ON SOME ASPECTS OF REAL AND APPARENT VISUAL MOVEMENT.

Abstract

Some of the parameters of real and apparent movement are considered in situations where these two types of movement are encountered. Some basic properties of real movement are represented by displacement and rate thresholds as well as by limiting upper thresholds. The depth cue for monocular movement parallax can be analyzed as representing a situation in which differential angular velocity thresholds may be determined. These latter thresholds turn out to be quite small, of the order of 30 to 40 sec of arc/sec. They are influenced by a number of variables, including rate of standard stimulus, luminance, and visual axis. Differential angular velocities help to determine certain aspects of perceived movements in the third dimension, and attention is paid to the case of Ames’ trapezoid window which provides an illusion of movement. An account of apparent movement is given with special reference to Korte’s laws. The question then is asked: What mechanisms might be expected to occur in real and apparent movement? Tentative suggestions on this problem are advanced, with special attention to real movement.