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Biomedical subjects

A Yonas

Publications and source records attributed to A Yonas.

At least 19 recordsLinked to original sources
PubMed1994

Infants perceive spatial structure specified by line junctions.

Lines in drawings can be perceived as the corners where surfaces intersect, outer boundaries of surfaces, or as markings on a surface. In this study infants' ability to distinguish between lines that indicate corners and edges and lines that indicate markings was investigated. Infants aged 7.5 months were habituated to line displays in which the lines specified a three-dimensional cube or two overlapping rectangles. Both displays contained lines indicating corners, edges, and surface markings. After habituation, infants viewed two test displays, one in which the corners or edges were deleted and one in which the surface markings were deleted. Infants looked significantly longer at the displays that lacked the corners or edges. The results suggest that infants attend to lines that depict corners and edges to a greater degree than they attend to lines that depict markings. Infants may do so because corners and edges specify the shapes of objects whereas markings do not.

Child Development↗
PubMed1993

Perceiving the affordance of contact in four- and five-month-old infants.

The focus of this study was on the ability of infants to perceive whether an object is positioned at a distance that would make contact possible. As a toy was presented, sometimes within and sometimes beyond reach, the initiation of reaching and leaning forward was scored. Infants were divided into leaning and nonleaning groups. Both leaning and nonleaning 5-month-olds changed their behavior dramatically when the object was placed beyond, as opposed to within, reach. The nonleaners showed a decline in reaching when this boundary for contact was crossed. The "leaners" did not; rather, they began to lean forward. These results suggest that 5-month-olds use information for the affordance of contact. 4-month-olds provided less evidence that arm length regulates reaching. 5-month-old infants acted as if they not only had some sensitivity to the absolute distance of an object but also to the effect that leaning forward has on their ability to make contact with a distant object.

Cognition↗
PubMed1993

Effective action by infants to contact objects by reaching and leaning.

The ability of infants aged 8-12 months to coordinate their arm and trunk movements to contact an object located in different positions was investigated in 2 experiments. In the first, 8- and 10-month-old infants reached for near objects but both reached and leaned for more distant ones indicating that they perceived that forward leaning extends the range of contact beyond that of reaching alone. In addition, arm and trunk movements were initiated simultaneously; visual information concerning object distance was sufficient to activate an integrated reaching-and-leaning response. Object distances were increased and a mechanical aid was provided on half the trials in the second experiment with 10- and 12-month-old infants. For both age groups the degree of leaning was reduced for objects that were out of reach without the aid. Only older infants were able to use the aid to extend partially their range of contact. Overall the results support the conclusions that, by at least 8 months, infants perceive that leaning extends their effective reaching space; by 10 months they perceive the limits within which reaching together with leaning is likely to be effective; and by 12 months they begin to perceive how this space may be extended by a mechanical aid.

Child Development↗
PubMed1990

Kinetic occlusion: further studies of the boundary-flow cue.

Previous work has demonstrated that human beings employ a processing assumption, the boundary-flow constraint, in perceiving the order of depth at an edge. Subjects perceive depth order of surfaces on the basis of the relative motions of an image boundary and a projected surface texture on either side of the boundary. In the present study, adult subjects viewed computer-generated kinematograms in which boundary-flow information provided the only cue for depth order. The results of Experiments 1 and 2 indicate that common motion between boundary and texture and differential motion between boundary and texture can independently generate the perception of ordered depths of surfaces. In Experiment 3, we examined the interaction of two processes involved in the extraction of depth order from boundary-flow displays: (1) the propagation of foreground and background surfaces from texture to boundary; and (2) the computation of depth order of surfaces on either side of the boundary. The results indicate that while the mechanism that computes depth from boundary-flow information functions reliably when the mean distance between texture and boundary is 8.1(0), surface propagation may be disrupted for distances of this magnitude.

Adult↗
PubMed1988

Infants' sensitivity to boundary flow information for depth at an edge.

We investigated infants' sensitivity to a recently discovered kinetic depth cue, boundary flow. 5-month-old infants viewed computer-generated displays in which the relation between the motion of a boundary, indicating an edge, and 2 regions of dots on either side of the boundary, indicating surfaces, provided the only information specifying the order of the 2 surfaces in depth. Infants showed a significant reaching preference for the apparently nearer region of the display. Since previous research has demonstrated that infants reach more frequently for the nearer of 2 surfaces, this result indicates that 5-month-old infants are sensitive to boundary flow information for depth at an edge.

Attention↗
PubMed1987

Four-month-old infants' sensitivity to binocular and kinetic information for three-dimensional-object shape.

4-month-old infants were tested for sensitivity to kinetic and binocular information for 3-dimensional-object shape. The study included 2 tests: a test for sensitivity to binocular disparity and a shape perception test. The disparity sensitivity test used a preferential looking procedure developed by Held, Birch, and Gwiazda. On the basis of the results of this test, infants were assigned to disparity-sensitive and disparity-insensitive groups. In the shape perception test, a "transfer-across-depth-cues" method was employed. Infants were habituated to a rotating object whose shape was specified by kinetic information and were then presented with stationary stereograms specifying the same object and a novel-shaped object. The disparity-sensitive infants looked significantly longer at the novel object than at the familiar object, whereas the disparity-insensitive infants showed no difference in looking time to the novel and the familiar objects. The results indicate that disparity-sensitive 4-month-old infants can perceive 3-dimensional-object shape from kinetic and binocular depth information.

Attention↗
PubMed1984

A comparison of monocular and binocular depth perception in 5- and 7-month-old infants.

Monocular depth perception was compared with binocular depth perception in 5- and 7-month-old infants. Reaching was used as the dependent measure. Two objects, identical except in size, were presented simultaneously to each infant. The smaller object was within reach for the infants while the larger object was just beyond reach. The two objects subtended equal visual angles from the infants' observation point. With binocular presentation, 96% of the 7-month-olds' reaches and 89% of the 5-month-olds' reaches were for the nearer object. With monocular presentation, 58% of the 7-month-olds' reaches and 65% of the 5-month-olds' reaches were for the nearer object. The reaching preferences observed in the monocular condition indicated sensitivity to monocular depth information (motion parallax, accommodation, and relative size information were available). Binocular viewing, however, resulted in a far more consistent tendency to reach for the nearer object. This result suggests that the infants' perception of the objects' distances was more veridical in the binocular condition than in the monocular condition.

Child Development↗
PubMed1984

Infants' perception of pictorially specified interposition.

Five- and seven-month-olds were tested for sensitivity to pictorial interposition in two experiments. Reaching was used as the dependent measure. Seven-month-olds gave evidence of sensitivity to pictorial interposition. In both experiments they showed a significant preference to reach for the pictorially nearer side of a flat interposition display which stimulated three overlapping surfaces and showed no reaching preferences when viewing control displays. Five-month-olds' reaching tendencies did not differ significantly between experimental (interposition) and control conditions in the second experiment. This result indicated that their responses may have been due to nonspatial proximal stimulus variables in the displays. Five-month-olds, therefore, gave no evidence of sensitivity to pictorial interposition. The finding that 7-month-olds are sensitive to pictorial interposition and the failure to find sensitivity in 5-month-olds is consistent with findings from other studies on infants' sensitivity to pictorial depth information. The cumulative results of these studies suggest that sensitivity to pictorial depth information first appears between 5 and 7 months of age.

Child Development↗
PubMed1984

Infants' sensitivity to accretion and deletion of texture as information for depth at an edge.

Based on Gibson's hypothesis that accretion and deletion of texture in the optic array provides unambiguous information for the spatial layout of surfaces, we sought evidence of early responsiveness to this information with infant subjects. 5- and 7-month-olds viewed computer-generated random-dot displays in which accretion and deletion of texture provided the only information for contours, specifying either a foreground surface moving in front of and occluding a moving background surface or 2 partially overlapping surfaces. The infants in both age groups showed significant preferences to reach for the apparently nearer regions in the displays. Since previous research has shown that infants reach more frequently for the nearer of 2 surfaces, these results indicate that 5- and 7-month-olds are sensitive to accretion and deletion of texture as information for the spatial layout of surfaces.

Depth Perception↗
PubMed1983

The effect of two-dimensional and three-dimensional distance on apparent motion.

The problem of how the visual system matches corresponding inputs from one instant to the next to produce the perception of motion has been experimentally examined. The specific concern was whether this correspondence problem is solved prior to the interpretation of three-dimensional distance. Observers judged the degree of apparent motion between pairs of lights in a conflicting motion display. Spatial separation of the lights was varied in two and three dimensions in order to assess whether retinal distance, actual depth, or some combination of these provided critical information for correspondence. The results support Ullman's contention that only two-dimensional (retinal) distances are used in establishing correspondence in motion perception.

Depth Perception↗
PubMed1982

Infants' sensitivity to familiar size as information for distance.

2 experiments tested the effectiveness of familiar size as information for perceived distance. In Experiment 1, under monocular viewing conditions, adults judged the distances to large and small (34.2 cm and 16.9 cm high) photographs of faces and to large and small checkerboard ovals equal to the faces in size. Familiar size influenced subjects' distance estimates. The small faces were judged to be more than twice the distance of the large faces. No significant difference was found between the judged distances to large and small checkerboards. In Experiment 2, the same displays were presented to 5- and 7-month-old infants. Faces were viewed either monocularly or binocularly; checkerboards were viewed monocularly. Duration of reaching was observed as a measure of perceived distance. 7-month-olds gave clear evidence of sensitivity to familiar size. In the monocular-face condition, the difference in duration of reaching to the large and small faces was significantly larger than in either the binocular-face condition or the monocular-checkerboard condition. This indicates that infants were not simply reaching to large faces or large objects without regard to spatial information. Rather, these results indicate that they perceived the large faces to be within reach and the small faces to be beyond reach in the monocular condition. 5-month-olds failed to provide evidence of sensitivity to familiar size.

Age Factors↗
PubMed1979

The role of frames of reference in the development of responsiveness to shading information.

The use of frames of reference in interpreting shading information in pictures was studied with children from 3 to 8 years of age. After learning to discriminate tactually between a convexity and a concavity, the subjects were presented a photograph of the convexity and the concavity in which the only information for differential shape was provided by the relationship between the orientation of the shading on the shapes and the frames of reference. By changing the position of the subject's head, rotating the display, and changing the location of the source of illumination, the relevance of egocentric, environmental, and lighting-specified frames of reference was manipulated. Children in this age range were found to be sensitive to shading information for depth, both when that information was specified by only a single frame of reference and when all three frames of reference were relevant. Differences in the responsiveness to individual frames of reference were found: the egocentric (head-retina) frame of reference was most effective, followed by the environmental reference frame, and finally by the frame of reference based on the location of the light source in the space surrounding the photograph. Responsiveness to the environmental and lighting-based frames of reference increased with age, while responsiveness to the egocentric frame of reference was high for all age groups and did not increase with age.

Child↗
PubMed1978

Development of sensitivity to pictorial depth.

Sensitivity to static pictorial information for depth develops between 22 and 26 weeks of age. When conflicting binocular and surface-texture information was minimized, 26- to 30-week-old infants directed their reaching to the apparently closer side of a photograph of a window rotated in depth. Younger infants, from 20 to 22 weeks of age, did not direct their reaching to the pictorially nearer side of the display but did reach with a high degree of directionality when presented with a real window rotated in depth.

Behavior↗