1. an effect in which the perception of a stimulus is influenced by one’s immediately preceding perceptions. It can be demonstrated in experiments that involve making successive changes to a stimulus that varies along some dimension and asking a participant to describe his or her perception. When values along the dimension are steadily increased, there comes a point at which the participant will begin to place the percept in a different category (e.g., a sound is loud rather than quiet). However, when values along the dimension are decreased, the crossover point will occur at a different point along the dimension.

2. in vision, the tendency for a perceptual state to persist under gradually changing conditions. For example, stereoscopic fusion can persist, producing the appearance of depth even when binocular disparity between the two images becomes so great that they would normally not be able to be fused. —hysteretic adj.