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Biomedical subjects

W C Gogel

Publications and source records attributed to W C Gogel.

At least 37 records · Page 2Linked to original sources
PubMed1979

Induced motion as a function of the speed of the inducing object, measured by means of two methods.

Induced motion is illustrated by the apparent motion imparted to a stationary disc by the horizontal motion of an enclosing frame. The present study examined the effect of frame speed, with a constant extent of frame motion, on the magnitude of induced motion for average frame speeds varying from 0.17 to 2.85 deg s-1. The induced motion was measured by two methods. (i) The observer adjusted the horizontal distance between comparison posts to indicate the extent of the horizontal induced motion in a physically stationary disc. (ii) The observer adjusted the slant of a comparison rod to indicate the apparent path of motion of the disc physically moving straight up and down in phase with the horizontal motion of the surrounding frame. The latter method requires the observer to integrate two apparent components of motion of the disc, one from its physical vertical motion and the other from its induced horizontal motion. The results from both methods show that substantial amounts of induction occurred at all of the frame speeds. The vector addition of apparent motions from real and from induced motion obtained from the second method, and the substantial amounts of induction found with the high frame speeds are interpreted to indicate that the processes underlying the perception of real and induced motion are essentially the same.

Adult↗
PubMed1979

Depth adjacency and induced motion.

Induced motion was investigated as a function of the stereoscopic separation of the test and inducing object and the instructions to attend to or to ignore the inducing object. It was found that stereoscopically displacing the test object from the inducing object with both kinds of instructions resulted in a decrease in the magnitude of induction particularly with crossed disparity. These results are consistent with the adjacency principle and with the ability of attention as well as adjacency to modify the magnitude of the induced motion.

Attention↗
PubMed1977

Eye fixation and attention as modifiers of perceived distance.

An error in the perceived distance of a physically stationary object results in an apparent horizontal motion of the object if the head is moved horizontally. Procedures have been developed to use this apparent motion to measure the apparent distance of the object. Research also has indicated that the apparent distance of an object will tend to be displaced toward the distance at which the eyes are fixated. In the present study head-motion procedures were used to measure the effect of eye fixation and attention upon the apparent distance of a point of light in two experiments. Substantial errors in perceived distance occurred in the predicted direction as a function of fixation distance. Attending to an object at a distance other than the distance of the fixated point of light had a much less effect upon the apparent distance of the point. It is concluded that the apparent conomitant motion which occurs in a variety of situations as a function of the distance of fixation indicates that substantial errors in perceived distance are common in most environments.

Attention↗
PubMed1976

An apparatus for indirect measurement of perceived distance.

Two methods of measuring perceived distance are contrasted. One of these, called a direct method, accepts the observer's direct response to perceived distance as a valid measure of the distance perceived. The other, called an indirect measure, uses the observer's direct response to a perception that is not perceived distance but which has a known relation to perceived distance in order to calculate the distance perceived. There are indications that the direct measure of perceived distance provided by the verbal report sometimes will be modified by cognitive factors. A procedure and apparatus for an indirect measure is suggested which is likely to be free of the cognitive effects found in verbal reports of distance. This apparatus adjusts the distance around which the line-of-sight to the object pivots as the head is moved laterally. The pivot distance at which no apparent motion of the object occurs with head motion is a measure of the perceived distance of the object.

Cognition↗
PubMed1975

Relation between judged and physical distance in multicue conditions as a function of instructions and tasks.

Using a rod adjustable in distance 48 Os produced equal depth intervals along a floor of a visual alley (interval reproduction) or bisected a given depth interval into two equal parts (bisection). Also, verbal reports were obtained of a depth interval located at a near and farther distance from O (absolute judgments). Two kinds of instructions, "apparent" and "objective," were used with different Os with each of the three tasks. There was an over-all tendency (p = .05 on two of three tasks) for apparent instructions to produce less over-constancy or more under-constancy of distance than that produced by objective instructions. This tendency is consistent with a cognitive interpretation of over-constancy of distance. Clear over-constancy was obtained only by the combination of objective instructions and the bisection task. Clear under-constancy was obtained only by the combination of apparent instructions and the method of absolute judgments. The reason for the effect of task on magnitude of distance constancy is not understood.

Cognition↗