In the last post we looked at the a number of images and altered single characteristics to assess the impact on the contrast illusion. The hypothesis generated was that the letter A when compared to a filled circle could with a graded background produce the illusion of heterogeneity within the same shape (i.e within the letter A). The underlying assumption was that the geometry of the letter A would impact on the perception of contrasting colours in the background and foreground to produce the illusion of variegation. The above diagram was created to test this hypothesis. A cursory examination of the diagram suggests that the hypothesis is incorrect. Nevertheless the more general contrast illusion persists. Both the A’s and the solid filled circles appear lighter on the right than on the left.
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