Psychophysical investigations of binocular interactions have shown that there are at least two binocular channels in the human visual system. In addition to an interocular channel that responds to input to either eye, there is evidence of a binocular channel that acts as a logical AND-gate. This second binocular mechanism will only respond to simultaneous stimulation of both eyes with similar images. Support for the existence of this \u27AND\u27 mechanism has been provided by adaptation (Wolfe & Held, 1981, 1982; Wilcox, Timney, & St. John, 1990), and detection experiments (Cohn & Lasley, 1976; Cogan, 1987).;In predicting the results of adaptation experiments several investigators have adopted a \u27neural averaging\u27 hypothesis which proposes that the output from all available monocular and binocular channels is averaged to produce the final percept. Experiments I and II evaluated this suggestion and a second proposal that all channels are independent, and that detection is mediated by the most sensitive of these channels. The results of both studies showed that there is interaction between the neural channels.;While there is convincing support for the existence of an AND channel, little is known about its response characteristics. Experiments III through V examined the temporal aspects, threshold sensitivity, and interocular spatial phase sensitivity, of an AND mechanism. Collectively, these experiments support the assumption that the AND channel requires binocular stimuli that are similar along a number of dimensions. The final experiment investigated a potential functional role of the AND mechanism in human vision. In this study, both adaptation and subthreshold summation procedures were used to assess the contribution of the AND channel to binocular summation. The results demonstrated that an AND mechanism makes a significant contribution to binocular summation.;It has been argued previously (Wolfe, 1986) that an AND mechanism is important to stereoscopic vision. Given Wolfe\u27s assertions and the results of Experiment VI, it appears that the output of the AND channel is not necessarily restricted to a single process, but could contribute to several visual tasks, including binocular summation and stereopsis
