The Scientific Reasons Why Introverts And Extroverts Are Different

The Scientific Reasons Why Introverts And Extroverts Are Different

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I’m standing in the crowd in front of the stage at the small gritty music club. My two friends—both extroverts—are on either side of me, swaying along with the crooning Indie singer and smiling. I was having fun for a while, but now I’m ready to head home and find my bed. The loud music, the dense crowd of strangers, and the small talk I’ve made all night have left me feeling drained. It’s just too much, for too long, for an introvert like me.

I’d rather be in the peaceful solitude of my apartment. Just me, no noise, maybe a good book or the Internet to help me turn inward and recharge after this much socializing. Yet, my extroverted friends could probably stay at the concert, chatting long past the encore. They’ll actually feel energized when they leave and won’t need any recovery time. So, why do I react so differently than my extroverted friends to the same situation? The answer has to do with some key differences in the way introverts’ brains are wired.

The dopamine difference

One major difference between the brains of introverts and extroverts is the way we respond to the neurotransmitter dopamine. Dopamine is a chemical released in the brain that provides the motivation to seek external rewards like earning money, climbing the social ladder, attracting a mate, or getting selected for a high-profile project at work. When dopamine floods the brain, both introverts and extroverts become more talkative, alert to their surroundings, and motivated to take risks and explore the environment.

It’s not that introverts have less dopamine present in their brains than extroverts do. In fact, both introverts and extroverts have the same amount of dopamine available. The difference is in the activity of the dopamine reward network. It is more active in the brains of extroverts than in the brains of introverts as Scott Barry Kaufman, the Scientific Director of The Imagination Institute, explains in this short video:

At the expectation of, say, getting the phone number of an attractive person or earning a promotion at work, extroverts become more energized than introverts. They buzz with an enthusiastic rush of good feelings, while introverts feel overstimulated.

For my extroverted friends, the noise and the crowd at the concert were simply all part of the fun. In fact, this intensity of stimulation acted as a cue to them that they were achieving their goal (the reward of socializing and a fun night out). Yet, for me, as the night wore on, the hubbub became annoying and tiring—even punishing—as I became overstimulated.

For introverts, acetylcholine is where it’s at

Introverts prefer to use a different neurotransmitter called acetylcholine, writes Christine Fonseca in her book Quiet Kids: Help Your Introverted Child Succeed in an Extroverted World. Like dopamine, acetylcholine is also linked to pleasure; the difference is, acetylcholine makes us feel good when we turn inward. It powers our abilities to think deeply, reflect, and focus intensely on just one thing for a long period of time. It also helps explain why introverts like calm environments—it’s easier to turn inward when we’re not attending to external stimulation. When I lounge at home in quiet solitude, lost in a book or watching Netflix, I’m basking in the pleasant effects of acetylcholine.

Nervous system differences

Another piece of the introvert-extrovert puzzle has to do with the nervous system, writes Dr. Marti Olsen Laney in her book The Introvert Advantage: How to Thrive in an Extrovert World. Acetylcholine is linked to the parasympathetic side of the nervous system, which is nicknamed the “throttle down” or “rest-and-digest” side. When we engage the parasympathetic side, our body conserves energy, and we withdraw from the outer environment. Our muscles relax; energy is stored; food is metabolized; pupils constrict to limit incoming light; and our heart rate and blood pressure lower. Basically, our body gets ready for hibernation and contemplation—two of the things introverts like the most.

Both introverts and extroverts use both sides of their nervous systems at different times, just like they use both neurotransmitters. But—no big shocker here—extroverts tend to favor the opposite side of the nervous system: the sympathetic side, known as the “full-throttle” or “fight, flight, or freeze” system. This side mobilizes us to discover new things and makes us active, daring, and inquisitive. The brain becomes alert and hyper-focused on its surroundings. Blood sugar and free fatty acids are elevated to give us more energy, and digestion is slowed. Thinking is reduced, and we become prepared to make snap decisions. While extroverts thrive on the dopamine-charged good feelings created when they engage the sympathetic side, for us introverts, it’s too much.

Do introverts dislike people?

If you don’t understand introversion, you might get the mistaken idea that introverts are antisocial, reclusive, or rude. At the concert, I bolted for the door the first chance I got, leaving my extroverted friends behind. I imagine they only reluctantly left after the last song was played, the lights came on, and a security guard brusquely ushered them toward the door. Yet, given how my introverted brain works, it makes sense that after a few hours of stimulation and socializing, I needed to get out of there. It’s not that I dislike people; it’s just that socializing is more effortful and tiring for me than it is for extroverts. Curled up back at home, in a calm, familiar environment, I unwound and relaxed. Sure, I would go to another concert and hang out with the extroverts again, but only after some soothing alone time—and not a moment sooner.

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