Abstract
Viewing a face can alter the appearance of subsequently seen faces. These adaptation effects may serve to calibrate a norm-based representation of faces, where individual instances are coded relative to an average face. The mechanisms controlling adaptation to multiple faces remain relatively unexplored, however. Here we demonstrate that the visual system can maintain adaptation to a first face while simultaneously fully adapting to a second one. Subjects viewed distorted faces and judged whether their eyes were either closer together than normal or further apart than normal. We measured the point of subjective equilibrium (PSE) where subjects were equally likely to respond "too close together" as they were "too far apart." On each trial a 2 sec presentation of an adapting face was followed by 0.2 sec presentation of a test face, and the distance between the eyes in the test face was increased or decreased by 0.064 deg using a staircase procedure. Following eight min of adaptation to the eyes-too-close face, subjects' average PSE shifted by 0.28 deg from a no-adaptation baseline, asymptoting at this level after approximately 1.3 min. When this same eight min of adaptation was preceded by 30 min of adaptation to an eyes-too-far-apart face, the PSE shifted by only 0.12 deg, asymptoting after approximately 3 minutes (difference in asymptotic levels, p <0.05). If adaptation to both faces were affecting the same mechanism, then a long enough period of eyes-too-close adaptation should be able to return the system to its previously attained asymptote. Its failure to do so implies that some amount of the initial adaptation effect is maintained even while the later adaptation reaches asymptote. This maintenance may occur at earlier stages of the visual processing hierarchy, where features of the eyes-too-close and eyes-too-far-apart faces differ and can be affected by adaptation independently.
Meeting abstract presented at VSS 2014