Infants' perception of kinetic depth and stereokinetic displays.

Examined infants' perceptions of 3-dimensional form, using a kinetic depth effect (KDE) display and displays containing subsets of the motion present in the KDE display. One subset consisted of "between-contour" motion, and the second consisted of "within-contour" motion. Research with adults has suggested that only between-contour motion leads to a compelling depth percept. In Exps 1 and 2, infants generalized habituation from a KDE display to the between-contour but not the within-contour changes. In Exps 3 and 4, infants generalized habituation from a KDE display to the between-contour display viewed from a novel orientation but not to the within-contour display viewed from the original orientation. Results indicate sensitivity to between-contour but not within-contour information, suggesting that infants perceive the 3-dimensional form of these displays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of transparency.

Four- and 7-month-old infants' perception of transparency was investigated with computer-generated achromatic or color displays depicting a semitransparent box occluding the center of a rod. Following habituation, infants viewed test displays consisting of either a two-color rod (corresponding to the habituation display's proximal characteristics) or a solid rod (corresponding to the distal characteristics of the event depicted by the habituation display). Looking-time results from 4-month-olds suggested perception of transparency in color displays but not in an achromatic display. An additional condition indicated that transparency perception may rely on the visibility of background texture through the transparent surface. Seven-month-olds, in contrast, provided some evidence of transparency perception in the achromatic display. Implications for the development of infants' responses to object properties and perceptual segregation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' detection of shearing motion in random-dot displays.

Random-dot kinematograms were used to estimate infants' thresholds for shearing motion in the absence of flicker and position cues. The principal advantage of these stimuli is that changes in dot position are camouflaged by the presence of numerous matching dots, thus necessitating the detection of motion before extraction of local pattern features. 13- and 20-wk-old infants were tested with a forced-choice preferential looking technique. The target stimulus resembled a vertically oriented corrugated pattern that oscillated at 1 Hz, if, and only if, shearing motion was detected. Infants were tested at different velocities, ranging from 0.7°/sec to 5.6°/sec, and the results revealed minimum velocity thresholds of 3.5°/sec and 1.2°/sec for 13- and 20-wk-old infants, respectively. Possible interpretations for these results based on position- or flicker-sensitive mechanisms are considered and are found inconsistent with the overall pattern of results. It is concluded that infants detect shearing motion in random-dot displays with a motion-sensitive mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' encoding of kinetic displays varying in relative coherence.

Two experiments were conducted to assess 3-month-old infants' processing of moving point-light displays depicting the biomechanical motions of a person walking. The displays were computer-generated and varied in stimulus coherence as measured by a version of coding theory. An infant-control habituation paradigm was used to measure both encoding and discrimination of the stimuli. Experiment 1 involved two point-light displays with identical absolute motions but different degrees of relative coherence. The results revealed that these two displays were discriminable and that encoding was systematically related to their relative coherence. Experiment 2 revealed that two new displays varying less in their coherence were also differentially encoded but were not discriminated. It was concluded that infants' processing of kinetic displays varies as a function of their relative coherence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' use of object parts in early categorization.

Two experiments involving object-manipulation tasks were performed to examine whether 1- to 2 year-olds form superordinate-like categories by attending to object parts. In Study 1, 14-, 18-, and 22-month-olds were tested with contrasts of animals, furniture, insects, and vehicles. Fourteen- and 18-month-olds behaved systematically toward categories with different parts (legs or wheels) but not toward categories with matching parts (legs or legs). In Study 2, infants were tested with novel animals and vehicles generated by removing or attaching legs or wheels. In the absence of part differences, all three age groups failed to form superordinate categories. The two younger groups chose to categorize by parts (i.e., legs or wheels) rather than by category membership (animal or vehicle). The results suggest a perceptual basis for categorization whereby infants form dynamic categories, on-line, that are based on the characteristics of the input. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' and adults' perception of scale structure.

Adults and 9-month-old infants were required to detect mistuned tones in multitone sequences. When 7-tone versions of a common nursery tune were generated from the Western major scale (unequal scale steps) or from an alternative scale (equal steps), infants detected the mistuned tones more accurately in the unequal-step context than in the equal-step context (Experiment 1). Infants and adults were subsequently tested with 1 of 3 ascending-descending scales (15 tones): (a) a potentially familiar scale (major) with unequal steps, (b) an unfamiliar scale with unequal steps, and (c) an unfamiliar scale with equal steps. Infants detected mistuned tones only in the scales with unequal steps (Experiment 2). Adults performed better on the familiar (major) unequal-step scale and equally poorly on both unfamiliar scales (Experiments 3 and 4). These findings are indicative of an inherent processing bias favoring unequal-step scales. (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)     

Perception of object unity in 2-month-old infants.

The perception of object unity in partial occlusion displays was examined in 72 2-month-old infants. The infants were habituated to 1 of 3 displays depicting a rod undergoing lateral motion behind a box. In each display, more of the rod was visible behind the box than was previously available in prior studies of young infants' perception of occlusion. Posthabituation test displays consisted of 2 rod pieces (broken rod) and a complete rod, presented 3 times each in alternation. Infants in all 3 conditions looked longer at the broken rod than at the complete rod, suggesting that the hidden region of the rod in the habituation display was inferred despite the absence of direct perceptual support. These findings suggest that very young infants' visual, attentional, or cognitive skills may be insufficient to consistently support perception of object unity, except under some display conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of musical relations in short transposed tone sequences.

Tested 104 infants (aged 7–11 mo) for their detection of a frequency relational change of 1 semitone in a 5-note melody. In Exp I, Ss were able to discriminate contrasting melodies that differed from the background melodies by 1 semitone. In Exp II, Ss detected a semitone difference more easily when the major triad was background and a relatively uncommon triad, the augmented triad, was the contrast. In Exp III, Ss discriminated the major and minor backgrounds used in Exps I and II from contrasting variations, called inversions, that did not differ in triad quality. Results indicate that infants can respond to precise relations between the component tones of a melody based on familiar or stable structures. Findings also imply that sets of tones that are unfamiliar or unstable may present encoding or memory difficulties for infants, as has been found for children and adults. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perception of flicker on raster-scanned displays

Experiments have verified the observations of Corbett and White that people are more sensitive to flicker on raster-scanned displays (e.g., television and visual display terminals) if the field scan direction is changed from the conventional top-to-bottom direction to bottom to top, left to right, or right to left. When measured by means of the flicker fusion frequency (FFF), this effect is present only when normal eye movements are permitted. With fixation, the FFF is similar for all scan directions. The effect is demonstrated by the different frequencies at which a directional component is detected in the flicker (which we have called the rolling flicker threshold frequency, or RFTF); the RFTF is lower for top-to-bottom scanning. The effect does not appear to be associated with any asymmetry in eye movements or with eccentricity of the retinal image. The hypothesis that this difference is a consequence of adaptation to televisions and VDTs is supported by the observation that the effect's magnitude correlates with daily exposure time to televisions and VDTs and by a pilot study showing that the effect is reduced when one views a television scanned from bottom to top for 1 h.     

The perception of surface folding in static and animated displays

How do we interpret outline drawings of surfaces? Although pictorial depictions are projectively ambiguous, observers demonstrate definite preferences of interpretation. Additionally, they commit typical errors. A study is reported of one specific arrangement of surfaces as it is represented in outline drawings, namely the arrangement that results when two arbitrary surfaces are joined at a common edge to form an angle in 3-D ('phenomenic folding'). With some of these arrangements, observers report that the angle formed by the two surfaces is zero (complete folding). With others, they report that the angles are greater than zero (incomplete folding). Both interpretations are actually valid. Several investigators have proposed that observer preferences such as these are due t a tendency to prefer a 3-D interpretation that will make the depicted 3-D shape regular. Three experiments were performed to test this regularisation hypothesis. In the first, observers were shown pairs of four-sided polygons joined at one equal side. Their task was to imagine how the smaller polygon could be folded completely towards the larger, and, subsequently, to report on its position after the ('mental folding'). Reported positions were consistent with 3-D interpretations that caused figural regularisations, In the second and third experiments, observers were shown drawings of diamonds and parallelograms folded along a number of differently positioned and oriented segment ('folding edge'). Their task was to estimate verbally the extent of the dihedral angle formed by the two surfaces. Results indicated that the perception of incomplete folding is determined by 3-D interpretation of the orientation of the drawing with respect of the picture plane. In a fourth experiment, observers were asked whether projective equivalences might be disambiguated by animating two kinds of displays that yield the 'incomplete folding' effect but that should be distinguishable on the basis of the trajectories of the vertexes of the folding parts. Results demonstrated that even in these conditions observers are unable to interpret the foldings correctly. These results might be taken to indicate that projective, static information leading to a simpler and more regular interpretation of the display can prevail over explicit motion information that should force the system to achieve a nonregular solution.     

Infants' sensitivity to effects of gravity on visible object motion.

A preference method probed infants' perception of object motion on an inclined plane. Infants viewed videotaped events in which a ball rolled downward (or upward) while speeding up (or slowing down). The infants were tested with events in which the ball moved in the opposite direction with appropriate or inappropriate acceleration. Infants aged 7 mo, but not 5 mo, looked longer at the test event with inappropriate acceleration, suggesting emerging sensitivity to gravity. A further study tested whether infants appreciate that a stationary object released on an incline moves downward rather than upward; findings again were positive at 7 mo and negative at 5 mo. A final study provided evidence, nevertheless, that 5-mo-old infants discriminate downward from upward motion and relate downward motion in videotaped events to downward motion in live events. Sensitivity to certain effects of gravity appears to develop in infancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Updating displays after imagined object and viewer rotations.

Six experiments compared spatial updating of an array after imagined rotations of the array versus viewer. Participants responded faster and made fewer errors in viewer tasks than in array tasks while positioned outside (Experiment 1) or inside (Experiment 2) the array. An apparent array advantage for updating objects rather than locations was attributable to participants imagining translations of single objects rather than rotations of the array (Experiment 3). Superior viewer performance persisted when the array was reduced to 1 object (Experiment 4); however, an object with a familiar configuration improved object performance somewhat (Experiment 5). Object performance reached near-viewer levels when rotations included haptic information for the turning object. The researchers discuss these findings in terms of the relative differences in which the human cognitive system transforms the spatial reference frames corresponding to each imagined rotation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young infants' perception of illusory contours in dynamic displays

Ninety-six 4-month-old infants were habituated to one of three computer-generated displays depicting two rod parts above and below an occluding box. In the first display, the surfaces and boundaries of the rod and box were specified by dense surface texture. Their depth segregation was specified by accretion and deletion of background texture and motion shear. In the second display, the unity of the rod parts and box, and their depth segregation, were specified only by illusory contours. In the third display, the boundaries of the rod and box were specified by illusory contours, perceptible only via spatiotemporal integration of accretion and deletion of sparse-background-texture elements. Infants appeared to perceive object unity, and segregate the rod and box surfaces, in all three displays, indicating use of illusory contours to perceive bounded surfaces in depth. The results suggest a cognitive contribution to perception of some illusory contours, abilities which seem to be present by at least 4 months of age.     

Cognition and perception in the object concept.

45 infants, divided into 3 matched groups, were measured on tests of object permanence, coordination of schemes, and "perceptual" permanence at 3 and 4 mo of age. Experimental groups were trained on 7 occasions between test dates. Group 1 was trained in the coordination of the schemes of vision and prehension; Group 2 was trained in the "perceptual" permanence behavior of visual tracking; Group 3 received no training but was also tested at 5 mo of age. No evidence was found of "perceptual" permanence by this age. The superior performance of Group 1 to other groups on object permanence tasks at 4 mo supported the Piagetian claim that the object concept develops from the coordination of schemes. (French abstract) (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of affordances of slopes under high- and low-friction conditions.

Three experiments investigated whether 14- and 15-month-old infants use information for both friction and slant for prospective control of locomotion down slopes. In Experiment 1, high- and low-friction conditions were interleaved on a range of shallow and steep slopes. In Experiment 2, friction conditions were blocked. In Experiment 3, the low-friction surface was visually distinct from the surrounding high-friction surface. In all three experiments, infants could walk down steeper slopes in the high-friction condition than they could in the low-friction condition. Infants detected affordances for walking down slopes in the high-friction condition, but in the low-friction condition, they attempted impossibly slippery slopes and fell repeatedly. In both friction conditions, when infants paused to explore slopes, they were less likely to attempt slopes beyond their ability. Exploration was elicited by visual information for slant (Experiments 1 and 2) or by a visually distinct surface that marked the change in friction (Experiment 3). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' manipulative exploration of objects: Effects of age and object characteristics.

Examined the ways that infants acquire information about the haptic and visual properties of objects. The 1st study was a cross-sectional investigation of exploratory behavior in 60 6-, 9-, and 12-mo-old infants. Each S was presented with 2 series of objects having some common characteristic. Several general behaviors—looking, handling, mouthing, and banging—were considered along with more specific measures—turning the object while looking, alternating between looking and mouthing, transferring the object from hand to hand, and fingering. Duration of mouthing and particular types of mouthing decreased with age, whereas fingering and other more precise forms of manipulation increased. There were significant stimulus effects showing that the Ss adjusted their behavior to the particular characteristics of the objects. Decrements with increasing familiarization were also observed in most behaviors. The 2nd study addressed the issue of whether the different behaviors are actually used to pick up information about object characteristics. 48 9- and 12-mo-old infants were presented with 3 problems that involved a period of familiarization followed by a trial in which the object was changed along 1 dimension: shape, texture, or weight. Ss' behavior in the change trials suggests that different types of manipulation are used to explore the different changes. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of expressive behaviors: Differentiation of multimodal information.

The literature on infants' perception of facial and vocal expressions, combined with data from studies on infant-directed speech, mother-infant interaction, and social referencing, supports the view that infants come to recognize the affective expressions of others through a perceptual differentiation process. Recognition of affective expressions changes from a reliance on multimodally presented information to the recognition of vocal expressions and then of facial expressions alone. Face or voice properties become differentiated and discriminated from the whole, standing for the entire emotional expression. Initially, infants detect information that potentially carries the meaning of emotional expressions; only later do infants discriminate and then recognize those expressions. The author reviews data supporting this view and draws parallels between the perceptions of affective expressions and of speech. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention and interference in the perception of brief visual displays.

Five experiments, with 61 undergraduates, examined an interference effect that occurs when 2 brief visual displays are presented closely in time. When a single target was displayed 100–200 msec after a 5-item array, Ss were remarkably poor at deciding whether or not the target was in the array; performance was much better when the target either preceded the array or followed it by a longer interval. This effect was independent of a number of visual display parameters, suggesting that it was not due to visual contour interaction. In addition, visual similarity did not interact with the effect, indicating that it probably did not occur during item identification. However, when Ss added one to a digit target before deciding whether it occurred in the array, the effect was substantially reduced. Results suggest a model in which abstract identity information about the target is confused with the array at certain temporal intervals. A quantitative version of this model fit the data quite well. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature binding, attention and object perception

The seemingly effortless ability to perceive meaningful objects in an integrated scene actually depends on complex visual processes. The 'binding problem' concerns the way in which we select and integrate the separate features of objects in the correct combinations. Experiments suggest that attention plays a central role in solving this problem. Some neurological patients show a dramatic breakdown in the ability to see several objects; their deficits suggest a role for the parietal cortex in the binding process. However, indirect measures of priming and interference suggest that more information may be implicitly available than we can consciously access.