Moving and the motion after-effect

Abstract

The movement after-effect (MAE) is caused by inspecting a pattern in which many stimulus elements in the visual field are in coherent movement; after inspection, stationary elements seem to move in the opposite direction. By far the commonest cause of such a retinal stimulus is movement of the observer, not movement of the environment. We suggest here, therefore, that the usual laboratory stimulus for inducing the MAE presents the observer with conflicting sensory cues. The optical input is normally associated with self motion, but other cues such as the vestibular input simultaneously tell the observer that he is stationary. In these circumstances a recalibration of the relationship between optical and other information might occur and we suggest that the after-effect may be at least in part a consequence of this recalibration, rather than being entirely due to a passive fatigue-like process.