Behavioral and psychological correlates of fluctuating asymmetry: a within-families study
Numerous studies have shown fluctuating asymmetry (FA), a physical manifestation of developmental instability, to be associated with a range of physical, behavioral and psychological traits in humans. Reported associations between FA and psychometric intelligence and social dominance were investigated using a within-families design. Methodological improvements in the measurement of FA using four repeated observations of each physical trait and using high-resolution photocopies of the traits rather than direct measurement were also implemented, resulting in an alpha reliability for FA of .89. Primary analyses involving 42 pairs of adult brothers found a statistically significant between-family correlation of -.32 between FA and intelligence test scores but no statistically significant correlation within-families. No statistically significant correlations were found between FA and social dominance. The results were interpreted as indicating that cross-assortative mating for FA and intelligence is responsible for the observed association between these variables in the general population. These results were not surprising in light of previous research with respect to mate preferences and mate choices. Implications for social stratification along an array of desirable traits were discussed, as were methodological considerations for future research involving mating and reproductively relevant traits.