There are two core factors:

1) Sensitivity to external stimulation

Dr Marti Olsen Laney explains in her book ‘The Introvert Advantage’ that the brains of introverts have a higher sensitivity to dopamine, the chemical that responds to external stimulus.

This means that introverts don’t need a lot of external stimulation in order to meet our dopamine needs.

For me, this explains why I am sensitive to noise, chatter, crowds, busy places, shops. My brain gets saturated by external stimulation quite quickly and I feel wiped out if my brain is flooded with excess dopamine.

Introverts feel good when we get a high dose of a different neurotransmitter called acetylcholine which releases feelings of calm, quiet and restfulness.

In contrast, an extrovert’s brain has low sensitivity to dopamine, so they require high levels of external stimulation to produce enough dopamine to make them feel good. They are energised by stimulation because it is boosting the dopamine that their brains crave.

2) Processing time

There is another biological difference between introverts and extroverts revealed by research from Dr Debra Johnson and her team at the University of Iowa.

PET scans show that blood flows through an introvert’s brain in longer, more complex pathways to areas that are involved in internal thought processing, problem solving, planning and long term memory. This pathway is activated by acetylcholine which produces pleasure in association with thinking deeply and reflecting.

It explains why introverts are often completely absorbed by our inner world of thoughts.

As blood flows through the long, meandering pathways in our brain, we can become preoccupied with internal processing, thinking, digesting, puzzling and planning.

“Quiet people have the loudest minds.” Stephen Hawking

PET scans also show that blood flows through shorter pathways in extrovert brains reaching areas associated with sensory processing of visual, auditory and touch sensations and this pathway requires repeated hits of dopamine which links to their need for lots of external stimulation.

So that helps to explain why introverts and extroverts feel and react differently.

For an extrovert, a busy family day out and about with full throttle social interactions leaves them buzzing with energy, stoked up on enough external sensory input to fuel their brain’s craving for dopamine.

It also explains why introverts can get saturated by this level of stimulation and feel happier in ‘rest and digest’ mode when our craving for acetylcholine is satisfied through activities like reading, thinking and concentrating deeply on one thing.

Like most introverts, I have a preference for 1-1 conversations where I can focus on processing a single channel of communication. I find that in groups of more than 2 or 3 people, I simply can’t process all that firehose of chatter and my brain freezes, it gets saturated and can’t process everything so I clam up. I literally find that I can’t speak.

I used to feel bad about myself for this - why can’t I think of anything to say in groups - or why do I think of just the right thing to say 6 hours later! Now I understand it has to do with the way blood flows through my brain and that makes sense.

So introverts don’t behave differently because we are awkward or lacking in social skills. It is a scientifically proven fact that introverts and extroverts have biological differences. The blood flows through our brains differently. We need different levels of neurotransmitters to feel good.

This evidence demonstrates that introverts need different environments in order to thrive. The everyday external world is typically not introvert friendly. The default norms tend to favour extrovert behaviour.

The expectations of work, family life, schools and social groups can provide particular challenges for introverts. So how can we shape our everyday lives to take into account our introvert needs without feeling bad about it?

If you would like to chat to me about how to identify and communicate your needs as an introvert parent so that you feel less overwhelmed day to day, you can book a call with me.

Or if your child is experiencing big emotions and you are feeling at your limit in terms of sensory overload, my short course will give you the 5 best practices to help your child learn how to regulate their emotions. We look at sensory needs, the nervous system and how this drives their behaviour as well as our reactions. It really helps make sense of things so you feel more on the front foot rather than the back foot. Instead of feeling swamped and overwhelmed, you will be able to focus your energy on what really matters.