Foundations Of Cognitive Science

Relative Velocity Principle

The relative velocity principle is a natural constraint that Dawson (1991) employed to solve the motion correspondence problem. According to this constraint, the visual system prefers to assign motion correspondence matches such that neighbouring elements in Frame I of an apparent motion display move in similar directions and at similar speeds. The closer the elements are to one another, the more influential is this constraint.

The relative velocity principle is important because it was rejected by Ullman (1979), who argued that only the nearest neighbour principle was required to solve the problem. However, Dawson (1987) reported the results of experiments that clearly demonstrated that the relative velocity priniciple affected human perceptions of apparent motion displays, and which indicated that Ullman's motion correspondence theory was therefore incomplete.


  1. Dawson, M. R. W. (1987). Moving contexts do affect the perceived direction of apparent motion in motion competition displays. Vision Research, 27, 799-809.
  2. Dawson, M. R. W. (1991). The how and why of what went where in apparent motion: Modeling solutions to the motion correspondence process. Psychological Review, 98, 569-603.
  3. Ullman, S. (1979). The interpretation of visual motion. Cambridge, MA: MIT Press.

(Added November 2009)