Fluctuations of visual awareness: Motion induced blindness and binocular rivalry

Abstract

Motion-induced blindness (MIB) and binocular rivalry (BR) are popular paradigms to study visual awareness. It has been suggested that both phenomena are related and share a common oscillator (Carter & Pettigrew, 2003). In two experiments we tried to determine whether BR affects MIB by creating an experimental paradigm that can elicit both. In the first experiment eighteen observers fixated the center of a display with a moving mask and a superimposed stationary target in a split-screen Wheatstone configuration for 30 sec. Each observer reported disappearance and reappearance of a salient target dot in the upper visual field by pressing and releasing a labeled key. The mask was a rotating grid of crosses or a drifting sine-wave grating. In a within-subjects design the mask was presented in rivalry or not; with opposite rotation and orthogonal drift in the left and right eye or with the same rotation and drift in both eyes. In addition, the target was presented to both eyes (binocular target) or to one eye only (dichoptic target). Results show that MIB as measured by normalized disappearance was significantly increased for dichoptic targets but remained unaffected by binocular rivalry in the different masks. Independence of MIB from BR was confirmed in a second experiment in which isoluminant red and green target dots were presented to the left or right eye and observers reported perceived color as a measure of binocular rivalry in addition to target disappearance. In conclusion, our preliminary results suggest that MIB is independent of BR. Further analyses on the dynamics of target perception will inform whether or not the two phenomena fluctuate independently of each other.