What sort of extrovert are you? MRI offers a clue

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  • Published: Mar 1, 2015
  • Author: David Bradley
  • Channels: MRI Spectroscopy
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Go-getting social animals

What sort of extrovert are you? MRI reveals the differences in the brains of

What sort of extrovert are you? A magnetic resonance imaging (MRI) study reveals the differences in the brains of "go-getters and "social animals".

It is all too easy to categorise people by their apparent personality traits, we talk of bashful, shy introverts, outgoing extraverts, although human nature is far more complicated than that and most people lie on a spectrum of those behaviours, some have mixed personalities and most of us have different levels of introversion and extraversion at different times. However, it is possible to generalise broadly and even to home in on specific types of character within any of those stereotypes.

For instance, many of us know two types of extrovert and psychological studies support this notion to some degree. There are the ambitious " go-getters" who flash a smile as they purse their goals and fulfil their personal ambition agenda and there are the social animals, the gregarious people-persons" whose agenda is finding reward in sharing affection and affiliation with others. Now, an MRI study has shown that there are overlapping yet distinct signatures in the anatomy of the brain among people with these two personality types.

Glimpsing a benchmark

"These are people just sharing with you how they tend to experience the world and what's important to them," explains behavioural and social scientist Tara White of Brown University School of Public Health in Providence, Rhode Island, USA. "The fact that that's validated in the brain is really exciting. There's a deep reality there," she adds.

The team carried out MRI scans on 83 men and women aged between 18 and 54, screened for good mental health and demonstrably extrovert. This is the first study to look at this age range; a previous study looked at older extroverts. Writing in the journal Cognitive, Affective, and Behavioral Neuroscience, White and her colleagues explain how this researchers offers what she calls "the first glimpse of a benchmark of what the healthy adult brain looks like with these [extrovert] traits." Technically, the people persons, the social animals are referred to as "affiliative" extroverts while the ambitious go-getters are called "agentic" extroverts by psychologists.

White is based in Brown's Center for Alcohol and Addiction Studies and is interested in the neural basis of personality and how such personality differences change the way people respond to drugs and alcohol. Graduate student Erica Grodin working for White was well aware of the particular regions of the brain that might be a useful focus of MRI from a review of the psychological literature on extroversion. These regions include the medial orbitofrontal cortex, which is involved in making choices based on reward. However, they also used a broader technique, voxel-based morphometry to look at the volunteers' brains as a whole.

What's the matter?

As anticipated, the MRI study revealed higher grey matter volume in either kind of extroversion in right and left medial orbitofrontal cortex. However, for the people with higher scores on the agentic extroversion test, the researchers also found that several other regions had significantly larger gray matter volumes, viz. the parahippocampal gyrus (involved in learning and memory for reward); the precentral gyrus, cingulate gyrus, and caudate (involved in the cognitive control of behaviour 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).

Of course, such studies only reveal an association between perceived character types and the structure of particular regions of the brain and the researchers caution that this study does not imply that the personality traits cause the differences or whether the differences cause the personality traits. Moreover, it says nothing about when such volumes changes might arise and how development progresses thereafter. The question remains as to whether if a person is born with a larger volume in the relevant regions that they will grow into one of two types of extrovert or whether brain growth occurs as a consequence of their being extroverted. The study also provides a baseline for understanding problems that arise in both forms of extroversion when people age and when they suffer neurodegenerative disease.

Related Links

Cognitive, Affective, Behav Neurosci, 2015, online: "The neuroanatomical delineation of agentic and affiliative extraversion"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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