Nathaniel E. Helwig

Associate Professor of Psychology and Statistics

Smile Study Design

In collaboration with Dr. Sofía Lyford-Pike and Dr. Stephen J. Guy, we designed a study to determine which combinations of smile features are most successful. We created a realistic 3D computer model of the human face, and generated 27 short smile animations by systematically manipulating three smile features: (i) smile angle, (ii) smile extent, and (iii) amount of teeth. We also explored how the dynamic symmetry of a smile's evolution affected a smile's perception, by delaying the start of the smile expression on the left side of the face. We then asked over 800 fairgoers at the 2015 Minnesota State Fair to rate the smiles in terms of their effectiveness, genuineness, pleasantness, and perceived emotional intent.

Smile Study Results

In our paper Dynamic Properties of Successful Smiles (published June 28, 2017 in PLoS ONE), we defined a successful smile as one that is rated to be 'effective', 'genuine', and 'pleasant'. We discovered that successful smiles require an optimal balance of angle, extent, and teeth, i.e., the smile 'sweet spot'. We also found that smiles with slight temporal asymmetries were rated as more successful than smiles that evolved in a perfect mirror image. However, temporal asymmetries greater than 125 ms were detrimental. Our results provide important benchmarks for patients that are recovering from facial reanimation surgery. Furthermore, our findings can improve animation of smiles in digital environments, which can be useful for developing personalized facial expession applications for smart phones and/or tablets.

Smile Study Media Coverage

Followup Studies