VISUAL-PERCEPTION OF INTENTIONAL MOTION

A series of experiments were performed to investigate how motion seque nces provide information about the intentional structure of moving fig ures or actors. Observers had to detect simulations of biologically me aningful motion within a set of moving letters. In the first two exper iments a factorial design was used, with type of instruction as a betw een-subject factor and six movement parameters (number of items, speed and directness of target and distractors, and 'relentlessness' of tar get movement) as within-subject factor; in the final two experiments, the visibility of the goal towards which the target moved and the use of a tracking movement to distinguish the target were varied. In such displays search time increases with increasing number of stimuli. It w as found that (a) the more direct the motion, the more likely it was t o be interpreted as intentional; (b) intentional motion was much easie r to detect when the target moved faster than the distractors than whe n it moved more slowly; (c) recognition of intentionality was impaired but not abolished if the goal towards which the target was moving was invisible; and (d) participants did not report intentional movement w hen the target was distinguished by brightness rather than the manner in which it moved. We argue that the perception of intentionality is s trongly related to observers' use of conceptual knowledge, which in tu rn is activated by particular combinations of features. This supports a process model, in which intentionality is seen as the result of a co nceptual integration of objective visual features.