The development of facial directional asymmetry in right-handed adolescents: a semi-longitudinal 3D study

Abstract This study investigates the development of facial asymmetry in healthy right-handed adolescents and young adults. Using 3D imaging and analytical methods, it aims to summarize age-related changes in directional asymmetry (DA). The material consisted of four-year semi-longitudinal sample of 46 right-handed participants (24 males), aged 15–20 years. DA was analysed using geometric morphometrics, specifically polygonal mesh analysis and multivariate statistics on IA PC scores, which revealed no significant effect of sex or age group on facial DA. All differences and changes were of localized nature only. These include right-sided protrusion of the lateral forehead, nose, both lips, and chin area; left-sided protrusion of the orbital area. In terms of changes across age groups, in the older categories, the areas of asymmetry on the frontal face tended to shift and expand to the lower portion of the face. Areas on the lateral part of the face showed no significant asymmetries. We conclude that, although no influence of sex and age on global asymmetry was observed, both sexes exhibit a small degree of different localized changes across studied age groups. These partially different trends may point to overall localized manifestation of facial DA or high degree of its inter-individual variability.