Abstract
Facial expressions form a limited and stereotyped set of stimulus categories that are readily recognizable and which may in part be encoded in distinct neural pathways. We used adaptation to examine the interactions between the perception of the six basic expressions (anger, fear, happiness, sadness, surprise and disgust). The Singular Inversions program FaceGen Modeller was used to create faces with varying degrees of expression relative to a neutral face with average characteristics. Observers used a seven-point scale to rate the perceived magnitude of these expressions before or after adapting to the neutral face or the extreme level from each of the six categories. In each case adaptation produced the strongest changes in the perceived intensity of the adapting expression, so that the aftereffects are selective for each category. Non-adapted expressions also tended to be reduced in perceived magnitude rather than enhanced (though weak enhancements were suggested in happy or sad faces after adapting to surprised faces, or vice versa), and the largest changes in the ratings occurred for moderate contrasts of the stimuli rather than in the neutral (zero-contrast) face. This general pattern of the adaptation effects is more consistent with partially separate representations of the different expressions rather than a strong opponent coupling between specific expressions.