Attentional limitations in the sensing of motion direction.

Attentional constraints in the perceptual analysis of motion direction were examined using two independent paradigms: redundant target visual search and the analysis of fluctuations in discrimination accuracy at threshold. Results from both methods implied that directions of object motion are analyzed in parallel when those motions are translations, independent of the observer's line of sight. The registration of rotation direction appears to be subject to a qualitatively different protocol, one that is highly capacity limited and serial-like. These results suggest that scene-based descriptions, as opposed to image-based descriptions of motion, mediate the allocation of attention.