Not all extroverts are made the same, and scientists from Brown University in Providence, R.I. have mapped out the differences and similarities in the brain that make "agentic" go-getters and "affiliative" people persons.
People-persons are those who thrive on sharing affection and get a charge from being around others. The go-getters are people who can turn on the charm, like a leader who flashes a smile. Not only do these personality traits overlap, but the brain anatomy of those who exhibit the traits also overlap.
"These are people just sharing with you how they tend to experience the world and what's important to them," said author Tara White, assistant professor of behavioral and social sciences in the Brown University School of Public Health, according to the press release from Brown University. "The fact that that's validated in the brain is really exciting. There's a deep reality there."
The study collected data from structural MRI scans of 83 men and women between ages 18 and 54. The study is the first to result in evidence of the physical differences in the brain between extrovert types in adulthood, according to the press release. (Another study was conducted, but it focused on seniors).
"This is the first glimpse of a benchmark of what the healthy adult brain looks like with these traits," White said. White and lead author Erica Grodin, a graduate student, looked at areas of the brain like the medial orbitofrontal cortex, a region that is involved in making choices based on reward. They also wanted to encompass more of the brain by using a technique known as called voxel-based morphometry.
As the researchers expected, based on psychological literature, both extroversion types "significantly correlated with higher gray matter volumes in the right and left medial orbitofrontal cortex, even after controlling for possible confounding factors such as age," according to the press release. "But among the people with higher agentic extroversion scores, they also found several other regions that had significantly larger gray matter volumes: the parahippocampal gyrus (involved in learning and memory for reward); the precentral gyrus, cingulate gyrus, and caudate (involved in the cognitive control of behavior and the initiation, planning, and execution of voluntary movement toward goals); and, among the men in the study, the nucleus accumbens (involved in incentive reward)."
The authors caution that larger volume of brain matter shows only an association - not a definitive diagnosis of personality traits. Why larger volumes develop in extroverts or if extroverts are born with more brain matter is unknown, according to the press release.
"[The] findings provide a developmental benchmark from which to better understand the etiology of problems in agentic extroversion and affiliative extroversion, such as can occur in normal aging and neurodegenerative disease," Grodin and White wrote in their report.
The duo's research was funded by grants from the National Institute on Drug Abuse (DA R01 020725, DA R21 029189), the Lifespan/Tufts/Brown Center for AIDS Research, the Foundation for Alcohol Research, and the National Institute on Alcohol Abuse and Alcoholism (AA P01 019072), according to source material.
The report by Grodin and White, titled "The neuroanatomical delineation of agentic and affiliative extraversion," was published in the journal "Cognitive, Affective, and Behavioral Neuroscience."
