ABSTRACT
Metacontrast, or Type B masking, is strongest when the Mask follows the Target by 60-100 msecs. The time of the peak effect at a substantially positive SOA comprises the defining characteristic of Metacontrast, and is the basis for an interesting theoretical question: Why should maximum interactions occur when effect appears to antedate cause by 100 msecs or more? I believe, the mechanism of Metacontrast involves the interaction of two branches of the visual system with interesting implications extending to the coordination of vision and eye movements. (Documentation, when not specifically cited here, can be found in a number of recent reviews: Alpern, 1953; Breitmeyer & Ganz, 1976; Lefton, 1973; Weisstein, 1972).
