Cyclopean tilt aftereffects can be induced monocularly: is there a purely binocular process?

Abstract

A series of experiments have been reported by Wolfe and Held which they have taken as evidence for the existence of more than one binocular process in human vision, specifically a simple binocular process (OR-gate) and a purely binocular process (AND-gate). In one of their studies, it was shown that tilt aftereffects induced with cyclopean stimuli produced measurable effects only when testing was binocular, which suggested that cyclopean adaptation affects only the AND-gate mechanism. If the two alleged mechanisms (AND or OR) are independent, monocular adaptation with luminance contrast stimuli should produce aftereffects which can only be measured with luminance contrast test stimuli. Cyclopean test displays would probe only the unadapted AND-mechanism. Results to the contrary are reported, casting doubt upon the functional independence, perhaps even the existence, of the so-called purely binocular process.