Stuart Anstis1. 1. Department of Psychology, UC San Diego, La Jolla, CA 92093-0109, USA. sanstis@ucsd.edu
Abstract
UNLABELLED: In a novel 'zigzag motion' display, random dots made alternate long and short jumps, 10 mm downward and 1 mm to the right. The zigs and zags were either at right angles (differing by 90 degrees) or in opposite directions (180 degrees). RESULT: The perceived direction of motion varied with the viewing distance or spatial scale. During close-up [or distant] viewing the display appeared to move in the direction of the short [or long] jumps. When the motion was stopped after 30 s, a motion aftereffect (MAE) was seen, driven by the short jumps but not the long jumps. Therefore, the perceived direction of motion was dissociated from its aftereffect. A picture rotated alternately 5 degrees clockwise (CW) and 1 degrees counterclockwise (CCW) and appeared to rotate jerkily CW. When stopped, a clockwise MAE was seen, appropriate to the small 1 degrees jumps. If the test field contained blurred, dynamic visual noise, the MAE was now CCW, appropriate to the large 5 degrees jumps; the large jumps drove the perceived motion direction and dynamic MAE, but the small jumps drove the static MAE. CONCLUSION: Winner-take-all competition between pathways tuned to fast and slow movements. Their independent adaptation gave opposite static and dynamic MAEs.
UNLABELLED: In a novel 'zigzag motion' display, random dots made alternate long and short jumps, 10 mm downward and 1 mm to the right. The zigs and zags were either at right angles (differing by 90 degrees) or in opposite directions (180 degrees). RESULT: The perceived direction of motion varied with the viewing distance or spatial scale. During close-up [or distant] viewing the display appeared to move in the direction of the short [or long] jumps. When the motion was stopped after 30 s, a motion aftereffect (MAE) was seen, driven by the short jumps but not the long jumps. Therefore, the perceived direction of motion was dissociated from its aftereffect. A picture rotated alternately 5 degrees clockwise (CW) and 1 degrees counterclockwise (CCW) and appeared to rotate jerkily CW. When stopped, a clockwise MAE was seen, appropriate to the small 1 degrees jumps. If the test field contained blurred, dynamic visual noise, the MAE was now CCW, appropriate to the large 5 degrees jumps; the large jumps drove the perceived motion direction and dynamic MAE, but the small jumps drove the static MAE. CONCLUSION: Winner-take-all competition between pathways tuned to fast and slow movements. Their independent adaptation gave opposite static and dynamic MAEs.