Perceived Movement in Depth as a Function of Luminance and Velocity

Abstract

The ability of subjects to perceive movement in depth of a luminous object in an otherwise stimulus-free surround has been studied. This research resulted from an analysis of anticipated visual skills required in certain manned space vehicle operations. This stimulus object subtended a visual angle of 40 min of arc at the onset of movement. Luminance was varied from 0.001 to 1.0 ft-Lambert. The speed of movement was varied so that the change in visual angle of the stimulus varied from approximately 1/4 min of arc per sec to approximately 2 min of are per sec. Both monocular and binocular viewing conditions were used. Detection of movement improved as the luminance increased from 0.001 to 0.1 ft-Lambert. A. further increase in luminance to 1.0 ft-Lambert did not affect performance significantly. Rate of movement interacted with the threshold criterion level; the higher rates of movement were superior for the higher threshold criteria. Binocular viewing was superior to monocular. Under optimum conditions 75 per cent correct detection was achieved when the visual angle increased or decreased by 2 per cent.