The physiological mechanism of apparent movement.

Abstract

Retinal induction caused by stroboscopic stimuli was measured by electro-stimulation. The retinal induction caused by a 1st stimulus is changed in character and magnitude by the action of a 2d stimulus successively delivered. This phenomenon is termed "conversion of retinal induction". The phenomenon of subjective color caused by intermittent white light may be attributed to conversion. With an adequate interval between 2 stimuli, the induction lying in the field between the retinal areas exposed to the stimuli acquires the same quality as the induction at the site of stimulation, so that the 2 physically separate stimuli become fused as retinal processes. This phenomenon gives a physiological basis for perception of fused optimal motion. A gradient of retinal induction directed from the 1st stimulus to the 2d is established by conversion. The gradient is seen over a wide range of interval and is independent of fusion processes. It is suggested that a gradient associated with fusion corresponds to optimal movement, while a gradient devoid of fusion corresponds to the phi phenomenon. The interval for optimal conversion decreases with increasing intensities of stimuli, and it increases as the distance between 2 stimuli increases. These relations correspond to Korte''s laws of apparent movement.