BINOCULAR BRIGHTNESS SUMMATION IN DARK ADAPTATION

Although Piper^1a and others, including Behr,² Cook,³ DeSilva and Bartley,⁴ Messmer⁵ and Stargardt,⁶ reported the presence of brightness summation in binocular vision, particularly under conditions of dark adaptation, some investigators either have failed to find evidence for summation or have attempted to explain the lower binocular thresholds of sensitivity to brightness without reference to central neural activity. Among the latter are : Müller,⁷ who accounted for lower binocular thresholds assuming that binocular judgments are more easily made; Sherrington,⁸ who worked with monocular and binocular flicker effects and found no summation, and Lohmann,⁹ who believed that lower binocular thresholds could be explained by the increase in the retinal areas involved when both eyes were used. Others who reported no summation include Abney and Watson,¹⁰ Best¹¹ and Graham.¹² That the various studies have not been in agreement is due largely to