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PubMed1996

The effect of polar projection on the perception of euclidean structure from motion.

The aim of the present study was to examine whether euclidean structure could be recovered from apparent motion sequences under polar projection. In Experiment 1, length judgments of two sides of a simulated triangle rotating in depth did not reveal effects of type of projection, polar or parallel, on the perception of euclidean structure. However, there was a significant correlation between simulated and produced slants. The results also indicated that absolute depth judgments could not be accounted for by a random mechanism suggested by Todd and Bressan (1990). Experiments 2 and 3, in which a continuous dot surface was substituted for the triangle, showed that polar projection information from a relatively large visual angle, 17.40 degrees, as compared with a small visual angle, 4.35 degrees, facilitated discrimination of depth. Produced height:width ratios were consistently related to simulated shape, although the depth dimension was underestimated. Finally, Experiment 4 showed significant correlations between simulated and produced height:width ratios that could be accounted for only by an analysis in which X and Y velocities were treated independently. As in previous experiments, the variation in the depth dimension was underestimated. It was concluded that the visual system utilizes the additional information that is available in polar projection when recovering structure from motion, but that for different reasons the perceived structure does not become euclidean. These reasons are discussed briefly.

Adult↗
PubMed1999

Symmetry and elongation of objects influence perceived direction of translational motion.

Five experiments were conducted to examine how perceived direction of motion is influenced by aspects of shape of a moving object such as symmetry and elongation. Random polygons moving obliquely were presented on a computer screen and perceived direction of motion was measured. Experiments 1 and 2 showed that a symmetric object moving off the axis of symmetry caused motion to be perceived as more aligned with the axis than it actually was. However, Experiment 3 showed that motion did not influence perceived orientation of symmetry axis. Experiment 4 revealed that symmetric shapes resulted in faster judgments on direction of motion than asymmetric shapes only when the motion is along the axis. Experiment 5 showed that elongation causes a bias in perceived direction of motion similar to effects of symmetry. Existence of such biases is consistent with the hypothesis that in the course of evolution, the visual system has been adapted to regularities of motion in the animate world.

Adult↗
PubMed1995

Cross-modality matches of finger span and line length.

Perceived finger span--the perceived spatial separation between the tip of the thumb and the tip of the index finger--was measured by using cross-modal matching to line length. In the first experiment, subjects adjusted finger span to match the length of line segments presented on a video monitor, and conversely, with both hands. Subjects also made estimates of finger span in physical units ("dead reckoning"). Finger spans were measured by using infrared LEDs mounted on the tip of the thumb and the finger tip, so the hand made no contact with any object during the experiment. Unlike in previous studies, the results suggest that perceived finger span is proportional to line length and slightly shorter than the actual span, provided that corrections are made for regression bias. The effect of finger contact was assessed in a second experiment by matching line length both to free span and to spans constrained by the pinching of blocks in the same session. The matching function when subjects were pinching blocks was accelerating, consistent with previous reports. In contrast, matched line length was a decelerating function of free span. The exponent of the free span matching function in the second experiment was slightly smaller than in the first experiment, probably due to uncorrected matching biases in the second experiment.

Adult↗
PubMed2005

Detecting event-based prospective memory cues occurring within and outside the focus of attention.

Event-based prospective memory cues are environmental stimuli that are associated with a previously established intention to perform an activity. Such cues traditionally have been placed in materials that receive focal attention during an ongoing activity. This article reports a direct comparison of event-based cues that occurred either within the focus of attention or at the periphery of such attention. When the cue occurred outside focal attention, manipulating that cue changed event-based prospective memory. The identical manipulation had no effect on event-based responding if the cue occurred within focal attention. These results suggest that cue characteristics can compensate for attention being directed away from an aspect of an ongoing task that contains event-based prospective memory.

Attention↗
PubMed1978

Attention to compounds by retarded adults.

Severely retarded adults were presented with a matching task in which each of the alternatives to the stimulus that was identical to the target stimulus differed from it on one dimension only. Matching performance was found to be good both when the target stimulus had two relevant dimensions and when it had three relevant dimensions. The findings were consistent with those of Tighe and Tighe (1972) and other (Cole, 1973; Tighe, 1973) that the salience of compounds is higher than that of components for persons of lower developmental level.

Adolescent↗
PubMed1978

Comparison of the performance of first-grade and mentally retarded students on the Peabody Mathematics Readiness Test.

The Peabody Mathematics Readiness Test was developed to assess mathematics readiness and identify children who would encounter difficulty in first-grade mathematics. In the present study, we compared performances of mentally retarded subjects and first-grade subjects on this test. Retarded subjects' mean scores were significantly lower than those of the nonretarded subjects on the drawing test; however, there were no significant differences between the mean scores of the groups on the other five subscales.

Adolescent↗
PubMed1980

[Visual perception disorders in depressive syndromes].

A wide range of psychopathological visual phenomena, part of which are traditionally considered as derealizational disturbances, are described in the structure of depressive states. Five main types of disordered visual perception are singled out, which differ by their structure and degree of correlation with the depressive affect and symptoms of depersonalization in a wide sense. The results point to certain dynamics in the described phenomena, their sensory basis. Electrooculographic studies of eye movements indicating a peculiar formation of a visual image in different forms of depressions are demonstrated.

Adolescent↗