Ullman S
Perception. 1980;9(6):617-26. doi: 10.1068/p090617.
The correspondence between line segments in apparent motion is shown to be affected by the similarity between them. Increase in orientation difference or in length ratio between lines in a competing motion configuration decreases the probability of perceived apparent motion between them. The results suggest the existence of a built-in preference metric that may reflect a measure of matching likelihood between elements in three-dimensional space.