As expected, exposure to happy or sad expressions shifts the psychometric function toward the adaptor. Here, we quantify sensory and decision-making contributions to adaptation in a facial expression paradigm. Changes in the decision-making process, however, may also be a component of adaptation. This phenomenon is commonly assumed to be sensory in origin. As a result, prolonged exposure to particular stimuli alters judgments about subsequent stimuli. Perceptual systems adapt to their inputs.
