REPRESENTATIONAL DEVELOPMENT OF DIRECTION IN MOTION PERCEPTION - A FRAGILE PROCESS

Response to a change in direction is more rapid if the target moves in a predictable direction before the change than if the pre-change dire ction is not predictable. However, if the target trajectory is viewed for approximately half a second before the change in direction, the ef fect of directional predictability disappears. Visual information gath ered prior to change in direction is used to construct an increasingly more accurate representation of target trajectory. To study this proc ess, we inject various temporal transients into the trajectory prior t o the change in direction. We find that extraction of directional info rmation is interrupted if: (i) motion continues along a constant traje ctory, but the target disappears briefly behind an implicit or real oc cluder, (ii) the target pauses briefly, but remains visible, or (iii) the target changes speed briefly, while continuing to move in the same direction. The theoretical implications for motion perception are dis cussed. These implications include a framework for understanding inter actions between stimulus-derived information and a priori information,