"Passive suppression" of optokinesis by stabilized targets.

Subjects gazed passively at a sinusoidally oscillating optokinetic stimulus. They made no attempt to look at a target which appeared, stabilized on the retina at one of several locations, yet the appearance of the target caused rapid and prolonged suppression of optokinesis. Suppression declined (optokinesis increased) as target eccentricity increased, but could be observed for eccentricities up to 15-20 deg. We propose that a target moving relative to a background is a stimulus for suppression of optokinesis, depending substantially on the visual properties of the target and not the act of attending to it.