Abstract
The perception of color afterimages has been recognized for centuries, and it is widely accepted that color afterimages reveal a categorical relationship between color percepts. The perception of facial expression afterimages is a much more recently recognized phenomenon, and it too can be used to map the categorical relationships between percepts. One theory predicts a symmetric relationship between categories of facial expressions, similar to a color wheel. In contrast, an evolutionary or functional perspective predicts a strongly asymmetrical relationship between categories of facial expressions. A series of three experiments test these predictions. In each experiment, subjects fixate on an image of a facial expression for 40 seconds, and then view a neutral image of the same person for 1000ms. Subject are then asked to report, in a forced choice paradigm, what facial expression the second image appeared to have. The first experiment revealed that happy and sad are opposites of one another, insofar as each symmetrically evokes the other afterimage. The second and third experiments reveals that given an image of fear, anger, surprise or disgust, the afterimage is perceived as a happy facial expression, whereas fixating on a happy face consistently results in the perception of a sad afterimage, suggesting an asymmetric relationship between categories of emotional facial expressions. The evolutionary and functional explanations for this asymmetry are discussed.
NSERC: National Sciences and Engineering Research Council of Canada