title: Gender differences in posed smiles using principal component analysis.
abstract: OBJECTIVE
  The purpose of this study was to clarify gender differences in posed smiles using principal component analysis (PCA).
  
  
  METHODS
  Fourteen adult volunteers, 7 males and 7 females, were enrolled. Using the motion analyzing system we developed, range images and 5 × 5 virtual grids were produced across the whole sequence while the volunteers were asked to smile. Two sets of all intersections of the virtual grids captured while the subject was smiling were regarded as PCA variables. Discriminate analysis was then applied to compare the males and females.
  
  
  RESULTS
  The first and second principal component scores (PCSs) were plotted on the x-axis and y-axis, respectively. The center of gravity of the PCSs is shown by the plus on the x-axis and minus on the y-axis for the males and by the minus on the x-axis and the plus on the y-axis for the females. Discriminate analyses of the PCSs revealed a correct gender classification rate of 74.4% for posed smiles.
  
  
  CONCLUSIONS
  While the sample size is too small to extrapolate from these results, we can conclude that PCA can be used to identify gender differences while smiling.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Yamaguchi University, Minami-kogushi 1-1-1, Ube City, Yamaguchi 755-8505, Japan. Electronic address: kmishima@yamaguchi-u.ac.jp.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Mishima
authors.affiliation: Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Yamaguchi University, Minami-kogushi 1-1-1, Ube City, Yamaguchi 755-8505, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Nakano
authors.affiliation: Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Yamaguchi University, Minami-kogushi 1-1-1, Ube City, Yamaguchi 755-8505, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Umeda
authors.affiliation: Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Yamaguchi University, Minami-kogushi 1-1-1, Ube City, Yamaguchi 755-8505, Japan.
authors.forename: Ruriko
authors.initials: R
authors.lastname: Shiraishi
authors.affiliation: Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Yamaguchi University, Minami-kogushi 1-1-1, Ube City, Yamaguchi 755-8505, Japan.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Ueyama
mesh_terms: D000328:Adult; D059925:Anatomic Landmarks / Q000033:anatomy & histology / Q000502:physiology; D016002:Discriminant Analysis; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D008046:Lip / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D010780:Photogrammetry / Q000706:statistics & numerical data; D025341:Principal Component Analysis; D012737:Sex Factors; D012904:Smiling; D014741:Video Recording / Q000706:statistics & numerical data; D055815:Young Adult
keywords: Discriminate analysis; Gender difference; Motion analysis; Posed smile; Principal component analysis