AUTOKINESIS AND PERCEPTION OF MOVEMENT - PHYSIOLOGY OF ECCENTRIC FIXATION

An after-image method was devised, by means of which the average direction of fixation could be measured to within one min of arc. During autokinesis fixation was found to lag behind the apparent movement. When a stationary target appeared to move during optokinetic stimulation, the mean eccentricity of fixation was 1 1 2 min of arc. Tracking a point of light which was really moving showed again that the fixation lagged behind the movement. The eccentricity of fixation was dependent upon the speed of the real movement. If, at very low speed, the mean eccentricity was less than 1 min of arc, real movement could not be distinguished from autokinesis. During fixation of a point of light in the dark, the mean eccentric fixation is the physiological correlate of the perception of movement and also the quantitative stimulus to tracking movements of the eye. © 1969.