VISUAL INERTIA OF ROTATING 3-D OBJECTS

Five experiments were designed to determine whether a rotating, transp arent 3-D cloud of dots (simulated sphere) could influence the perceiv ed direction of rotation of a subsequent sphere. Experiment 1 establis hed conditions under which the direction of rotation of a virtual sphe re was perceived unambiguously. When a near-far luminance difference a nd perspective depth cues were present, observers consistently saw the sphere rotate in the intended direction. In Experiment 2, a near-far luminance difference was used to create an unambiguous rotation sequen ce that was followed by a directionally ambiguous rotation sequence th at lacked both the near-far luminance cue and the perspective cue. Obs ervers consistently saw the second sequence as rotating in the same di rection as the first, indicating the presence of 3-D visual inertia. E xperiment 3 showed that 3-D visual inertia was sufficiently powerful t o bias the perceived direction of a rotation sequence made unambiguous by a near-far luminance cue. Experiment 5 showed that 3-D visual iner tia could be obtained using an occlusion depth cue to create an unambi guous inertia-inducing sequence. Finally, Experiments 2, 4, and 5 all revealed a fast-decay phase of inertia that lasted for approximately 8 00 msec, followed by an asymptotic phase that lasted for periods as lo ng as 1,600 msec. The implications of these findings are examined with respect to motion mechanisms of 3-D visual inertia.