Abstract
What we see is a function not only of incoming stimulation, but of unconscious inferences in visual processing. Perhaps the most powerful demonstrations of this are bistable images, wherein the same stimulus alternates between two very different percepts, corresponding to two competing stable states of an underlying dynamic system. What causes the percepts to switch? Previous research has implicated voluntary effort (e.g. mediated by attention) and stochastic processing. Here we explore a third possibility, wherein percepts may switch as a result of data-driven manipulations, even when those manipulations are brief and observers are unaware of them. This is difficult to study with most bistable images, since the percepts are so volatile and the switching so frequent. A notable exception is the Spinning Dancer animation: a spinning woman is depicted in silhouette, so both her orientation in depth and direction of rotation are ambiguous. Still, many observers see her rotating in the same direction for long periods of time, interrupted only rarely by involuntary switches. We introduced disambiguating information into this display, in the form of explicit contours on the silhouette that indicated occlusion (e.g. which leg is behind the other). These contours were subtle and presented quickly enough that most observers failed to notice them throughout the entire experiment. Nevertheless, their impact on switching was strong and systematic: the cue typically led to a perceptual switch shortly thereafter, especially for contours that conflicted with the observer's current percept. Yet to the observers, the switches seemed stochastic. These results show not only how transient disruptions can shock a stochastic system into a new stable state, but also how the visual inferences that determine perception extract the content of incoming visual information to constrain conscious percepts — even when neither the content nor the brute existence of that information ever reaches awareness.
Meeting abstract presented at VSS 2013