Misperception of non-Happy Facial Features: Overshadowing and Priming by a Smiling Mouth

A smile underlies the well-known recognition advantage of prototypical happy faces in expression categorization tasks. However, a smiling mouth also has ‘side effects’: It biases a tendency to incorrectly judge as “happy” blended expressions with non-happy eyes (neutral, sad, etc.). This reveals interference with the accurate processing of such mixed-smile expressions, which are otherwise ubiquitous in social settings. To account for this effect, we investigated two mechanisms: Perceptual overshadowing driven by the smile visual saliency, and categorical priming driven by the smile diagnostic value. In Experiment 1, we obtained diagnostic values for the mouth and eye regions of facial expressions of emotion. In Experiment 2, facilitation and interference effects of prime mouths on probe eyes were examined as a function of diagnostic values. In Experiment 3, overshadowing and priming were compared. Results showed, first, a high diagnostic value of the smiling mouth, followed by disgusted, sad, and angry mouths. Second, in accordance with the diagnostic values, the mouth expressions, especially the smile, facilitated the recognition of congruent eye expressions and interfered with the recognition of incongruent eye expressions. This supports the categorical priming hypothesis. And, third, the smiling mouth still caused some (albeit limited) interference with the processing of facial information unrelated to expression (masculine/feminine appearance of the expresser). This would be consistent with an overshadowing-inattentional blindness hypothesis. An alternative affective priming hypothesis is discussed.