The role of depth and 1/f dynamics in perceiving reversible figures

When confronted with a reversible figure, such as the Necker Cube, viewers experience a spontaneously changing percept. We assess the dynamic of how the human visual system resolves perceptual ambiguity in stimuli that offer multiple interpretations. Subjects observed the Necker cube for one of three viewing durations during which they pressed a key each time they perceived a change in the orientation of the cube. Manipulations of binocular disparity served as a parameter to control perceptual stability. Low-depth conditions yielded more perceptual reversals than high-depth conditions. A Fourier analysis performed on the time series of reversals show 1/f (pink) noise was evident in their power spectra. These results together with theoretical models of complex systems (e.g., Bak, Tang, and Wiesenfeld, 1987) suggest that depth information may guide our perceptual system into a self-organized state to assist us in resolving ambiguous information. Moreover, slopes of the spectra were steeper in high-depth and brief viewing conditions, suggesting that the visual system relies more on previous perceptual states and filters more white noise in these conditions.