Speed change detection in foveal and peripheral vision.

Perception of constant motion has been extensively studied both psychophysically and physiologically, but the human ability to detect dynamic changes in motion, such as rapid speed changes, is only poorly characterized and understood. Yet, perception and representation of such dynamic changes is of strong behavioral relevance, as illustrated by their potential for attentional capture. In the present study, we measured and compared detection thresholds for instantaneous accelerations and decelerations of drifting Gabor patches at different retinal eccentricities. As a main result, we find that detection performance depends strongly on eccentricity. Under foveal viewing conditions, average thresholds were lower for accelerations than for decelerations. However, between 5° and 15° eccentricity, this relation is inverted, and deceleration detection becomes better than acceleration detection. Results of an additional experiment suggest that this can be explained by a fast eccentricity-dependent adaptation effect. Our findings are discussed with special emphasis on their relation to data from neurophysiological experiments.