The Brain Chemistry of Extroverts vs. Introverts

brain- intravert or extrovert

Brain Chemistry

Some people are natural extroverts, becoming the life of the party and everyone’s best friend as soon as they walk in the door. Other people are happiest at home enjoying their favorite book or television show. It seems that no matter how much you may try to change, you are typically either one or the other, although there are some people who do fall within the two extremes. Sometimes, it is hard for extroverts and introverts to understand one another, as their needs differ so much. Scientists have tried to understand the difference for a long time.

The psychology of extroverts verses introverts has a long history. Carl Jung studied the phenomenon, and even coined the phrase extrovert (although he spelled it extravert), in the beginning of the 20th Century. Although psychology continues to study the difference between extroverts and introverts, including how to educate them, work with them, and interact with them, new studies are shedding additional light on the reason why some people may be extroverts and others are more inclined to be introverts.

These studies reach back to 1960 when a psychologist, Hans Eysenck, suggested that there might be a difference in the levels of physiological arousal (not sexual). Arousal in this sense is how the body reacts to stimulation. Extroverts, according to Eysenck, had a lower rate of stimulation response, and so needed to work harder to be stimulated. Therefore they seek company and experiences. It is almost as if they are more bored by things and so need to go out and try new adventures. Alternatively, introverts become easily over stimulated, so they seek out the quiet and restful activities.

Further study in 2005, led by Michael Cohen, looked at the link between dopamine, your brain’s reward system, and extroversion. Dopamine plays an important role in the reward system, the learning part of your brain, and the novelty response. They discovered that how your brain responds to rewards may be what makes you into an extrovert or introvert. Using brain scans to record activity that occurs deep within the brain, while also looking at participant’s genetic profile, revealed a possible code behind the chemical signaling system used by the brain that determines extroversion.

In this study, the participants initially filled out a personality profile and provided a genetic analysis, which aided the scientists in knowing whether the participants were extroverts or introverts, along with their genetic make up for the brain chemistry. While hooked into a brain scanner, the participants gambled. As expected, the researchers found different brain activity in the extroverts versus the introverts.

Extroverts had a stronger response in the amygdala and the nucleus accumbens, parts of the brain. The amygdala is the emotional stimuli part of the brain, while the nucleus accumbens works the brain’s reward circuitry and helps control the dopamine system. Therefore, extroverts process unexpected rewards, like winning at gambling, differently. Additionally, the extroverts, or the participants with a stronger responsiveness of dopamine system, also displayed increased brain activity when they actually won in the game.

This means that those more prone to being extroverts actually have a stronger response when a gamble pays off. Because their reward system has a stronger reaction, and a pleasant one at that, they will be more willing to take bigger risks in order to gain this stronger reward. Genetics will play a role, as they will shape and develop the brain. However, the dopamine function is key to the difference between the two personality types. Therefore, any gene that deals with dopamine will also predict any personality differences, including whether someone will enjoy unfamiliar activities or surroundings and seek out novelty.

Another study, done at Cornell University and published in June of 2013 in the Frontiers in Human Neuroscience, also looked at the link between dopamine and extroverts. In this study, they took it one step further. They took a group of 70 participants who first did a test to see if they were extroverts or introverts. Then, using a double-blind procedure, they gave some participants Ritalin, which stimulates the release of dopamine. They were then given videos to watch and asked to provide their response to the video, lab environment, and Ritalin. Those who took Ritalin had a strong reaction to the Ritalin, and they also associated the environment and context with these rewards. Alternatively, introverts were not affected from Ritalin. The Cornell team believes this is due to introverts responding to internal cues more strongly than external motivation and reward cues.

However, if you are to take these two research studies together (from a non-expert/biologist/neuroscientist or psychologist), it seems as if the way the brain utilizes dopamine and reward response creates the difference between the two personality types. Even when provided with extra dopamine via Ritalin, the introverts still did not have similar reward responses as the extroverts did. Although I will continue to leave it to the experts to decide how our brain chemistry creates our personality, it does make for an interesting hypothesis as to how our brain reward system creates whether we prefer to be extroverts and high-risk individuals or introverts who prefer a quieter life. If you are an introvert, next time someone bugs you about being a party pooper, you can just blame the genetic make up of your brain and its reward response. Alternatively, all you extroverts and risk takers out there can just say you are addicted to your brain’s reward response and the stimulus from dopamine.

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Kendra Whitmire is a freelance writer and editor with a passion for nutrition and alternative medicine. She graduated cum Laude from USC with a BA in English and German and has two masters degrees in English from the Shakespeare Institute at the University of Birmingham in England, specializing in Shakespeare Studies. Kendra also manages a talented cinematic pianist, Paul Spaeth. In her spare time, she enjoys running, yoga, being outdoors, and reading.

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