Friday, November 03, 2006

Are you out of shape?

AGGRESSIVE TENDENCIES MAY BE REVEALED BY ASYMMETRY IN BODY PARTS, STUDY FINDS

COLUMBUS, Ohio – Researchers may get some indication of how aggressively an angry person will react by measuring the size relationship between a person’s ears and other body parts, according to a new study.

Research showed that the farther certain paired body parts were from symmetry – if one ear, index finger or foot was bigger than another, for example – the more likely it is was that a person would show signs of aggression when provoked. The symmetry effects were different in men and women, however.

While the findings may seem strange, there is a plausible explanation, said Zeynep Benderlioglu, co-author of the study and a post-doctoral researcher at Ohio State University.

Deviations from symmetry are thought to reflect stressors during pregnancy – such as poor health, alcohol and tobacco use – that may affect development of the fetus in a variety of ways.

"Paired body parts are presumably controlled by similar genetic instructions, so if everything goes perfectly you would expect paired body parts to be the same size," Benderlioglu said.

"But stressors during pregnancy may lead to asymmetrical body parts. The same stressors will also affect development of the central nervous system, which involves impulse control and aggression," she said. "So while asymmetry doesn’t cause aggression, they both seem to be correlated to similar factors during pregnancy."

Benderlioglu conducted the study with Randy Nelson, a professor of psychology and neuroscience, and Paul Sciulli, professor of anthropology, both at Ohio State. Their results were published in a recent issue of the American Journal of Human Biology....

Benderlioglu said the same conditions in pregnancy that lead to asymmetry in body parts probably affects development of parts of the central nervous system that deal with impulse control. The result is that people with higher levels of asymmetry also have a harder time controlling their aggressive impulses.

Other studies have indicated that testosterone is related to a tendency toward anger. So people who show both high levels of asymmetry and high levels of testosterone may react particularly aggressively when provoked, she said....

The results emphasize once again the importance of healthy habits during pregnancy, Benderlioglu said. Smoking and heavy alcohol use are among the stressors that may lead to both asymmetry and poor impulse control....

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