Adaptation and prolonged inhibition as a main cause of motion-induced blindness.

Motion-induced blindness (MIB) is one of the most enigmatic perceptual disappearance phenomena. Here we suggest that MIB may be caused by the combined effects of two distinct adaptation processes: one shared with two other non-MIB configurations and entailing a response-gain reduction, and a second, MIB-specific transient-to-sustained incremental inhibition causing a contrast-gain reduction. Response-gain reduction is evidenced by brightness-tracking experiment where the 1-minute brightness time course of an MIB target is compared to the time courses of the same target superimposed on a static mask (SM) and on no mask at all (absent mask; AM). MIB and SM yield about the same brightness time courses with a faster initial drop and reaching a lower plateau than AM. While the frequency of phenomenal suppressions and their duration are very much reduced under SM and AM conditions, they increase as for MIB within the first 5-15 s of inspection and level off thereafter. Contrast-gain reduction over time is evidenced in a detection experiment showing that MIB target thresholds are higher and increase more steeply with inspection time than AM or SM thresholds. The interplay between these noisy adaptation and prolonged inhibition processes may well account for MIB's specificity.