Human vision favors centrifugal motion.

Reaction times to motion onset were measured for targets in the peripheral field. Horizontal motion away from fixation evoked faster reactions than did motion toward fixation. The difference between motion toward fixation and motion away from fixation (i) increases with stimulus eccentricity, (ii) is not found when motion is along a vertical axis, and (iii) fails to affect contrast thresholds. The anisotropy between centrifugal and centripetal motion is correlated with differences in the apparent speed of targets moving in the two directions.