Genetics of Personality

Parents observe the emergence of distinct personalities in children from the earliest days of infancy. Personality is determined largely by a person’s genetic makeup. And a person’s personality goes a long way toward determining how that person will adapt to his life circumstances, and make his way through the inevitable obstacles and briar patches that lie in his path.

Cornell scientists studied 70 young adult males to determine some of the innate brain mechanisms that make up the personality, from before birth onward.

People’s brains respond differently to rewards, say the neuroscientists. Some people’s brains release more of the neurotransmitter dopamine, which ultimately gives them more reasons to be excited and engaged with the world, says Richard Depue, professor of human development in the College of Human Ecology, who co-authored the study with graduate student Yu Fu.

Their study, published in Frontiers in Human Neuroscience (Vol. 7) in June, sheds new light on how differences in the way the brain responds to reward translate into extraverted behavior, the authors say.

“Rewards like food, sex and social interactions as well as more abstract goals such as money or getting a degree trigger the release of dopamine in the brain, producing positive emotions and feelings of desire that motivate us to work toward obtaining those goals. In extroverts, this dopamine response to rewards is more robust so they experience more frequent activation of strong positive emotions,” Depue says.

“Dopamine also facilitates memory for circumstances that are associated with the reward. Our findings suggest this plays a significant role in sustaining extroverted behavior,” Depue adds. “The extroverts in our study showed greater association of context with reward than introverts, which means that over time, extroverts will acquire a more extensive network of reward-context memories that activate their brain’s reward system.”

Some scientists confuse “reward” with “interest” or “anticipation of reward.” Dopamine is more closely associated with anticipation of reward or pleasure, than with the pleasure itself.

Previous studies show that drinking non-alcoholic beer can trigger dopamine release — a sure sign of anticipatory brain activity. Alcohol itself triggers release of opiate-like pleasuring chemicals, then goes on to muddle the workings of the brain in inebriation.

But the central point is the genetic component of innate personality formation, something that science is just beginning to learn about.

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