Do pigeons perceive the motion aftereffect? A behavioral study.

The motion aftereffect (MAE) describes an illusory motion in the opposite direction after the sudden halt of a prolonged moving visual stimulus. Behaviorally, this illusion was mostly analyzed in humans and other mammals. Up to now, birds were never tested. Since a new neural mechanism for the MAE was recently discovered in the pigeons' midbrain, the aim of this study was to investigate if pigeons can perceive this illusion. In two successive experiments, we trained animals to discriminate black and white grating patterns with two moving directions: upward or downward, or standing still. During transfer tests, animals were shortly confronted with the static pattern after prolonged exposure to a moving stimulus. The choice behaviors of these animals were highly indicative for the perception of an MAE. The possible neuronal substrate for the movement aftereffect is discussed.