- May 8, 2008
- Type me.
Conventional comparisons between identical and fraternal twins indicate that nearly half of individual differences in personality traits have some underlying genetic cause. So people have tended to think of personality traits as largely determined by genes, says evolutionary psychologist Aaron Lukaszewski of the University of California at Santa Barbara.
He felt there was a flaw in this thinking: if personality were rigidly determined, individuals could end up with the "wrong" personality type for their circumstances. Being extrovert, for instance, exposes people to social conflict. Wimpy men are more likely to suffer in such encounters, while hunkier men may benefit from putting good genes on display. To avoid mismatches, Lukaszewski reasoned, evolution must have favoured a more flexible system.
To test this idea, he measured the strength of 85 male and 89 female students and asked them to rate their own attractiveness relative to their peers. Then he gave each a standard personality test to measure how extrovert they were. Sure enough, stronger and more attractive men, and more attractive women, were more extrovert, Lukaszewski reported at a June meeting of the Human Behavior and Evolution Society in Eugene, Oregon.
Independent ratings of attractiveness showed extroverts didn't simply tend to rate themselves more highly. In fact, physical strength and how people rated themselves explained a whopping 30 per cent of the variation in extroversion between the volunteers - a huge effect for something as nebulous as personality. "That's surprisingly high to me," says Robert Plomin of the Institute of Psychiatry in London. "That makes it much more interesting."
I haven't noticed any correlation like this in my personal experience, but in an evolutionary context, it makes sense.