Motion perception modified by eye movements

Evidence is presented that eye movements have a strong modulation effect on perceived motion of an object in an induced motion situation. It was investigated whether pursuit eye movements affect motion perception, particularly target velocity perception, under the following stimulus conditions: (1) laterally moving objects on the computer display, (2) recurrent simple target motion and, (3) a unilaterally scrolling grid. The observers' eye movements were recorded and, at the same time, their responses with respect to their velocity perception were registered and analyzed in synchronization with the eye movement data. In most cases, when pursuit eye movements were synchronized with the movement of the target, the velocity of the target was judged to be slow or motionless. An explanation of the results is presented which is based on two sources of motion information: (1) A displacement detector in terms of retinal coordinates, and (2) a proprioceptive sensing unit associated with the eye movements. The veridicality of the judgments of the velocity of the object motion was determined by the complexity of the processes for integrating the signals from the two channels.