All Smiles are Not Created Equal: Morphology and Timing of Smiles Perceived as Amused, Polite, and Embarrassed/Nervous

Zara Ambadar, Jeffrey F. Cohn, and Lawrence Ian Reed
Department of Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania


We investigated the correspondence between observer judgments of smiles and the morphological and dynamic characteristics of the smiles that map onto those meanings. Morphological characteristics included co-activation of Orbicularis oculi (AU 6), smile controls, mouth opening, amplitude, and asymmetry of amplitude. Dynamic characteristics included duration, onset and offset velocity, asymmetry of velocity, and head movements. Observers (N=101) judged 122 smiles as amused, embarrassed, nervous, polite, or other. Fifty-four smiles met criteria for classification as perceived amused, embarrassed/nervous, polite, or other. Characteristics of these smiles were measured using the Facial Action Coding System (Ekman, Friesen, & Hager, 2002) and Automated Facial Image Analysis (Cohn & Kanade, 2007). In comparison with perceived polite, perceived amused more often included Orbicularis oculi co-activation (AU 6), open mouth, smile controls, larger amplitude, larger maximum onset and offset velocity, and longer duration. In comparison with perceived embarrassed/nervous, perceived amused more often included AU 6, lower maximum offset velocity, and smaller forward head pitch. In comparison with perceived polite, perceived embarrassed more often included mouth opening and smile controls, larger amplitude, and greater forward head pitch. Occurrence of the AU 6 in perceived embarrassed/nervous and polite smiles questions the assumption that this action together with a smile is sufficient to communicate felt enjoyment. By comparing three perceptually distinct types of smiles, we found that perceived smile meanings were related to specific variation in smile morphological and dynamic characteristics.


Example of perceived Amused smile:



Example of perceived Embarassed/nervous smile:


Example of perceived Polite smile: