Orientation-sensitive After-effects of Dichoptically Presented Colour and Form

Abstract

MCCOLLOUGH¹ discovered that if a grating pattern of (say) red vertical stripes is viewed alternately with one of green horizontal stripes for some minutes, an orientation-specific colour after-effect is observed when viewing a black-and-white test grating. White stripes in a given orientation appear tinted with the hue complementary to the hue presented at that orientation in the original stimulus. McCollough observed that if only one eye was exposed to the original sequence of stimuli, no after-effect was seen when the other eye was used to view the test grating. From this she concluded that the adaptation responsible for the after-effect must occur somewhere in the uniocular pathway before signals from left and right eyes are combined. She suggested as a possible explanation that orientation-sensitive channels in the uniocular nervous system (“edge-detectors”) may be colour-coded, so that strong adaptation with bars of red light in one orientation leads to a “minus-red” after-response from the adapted channels to similarly oriented colourless bars. Harris and Gibson² have confirmed that the effect persists in conditions ruling out ordinary negative afterimages, which Murch and Hirsch³ have shown sufficient to induce it. Held and Shattuck⁴ have demonstrated a corresponding after-effect of colour upon the perceived orientation of test bars.