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.     

Effects of arm weight on C-not-B task performance: implications for the motor inhibitory deficit account of search failures

Toddlers have been found to fail on a three-location search task involving the invisible displacements of an object, namely the C-not-B task. In this task, a child is shown the experimenter's hand that contains a toy. The toy then successively disappears under the three cloths (A, B, then C). The examiner silently releases the toy under the second cloth (B). The hidden object makes a bump in the B cloth that covers it. Young children emit a strong bias toward the last cloth that the experimenter's hand passes under, and this has been labeled the C-not-B error. One possible explanation for toddlers' failures in the C-not-B task is that children lack the motor inhibitory mechanisms. To test this hypothesis, the robustness of the C-not-B error was tested, in a first experiment, against variations in body parameters. By putting additional weights on the arm, the C-not-B error was reduced substantially and the C-not-B task had a higher rate of success. Indeed, in contrast to control participants, who ignored a visual clue indicating the correct location of the hidden object and reached for the last location of the experimenter's hand, the participants with arm weights initiated their reaching movements by using the visual clue. The findings from the second control group indicate that the dramatic increase in successful performance by children with arm weights is not merely a consequence of the focus on the attention to arm movements. The motion of the experimenter's hand in space appears to have made the task difficult because toddlers had no problems inferring that a lump under a cloth indicates the existence of an object without actually having watched an object be hidden there, as demonstrated in a second experiment. The findings are consistent with the hypothesis that C-not-B task content activates a prepotent motor response that preempts full consideration of a visual clue indicating the correct location of the hidden object. We propose that the success in the C-not-B task of toddlers with additional arm weights could result from a disruption of automatic hand movement that is triggered by sensory signals, namely salient features of the C-not-B task.     

Will infants search when ‘no toy’ is hidden? A study of implicit assumptions about the development of object permanence

In the Piagetian tradition, presence or absence of a sense of object permanence is inferred from whether an infant does or does not search when an object is occluded. This line of reasoning entails an implicit assumption, i.e. an infant will not search if no object is seen to disappear. This assumption was evaluated in three studies of 9- and 12-month-old infants' responses to ‘hiding’ toy and ‘no toy’ in different orders in one and two positions. The infants did not search for ‘no toy’ when it preceded toy hiding, but they did search for ‘no toy’ when it followed ‘toy’ under some conditions.     

What comes first? How selective attentional processes regulate the activation of a motor routine in a manual search task

An intriguing error has been observed in toddlers presented with a 3-location search task involving invisible displacements of an object, namely, the C-not-B task. In 3 experiments, the authors investigated the dynamics of the attentional focus process that is suspected to be involved in this task. In Experiment 1, 2.5-year-old children were tested on a new adaptation of the C-not-B task in which the opening of the experimenter's hand between cloths provided visual information about the correct localization of the toy. Children still emitted a strong response bias toward the last hiding place. In Experiment 2, 2.5-year-old children were tested on a new version of the task that was designed to investigate the role of the central location in the task. This 2nd experiment demonstrated that changing the hand's movement from A to C to B did not enable children to succeed in the task. In Experiment 3, 2.5-year-old children were tested in a situation that is analogous to the C-not-B with open hands task except for the fact that the experimenter dropped the toy under the 1st cloth in the path. Toddlers succeeded when the toy was hidden at Location A but not when it was hidden at Location B. Data indicate that attentional focus on the experimenter's hand motion is contingent on whether that stimulus is critical to performing the task. We argue that these findings provide a potential mechanism through which motor routines can be regulated in accordance with strategic intentions.     

Maternal responsiveness and search for hidden objects and contingency learning by infants

The relationship between maternal responsiveness and infant cognition was examined during two activities: the search for hidden objects and the learning of a contingency rule. Thirty-four mother–infant dyads were observed in a laboratory setting when the infants were 11 months old. The experimental session included three phases: a search for hidden objects (Piagetian tasks), the learning of a contingency rule on a touch screen, and a mother–infant play session using a standardised toy. The results indicated a link between performances in the search and contingency tasks. Moreover, infants who succeeded in both tasks had mothers who displayed higher responsiveness score. The findings are discussed in terms of the infant's detection of relevant stimulus information. © 1998 John Wiley & Sons, Ltd.     

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.     

Object permanence after a 24-hr delay and leaving the locale of disappearance: the role of memory, space, and identity

Fourteen-month-old infants saw an object hidden inside a container and were removed from the disappearance locale for 24 hr. Upon their return, they searched correctly for the hidden object, demonstrating object permanence and long-term memory. Control infants who saw no disappearance did not search. In Experiment 2, infants returned to see the container either in the same or a different room. Performance by room-change infants dropped to baseline levels, suggesting that infant search for hidden objects is guided by numerical identity. Infants seek the individual object that disappeared, which exists in its original location, not in a different room. A new behavior, identity-verifying search, was discovered and quantified. Implications are drawn for memory, spatial understanding, object permanence, and object identity.     

A computational and neuropsychological account of object-oriented behaviours in infancy

Infants under 7 months of age fail to reach behind an occluding screen to retrieve a desired toy even though they possess sufficient motor skills to do so. However, even by 3.5 months of age they show surprise if the solidity of the hidden toy is violated, suggesting that they know that the hidden toy still exists. We describe a connectionist model that learns to predict the position of objects and to initiate a response towards these objects. The model embodies the dual-route principle of object information processing characteristic of the cortex. One route develops a spatially invariant surface feature representation of the object whereas the other route develops a feature blind spatial–temporal representation of the object. The model provides an account of the developmental lag between infants’ knowledge of hidden objects and their ability to demonstrate that knowledge in an active retrieval task, in terms of the need to integrate information across multiple object representations using (associative) connectionist learning algorithms. Finally, the model predicts the presence of an early dissociation between infants’ ability to use surface features (e.g. colour) and spatial–temporal features (e.g. position) when reasoning about hidden objects. Evidence supporting this prediction has now been reported.     

The role of visual and body movement information in infant search

Three experiments investigated the use of visual input and body movement input arising from movement through the world on spatial orientation. Infants between 9 1/2 and 18 months participated in a search task in which they searched for a toy hidden in 1 of 2 containers. Prior to beginning search, either the infants or the containers were rotated 180 degrees; these rotations occurred in a lit or dark environment. These experiments were distinguished by the environmental cues for object location; Experiment 1 used a position cue, Experiment 2 a color cue, and Experiment 3 both position and color cues. Accuracy was better in Experiments 2 and 3 than in Experiment 1. All studies found that search was best after infant movement in the light; all other conditions led to equivalently worse performance. These results are discussed relative to a theoretical characterization of spatial coding focusing on the uses of spatial information.     

Understanding the effects of one's actions upon hidden objects and the development of search behaviour in 7‐month‐old infants

Infants' understanding of how their actions affect the visibility of hidden objects may be a crucial aspect of the development of search behaviour. To investigate this possibility, 7‐month‐old infants took part in a two‐day training study. At the start of the first session, and at the end of the second, all infants performed a search task with a hiding‐well. On both days, infants had an additional training experience. The ‘Agency group’ learnt to spin a turntable to reveal a hidden toy, whilst the ‘Means‐End’ group learnt the same means‐end motor action, but the toy was always visible. The Agency group showed greater improvement on the hiding‐well search task following their training experience. We suggest that the Agency group's turntable experience was effective because it provided the experience of bringing objects back into visibility by one's actions. Further, the performance of the Agency group demonstrates generalized transfer of learning across situations with both different motor actions and stimuli in infants as young as 7 months.     

The development of spatial understanding in infancy

This paper examines the development of spatial understanding between 8 and 24 months. In particular, it examines whether young infants code changes in the position of an object or themselves in geographic or egocentric terms. The infants sat in a baby chair which was attached to a circular table in such a way that either the infant could be rotated around the edge of the table or the table-top itself could be rotated. Rotation of infant or table could be performed independently or simultaneously. Infants were shown an object which was then hidden under one of either two or three identical cups sitting on the table. Before the infant was allowed to search for the toy, either the table, the infant, or both were rotated, a procedure which resulted in an invisible displacement of the object in terms of geographical and/or egocentric spatial position. Rotations of 60, 90, 120, and 180° were used. Three groups of infants were tested, one cross-sectional (12–24 months), one longitudinal (12–24 months), and one consisting of a group of infants already known to be accelerated in object concept development (8–20 months). The cross-sectional results indicated that egocentric responding continues well into the second half of the second year of life. Even with fortnightly exposure to the tasks, egocentric responding was still evident in some longitudinal babies as late as 19 months. The results of the accelerated group suggest that acceleration through the sequence of object concept development facilitates development of spatial understanding in a wider sense, that is, in the sense of understanding the interrelation of positions in space. The implications of these results for competing theories of the source of object concept errors are discussed.     

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

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

Object disappearance and error in Piaget's Stage IV task

Piaget attributes perseverative error in infant manual search to the failure of the infant to conceive of objects as permanent entities which retain their identity when hidden at successive locations A and B. An experiment was performed to test this explanation in which search was compared under three conditions: when the object was hidden at A and B, when the object was covered but visible at A and B, and when the object was visible and uncovered at A and B. Errors occurred under all three conditions taking the form of a conflict in which infants searched persistently either at A or at B. The conflict was at a maximum when the object was hidden, but was evident even when the object was visible but covered. It is suggested that errors may reflect lack of coordination between egocentric and visual frames of reference in relation to which the object is located.     

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.     

Factors affecting infants' manual search for occluded objects and the genesis of object permanence

Two experiments systematically examined factors that influence infants’ manual search for hidden objects (N = 96). Experiment 1 used a new procedure to assess infants’ search for partially versus totally occluded objects. Results showed that 8.75-month-old infants solved partial occlusions by removing the occluder and uncovering the object, but these same infants failed to use this skill on total occlusions. Experiment 2 used sound-producing objects to provide a perceptual clue to the objects’ hidden location. Sound clues significantly increased the success rate on total occlusions for 10-month-olds, but not for 8.75-month-olds. An identity development account is offered for why infants succeed on partial occlusions earlier than total occlusions and why sound helps only the older infants. We propose a mechanism for how infants use object identity as a basis for developing a notion of permanence. Implications are drawn for understanding the dissociation between looking time and search assessments of object permanence.     

The effects of cue distinctiveness on infants' manual search

Nine- and sixteen-month-old infants were repeatedly presented a manual search problem in which a toy was hidden in one of two containers, which were then moved into reach. The distinctiveness of the containers or their closeness during the movement was varied in different conditions. Overall, the older infants performed better than younger infants, performance improved across trials, and there were more correct searches when the containers or trajectories were distinctive. Analyses of visual orienting indicated that infants learned to restrict their looking to the hiding place. The ability to maintain attention to discriminative cues may be instrumental to progress in delayed-reaction and object permanence tasks.     

One-year-olds’ understanding of nonverbal gestures directed to a third person

We investigated whether infants comprehend others’ nonverbal communicative intentions directed to a third person, in an ‘overhearing’ context. An experimenter addressed an assistant and indicated a hidden toy's location by either gazing ostensively or pointing to the location for her. In a matched control condition, the experimenter performed similar behaviors (absent-minded gazing and extended index finger) but did not communicate ostensively with the assistant. Infants could then search for the toy. Eighteen-month-old infants were skillful in using both communicative cues to find the hidden object, whereas 14-month-olds performed above chance only with the pointing cue. Neither age group performed above chance in the control condition. This study thus shows that by 14–18 months of age, infants are beginning to monitor and comprehend some aspects of third party interactions.     

Sharing attention and pointing to objects at 12 months: is the intentional stance implied?

The goal of the present research was to assess whether communicative gestures, such as gazing and declarative pointing of 12-month-old infants indicate that infants perceive people as intentional agents, or whether infant communicative behaviors are merely triggered by specific perceptual cues in joint visual attention situations. Two experiments were conducted. In Experiment 1, thirty-two 12-month-olds were conditioned to follow the gaze of a contingently interacting person or object. They were then submitted to a paradigm designed to incite them to initiate communicative gestures to the person or object. The temporal coordination between pointing, gazing, and vocalizations occurred at a significantly higher rate in the Person than in the Object condition. In Experiment 2, the effect of the attentional focus of others on the gaze, points and vocalizations of thirty 12-month-olds was investigated. Infants were assessed in conditions where the experimenter vocalized while looking at the same (In-focus), or a different (Out-of-focus) toy than the infants. Infants who pointed produced more co-occurrences of gaze, vocalizations and points in the Out-of-focus condition than in the In-focus condition. Thus, by 12 months, infants are aware of the attentional state of the person. Discussion centers on the implications of these findings for theories of social and cognitive knowing.     

Young infants' perception of unity and form in occlusion displays

Young infants have been reported to perceive the unity of a center-occluded object when the visible ends of the object are aligned and undergo common motion but not when the edges of the object are misaligned (Johnson & Aslin, 1996). Using a recognition-based paradigm, the authors investigated the possibility that past research failed to provide sufficiently sensitive assessments of infants' perception of the unity of misaligned edges in partial occlusion displays. Positive evidence was obtained in 4-month-olds for veridical perception of the motion and location of a hidden region but not its orientation, whereas 7-month-olds, in contrast to the younger infants, appeared to respond to the orientation of the hidden region. Overall, the results suggest that habituation designs tapping recognition processes may be particularly efficacious in revealing infants' perceptual organization. In addition, the findings provide corroborative evidence for the importance of both motion and orientation in young infants' object segregation and for the difficulty in achieving percepts of the global form of a partly occluded object.