Contribution of bottom-up and top-down motion processes to perceived position

Perceived position depends on many factors, including motion present in a visual scene. Convincing evidence shows that high-level motion perception—which is driven by top-down processes such as attentional tracking or inferred motion—can influence the perceived position of an object. Is high-level motion sufficient to influence perceived position, and is attention to or awareness of motion direction necessary to displace objects ’ perceived positions? Consistent with previous reports, the first experiment revealed that the perception of motion, even when no physical motion was present, was sufficient to shift perceived position. A second experiment showed that when subjects were unable to identify the direction of a physically present motion stimulus, the apparent locations of other objects were still influenced. Thus, motion influences perceived position by at least two distinct processes. The first involves a passive, preattentive mechanism that does not depend on perceptual awareness; the second, a top-down process that depends on the perceptual awareness of motion direction. Each contributes to perceived position, but independently of the other