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At least 55 records · Page 3Linked to original sources
PubMed1992

Occlusion as a depth cue in the Wheatstone-Panum limiting case.

We examined the hypothesis (Ono & Wade, 1985) that occlusion of far stimuli by a near one on the same visual line can operate as a depth cue in stereograms containing different numbers of targets in the two eyes. By controlling eye positions, we created conditions in which the visual system could interpret the retinal images as originating from stimuli on the visual axis of one eye and also created other conditions in which the origin of the retinal images was ambiguous. In Experiment 1, we presented two lines to one eye and a single line to the other eye. When the image of the line on the temporal side of the line pair on one retina fused with the image of the single line on the other retina, the nonfused line appeared farther away more often than it did when the image on the nasal side fused. In Experiment 2, we used two differently shaped stimuli. In the condition in which the nonfused stimulus represented an object being occluded, it appeared farther away more often than in the four conditions in which it did not. In Experiment 3, we extended the idea to three different objects. When the middle of the three images fused with the single image, the nonfused stimulus appeared farther when it could be interpreted as being occluded than when it could not. In the condition in which the most temporal image fused with the single image, the nonfused stimuli appeared farther than in the condition in which the most nasal one fused. The results supported the hypothesis that occlusion plays a role in depth perception in the Wheatstone-Panum limiting case.

Adult↗
PubMed1991

Adaptation to form distortion of a familiar shape.

Adaptation to the shape distortion produced by an arrangement of cylindrical lenses was demonstrated. Adaptation was produced by exposing subjects to a series of photographs of faces, which appeared horizontally stretched when seen through the lens arrangement. A 16-min adaptation procedure caused a change when the width of a test face was gradually varied and the subject indicated that it looked normal. An alteration in the perceived shape of a test face and an ellipse was also demonstrated when subjects gave estimates of the height and width of these test objects. These studies provide evidence for the operation of memory representations as the veridical cue in process assimilation.

Adaptation, Ocular↗
PubMed1991

Movement and focused attention: a failure to replicate.

Our original goal was to explore the nature of the grouping-by-movement phenomenon reported by Driver and Baylis (1989). In their studies, distractors that moved in common with a centrally located target had a larger influence on focused-attention performance than did more proximate but stationary distractors. These results seemed particularly important since they suggested, contrary to the predictions of space-based models of attention, that attention could be allocated to noncontiguous regions of the visual field. Their results also suggested mandatory processing of stimuli with common motion. Unfortunately, we were unable to replicate this grouping-by-movement effect. In the conditions of Experiment 1 in which we replicated Driver and Baylis's methodology, stationary distractors produced a larger response-compatibility effect than did the more distant distractors that moved in common with the target. In Experiment 2, we redundantly coded the centrally located target and the far distractors with common movement and color. However, the results were identical to those obtained in Experiment 1. The stationary near distractors that appeared in a different color from the target and the far distractors produced the largest response-compatibility effect. In a final experiment, we attempted to compensate for the reduced acuity of the moving distractors by adjusting their size by a cortical magnification factor. However, even with this manipulation, we found a larger response-compatibility effect for the stationary near distractors than for the moving distant distractors. Our results suggest that subjects are capable of selectively processing a target item that moves in common with distractors.

Adolescent↗
PubMed1992

Active regulation of altitude as a function of optical texture.

Two empirical studies are reported that examine active regulation of altitude as a function of the type of ground texture. Three ground textures were examined: lines perpendicular to the direction of motion, lines parallel to the direction of motion, and the combination (i.e., square or checkerboard texture). Although subjects only controlled altitude, disturbances were introduced on three axes: vertical, lateral, and fore-aft. The results show a clear advantage for texture parallel to the direction of motion. However, in considering these results in the context of previous research on altitude control, the argument is made that there is no compelling evidence that suggests either parallel (splay) or perpendicular (density) texture is privileged with regard to altitude control. Rather, the most effective display for altitude control will be the one that best isolates the optical activity associated with changing altitude from the optical activity arising from other sources of disturbance (such as forward locomotion). Such a display will make it easier for the observer to distinguish and respond specifically to the disturbances of altitude.

Adult↗
PubMed1975

Tests of the psychological meaning of the power law.

The purpose of this study was to establish a theoretical framework for Stevens' empirically derived power law. Three models were proposed to explain the power law. They respectively outline how sensory, stimulus, and response variables determine the judgmental behavior in a psychophysical task. A correlational study on individual differences in exponents was carried out to test the predictions derived from each model. The use of four different sensory continua and four scaling procedures provided the experimental means of manipulating the sensory, stimulus, and response variables in the scaling situation. The results showed that response variables are important determinants of judgmental behavior in psychophysical scaling. These findings suggest that subjects' responses to stimulus intensities in a scaling task are largely cognitive.

Adolescent↗
PubMed1977

Coordination of vision and prehension in young infants.

Infants aged 3, 5, and 7 months were shown solid objects and comparable intangible images of objects both within and beyond possible arm's reach. The infant's emotional reactions and reaching behavior in the presence of the image stimuli were very similar to their responses to the solid objects. The results do not support the reports of previous studies using a similar tactual-visual conflict situation that young infants become emotionally distressed when presented with discordant visual and tactual information. It was concluded that the initation of reaching attempts by young infants is predominantly visually controlled and any tactual-kinesthetic feedback from prehension seems to produce very little modification of young infants' reaching behavior.

Age Factors↗
PubMed1978

Effect of perspective and slant on perception of apparent size and distance.

An experiement was performed to re-examine the role of linear perspective and floor slant on apparent size and distance scales. Misleading perspective cues did not alter the observers' apparent distance scales but did influence the absolute magnitude of distance judgments; floor slant exerted little influence on apparent distance scales or the absolute magnitude of distance judgments. Neither perspective nor slant manipulation reliably affected apparent size scales or exerted more than a minor influence on the absolute magnitude of size judgments.

Cues↗
PubMed1977

The moon illusion: a test of the vestibular hypothesis under monocular viewing conditions.

The results of earlier monocular experiments on the moon illusion have been either negative or confounded. To test the role of vestibular function, 24 subjects made forced-choice distance comparisons between stimuli mounted in translucent tubes. The stimulus tube for standard distance could be positioned in three viewing angles (45 degrees up, horizontal, and 45 degrees down). A comparison tube adjustable for distance was mounted horizontally. There was a greater perception of depth in the downward looking condition. The relatively weak effects are discussed in terms of a two-hypothesis explanation of the real-life moon illusion and the poor cues for depth perception in monocular viewing.

Astronomical Phenomena↗
PubMed1991

Effect of geometric parameters of perspective on judgements of spatial information.

15 university students performed an exocentric judgement task in which they estimated the azimuth and elevation separating two computer-generated cubes, using a perspective display. The perspective displays were created by varying two geometric parameters of perspective, the geometric field of view and station-point distance. Further, the radial distance separating the computer-generated images was varied. Analysis indicated that azimuth errors varied as a function of geometric field of view, radial distance, and station-point distance, while elevation errors varied as a function of geometric field of view and radial distance.

Adult↗
PubMed1991

Perceived depth scales with disparity gradient.

Perceived difference in depth between two adjacent stimuli decreases with increasing disparity gradient even if the disparity stays constant, ie when the stimuli approach each other along paths within fronto-parallel planes. This depth scaling effect is more pronounced with line stimuli than with two isolated points or two small symbols and is insignificant for easily discriminable symbols. The decrease in perceived depth is more pronounced for horizontal orientation than for oblique or vertical orientation. The ratio of perceived depth difference to displayed disparity difference also decreases when the distance between the stimuli increases at a constant gradient in depth. This is to say that we are more correct in our depth estimates for steep gradients in depth when the euclidean distance between the stimuli is short.

Attention↗
PubMed1991

Induced motion: isolation and dissociation of egocentric and vection-entrained components.

Induced motion (IM) is illusory motion of a stationary test target opposite to the direction of the real motion of the inducing stimulus. We define egocentric IM as an apparent motion of the test target relative to the observer, and vection-entrained IM as an apparent motion of a stationary object along with an apparent motion of the self (vection) induced by the same stimulus. These two forms of IM are often confounded, and tests for distinguishing between them have not been devised. We have devised such tests. Our test for egocentric IM relies on evidence that this form of IM is due mainly to a misregistration of eye movements when optokinetic nystagmus (OKN) is inhibited, and on evidence that OKN is evoked only by stimuli in the plane of convergence. Our test for vection-entrained IM relies on evidence that vection is evoked only by the more distant of two superimposed inducing stimuli. Thus we found egocentric IM to be induced without vection or vection-entrained IM when subjects converged on a foreground moving display with a stationary display in the background, and vection-entrained IM to be induced without egocentric IM when subjects converged on a stationary-foreground display with a moving display in the background. The two types of IM were evoked in opposite directions at the same time when subjects converged on a foreground moving display while a background display moved in the opposite direction. The two forms of IM showed no signs of interaction, and we conclude that they rely on independent motion mechanisms that operate within distinct frames of reference. A control experiment suggested that the depth adjacency effect in IM is determined by the depth adjacency of the inducing stimulus to convergence, not just to the test target.

Acceleration↗