Adaptation of face gender, expression, and head direction from random-noise adaptation images: A surprising prediction of Li and Atick’s efficient binocular coding theory

We present a novel face adaptation paradigm that follows from Li and Atick’s (1994) theory of efficient binocular encoding. In this theory, the inputs to the two eyes are combined using separately adaptable binocular summation and differencing channels. We designed a dichoptic test stimulus for which the summation channel sees one face image, and the differencing channel sees a different face image. The pairs of faces seen by the two channels were male/female, happy/sad, or turned slightly to the left/right. The face perceived by the observer depended on the relative sensitivities of the two channels. We manipulated channel sensitivity by selective adaptation with images that were low-pass filtered white noise. In correlated adaptation, each eye received the same adaptation image, which selectively adapted the summation channel; in anticorrelated adaptation, the adaptor contrast was reversed between the eyes, selectively adapting the differencing channel. After adaptation, we presented the dichoptic test stimulus, and found that the observer perceived the summation channel’s face image most often after anticorrelated adaptation, and perceived the differencing channel’s face image most often after correlated adaptation. For male/female and left/right judgements, perception was generally biased towards the summation channel; for happy/sad judgements, there was little or no bias