Binocular Brightness Averaging and Contour Information

Binocular brightness averaging has been investigated under two conditions: with identical contour information in both eyes and with different contour information. Equibrightness curves are presented for the simple case, in which right and left test fields are identical in pattern but different in luminance. These curves are for the most part linear; i.e. if the weighted sum of left and right luminance is constant, the same binocular brightness impression is produced. The sum of the weighting co‐efficients is unity (law of complementary shares). In the absence of eye dominance, the weights are equal; otherwise a correction for eye dominance must be made. If monocular contour information is present in one test field, brightness averaging remains linear, but the weight for that eye increases at the cost of the weight for the other eye. In a region close to a monocular contour (within 1° of visual angle), the weight approaches unity, so that binocular brightness in this region is dependent upon the luminance in one eye only. A suggested explanation of Fechner's paradox is given, and the implications of the approach for the mechanism of binocular rivalry are considered.