Fluctuating Asymmetry

Fluctuating asymmetry (FA) is believed to be a measure of an individual's genetic quality. The basic idea behind FA is that the genes within an individual should code for both sides of the body equally. That is, your left lung should develop just like your right lung. Your left eye just like your right eye. Your left ear just like your right ear. Etc. However, random events in the outside environment can interfere with this development. The better able an individual is to resist those outside interferences, the better quality they (and thus their genes) are. In a variety of animals, and to a degree adult humans, FA has been positively associated with health and attractiveness.

As our earlier (Volk & Quinsey, 2002) work has shown, adult hypothetical adoption decisions are influenced by infant facial cues of health. We therefore once again turned to digital manipulation of infant and child faces to simulate cues of FA. We predicted that as with Fetal Alcohol Syndrome and Body Weight, adults would give significantly higher hypothetical adoption, cuteness, and health ratings to "normal" faces versus faces with exagerrated FA.

Normal face on the left, asymmetrical face on the right

We failed to find any significant differences between the ratings of the faces. This may be due to two factors. Number one, children have a large degree of asymmetry. Contrary to popular belief, humans start off with significant asymmetry, and become more symmetric as the age- up to 18 years of age or so. Then they experience a peak of symmetry, before once again become more asymmetric as they age. So our results could have been masked by large degrees of age-appropriate asymmetry. Number two, our manipulations might not have been strong enough to elicit an effect. We do suspect that gross asymmetries would produce an effect, but we weren't interested in simulation gross asymmetries.

Nevertheless, this study was important because it address two potential methodological problems with our Hypothetical Adoption Paradigm. First, these results demonstrate that simply manipulating a face doesn't guarantee a significant difference. Second, they demonstrate that simply viewing multiple copies of a particular face also doesn't guarantee a significant difference. Our null results in this study therefore actual help give credibility to the positive results we find in our other studies! For instance, we can be more confident that our effects regarding body weight or Fetal Alcohol Syndrome are due to the type of manipulation we performed, not simply the presence of a manipulation.

Other Infant and Child Facial Cues that we've studied include:

Back to the Infant Faces Page.

Created on ... May 26, 2006