title: Mystery of the anti-McCollough effect.
abstract: The McCollough Effect (ME) is a complex perceptual aftereffect that remains of interest half a century after its discovery. It is argued that a recently reported variant, dubbed the anti-McCollough effect, is not the reverse of the ME, with aftereffect colors in the same direction as the inducing stimuli. A red-horizontal stimulus leads to a reddish aftereffect not because of red-horizontal parings, but despite them. The anti-ME is a weak standard-direction ME produced by complementary afterimage colors (afterimage green with horizontal), rather than by environmental colors, first shown decades ago. It is not a new type of contingent aftereffect. The red-horizontal pair does not interfere with the afterimage green-horizontal pair it produces because a single color-orientation pairing provides more ambiguous input than does the standard two orientation-color pairings (red-horizontal, green-vertical) of the ME. It is also argued that not even one orientation-contingent color aftereffect is convincingly shown in the "anti"-ME, let alone, as has previously been suggested, two simultaneous orientation-contingent color aftereffects in opposite directions at different levels of the visual system, in which the higher-level effect suppresses the downstream effect from reaching consciousness. The "anti"-ME can be explained by existing theories of contingent aftereffects, including perceptual-learning theory.
authors.affiliation: University of Arizona, Tucson, Arizona 85721, USA. bedford@u.arizona.edu
authors.forename: Felice L
authors.initials: FL
authors.lastname: Bedford
mesh_terms: D001244:Association; D001288:Attention; D001364:Awareness; D003118:Color Perception; D015350:Contrast Sensitivity; D005366:Figural Aftereffect; D006801:Humans; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics; D013028:Space Perception