Natural split-brain? Lateralized memory for task contingencies in pigeons.

The motion aftereffect (MAE) is an illusory motion in the opposite direction after the sudden halt of a prolonged visual moving stimulus. Birds could perceive the MAE as humans and other mammals. The present study was to investigate whether hemispheric asymmetries of visual processes affect this illusion. To this end, pigeons were trained to discriminate grating patterns which moved up, or down or stood still. The transfer tests were conducted under the binocular or monocular viewing condition. The choice behaviors of pigeons under the binocular and right-eye viewing condition (left hemisphere) were highly indicative for the perception of a MAE. However, the animals under the left-eye viewing condition (right hemisphere) did not change their choice patterns according to the different task displayed on the central stimulus key, but always stuck to the default option of pecking the response key ipsilateral to the open eye. We assume that memory for task contingencies were confined to the left hemisphere and could not be reached by the right half brain due to the absence of the corpus callosum.