The reversal of simultaneous brightness contrast.

Abstract

Two physically identical gray figures, mounted on adjacent black and white grounds, were compared for apparent brightness by various observers. A minority of the reports indicated a reversal of the classical contrast effect, viz., the gray figure on the black ground appeared darker than the gray on the white. This anomaly was investigated with controlled modification of several variables including the design of the figures, the sophistication of the subjects, the distance of observation, and the technique of evaluating the apparent brightness. The reversed effect lacked stability and exhibited large individual differences. Factors which favored reversal were: complexity and outline in figures as compared with simplicity and soJid silhouettes; unfamiliarity of observers with the nature of the usual classical contrast effect; and relatively near distances of viewing which permit perception of fine detail. Evidence is advanced for the view that the reversals were the result of opposition or conflict between the conditions of so-called brightness constancy and brightness contrast.