Abstract
Continuous viewing of a rotating transparent object with an axis inside of the object may lead to perceptual alternation between two opposite rotations. The current consensus maintains that the bi-stable phenomenon depends on simultaneous stimulation by multiple depths defined by elements moving in different directions (1). By using a single specifically designed non-transparent object with a rotation axis outside of the object, this abstract shows that for perceiving rotation alternation the requirement for simultaneous stimulation by the elements in different depth moving in different directions is not necessary. If the rotation axis is outside, the object when moving rightward does not appear simultaneously with the same object when moving leftward at a different time, or vice versa, regardless of the real rotation leftward or rightward. Our experiments demonstrate that continuous viewing of the rotation leads to perceptual alternation also. In addition to the commonly perceived two opposite rotations, two new stable percepts occur as well. In other words, total four different stable percepts may occur (a quadri-stable phenomenon): rightward rotation; leftward rotation; two rotations following the infinite symbol ∞-like tracks: &uArr∞ &uArr and ⇓∞⇓. The arrow symbol indicates the moving direction of the object towards to the viewer (⇓) or away from the viewer (⇑) at the both ends of the ∞-like track. Because the elements of different depth moving in different directions do not appear simultaneously, the quadri-stable phenomenon signifies that some kinds of perceptual memory facilitate perceptual alternation. It is interesting to note that the perceptual memory, on the contrary, also stabilize percepts in perceptual rivalry (2). The quadri-stable phenomenon also suggests that using depth ambiguity to explain depth reversal is not completely satisfactory (2).
(1). Blake Nawrot. Science 244, 716-718 (1989).
(2). Leopold, etal. Nature Neuroscience. 5, 605-609> (2002).