Anti-expression aftereffects reveal prototype-referenced coding of facial expressions.

Adaptation is a powerful experimental technique that has recently provided insights into how people encode representations of facial identity. Here, we used this approach to explore the visual representation of facial expressions of emotion. Participants were adapted to anti-expressions of six facial expressions. The participants were then shown an average face and asked to classify the face's expression using one of six basic emotion descriptors. Participants chose the emotion matching the anti-expression they were adapted to significantly more often than they chose any other emotion (e.g., if they were adapted to antifear, they classified the emotion on the average face as fear). The strength of this aftereffect of adaptation decreased as the strength of the anti-expression adapter decreased. These findings provide evidence that visual representations of facial expressions of emotion are coded with reference to a prototype within a multidimensional framework.