We investigated the correspondence between perceived meanings of smiles and their morphological and dynamic characteristics. 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. Smile characteristics were measured using the Facial Action Coding System (Ekman, Friesen, & Hager, 2002) and Automated Facial Image Analysis (Cohn & Kanade, 2007). Observers judged 122 smiles as amused, embarrassed, nervous, polite, or other. Fifty-three smiles met criteria for classification as perceived amused, embarrassed/nervous, or polite. In comparison with perceived polite, perceived amused more often included 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 AU 6 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.
Keywords dynamic characteristics; morphological characteristics; smile interpretation; FACS; automatic facial image analysisWhat does it mean to you when someone smiles at you? You may think that the person is happy, they like you, they want to approach, they are hiding something or they are just being polite. Often, we have strong impressions about the meaning of a smile. An emerging view is that characteristics of the smile dramatically alter a smile's perceived meaning. This paper is about characteristics of smiles that influence perception of one meaning versus another. With the many possible meanings that smiles may communicate, knowledge of the distinction among different kinds of smiles and how they influence interpretation is critical to social adaptation (Abe, Beetham, & Izard, 2002;Brannigan & Humphries, 1972;Cheyne, 1976;Garotti, Caterina, Brighetti, Giberti, & Ricci-Bitti, 1993;Harrigan & Taing, 1997;Kraut & Johnston, 1979;Krull & Dill, 1998;Messinger, Fogel, & Dickson, 1999;Otta, Folladore Abrosio, & Hoshino, 1996;Scharlemann, Eckel, Kacelnik, & Wilson, 2001;Vrugt, Duijnhouwer, & Stam, 2004).Correspondence concerning this manuscript should be addressed to: Zara Ambadar, 4323 Sennott Square, 210 S. Bouquet St., Pittsburgh, PA 15260, Telephone: 412-624-9348, Fax: 412-624-2023, Email: E-mail: ambadar@pitt.edu.
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