Multistability of overlapped face stimuli is dependent upon orientation

Stimuli composed of two overlapped faces, one rotated 45 degrees clockwise and the other 45 degrees counterclockwise. produce perceptual rivalry where by both faces cannot be simultaneously perceived. We obtained subjective an d quantitative measures of this rivalry effect and examined if it persists with inverted stimuli. Our results show that upright stimuli are multistabl e, with alternations occurring From one face to the other within 2 s. Inver ted stimuli were instead perceived as ambiguous in half of the trials, indi cating weaker perceptual rivalry in that condition. We suggest that overlap ped faces produce perceptual rivalry because each face is readily interpret ed into a Gestalt, an effect that in turn is dependent upon orientation.