Movement Differences between Deliberate and Spontaneous Facial Expressions: Zygomaticus Major Action in Smiling

Previous research suggests differences in lip movement between deliberate and spontaneous facial expressions. We investigated within participant differences between deliberately posed and spontaneously occurring smiles during a directed facial action task. Using automated facial image analysis, we quantified lip corner movement during periods of visible Zygomaticus major activity. Onset and offset speed, amplitude of movement, and offset duration were greater in deliberate smiles. In contrast to previous results, however, lip corner movement asymmetry was not greater in deliberate smiles. Observed characteristics of deliberate and spontaneous smiling may be related to differences in the typical context and purpose of the facial signal. Karen L. Schmidt, Zara Ambadar, Jeffrey F. Cohn, and L. Ian Reed are affiliated with the University of Pittsburgh, Pittsburgh, PA 15260, USA. Jeffrey F. Cohn is also affiliated with the Carnegie Mellon University, Pittsburgh, PA 15260, USA. This research was supported by NIMH Grants MH15279 and 167376 to Karen L. Schmidt, and NIMH Grant MH 51435 to Jeffrey F. Cohn. We gratefully acknowledge the assistance of Adena Zlochower in digitizing videotape used in this analysis and Rachel Levenstein in the analysis of data described in this paper. Address correspondence to Karen L. Schmidt, University of Pittsburgh, 121 University Pl, Pittsburgh, PA 15260, USA; E-mail: kschmidt@pitt.edu