Have you ever wondered why introverts and extroverts are so different? How can one person thrive on social interaction and another is so drained by it? Why can someone read a book in one sitting when the other has not read a book in years? Finally, are these tendencies learned, or are they genetic?
We seem to live in a society that favours extroversion. Success is determined by what you present to the outside world. However, fifty percent of the general population now identifies as an introvert. With this shift in population dynamic, it is important to understand what makes an introvert an introvert.
Because of societal acceptance of extroversion there are now many misconceptions about introverts. Introverts are not rude, weird, quiet, or loners. They are not trying to avoid you and are not afraid of you. Instead, introverts are just wired differently than the extrovert — neither one is better than the other.
Scientists have determined that tendencies towards introversion versus extroversion are determined by a few main factors: differences in dopamine and reactions to it, the brain’s relationship with acetylcholine, pleasure thresholds, and nervous system preferences.
Difference in Dopamine
If you are an introvert, you have probably mastered the art of leaving a party. It’s not that you don’t like the people there, you’ve just had enough and would prefer to be in pyjamas!
The first major neurological difference between introverts and extroverts is the brain’s relationship to dopamine. We have all heard of this neurotransmitter: it is one of the building blocks of neuroscience. Dopamine has become known as the “reward” drug, the messenger in your brain that causes you to seek out new, pleasurable experiences.
Dopamine reacts to things and situations that bring you external pleasure: think sex, money, junk food. When you encounter a situation that brings you pleasure, the brain releases a flood of dopamine that physically reinforces your enjoyment. The flood of dopamine and this pleasurable neurological experience causes you to continuously seek out these situations.
Are your extroverted friends deemed fun and carefree while you are considered a wet blanket? Introverts and Extroverts do not have different levels of dopamine in the brain. Instead, the difference is that introverted brains react differently to the effects of dopamine. Scientists have found that people who identify as extroverts have more active brain activity when they experience an event they identify as pleasurable. This does not mean that an introvert doesn’t feel pleasure the same way, they just do not get such an as intense “reward” when they experience a pleasurable event.
A study conducted in 2005 at the University of Amsterdam illustrates the difference between extroverted and introverted reactions. Volunteers that identified as introverts and extroverts were asked to gamble while researchers monitored their brain activity. The scientists found that the people who identified as extroverts had more activity in the amygdala (the part of the brain that reflects emotions) and the nucleus accumbens (the part of the brain that processes dopamine).
This heightened activity showed that extroverts’ brains are hardwired to reward new experiences and risky behaviours, while the introverted brain doesn’t get the same benefit out of this excitement.
Why do extroverts always seem to be on the go? Why are they always looking forward to the next event? Simply put, extroverts need much more stimulation than introverts do to feel the same amount of pleasure. Introverted brains have a lower pleasure threshold. This explains why extroverts can feel worn out if they have been “cooped up” too long while introverts can be exhausted from one night of going out. This difference in pleasure thresholds helps shape the introverted versus extroverted personality.
As an extrovert, you are more likely to seek out rewarding situations because you need more to get your dopamine network to react. You are more inclined to go to that party with no one you know or to try gunning for that new position at work. Introverts, however, don’t have the same pleasure experience while pursuing these things. Introverts get the same reward experience from seeking simple pleasures like reading a book or hanging out with an old friend. Ultimately, introverts find more pleasure from looking inward.
If you are an extrovert, you are probably baffled by your introverted friend’s ability to stay in weekend after weekend. How much more relaxing can they handle? Another chemical difference in the brain between introverts and extroverts involves the neurotransmitter acetylcholine. Acetylcholine is also linked to the brain’s pleasure centre, but rewards different actions. In fact, acetylcholine makes us feel pleasure when we look inward. Because high levels of dopamine can “overwhelm” the introverted brain, introverts prefer the feedback it gets from acetylcholine.
Unlike dopamine, acetylcholine floods the brain during introspective activities. It controls the brain’s ability to think deeply, be reflective, and concentrate. Activities that introverts prefer like reading, journaling, and alone-time stimulate this neurotransmitter. Acetylcholine also rewards the brain with a sense of calm and content, differing from the dopamine adrenaline punch.
Introverts thrive off of the effects of acetylcholine and model their behaviors off of it’s effect. While extroverts need large amounts of dopamine to feel anything, their brains barely even register the effects of acetylcholine. This causes extroverts to avoid alone time — why would they waste their time doing something they receive no benefit from?
Introverts register the calming effects of acetylcholine in a totally different way. This sensitivity to acetylcholine’s calming effects helps explain the difference between introvert and extrovert preferred activities. It is much easier to reflect inward if you are not busy chasing the next dopamine high. Introverts prefer to relax at home on a friday night instead of heading out to the bars because they are physiologically rewarded for choosing alone time. They are soaking up the benefits of acetylcholine.
Nervous System Differences
Have you ever wondered how extroverts can just “go with the flow”? How they seem to make impulsive decisions all the time? Another difference between introverts and extroverts involves the nervous system. Introverts and extroverts actually “prefer” to use different parts of their nervous system. Everybody has two sides to their nervous system– the sympathetic and parasympathetic. The sympathetic nervous system works gears up the body for physical activity and is often referred to as the body’s “fight or flight” response. The parasympathetic side slows the body down to “rest and digest”.
When the sympathetic part of your nervous system is stimulated, your body gets ready for action. Your body releases adrenaline, wakes up your muscles, and gives you more oxygen. The parts of your brain that control thought processes are deactivated and your brain relies on dopamine to stay focused. The parasympathetic side relaxes your body, preserves your energy, and uses acetylcholine to keep your brain alert.
In her book The Introvert Advantage: How to Thrive in an Extrovert World, Dr. Marti Olsen Laney explains that (surprise!) extroverts prefer when their sympathetic side activates while introverts thrive under their parasympathetic system. The impulsivity and “full-throttle” effect that the fight or flight side engages is like a drug to extroverts, but is too much for the introvert. Introverts enjoy the slow and calming effects that the parasympathetic gearing down provides.
Connecting With Others
Introverts are often deemed “unsocial”. This, however, is not the case. They simply are content to stick to what they know. Studies have also shown that the introverted brain reacts differently when exposed to new human faces. Introverts simply don’t get as much out of human interaction as extroverts do. Another study conducted in 2010 attempted to examine how the unconscious brain reacts to new experiences. Test subjects were asked to look at images of flowers and then were exposed to pictures of human faces.
The extroverts, not surprisingly, reacted much more intensely to the series of human faces. Their brain activity was much more intense when they encountered a new human faces than when they saw a new flower. Introverted subjects had the same reaction to a new flower as they did a human face.
This does not mean that introverts equate humans to flowers (although maybe some do), but instead, illustrates the extent of their difference in experience. Extroverted brains receive positive reinforcement when they are meeting new people, while introverted brains stay neutral. This helps explain why introverts have a close circle of friends an prefer to socialise in small groups. Introverts brains do not train them to constantly seek out new people in order to feel that reward. Instead, they are completely content keeping their circle close.
Who would have thought that introverts prefer planned experiences! We all have that friend who needs to know every detail two weeks in advance before they head out the door. This person is not trying to be difficult, their brain just fuels their planning mechanism. Typically, these people are also introverts.
Introverted and extroverted brains actually have different types of blood flow. Studies have shown that introvert’s brains have more blood flow to the parts of the brain that control things like problem solving and planning. The brains of extroverts have greater blood flow to the areas of the brain that allow the brain to interpret the outside world.
These different blood flows show how introverts and extroverts have different priorities when it comes to planning. While extrovert brains prioritise the immediate present, introverts operate better when they are structured in the future and past.
Even though we can’t change our genes, Dr. Marti Olsen Laney explains how introvert-friendly genes can become flexible over time. As our environment helps shapes our personalities at a young age, Laney explains that your environment can also establish “set points” for your introversion. Set points are defined as the “upper and lower limits of how much extroversion your brain can handle”.
Laney compares these set points to a thermostat: if your comfort threshold set between 68 and 70 degrees, your inner thermostat will work to keep you within that zone. For example, if an introvert is getting too close to the low point of their threshold, they might crave some social attention. Maybe they will agree to go see a movie with friends instead of reading a book all afternoon. Similarly, if an introvert is getting too close to their high temperature, they will retreat to be alone for a while. Simple things like talking to someone on the phone might totally drain them at this point.
These thresholds can change throughout an introvert’s lifetime, allowing two introverts with the same set of genes to be able to handle certain situations at different times in their lives. If an introvert grows up in a home where their parents hold parties regularly or have multiple siblings, their thermostat setting could be higher. Introverts who grow up as an only child might like to keep their “room” colder than other introverts. They can’t handle the same amount of exposure.
Life events can also help shift an introvert’s genetic predisposition. Maybe opposites really do attract and an introvert ends up marrying and extremely outgoing person. This partner could help the introvert understand extroverts better and expand their comfort threshold. Negative events can have an impact too. The same extrovert might end up betraying your trust and causes you to retreat even more into yourself than before.
Even though Dr. Laney notes that preference towards introversion or extroversion is generally set within your first four months of life, these “set points” allow introverts and extroverts to grow with each other. Comfort thresholds help a person to grow outside of their genetic predisposition without changing who they truly are.
Overall, a person’s introversion or extroversion is mostly determined by genetics. DNA shapes the way we process and use different neurotransmitters, how we experience pleasure, and the way we react to outside stimuli. Our DNA makes us who we physically are, but our mind can help us determine what is inside. No one should try to change who they truly are, but there are always methods to embrace some of the “other side”!