Contributed Talks I: A paradoxical misperception of relative motion at the fovea.

Abstract

Images moving in a direction consistent with retinal slip appear stable even if that motion is amplified. This persists even in the presence of a world-fixed background, giving rise to a misperception of relative motion. This was previously explored 2° away from the line-of-sight. We asked: Does this phenomenon persist closer to the fovea? Would an image slipping with only a quarter of the retinal slip relative to a world-fixed image be perceived as stable? We implemented a novel method presenting: a fixation target and two circular images offset on either side horizontally by 0.43°, through an adaptive optics scanning light ophthalmoscope. The left image moved independently on a random walk and the right image moved contingent to retinal motion. Subjects adjusted the random walk image's magnitude of motion until it appeared to match the retina-contingent image's motion, quantifying its perceived motion. We found a surprising discontinuity in the results: with background content present, images slipping consistent with the eye's motion appeared stable, even if slipping with a quarter of the retinal slip, while images moving inconsistent with retinal motion appear to move. When all background content was removed, the perception of motion was entirely different. These results confirm that in the fovea, the visual system perceptually suppresses motion of images that move in directions consistent with retinal slip and that background content is crucial for this computation.