Peripheral Movement,Induced Movement,and Aftereffects from Induced Movement

Substantial rotatory induced movement and aftereffects associated with induced movement were observed in a large static patterned disc bounded at its periphery by a rotating patterned annulus. The area of the annulus was less than one tenth that of the disc, so its peripheral location seemed to be important in eliciting these phenomena. This was confirmed in two experiments comparing a peripheral annulus and a relatively central annulus in their ability to elicit induced movement and aftereffects in the same large static field. Aspects of the vection (induced self-movement) phenomenon may have been involved in generation of induced movement. This suggested that the motion-inducing properties of the peripheral annulus might have derived from: (i) its eccentric location in the perceiver's visual field; or (ii) its location with regard to the display itself. Two further experiments showed that (ii) was important for the elicitation of both induced movement and the aftereffects, and (i) was important for the elicitation of induced movement. Neurons responsive to relative movement in conjunction with lateral inhibition may provide a partial explanation for these effects. However, they do not explain why the visual system can assign considerable movement to a large static field under the conditions of these experiments.