Fig. 2.

Results. Percentage of trials on which the physically matching pair of stimuli was selected as more similar to one another than the contrast matching pair. In D.B.'s right hemianopic visual field, he judges a pair of discs such as those seen in Fig. 1e as being similar, although, in both his normal and damaged fields, he is subject to the luminance illusion corresponding to that which makes us see the discs presented in Fig. 1e as different. Error bars are 95% binomial confidence intervals.