Role of Retinal Image Motion in Evoking the McCollough Effect

Abstract

MCCOLLOUGH¹ has described a phenomenon whereby after repeated, successive and alternate inspections of a black and orange straight line grating orientated vertically, the vertical white elements in an achromatic grating appeared pink and the horizontal white elements appeared greenish. This phenomenon has been termed the “McCollough effect”. The effect has been reported to persist for several days, and to be orientation specific, both with respect to head inclination and grating element orientation. Typically, in inducing the McCollough effect, subjects alternately view, for about 10 s each, a black and white grating and a homogeneously coloured field over a period of approximately 10 min (termed the inspection period). After this the subjects view two black and white straight line gratings, the elements of one being at right angles to those of the other. One of the gratings occupies the same orientation as that observed during the inspection period. Subjects report the presence (or absence) of colour in these two gratings. This is termed the test period.