Wednesday, September 24, 2008

Finger Length Tied to Enthusiasm For Exercise

“Finger length may help differentiate the couch potatoes from the exercise junkies, if new animal research is any indication. A number of human studies have linked finger length ratio -- specifically, the length of the index finger in relation to the ring finger -- to certain behaviors and traits, including aggression, athletic ability and academic skills. Generally speaking, men tend to have a shorter index finger relative to the ring finger, whereas the two tend to be more equal in length in women. Studies have the linked the ‘male’ pattern -- whether it's in men or women -- to higher aggression levels and greater athletic prowess, for example, whereas the ‘female’ pattern has been associated with sharper verbal skills. So can couch potatoes blame it on their finger length? Probably not, according to Dr. Hurd, an associate professor of psychology at the University of Alberta in Edmonton, Canada. ‘The effect sizes for digit ratios on behavior in humans are really small, making it virtually impossible to tell anything about a single individual from their hands,’ Hurd told Reuters Health. ‘The pattern only emerges when a great many people are examined.’ Instead, he explained, research on finger length and behavior is interesting because it suggests that there are things about people's personalities -- in this case, a propensity for physical activity -- that are ‘fixed’ during early development, probably in the womb. In the past, researchers have speculated that testosterone exposure in the womb explains the relationship between finger length and certain behaviors in humans. Greater fetal exposure to the hormone tends to result in relatively short index fingers. However, Hurd said, the situation may not be so simple. He explained that it would be difficult to reconcile the current study's findings with such a ‘testosterone effect.’ Instead, something more complex than a ‘simple testosterone-driven manliness metric’ seems to be at work, according to Hurd. Prenatal exposure to stress hormones could play a role, he and his colleagues assert -- as could other factors that regulate gene expression. Women tend to have higher levels of corticosterone stress hormones than men, though the effects of such hormones on finger length are not clear. Whatever the reason for the findings, Hurd and his colleagues conclude, they add to evidence of a connection among the brain, behavior, personality and the shape of the hand.”

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