Prism adaptation with simultaneous receipt of normal input

A 20-diopter vertically-displacing prism was worn on one eye in conjunction with plane glass on the other. Five groups ofSs differed in the density of a neutral filter worn over one eye. No aftereffect could be measured in either eye in any condition where the luminance of the “normal” field was equal to or greater than that of the prism field. As the luminance of the “normal” field is decreased below that of the prism field, the magnitude of aftereffect increases and is measurable in each eye.