Automated Face Analysis (AFA) distinguishes deliberate from spontaneous smiles on the basis of quantitative differences in intensity and asymmetry

People smile for a wide variety of reasons (e.g., express enjoyment or signal affiliation). Smiles may arise spontaneously or they may be deliberately performed to serve the displayer's purpose. Because deliberate and spontaneous smiles differ in their neural control, clues to the meaning of smiles may be revealed in their production. That is, there is evidence to suggest that spontaneous smiles may be distinguished from deliberate ones by activation of the orbicularis oculi (Duchenne marker), differences in intensity and temporal pattern, and relative absence of expression asymmetry. Both human observer based methods and EMG have been used to measure these differences with limited success.; We used Automated Face Analysis (AFA; Cohn, Zlochower, Lien, & Kanade, 1999; Tian, Kanade, & Cohn, 2001) to investigate differences between spontaneous and deliberate smiles because it is an objective system that has the capacity to utilize quantitative, dynamic information on a frame-by-frame basis, and small pixel-wise changes may be analyzed. The purpose of this study was to distinguish deliberate from spontaneous smiles on the basis of quantitative differences in intensity, asymmetry, and timing.; Results indicated that deliberate and spontaneous smiles were discriminated on the basis of differences in intensity and asymmetry with an accuracy of 73%. Follow-up analyses indicated that spontaneous smiles showed more intense eye narrowing (AU 6), while deliberate smiles showed more intense lip motion (AU 12). In contrast to our predictions, spontaneous smiles were more asymmetric than deliberate ones, though the asymmetry was not specific to one side of the face or the other. In contrast to our predictions, deliberate and spontaneous smiles did not exhibit different temporal patterns. Finally, while the two types of smiles did not differ with respect to the presence or absence of AU 6 (Duchenne marker), they did differ in the intensity of AU 6, as reflected in eye narrowing. These results indicate that AFA measures of intensity and asymmetry may be used to differentiate among smiles occurring in the context of interpersonal interaction.