title: Kinematic analysis of a Duchenne smile.
abstract: OBJECTIVE
  Facial expressions are communicative motor outputs, whose kinematics likely are due to musculoskeletal anatomy, neuromotor activity and the well-being and internal states of the individual. However, little has been published on the kinematics of facial expression. This study quantified lip, eye and cheek movements during the production of a Duchenne smile involving movement of lips and tissues surrounding the eyes.
  
  
  METHODS
  The three-dimensional positions of 20 markers placed around the eyes, cheeks, lips and chins of 24 young adult female subjects were digitized while they performed smiles after practicing to feedback from an investigator trained in the facial action coding system (FACS). Displacement, velocity and acceleration variables were extracted and analyzed from the markers.
  
  
  RESULTS
  Results demonstrated several consistencies across subjects including: (1) relatively high peak velocities, accelerations and displacements for lip and cheek markers in the vertical and anteroposterior dimensions, (2) relatively large movements of the lower lateral eye region compared with other eye regions.
  
  
  CONCLUSIONS
  The results indicate that there is significant movement in the anteroposterior dimension that is not observable in frontal views of the face alone.
authors.affiliation: Department of Biomolecular Sciences, College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, MI 48109, USA. Electronic address: hjaffer@umich.edu.
authors.forename: H
authors.initials: H
authors.lastname: Jaffer
authors.affiliation: Department of Anesthesiology, School of Medicine, University of Michigan, 24 Frank Lloyd Wright Dr. Lobby M, Ann Arbor, MI 48109, USA. Electronic address: eichesco@med.umich.edu.
authors.forename: E
authors.initials: E
authors.lastname: Ichesco
authors.affiliation: Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA. Electronic address: geger@umich.edu.
authors.forename: G E
authors.initials: GE
authors.lastname: Gerstner
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002508:Cephalometry / Q000379:methods; D002610:Cheek / Q000000981:diagnostic imaging / Q000502:physiology; D005152:Facial Muscles / Q000000981:diagnostic imaging / Q000502:physiology; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008046:Lip / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D009055:Mouth / Q000000981:diagnostic imaging / Q000502:physiology; D012904:Smiling / Q000502:physiology*; D055815:Young Adult
keywords: Face; Kinematics; Motor behavior; Smile; Soft tissue movement