Seeing the forest without losing sight of the trees: Details are processed despite reversal insensitivity in structure from motion

Presenting a subject with two random-dot flow fields produces a persuasive 3D percept of a rotating cylinder whose perceived direction of rotation is bi-stable and reverses spontaneously. When real reversals are introduced subjects rarely perceive them. It is possible that although these reversals are consciously ignored, they are registered and available to the visual system for potential later use. We tested this prediction by comparing the number of spontaneously perceived reversals with and without real reversals. We found that although the actual reversals were usually not perceived, they nonetheless increased the number of spontaneous flips. The visual system apparently prefers to retain global structure rather than perceive a motion change of every element in the stimulus. However, it does not completely ignore the changes and incorporates them into other emerging interpretations. These findings argue against the fatigue hypothesis of spontaneous reversals which would predict a decrease in the number of reversals and can be interpreted as supporting the information-processing view by noting that due to the real reversals, the visual system continues to accrue data that argues against the current representation and facilitates switching to the rival representation.