Two factors in the perception of velocity at a distance

Abstract

Six experiments dealing with the effect of the surrounding framework on the perceived velocity of movement were reported. Experiment 1 reproduced Brown's 11931) transposition of velocity effect. Experiment 2 demonstrated the application of relational determination to the explanation of speed constancy. Experiment 3 showed that the relational effect is independent of the perceived sizes and perceived distances of the frameworks of movement. Only relative retinal size need be considered. Experiment 4 showed that relational factors can generate large deviations from speed constancy. Experiments 5 and 6 showed that only the immediately proximate frame needs to be taken into account in assessing effects on velocity. Despite the successes of the hypothesis of relational determination, it was argued that two factors are needed to explain perceived velocity: relative object-relative displacement accounting for perceived relative velocity, and a distance calibration mechanism explaining perceived absolute velocity. © 1978 Psychonomic Society, Inc.