Introverts and extroverts have different brains!
- pH7 Science Blog
- Jul 22, 2015
- 4 min read

(Source: Blink Magazine)
‘Introvert’ and ‘extrovert’ are two terms proposed by the psychologist Carl Jung way back in the 1920s, in order to describe how different people obtain their energy and recharge when necessary. We throw these terms around quite often, but do we really know what makes us different to each other?
The theory is that introverts find excessive social interaction a drain, whilst extroverts are boosted by social interaction. In general terms, introverts are those who are more likely to focus on thoughts, feelings and ideas rather than voicing their concerns and putting their thoughts into action like extroverts tend to do.
Extroverts make up the majority of the population with famous examples including Steve Jobs and Oprah Winfrey, whilst well-known introverts include people such as J.K. Rowling and Albert Einstein.
Arousal in the physiological sense is the extent to which our bodies and minds are alert and therefore able to respond to stimulation. One theory put forward by Hans Eysenck suggested that extroverts naturally have a lower level of arousal than introverts who are the opposite. This state of arousal is in part governed by the ascending reticular activating system (RAS), which is an area of the brainstem that aims to ensure that the brain receives optimum stimulation and is regulated by socialisation. Too little stimulations and you run the risk of depression, too high and the result may be stress.
Introverts have a higher amount of stimulation going on already, therefore they don’t need the additional stimulation in order to be happy and are therefore at risk of pushing their level too high and as previously explained, extroverts have a lower level naturally and are therefore more likely to be motivated to seek out people and novel experiences in order to top themselves up.
Interestingly, the RAS also responds to stimuli such as food and in the ‘lemon juice experiment’ those who salivate more in response to lemon juice are more likely to be introverted as they have a higher basal activity of the RAS.
Dopamine is a neurotransmitter that is involved in both learning and reward mechanisms of the brain and is also thought to play a role in whether you display introverted or extroverted behaviour.
A 2005 study asked the subjects to fill in a personality profile before participating in a gambling task whilst inside a functional MRI scanner. When a gamble proved successful, it was found that the extroverts displayed a stronger response in the nucleus accumbens, a major part of the neural reward system and the amygdala, associated with processing emotional stimuli.
Dopamine gives you an instant hit of ‘happiness’ when you act quickly and take risks, whereas acetylcholine (Ach) rewards us in a way that makes us feel more relaxed and calm. It has been suggested that introverts are more sensitive to dopamine than extroverts in that too much of it can make them feel overwhelmed and anxious. Extroverts on the other hand are thought to not respond to the gentler buzz provided by Ach.
Ach works with the parasympathetic nervous system, which promotes the ‘rest and digest’ response leading to muscle relaxation, with Ach increasing blood flow to the frontal lobe of our brains, which is responsible for cognition.
The opposite of this is the sympathetic nervous system, which acts in the ‘fight or flight’ response, which primes the body for action and directs blood to muscles where it’s potentially needed, with dopamine being more active in the back of your brain to increase alertness.
It is thought that extroverts prefer this high-energy sympathetic side of our nervous system, whilst the introverts amongst us prefer the parasympathetic.
What if I don’t think that I’m either?
It’s clear that there are many systems that control our actions and it’s quite a personal thing, therefore not everyone is defined by either extreme. It’s possible to have traits of both an introvert and an extrovert and if, like myself, you think you’re one of those, then you fall under the term ‘ambivert’.
Is it better to be an introvert or an extrovert?
Introverts tend to direct their thoughts inwards and consider things more, which is surely a good thing in situations that require planning, but not so much when faced with a quick decision.
It may be true that being an extrovert may be viewed as being advantageous as they are more likely to get out there and seize every opportunity and therefore potentially be more successful. However, it’s also thought that extroverts are more likely to take risks and therefore endanger themselves with activities such as extreme sport, so introverts, don’t dwell on this one too much.
Whether you’re an introvert or an extrovert, it all boils down to your energy and how you prefer to obtain yours, whether it be by surrounding yourself with others or by contemplating life in solitude. Either way, we all know what suits us and we therefore adapt to our environment to fulfill our personal needs. The way that we perceive the world is ultimately what will alter our brain activity and hence, our potential chances of being what we each individually believe to be ‘successful’ in the long run.
So, what do you think you are?
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