Representational development of direction in motion perception: A fragile process

Empircial and theoretical study of process by which directional information is extracted from a moving target's trajectory

Abstract
Response to a change in direction of motion is more rapid if the target moves in a predictable direction before the change than if the pre-change direction is not predictable. However, if the target trajectory is viewed for approximately 500 msec prior to direction change, the effect of directional predictability disappears.

The visual system uses information wrung from the display prior to change in direction to construct a representation of target trajectory that is increasingly accurate as exposure increases. To study this process we injected various temporal transients into the trajectory prior to the change in direction.

Results show that extraction of directional information is interrupted if:

  • motion continues along a constant trajectory, but the target disappears briefly behind an implicit or real occluder
  • the target pauses briefly, but remains visible
  • the target changes speed briefly, while continuing to move in the same direction.

    The discussion covers the findings' implications for a theory of motion processing. These implications include a framework for understanding interactions between stimulus-derived (exogenous) and a priori (endogenous) information.