FLUCTUATING ASYMMETRY AND AGGRESSION IN BOYS

Fluctuating asymmetry (FA) is small deviations from perfect symmetry i n normally bilaterally symmetrical traits. We examined the relationshi p between FA of five body traits (ear height, length of three digits, and ankle circumference) and self-reported scores of physical and verb al aggression in a sample of 90 boys aged 10 to 15 years. The relation ships between FA and scores of aggression (particularly physical aggre ssion) were found to be negative; in other words, the most symmetrical boys showed highest aggression. One trait (ankle circumference) showe d the characteristics of ''ideal'' FA-parametric mean of zero and a no rmal distribution. Mean asymmetries calculated from six repeated measu res of ankle FA in 30 subjects taken over a period of five months show ed strong negative associations with scores of physical aggression whi ch were independent of age, height, and weight. It is argued that soft tissue ''cyclical'' FA (as opposed to ''fixed'' bony FA) is dependent on the secretion of hormones: for example, cortisol. Causal associati ons between behavioral traits such as aggression and hormones will lea d to similar correlations between FA and behavior.