Movement detection by cats: invariance with direction and target configuration.

Absolute thresholds for movement detection were measured in three cats and two human subjects under similar conditions. A two-alternative spatial forced-choice procedure was used with the method of constant stimuli. When targets were moving random-dot patterns, cat thresholds ranged from .6 degrees to 2.3 degrees/sec, while human thresholds were approximately .05 degrees/sec. Similar thresholds were found for cats tested with square wave gratings ranging in spatial frequency from .18 to 1 cycle/degree. Neither cats nor humans showed any directional asymmetry for motion detection.