Asymmetric facial expressions such as smirk express negative emotions in everyday communication. Asymmetry in smile shows emotions of contempt, doubt, disapproval, etc. Ekman et al. conducted a study to determine the dynamics of asymmetry of spontaneous and deliberate smiles on the sides of face.
In the first part of study, 36 children were asked to imitate facial expressions shown on screen. Correctly imitated expressions were chosen to study asymmetric deliberate expressions. To study asymmetric spontaneous expressions, experimenter told them jokes to elicit spontaneous smiles. In second part of study, 35 female adults were shown a pleasant film and a stress inducing film. Their responses while watching these films were recorded.
The asymmetry in Zygomatic Major, which is a primary muscle involved in smile was evident in data collected from children and adults.
The asymmetrical deliberate smiles occurred frequently on the left side of face; while asymmetrical spontaneous smiles occurred frequently on the both sides of face. Asymmetrical spontaneous smiles were evenly divided between left and right side of face. This implies that asymmetry is more prevalent on left side of face when it comes to posed expressions.
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Reference - P. Ekman, Wallace Friesen and J.C. Hager. University of California, San Francisco.
Research paper name – The Symmetry of Emotional and Deliberate Facial Actions.
Published in - American Association for the Advancement of Science (1980)
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