitivity, age, and motor sophistication on search tasks. The results suggest that motor competence might be a limiting factor in infants' abilities to link motoric responses to notions about an object.     

Infants' perception of illusions in sound localization: reaching to sounds in the dark.

Sixteen infants each at 4, 6, and 8 months of age were tested for reaching to sounding toys in the dark under two auditory illusion conditions: the Haas-effect, which creates the illusion of a single lateralized sound based on an interaural intensity difference (the toy was visible and invisible under some test conditions); and the midline illusion, which creates the illusion of a single sound at midline due to an absence of any interaural time or intensity differences (invisible toy condition only). No-sound control trials indicated the level of spontaneous reaching in the dark. Results indicate that by 4 months infants perceive both the Haas-effect and midline illusions. The ability to reach both for invisible and visible sounding objects in the dark was well developed by 4 months of age, although developmental changes in aspects of reaching behavior were observed and, at all ages, object contact was most frequent when visual localization cues accompanied sound localization cues. The incidence of spontaneous reaching in the dark was low and did not vary with age. Theoretical and methodological implications of this research are discussed.     

Unwilling versus unable: infants' understanding of intentional action

Infants experienced a female adult handling them toys. Sometimes, however, the transaction failed, either because the adult was in various ways unwilling to give the toy (e.g., she teased the child with it or played with it herself) or else because she was unable to give it (e.g., she accidentally dropped it). Infants at 9, 12, and 18 months of age reacted with more impatience (e.g., reaching, looking away) when the adult was unwilling to give them the toy than when she was simply unable to give it. Six-month-olds, in contrast, showed no evidence of this differentiation. Because infants' behavioral responses were appropriately adapted to different kinds of intentional actions, and because the adult's actions sometimes produced results that did not match her goal (when having accidents or failed attempts), these findings provide especially rich evidence that infants first begin to understand goal-directed action at around 9 months of age.     

Learning to reach with “sticky” or “non-sticky” mittens: A tale of developmental trajectories

The effects of “sticky” and “non-sticky” mittens upon the progression of intentional reaching were examined over 16-day training in 24 non-reaching infants aged 2 months and 21 days. Thirteen age-matched controls did not receive training. Both mittens groups progressed over time; however, by day 16, only the “non-sticky” group made significantly more toy contacts than the controls when looking at the toy. Infants in the “non-sticky” group also directed their looking at the toy more than infants in the “sticky” mittens group. These results support the interpretation that repeated task exposure, with active, reaching-specific experience, was more likely to enhance the formation of object-directed behaviors than with the added provision of grasping simulation via “sticky mittens.”     

Developmental changes in associations between auditory-visual events

The goal of the present study was twofold: to examine the influence of two amodal properties, co-location and temporal synchrony, on infants' associating a sight with a sound, and to determine if the relative influence of these properties on crossmodal learning changes with age. During familiarization 2-, 4-, 6- and 8-month-olds were presented two toys and a sound, with sights and sounds varying with respect to co-location and temporal synchrony. Following each familiarization phase infants were given a paired preference test to assess their learning of sight-sound associations. Measures of preferential looking revealed age-related changes in the influence of co-location and temporal synchrony on infants' learning sight-sound associations. At all ages, infants could use temporal synchrony and co-location as a basis for associating an auditory with a visual event and, in the absence of temporal synchrony, co-location was sufficient to support crossmodal learning. However, when these cues conflicted there were developmental changes in the influence of these cues on infants' learning auditory-visual associations. At 2 and 4 months infants associated the sounds with the toy that moved in synchrony with the sound's rhythm despite extreme violation of co-location of this sight and sound. In contrast, 6- and 8-month-olds did not associate a specific toy with the sound when co-location and synchrony information conflicted. The findings highlight the unique and interactive effects of distinct amodal properties on infants' learning arbitrary crossmodal relations. Possible explanations for the age shift in performance are discussed.     

Additional weight influences the reaching behavior of low-risk preterm infants

The authors investigated the influence of additional weight in the reaching behavior of preterm infants. Nine low-risk preterm and 10 full-term infants age 5-7 months participated. A toy was presented in two procedures: (a) baseline and (b) additional weight (bracelet with weight of 20% of the infant's upper limb mass). The additional weight reduced the straightness index at 5 months, increased the mean velocity and decreased the movement units at all months, and increased unsuccessful grasps at 5 and 7 months in preterm infants. Preterm infants showed less movement units at all months and less unsuccessful grasps at 6 months compared with full-term infants. Weight disturbance seems to change the intrinsic dynamics involved in reaching movements of 5-7-month-old preterm infants.     

The role of goal-directed behavior in intention attribution in children

In this study, we addressed the question of the nature of the information needed by 13-month-old infants to understand another agent's intentions. In two experiments, an experimenter was either unable or unwilling to give a toy to an infant. Importantly, an implement (a gutter in which the toy could roll down toward the infant) was used to make the experimenter's behavior as similar as possible in the two conditions. When the experimenter remained still in both conditions, infants did not behave differently according to the experimenter's intentions, suggesting that they did not infer them. By contrast, in a second experiment, where the experimenter performed an action directed toward the gutter in both conditions, the infants looked away from the experimental setting more often and longer in the unwilling condition than in the unable condition. They also looked more toward the experimenter in the unable condition than in the unwilling condition. Therefore, we conclude that an agent's intentional attitude can already be inferred by a 13-month-old provided that this intention is concretely shown through a goal-directed action.     

Individual differences in 3.5-month-olds’ visual attention: what do they predict at 1 year?

Individual differences in infants’ attentional style at 3.5 months are only moderately stable across the first postnatal year. However, infants designated as short lookers based on a pattern examination pretest task at 3.5 months had better recognition memory at 1 year and were briefer in toy examination on post-habituation tests than were long lookers. When these infants were 8–12 months old, peak-look duration during habituation was a better predictor of concurrent task performance than was the original pattern examination task when given at the follow up. Short and long lookers did not differ on a deferred imitation task.     

Infant and maternal behaviors regulate infant reactivity to novelty at 6 months

Three issues were investigated: (a) the regulatory effects of presumed infant and maternal regulation behaviors on infant distress to novelty at 6 months, (b) stability of infant regulatory effects across contexts that vary in maternal involvement, and (c) associations and temporal dynamics between infant and maternal regulation behaviors. Participants were 87 low-risk infants and their mothers, observed at 6 months postpartum during infant exposure to novel toys. Contingencies derived from sequential analyses demonstrate that, by 6 months, some infants reduce their own distress to novelty by looking away from the novel toy or self-soothing, maternal engagement and support have comparable effects, and certain infant and maternal behaviors co-occur. Moreover, infants whose mothers engaged contingently when they looked away from the novel toy expressed less distress than comparable infants whose mothers did not. These findings implicate both infants and mothers in the development of emotion regulation during the infant's first year.     

Triadic interactions support infants’ emerging understanding of intentional actions

Infants’ understanding of the intentional nature of human action develops gradually across the first year of life. A key question is what mechanisms drive changes in this foundational social‐cognitive ability. The current studies explored the hypothesis that triadic interactions in which infants coordinate attention between a social partner and an object of mutual interest promote infants’ developing understanding of others as intentional agents. Infants’ spontaneous tendency to participate in triadic engagement was assessed in a semi‐structured play session with a researcher. Intentional action understanding was assessed by evaluating infants’ ability to visually predict the goal of an intentional reaching action. Study 1 (N = 88) revealed that 8‐ to 9‐month‐olds who displayed more bouts of triadic engagement showed better concurrent reasoning about the goal of an intentional reaching action. Study 2 (N = 114) confirmed these findings using a longitudinal design and demonstrated that infants who displayed more bouts of triadic engagement at 6–7 months were better at prospectively reasoning about the goal of an intentional reaching action 3 months later. Cross‐lagged path analyses revealed that intentional action understanding at 6–7 months did not predict later triadic engagement, suggesting that early triadic engagement supports later intentional action processing and not the other way around. Finally, evidence from both studies revealed the unique contribution of triadic over dyadic forms of engagement. These results highlight the importance of social interaction as a developmental mechanism and suggest that infants enrich their understanding of intentionality through triadic interactions with social partners.     

Are infants in the dark about hidden objects?

Infants appear to search for objects hidden by darkness earlier in development than they search for objects hidden by an occluder in the light. However, these two types of search tasks have differed in numerous ways that may have contributed to better performance in the dark (e.g. in whether the hidden objects made sound, in the number of familiarization trials with visible objects). The current studies controlled such incidental differences between search tasks, so that they could be directly compared. Six‐and‐a‐half‐month‐olds received four types of test events, in which either a toy or no toy was presented and then hidden in the dark or under a cloth in the light. Infants searched more often on toy than no‐toy trials in the dark than with a cloth. The advantage in searching for hidden objects in the dark thus appears to be genuine. Theoretical implications are discussed.     

Seven‐ to 9‐month‐old infants use facial expressions to interpret others' actions

In Study 1, 7‐month‐old infants (N = 58) looked reliably more at an adult's face when she playfully pulled a toy away from them compared with when she simply handed them the toy. In Study 2, 7‐ and 9‐month‐old infants (N = 36) interacted with an adult who played a teasing game and then held a neutral or happy facial expression. Compared with a baseline in which infants looked equally to both expressions, after the tease, infants looked longer at the neutral compared with the happy expression. By 7 months, infants may use facial expressions to disambiguate others' actions.     

Evidence for a unitary goal concept in 12-month-old infants

We investigated whether infants can transfer their goal attribution between situations that contain different types of information about the goal. We found that 12-month-olds who had attributed a goal based on the causal efficacy of a means-end action generated expectations about the actor's action in another scenario in which the actor could choose between alternative outcomes. This finding suggests that, by 12 months, infants possess a unitary concept of goal.     

Infant behavioral responses to infant-directed singing and other maternal interactions

Seventy, 6-9-month-old infants were videotaped during six interactions: mother sings assigned song, "stranger" sings assigned song, mother sings song of choice, mother reads book, mother plays with toy, and mother and infant listen to recorded music. Infant-directed (ID) singing conditions elicited moderately positive cognitive behavior, low levels of positive physical behavior and minimal amounts of vocal behaviors, mostly negative. Across all conditions, cognitive scores remained positive at low to moderate levels. Physical responses were most positive during book and toy, most negative during recorded music, and differed by gender, especially during ID singing. Vocally, infants responded positively to toy, and 8-month-old infants vocalized more than younger infants, particularly during ID singing conditions. ID singing appears just as effective as book reading or toy play in sustaining infant attention and far more effective than listening to recorded music, while interactions involving objects may provide opportunity for shared attention.     

Understanding attention: 12- and 18-month-olds know what is new for other persons

Infants at 12 and 18 months of age played with 2 adults and 2 new toys. For a 3rd toy, however, 1 of the adults left the room while the child and the other adult played with it. This adult then returned, looked at all 3 toys aligned on a tray, showed great excitement ("Wow! Cool!"), and then asked, "Can you give it to me?' To retrieve the toy the adult wanted, infants had to (a) know that people attend to and get excited about new things and (b) identify what was new for the adult even though it was not new for them. Infants at both ages did this successfully, lending support to the hypothesis that 1-year-old infants possess a genuine understanding of other persons as intentional and attentional agents.