Bodily symmetry increases across human childhood

Background: Although bodily symmetry is widely used in studies of fitness and individual differences, little is known about how symmetry changes across development, especially in childhood. Aims: To test how, if at all, bodily symmetry changes across childhood. Study design: We measured bodily symmetry via digital images of the hands. Participants provided information on their age. We ran polynomial regression models testing for associations between age and symmetry. Subjects: 887 children attending a public science event aged between 4 and 15 years old. Outcome measures: Mean asymmetry for the eight traits (an average of the asymmetry scores for the lengths and widths of digits 2 to 5). Results: Symmetry increases in childhood and we found that this period of development is best described by a nonlinear function. Conclusion: Symmetry may be under active control, increasing with time as the organism approaches an optimal state, prior to a subsequent decline in symmetry during senescence. The causes and consequences of this contrasting pattern of developmental improvement in symmetry and reversal in old age should be studied in more detail. (C) 2013 Elsevier Ireland Ltd. All rights reserved.