title: Gender and age differences in facial expressions.
abstract: The aim of this research was to determine a reliable method for quantitatively evaluating the facial expressions of children and adults in order to assess their dependence on age and gender. This study evaluated 80 healthy subjects divided into four groups: 20 girls (mean age 10.6 years), 20 boys (mean age 10.8 years), 20 females (average age 25.6 years), and 20 males (average age 27.0 years). A video was used to record each individual executing three facial expressions: a rest pose, a lip pucker, and a posed smile. Representative video frames were chosen for each individual's expressions; they were digitized and then analysed with software that extracted a set of horizontal and vertical distances of the face. All distances measured in the posed smile and lip pucker were expressed as a percentage change from the rest pose. Statistical analysis with a two-way multivariate analysis of variance (MANOVA) was performed, with gender and age as the independent variables. It was evident that the ability to produce certain facial expressions differs between groups of individuals due to gender and age. Males had a greater upward vertical movement capacity in the studied facial expressions than females. Females had a more pronounced horizontal component in the posed smile. There was a trend from childhood to adulthood showing an increase in the percentage change in most vertical movements. This trend was present in both genders, though more pronounced in males. Using a robust quantitative method for collecting and analysing facial expressions, gender differences in adults were detected as well as differences between adults and children. The trend toward increasing vertical movements in adults compared with children suggests the possibility that the mimic musculature is developmentally regulated.
authors.affiliation: Department of Orthodontics, School of Dentistry, University of Geneva, Switzerland. odyssia@gmail.com
authors.forename: Odyssia
authors.initials: O
authors.lastname: Houstis
authors.forename: Stavros
authors.initials: S
authors.lastname: Kiliaridis
mesh_terms: D000328:Adult; D000367:Age Factors; D002508:Cephalometry; D002648:Child; D005145:Face / Q000033:anatomy & histology; D005149:Facial Expression; D005152:Facial Muscles / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008046:Lip / Q000033:anatomy & histology; D008297:Male; D012737:Sex Factors; D012904:Smiling / Q000502:physiology; D014741:Video Recording; D055815:Young Adult