Abstract
While viewing binocular rivalry between two annular shaped rival targets — a stationary concentric grating and a rotating, radial grating — we noticed a novel, compelling illusion: during transitions from dominance to suppression of the radial grating, its perceived speed of rotation appeared to accelerate markedly. Intrigued by this transient illusion, we devised a matching procedure to measure the magnitude of perceived acceleration and used interocular flash suppression to control the onset of suppression of the radial grating.
Results from both experienced and naïve observers show that the magnitude of illusory acceleration increases with the contrast of the stationary pattern that suppresses the rotating radial grating. Acceleration was not experienced, however, when the contours of the radial grating were isoluminant. Nor was acceleration seen when the two dissimilar patterns were physically superimposed and viewed dioptically; interocular rival stimulation is essential to experience the illusion. By varying the duration of the interocular stimulation, we confirmed that illusory acceleration is associated with the transition from dominance to suppression, not with the state of suppression itself. Using an adaptation procedure we confirmed that illusory acceleration is not attributable to contrast or motion adaptation. Moreover, the reported acceleration is opposite to the effects of lowering the contrast of a moving stimulus, a maneuver that strongly decelerates perceived speed as we verified in a control experiment.
Motion perception, it is commonly thought, represents the culmination of neural activity arising in multiple cortical areas within the visual hierarchy. During normal viewing, that distributed activity is seamlessly coordinated, but the illusion described here implies that the onset of interocular suppression can temporarily disrupt that coordination.
This work was supported by NIH grant EY13358