A Velocity Analogue of Brightness Contrast

Abstract

A velocity illusion is reported which is analogous to results obtained in the case of brightness contrast. When two targets move with the same velocity against a background of smaller moving dots which have a velocity gradient, the target which is moving faster than its immediate surround appears to move faster than the target which is moving slower than its immediate surround. Apparent velocity of a target therefore depends strongly on its velocity in relation to its immediate surround; we interpret this in terms of motion-sensitive cells which have center–surround antagonisms analogous to the physiological interpretation of brightness contrast.