Dark adaptation and the Hermann grid illusion

Abstract

The latency of the perception of the dark spot at the intersection of a Hermann grid was measured before and after dark adaptation. It was found that dark adaptation significantly increased the latency of perception of the spot while light adaptation had no effect. This finding was predicted from the Jung and Spillman account of the Hermann grid illusion and from the Kuffler et al. finding that inhibitory receptive fields of the cat’s retinal ganglion ceils are reduced in size and responsiveness after dark adaptation. The significance of this finding in relation to other simultaneous contrast phenomena is discussed.