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.     

Development of infants' use of continuity cues in their perception of causality.

Two experiments investigated the role of continuity cues in infants' perception of launching events as causal. Exp 1 showed that 7-mo-old infants can use spatial and temporal contiguity to perceive causality: Infants who were habituated to a causal event dishabituated to novel noncausal events, in which either spatial or temporal contiguity was violated, and those who were habituated to a noncausal event dishabituated to a novel causal but not a novel noncausal event. Experiment 2 showed that 10-mo-olds, but not 7-mo-olds, perceived the causality of launching events in which the objects moved along dissimilar paths. Thus, younger infants do not appear to attend to causality when the objects move along different paths. Results are discussed in terms of the development of the use of continuity cues in causal judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predictive action in infancy: tracking and reaching for moving objects

Because action plans must anticipate the states of the world which will be obtained when the actions take place, effective actions depend on predictions. The present experiments begin to explore the principles underlying early-developing predictions of object motion, by focusing on 6-month-old infants' head tracking and reaching for moving objects. Infants were presented with an object that moved into reaching space on four trajectories: two linear trajectories that intersected at the center of a display and two trajectories containing a sudden turn at the point of intersection. In two studies, infants' tracking and reaching provided evidence for an extrapolation of the object motion on linear paths, in accord with the principle of inertia. This tendency was remarkably resistant to counter-evidence, for it was observed even after repeated presentations of an object that violated the principle of inertia by spontaneously stopping and then moving in a new direction. In contrast to the present findings, infants fail to extrapolate linear object motion in preferential looking experiments, suggesting that early-developing knowledge of object motion, like mature knowledge, is embedded in multiple systems of representation.     

Object segregation in 8-month-old infants

Two experiments examined 8-month-old infants' use of configural and physical knowledge in segregating three-dimensional adjacent displays. The infants in Experiment I saw two identical yellow octagons standing side by side: in the test events, a hand grasped the right octagon and pulled it to the side. The infants looked reliably longer when the octagons moved apart than when they moved together, suggesting that the infants (a) perceived the octagons as a single unit and hence (b) expected them to move together and were surprised when they did not. The infants in Experiment 2 saw a yellow cylinder and a blue box: a hand grasped the cylinder and pulled it to the side. The infants looked reliably longer when the box moved with the cylinder than when the box remained in place, suggesting that they (a) viewed the cylinder and box as distinct units and thus (b) expected the cylinder to move alone and were surprised when it did not. These results indicate that, by 8 months of age, infants use configural knowledge when organizing adjacent displays: they expect similar parts to belong to the same unit and dissimilar parts to belong to distinct units. Additional results revealed that 8-month-old infants' interpretation of displays is affected not only by configural but also by physical consideration. Thus, infants in Experiment 1 who saw a thin blade lowered between the octagons viewed them as two rather than as one unit. Similarly, infants in Experiment 2 who saw the cylinder lying above instead of on the apparatus floor perceived the cylinder and box as one rather than two units. These results indicate that 8-month-old infants bring to bear their knowledge of impenetrability and support when parsing adjacent displays. Furthermore, when faced with two conflicting interpretations of a display, one suggested by their configural and one by their physical knowledge, infants allow the latter to supersede the former. Together, these findings suggest that, by 8 months of age infants approach to segregation is fundamentally similar to that of adults.     

Evidence of location memory in 8-month-old infants in a nonsearch AB task.

Recent studies have shown that when an object is hidden in a location A and then in a location B, 8-month-old infants tend to search in A if forced to wait 3 s before retrieving the object, and to search randomly in A or B if forced to wait 6 s before retrieving the object (e.g., Diamond, 1985). A non-search method was devised to examine 8-month-olds' ability to remember the location of a hidden object. The infants saw an object standing on one of two placemats located on either side of the midline. Next, screens were pushed in front of the placemats, hiding the object from view. After 15 s, a hand reached behind one of the screens and reappeared holding the object. The infants looked reliably longer when the hand retrieved the object from behind the "wrong" as opposed to the "right" screen (where the object was actually hidden). This result suggests that the infants (a) remembered the object's location during the 15-s delay and (b) were surprised to see the object retrieved from behind the right (left) screen when they had last seen it on the left (right) placemat. These results indicate that 8-month-old infants' ability to remember the location of a hidden object is far better than their performance in the AB search task suggests. As such, the present results cast serious doubts on accounts that attribute infants' perseverative and/or random search errors to limited memory mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' attention to object structure in early categorization.

Three experiments with object-manipulation tasks examined the effect of object structure on 14-, 18-, and 22-month-olds' categorization. In Experiment 1, categorization of animals and vehicles was tested when object structure was normal and when it was violated by moving parts (legs or wheels) into a novel configuration. In Experiment 2, categorization of animals, vehicles, and furniture was examined when object structure was modified in orientation (e.g., legs inverted) or in configuration (e.g., legs at tangential angles). In Experiment 3, infants' attention to texture in categorization was tested. The results of the studies showed that 14- to 22-month-olds attend to object parts and structural configuration to categorize and that they do not attend to object texture. There is a perceptual basis for early categorization at the superordinate-like level, and infants are constrained in the parts and object structures they recognize in this process. (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.     

Spatial factors in the development of the object concept.

Conducted 2 studies in which 19 infants' understanding of spatial relations during the period following attainment of active search for hidden objects was examined. The findings of a longitudinal study indicate that infants who have recently achieved this level of object search tend to localize objects globally in relation to available landmarks. Changes in infants' search performance during the course of longitudinal testing were consistent with a shift from more global to more precise differentiation of spatial relations. The findings of a cross-sectional replication study suggest that the spatial relations which infants construct among a set of objects may vary considerably, depending on which aspect of the spatial arrangement they take as dominant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The drawbridge phenomenon: Representational reasoning or perceptual preference?

Two experiments investigated whether infants would look longer at a rotating "drawbridge" that appeared to violate physical laws because they knew that it was causally impossible, as claimed by R. Baillargeon, E. S. Spelke, and S. Wasserman (1985) and R. Baillargeon (1987a). Using a habituation paradigm, they reported that infants looked longer at a display that appeared impossible (rotated 190° while an obstructing box was behind it) than at one that appeared possible (rotated only 112°, appearing to stop at the box). Experiment 1 eliminated habituation to 180° screen rotations. Still, infants looked longer at the 180° impossible rotations. Critically, however, infants also looked longer at possible 180° rotations in Experiment 2, in which no obstruction was present. Moreover, no difference in effect size was found between the 2 experiments. These findings indicate that infants' longer looking at 180° rotations is due to simple perceptual preference for more motion. They question R. Baillargeon's (1987a) claim that it is due to infants' representational reasoning about physically impossible object permanence events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' understanding of visible displacements.

Two studies examined 54 9-mo-old and 54 12-mo-old infants' understanding of visible displacements and whether infants understand that the object has been deleted from its initial hiding place as part of its displacement to a new location. Displacement problems were compared with 2-object problems on which separate objects were hidden at the 1st and 2nd hiding place so that the initial object was not deleted from the 1st displacement location. Nondisplacement problems, on which the object remained at the 1st hiding place while the experimenter moved her visibly empty hand to the 2nd place, were also included in the 1-object condition. Although Exp I showed equivocal results, Exp II provided clear evidence that even 9-mo-olds have at least a limited sensitivity to the deletion component of displacements. In that experiment, the 9-mo-olds searched significantly more at the 2nd than at the 1st hiding place on displacement problems, and the distribution of their searches across the 2 visited locations on those problems was significantly different than on 2-object problems. Although their performance was less consistent than that of 12-mo-olds, there was no evidence that they suffered from any systematic misunderstanding that separated them from the older Ss. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

Make the first move: How infants learn about self-propelled objects.

In 3 experiments, the author investigated 16- to 20-month-old infants' attention to dynamic and static parts in learning about self-propelled objects. In Experiment 1, infants were habituated to simple noncausal events in which a geometric figure with a single moving part started to move without physical contact from an identical geometric figure that possessed a single static part. Infants were then tested with an event in which the parts of the objects were switched. In Experiments 2 and 3, infants were habituated and tested with identical events except that the part possessed by each object during habitation was switched relative to the first experiment. Results of the experiments revealed that 16-month-olds failed to encode the relation between an object's part and its onset of motion, 18-month-olds were unconstrained in the relations involving self-propulsion that they would encode, and 20-month-olds were constrained in the relations they would encode. The results are discussed with regard to the developmental trajectory of learning about motion properties and the mechanism involved in early concept acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' understanding of the link between visual perception and emotion: "If she can't see me doing it, she won't get angry."

Two experiments investigated 18-month-olds' understanding of the link between visual perception and emotion. Infants watched an adult perform actions on objects. An emoter then expressed neutral affect or anger toward the adult in response to the adult's actions. Subsequently, infants were given 20 s to interact with each object. In Experiment 1, the emoter faced infants with a neutral expression during each 20-s response period but looked at either a magazine or the infant. In Experiment 2, the emoter faced infants with a neutral expression, and her eyes were either open or closed. When the emoter visually monitored infants' actions, the infants regulated their object-directed behavior on the basis of their memory of the emoter's affect. However, if the previously angry emoter read a magazine (Experiment 1) or closed her eyes (Experiment 2), infants were not governed by her prior emotion. Infants behaved as if they expected the emoter to get angry only if she could see them performing the actions. These findings suggest that infants appreciate how people's visual experiences influence their emotions and use this information to regulate their own behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Self-experience as a mechanism for learning about others: A training study in social cognition.

Using a gaze-following task, the authors assessed whether self-experience with the view-obstructing properties of blindfolds influenced infants' understanding of this effect in others. In Experiment 1, 12-month-olds provided with blindfold self-experience behaved as though they understood that a person wearing a blindfold cannot see. When a blindfolded adult turned to face an object, these infants gaze followed significantly less than control infants who had either (a) seen and felt the blindfold but whose view had not been obstructed by it or (b) experienced a windowed blindfold through which they could see. In Experiment 2, 18-month-olds experienced either (a) a trick blindfold that looked opaque but could be seen through, (b) an opaque blindfold, or (c) baseline familiarization. Infants receiving trick-blindfold experience now followed a blindfolded adult's gaze significantly more than controls. The authors propose 3 mechanisms underlying infants' capacity to use self-experience as a framework for understanding the visual perception of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning about tools in infancy.

These experiments explored the role of prior experience in 12- to 18-month-old infants' tool-directed actions. In Experiment 1, infants' use of a familiar tool (spoon) to accomplish a novel task (turning on lights inside a box) was examined. Infants tended to grasp the spoon by its handle even when doing so made solving the task impossible (the bowl did not fit through the hole in the box, but the handle did) and even though the experimenter demonstrated a bowl-grasp. In contrast, infants used a novel tool flexibly and grasped both sides equally often. In Experiment 2, infants received training using the novel tool for a particular function; 3 groups of infants were trained to use the tool differently. Later, infants' performance was facilitated on tasks that required infants to grasp the part of the tool they were trained to grasp. The results suggest that (a) infants' prior experiences with tools are important to understanding subsequent tool use, and (b) rather than learning about tool function (e.g., hammering), infants learn about which part of the tool is meant to be held, at least early in their exposure to a novel tool. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Egocentric versus allocentric spatial coding in nine-month-old infants: Factors influencing the choice of code.

Presented 32 9-mo-old infants with a problem in which they saw an object hidden in 1 of 2 places but were prevented from searching for it until after the spatial relationship between infant and object had been changed in some way. Findings show the following: (a) Previous search experience at 1 place promoted response perseveration or egocentric spatial coding on later trials. (b) Infants were better at locating the object after they had moved than they were after the object had moved. (c) Differentiation of the covers for the 2 locations provided a more salient cue to allocentric position than differentiation of the surrounds of the 2 locations. The 2nd finding is taken as support for the hypothesis that as infants begin to crawl, they become better able to take into account their own displacements within a stable space but difficulties remain with the displacements of objects. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-month-old infants' sensitivity to changes in arbitrary syllable–object pairings: The role of temporal synchrony.

To explore early lexical development, the authors examined infants' sensitivity to changes in spoken syllables and objects given different temporal relations between syllable–object pairings. In Experiment 1, they habituated 2-month-olds to 1 syllable, /tah/ or /gah/, paired with an object in synchronous (utterances coincident with object motions, N = 16) or asynchronous (utterances erratic relative to object motions, N = 16) conditions. In the asynchronous condition, the audio track preceded or succeeded the visual track by 1,200 ms. On test, infants in the synchronous condition alone detected the changes. Post hoc computational analyses confirmed lower time separation, interpreted as greater synchrony, between peaks and onsets–offsets of visual motion and audio energy in the synchronous relative to the asynchronous condition. Further examining lexical development, in Experiment 2 they habituated 2-month-olds (N = 16) to two synchronous syllable–object pairs and tested them on switch versus same pairings. Infants failed to detect the switch in the pairings. These results suggest that 2-month-olds use synchrony to detect changes in one novel syllable–object pairing at a time, providing a basis for further word mapping development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Covariation of color and luminance facilitate object individuation in infancy.

The ability to individuate objects is one of our most fundamental cognitive capacities. Recent research has revealed that when objects vary in color or luminance alone, infants fail to individuate those objects until 11.5 months. However, color and luminance frequently covary in the natural environment, thus providing a more salient and reliable indicator of distinct objects. For this reason, we propose that infants may be more likely to individuate when objects vary in both color and luminance. Using the narrow-screen task of Wilcox and Baillargeon (1998a), in Experiment 1 we assessed 7.5-month-old infants' ability to individuate uniformly colored objects that varied in both color and luminance or luminance alone. Experiment 2 further explored the link between color and luminance by assessing infants' ability to use pattern differences that included luminance or color to individuate objects. Results indicated that infants individuated objects only when covariations in color and luminance were used. These studies add to a growing body of literature investigating the interaction of color and luminance in object processing in infants and have implications for developmental changes in the nature and content of infants' object representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)