Abstract: This experiment investigated the decay process of the opposite monocularand binocular McCollough effects. The strength of the after-effect wasmeasured by matching it with another light from a three color colorimeter,then the chromaticity of the matched light was computed. It was found thatboth the monocular and binocular after-effects decreased in excitation puritywith time. It showed a sharp decrease in the first 3 hours, afterwards thistrend slowed down and lasted to as long as 24 hours. However, with the eyesclosed for 9 hours after adaptation, there was no decay, the strength of theafter-effects remained almost the same as those immediately after adaptation. It seemed that the restoration to equilibrium for pattern coritingent colorafter-effects is not endogenous but dependent upon retinal stimulation. Thiswas unlike the tilt after-effect which decayed both with eyes open or witheyes closed.

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