On the measurement and analysis of asymmetry with applications to facial modelling

• Published in: Applied statistics 2006-01, Vol.55 (1), p.77-91
• Main Authors: Bock, Mitchum T., Bowman, Adrian W.
• Format: Article
• Language: English
• Subjects: Applications; Asymmetry; Babies; Body; Centroids; Children; Cleft lip; Cleft lip and palate; Combinatorics; Combinatorics. Ordered structures; Cross-validation; Curve data; Designs and configurations; Exact sciences and technology; Face; Facial modelling; Functional data; Landmark data; Landmarks; Mathematical models; Mathematics; Medical disorders; Medical research; Methodology; Modeling; Modelling; Mouth; Population statistics; Probability and statistics; Procrustes analysis; Rotation; Sciences and techniques of general use; Shape analysis; Statistical methods; Statistical models; Statistics; Studies; Symmetry
• ISSN: 0035-9254; 1467-9876
• DOI: 10.1111/j.1467-9876.2005.00532.x

Asymmetry is a feature of shape which is of particular interest in a variety of applications. With landmark data, the essential information on asymmetry is contained in the degree to which there is a mismatch between a landmark configuration and its relabelled and matched reflection.This idea is explored in the context of a study of facial shape in infants, where particular interest lies in identifying changes over time and in assessing residual deformity in children who have had corrective surgery for a cleft lip or cleft lip and palate. Interest lies not in whether the mean shape is asymmetric but in comparing the degrees of asymmetry in different populations. A decomposition of the asymmetry score into components that are attributable to particular features of the face is proposed. A further decomposition allows different sources of asymmetry due to position, orientation or intrinsic asymmetry to be identified for each feature. The methods are also extended to data representing anatomical curves across the face.