Dynamic properties of successful smiles

PLoS One. 2017 Jun 28;12(6):e0179708. doi: 10.1371/journal.pone.0179708. eCollection 2017.


Facial expression of emotion is a foundational aspect of social interaction and nonverbal communication. In this study, we use a computer-animated 3D facial tool to investigate how dynamic properties of a smile are perceived. We created smile animations where we systematically manipulated the smile's angle, extent, dental show, and dynamic symmetry. Then we asked a diverse sample of 802 participants to rate the smiles in terms of their effectiveness, genuineness, pleasantness, and perceived emotional intent. We define a "successful smile" as one that is rated effective, genuine, and pleasant in the colloquial sense of these words. We found that a successful smile can be expressed via a variety of different spatiotemporal trajectories, involving an intricate balance of mouth angle, smile extent, and dental show combined with dynamic symmetry. These findings have broad applications in a variety of areas, such as facial reanimation surgery, rehabilitation, computer graphics, and psychology.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Emotions / physiology*
  • Facial Expression*
  • Facial Recognition*
  • Female
  • Humans
  • Interpersonal Relations*
  • Male
  • Middle Aged
  • Photic Stimulation
  • Smiling / psychology*
  • Social Perception*
  • Young Adult

Grant support

This work was supported by faculty start-up funds from the University of Minnesota (NEH, SJG, SL-P).