Stimulus length and orientation variables interact in peripheral motion perception.

To determine the effects of stimulus length and orientation on the perception of motion, 5 experienced subjects responded with a simple reaction to accelerating lines in peripheral vision while fixating on a reference cross at the center of a cathode-ray tube. Three experimental variables were involved: (a) line length, (b) direction of motion, and (c) orientation of the line with respect to the motion. Simple reaction time (RT) was significantly longer for vertical than for horizontal motion and for lines oriented in-line with the direction of motion than for lines oriented perpendicular to the direction of motion. A significant interaction was found between line length and orientation. The results show that the generalization that RT is shorter for small objects than for large objects must be modified in terms of the orientation of the object.