The sound of darkness: Why do auditory cues aid infants' search for objects hidden by darkness but not by visible occluders?

In manual search tasks designed to assess infants' knowledge of the object concept, why does search for objects hidden by darkness precede search for objects hidden by visible occluders by several months? A graded representations account explains this décalage by proposing that the conflicting visual input from occluders directly competes with object representations, whereas darkness merely weakens representations. This study tests the prediction that representations of objects hidden by darkness are strong enough for infants to bind auditory cues to them and support search, whereas representations of objects hidden by occluders are not. Six-and-half-month-olds were presented with audible or silent objects that remained visible, became hidden by darkness, or became hidden by a visible occluder. Search required engaging in the same means-end action in all conditions. As predicted, auditory cues increased search when objects were hidden by darkness but not when they were hidden by a visible occluder. Results are discussed in the context of different facets of object concept development highlighted by graded representations perspectives and core knowledge perspectives and in relation to other work on multimodal object representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of Piagetian object permanence in grey parrot (Psittacus erithacus).

The authors evaluated the ontogenetic performance of a grey parrot (Psittacus erithacus) on object permanence tasks designed for human infants. Testing began when the bird was 8 weeks old, prior to fledging and weaning. Because adult grey parrots understand complex invisible displacements (I. M. Pepperberg & F. A. Kozak, 1986), the authors continued weekly testing until the current subject completed all of I. C. Uzgiris and J. Hunt's (1975) Scale 1 tasks. Stage 6 object permanence with respect to these tasks emerged at 22 weeks, after the bird had fledged but before it was completely weaned. Although the parrot progressed more rapidly overall than other species that have been tested ontogenetically, the subject similarly exhibited a behavioral plateau part way through the study. Additional tests, administered at 8 and 12 months as well as to an adult grey parrot, demonstrated, respectively, that these birds have some representation of a hidden object and understand advanced invisible displacements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early knowledge of object motion: continuity and inertia

Experiments investigated whether infants infer that a hidden, freely moving object will move continuously and smoothly. Infants aged 6 and 10 months, like the 4-month-old infants in previous experiments, inferred that the object's path would be connected and unobstructed, in accord with the principle of continuity. In contrast, 4- and 6-month-old infants did not appear to infer that the object's path would be smooth, in accord with the principle of inertia. At 8 and 10 months, knowledge of inertia appeared to be emerging but remained weaker than knowledge of continuity. These findings are consistent with the view that common sense knowledge of physical objects develops by enrichment around constant core principles.     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retarded object permanence development in methylmercury exposed Macaca fascicularis infants.

Mothers of 12 full-term, normal birth-weight Macaques (Macaca fascicularis) received methylmercury (MeHg) hydroxide orally in apple juice at 50 μg/kg/day for 4 mo to 2 yrs before conception and at individual doses during pregnancy. Mothers of 12 control infants received apple juice without MeHg. Infants were separated from their mothers on delivery and were laboratory reared. Beginning at 14 days of age, infants were tested for object permanence development using a plain reach task and hiding tasks. Results indicate that the performance of the MeHg-exposed infants on the full hiding task was significantly retarded compared with controls. On average, exposed infants required nearly twice as many sessions and were over 1 mo older than control infants when they would retrieve the fully hidden object. Although not all of the MeHg-exposed infants who exhibited retarded object permanence development showed signs of attentional problems, it is suggested that for some infants, these attentional problems may be an early precursor to later cognitive deficits. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The development of perceptual completion abilities: infants' perception of stationary, partially occluded objects

We explored infants' ability to perceive stationary, partially occluded objects as connected units (Experiments 1 and 2) with specific appearances (Experiment 3). In each experiment, the infants saw 2 test events involving what appeared to adults to be a tall rectangular object whose middle portion was hidden behind a narrow screen. During the test events, the screen alternately uncovered and covered the object. In Experiments 1 and 2, removal of the screen revealed either a single, connected rectangle (complete object event) or an interrupted rectangle with a gap where the screen had been (broken object event). In Experiment 3, removal of the screen revealed either a rectangle (rectangle event) or a cross-shaped object (cross-shape event). The pattern of infants' looking times at these events suggest that they perceive the unity of the partially occluded object by 6.5 months of age but did not perceive the form of the hidden part of the object until 8 months. The results of baseline control conditions support this interpretation.     

The development of caching and object permanence in western scrub-jays (Aphelocoma californica): Which emerges first?

Recent studies on the food-caching behavior of corvids have revealed complex physical and social skills, yet little is known about the ontogeny of food caching in relation to the development of cognitive capacities. Piagetian object permanence is the understanding that objects continue to exist even when they are no longer visible. Here, the authors focus on Piagetian Stages 3 and 4, because they are hallmarks in the cognitive development of both young children and animals. Our aim is to determine in a food-caching corvid, the Western scrub-jay, whether (1) Piagetian Stage 4 competence and tentative caching (i.e., hiding an item invisibly and retrieving it without delay), emerge concomitantly or consecutively; (2) whether experiencing the reappearance of hidden objects enhances the timing of the appearance of object permanence; and (3) discuss how the development of object permanence is related to behavioral development and sensorimotor intelligence. Our findings suggest that object permanence Stage 4 emerges before tentative caching, and independent of environmental influences, but that once the birds have developed simple object-permanence, then social learning might advance the interval after which tentative caching commences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of perceptual completion originates in information acquisition.

Adults have little difficulty perceiving objects as complete despite occlusion, but newborn infants perceive moving partly occluded objects solely in terms of visible surfaces. The developmental mechanisms leading to perceptual completion have never been adequately explained. Here, the authors examine the potential contributions of oculomotor behavior and motion sensitivity to perceptual completion performance in individual infants. Young infants were presented with a center-occluded rod, moving back and forth against a textured background, to assess perceptual completion. Infants also participated in tasks to assess oculomotor scanning patterns and motion direction discrimination. Individual differences in perceptual completion performance were strongly correlated with scanning patterns but were unrelated to motion direction discrimination. The authors present a new model of development of perceptual completion that posits a critical role for targeted visual scanning, an early developing oculomotor action system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object Permanence in Common Marmosets (Callithrix jacchus).

A series of 9 search tasks corresponding to the Piagetian Stages 3-6 of object permanence were administered to 11 common marmosets (Callithrix jacchus). Success rates varied strongly among tasks and marmosets, but the performances of most subjects were above chance level on the majority of tasks of visible and invisible displacements. Although up to 24 trials were administered in the tests, subjects did not improve their performance across trials. Errors were due to preferences for specific locations or boxes, simple search strategies, and attentional deficits. The performances of at least 2 subjects that achieved very high scores up to the successive invisible displacement task suggest that this species is able to represent the existence and the movements of unperceived objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of object unity in translating and rotating displays

In 3 experiments, the authors examined the sensitivity of infants to the unity of a partly occluded moving rod undergoing translation, rotation, or oscillation. Four-month-old infants were sensitive to the unity of the partly occluded rod when it translated, but not when it rotated, behind an occluder. Six-month-old infants perceived the rotating rod as continuing behind the occluder, but they did not perceive the unity of a rod that oscillated back and forth behind the occluder. Finally, 6-month-old infants showed an ambiguous response to a rotating rod when the shape of the occluder was changed from rectangular to round. These findings suggest that all types of common motion are not equivalent for specifying infants' perceptions of occluded objects. Additional factors should be considered that take into account the information specified by different types of motion and by different conditions at the intersection of the occluder and the object.     

A theory of dynamic occluded and illusory object perception.

Humans see whole objects from input fragmented in space and time, yet spatiotemporal object perception is poorly understood. The authors propose the theory of spatiotemporal relatability (STR), which describes the visual information and processes that allow visible fragments revealed at different times and places, due to motion and occlusion, to be assembled into unitary perceived objects. They present a formalization of STR that specifies spatial and temporal relations for object formation. Predictions from the theory regarding conditions that lead to unit formation were tested and confirmed in experiments with dynamic and static, occluded and illusory objects. Moreover, the results support the identity hypothesis of a common process for amodal and modal contour interpolation and provide new evidence regarding the relative efficiency of static and dynamic object formation. STR postulates a mental representation, the dynamic visual icon, that briefly maintains shapes and updates positions of occluded fragments to connect them with visible regions. The theory offers a unified account of interpolation processes for static, dynamic, occluded, and illusory objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The onset of representation and entry into Stage 6 of object permanence development.

Attempted to determine whether infants' performance in 2 search tasks was related to their entry into Stage 6 of object permanence development and thereby to test Piaget's claim that only Stage 6 infants possess the capacity for representation. Ss were 85 10-mo-olds. In these tasks, Ss found either the same toy as or a different toy than they had seen hidden (Task 1) or which their mother had told them to find (Task 2). Two dependent measures used in each task were the Ss' continuation of search and their smiling in reaction to finding a toy. In both longitudinal and cross-sectional designs, Ss in early Stage 6 (i.e., solving a single invisible displacement), but not in Stage 5, responded differentially on these measures. The early Stage 6 Ss continued to search more frequently in reaction to finding the toy in the different than same condition, while they smiled longer and earlier in the same than different condition. Results suggest that infants begin to demonstrate some representative capacity during early Stage 6 of object permanence development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory of domestic dogs (Canis familiaris) for hidden objects in a detour task.

Spatial memory of domestic dogs (Canis familiaris) for hidden objects was investigated via a visible displacement problem of object permanence with a detour paradigm. Experiment 1 showed that dogs were able to spontaneously locate a disappearing object in a detour situation. In Experiments 2 and 3, dead reckoning and allocentric spatial information were put in conflict. Results revealed that dogs simultaneously encoded both sources of information when they had to bypass an obstacle to locate a hidden object. Experiment 3 also revealed that, over the course of testing, dogs gradually learned to rely predominantly on allocentric cues when the detour involved several reorientations. The current study reveals that spatial memory of dogs for hidden objects in a detour task was guided by flexibility in processing spatial information. Dogs could simultaneously encode dead reckoning and allocentric information to locate a disappearing object and used them hierarchically according to the complexity of the detour they encountered in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object and event representation in 6?-month-old infants.

Two experiments were conducted in which infants had to use remembered knowledge of auditory visual events to guide their reaching and grasping. The events involved a ball falling noisily through a tube and coming to rest at 1of 2 locations, with either resting site specified by distinctive auditory information. The events were presented initially in the light and then in the dark to determine whether infants would remember and use the auditory cues when they could no longer see where the ball fell. In both experiments, infants' reaching behavior was initiated and carried out after the sound ended, which ensured that search for the ball took place without support from ongoing visual or auditory cues. Accurate searching for the ball depended on infants' experience in the light. The authors conclude that 6 ?-month-olds can represent unseen objects and events and use this knowledge to guide their actions to achieve a goal. The success in this task was contrasted with the failures of infants this age in the Piagetian hidden object task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Le décalage dans le développement de la notion d'objet: Mobilité et immobilité de l'objet.

Studied the development of object–person divergence in infants and the association of this divergence or decalage with the physical properties of the objects. Human subjects: 15 male and female Canadian infants (mean age 9 mo). Ss were given 5 identification tasks using mobile and immobile objects: (1) reorientation; (2) disappearance in place; (3) substitution; (4) disappearance in movement of dissimilar objects; and (5) disappearance in movement of similar objects. Ss were asked to indicate if the object was the same after a spatial-temporal transformation. Responses of the subjects to the identification task were recorded and classified by observers into 6 categories: disinterest, looking at object without moving, picking up the transformed object, picking up the nontransformed object, picking up 2 objects, and reproducing the transformation. The results were analyzed statistically and compared with those of another group of 16 infants performing a permanence test. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of object permanence in food-storing magpies (Pica pica).

The development of object permanence was investigated in black-billed magpies (Pica pica), a food-storing passerine bird. The authors tested the hypothesis that food-storing development should be correlated with object-permanence development and that specific stages of object permanence should be achieved before magpies become independent. As predicted, Piagetian Stages 4 and 5 were reached before independence was achieved, and the ability to represent a fully hidden object (Piagetian Stage 4) emerged by the age when magpies begin to retrieve food. Contrary to psittacine birds and humans, but as in dogs and cats, no "A-not-B error" occurred. Although magpies also mastered 5 of 6 invisible displacement tasks, evidence of Piagetian Stage 6 competence is ambiguous. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective information use and perseveration in the search behavior of infants and young children

Two experiments examined the early development of selective information use in search. The first experiment tested 9- and 16-month-olds on a modification of Piaget's Stage IV object permanence task. It examined infants' use of information from previous experiences with an object (prior information) and from the most recent hiding (current information) to locate a hidden object. In the second experiment, 2-, 2 1/2-, and 4-year-old children received these same sources of information along with new forms of prior and current information: information about the typical locations of objects (location specificity) and verbal information. No systematic perseveration was observed at 9 months, although previous findings related to perseveration were replicated. Perseveration was found at 16 months, but there was also evidence of selectivity at that age. When errors occurred, they tended to be to the prior location, but they were infrequent in comparison to correct searches at the current location. The preschoolers, while continuing to show perseveration, were more consistently selective than the infants. They also showed considerable generality in extending their selectivity to new sources of information.     

Object permanence in orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus).

The authors tested orangutans (Pongo pygmaeus) and squirrel monkeys (Saimiri sciureus) on object permanence tasks. In Experiment 1, orangutans solved all visible displacements and most invisible displacements except those involving movements into 2 boxes successively. In Experiment 2, performance of orangutans on double invisible displacements and control displacements (assessing simple strategies) was compared. Orangutans did not use the simple strategy of selecting the box visited last by the experimenter. Instead, poorer performance on double invisible displacements may have been related to increased memory requirements. In Experiment 3, squirrel monkeys were tested using the procedure of Experiment 1. Squirrel monkeys solved visible but did not comprehend invisible displacements. Results suggest that orangutans but not squirrel monkeys possess Stage 6 object permanence capabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Precursors to the development of intention at 6 months: Understanding people and their actions.

Under investigation was whether 6-month-old infants expect people to behave differently toward persons and inanimate objects. Infants were randomly assigned to experimental and control conditions. In the experimental conditions, infants were habituated to an actor who either talked to or reached for and swiped with something hidden behind an occluder. In the test events the actor was occluded, but the infants were shown either a person or an object. In the control condition, infants only saw the person or object stimulus. Results showed that infants who had been habituated to an actor who was talking looked longer at the object, and infants who had been habituated to an actor who was reaching and swiping looked longer at the person. No difference in looking at the stimuli was observed in the control condition. This suggests that infants expect people's actions to be related to objects in ways that are continuous with more mature, intentional understandings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stages in the development of intentional search by young infants.

Piaget maintained that intentional search is preceded by a phase of transitional search in which infants remove covers but do not show intention to find the hidden object. If there is such a transitional phase, reports of search by infants as young as 5 mo are difficult to evaluate because the type of search has not been identified. Two experiments examined changes in search behavior in 38 infants at age 6, 7, and 8 mo. Exp I revealed that the majority of Ss displayed transitional search before intentional search. Exp II showed that Ss' awareness of the hidden object developed gradually; early transitional search demonstrated minimal awareness, but later transitional search revealed knowledge of the hidden object. An account of search development is given that is in close agreement with Piaget's, and caution is advised in the interpretation of studies with young infants that fail to distinguish different types of search. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)