Delayed one-trial extinction of the McCollough effect

Initial tests of the McCollough effect were made on separate groups at delays of 4, 24 or 96 h after induction, with little apparent decrement. Subsequent tests were made at 4, 24 and 96 h after each initial test delay, again using separate subject groups in order to avoid test-induced extinction. All tests consisted of magentagreen nulling of the aftereffect. A single test session, whenever administered, seems to initiate a decay or extinction process lasting several days, resembling the time course shown by repeated testing. These results are difficult to reconcile with a perceptual conditioning model of the McCollough effect.