What physiologically makes an introvert an introvert and an extrovert an extrovert?
There is more to the introvert/extrovert comparison than how each one socializes.
It’s in your genes
According to Dr. Marti Olsen Laney in The Introvert Advantage, there has been sufficient research done on the ‘novelty seeking’ gene, D4DR. Although no one gene determines temperament, D4DR is found on the 11th chromosome which has been deemed the personality chromosome by British journalist and member of the House of Lords, Matt Ridley, because of its influence on behavior, particularly exhilaration and excitement. Thrill seekers (extreme extroverts according to Dr. Marti Olsen Laney of The Introvert Advantage) examined in geneticist Dr. Dean Hamer’s study were shown to have a long D4DR gene and were less sensitive to the neurotransmitter dopamine. Those participants with more reflective and slower paced natures had shorter D4DR genes and a higher sensitivity to dopamine.
Dopamine: The want, desire, seek out and search neurotransmitter
According to the 2012 Psychology Today article titled, Why We’re All Addicted to Texts, Twitter and Google, the neurotransmitter, dopamine, was discovered in Sweden in 1958. It is created in various parts of the brain and is involved in such brain functions as thinking, moving, sleeping, mood, attention, motivation, seeking and reward.
Most people think of dopamine as the pleasure or reward brain chemical but recent research states that those attributes are more strongly correlated with the opioid system in the body. Dopamine is the neurotransmitter that makes us want, desire, seek out and search. It increases our level of arousal and goal-directed behavior. It motivates us to move, learn and survive. Not only does dopamine move us regarding physical needs such as food and sex but it also makes us curious about abstract concepts such as ideas and information.
The extroverted brain
Advances in brain technology such as PET scans and MRIs have given us a peek inside the brains of extroverted and introverted individuals (determined by questionnaires filled out prior to participation in the scans). Such scans note where blood flows in the brain.
During a study conducted by Dr. Debra Johnson and reported in The American Journal of Psychiatry, it was discovered that extroverts’ blood flowed in shorter (why they can process faster and speak off the cuff) pathways toward parts of the brain where visual, auditory, touch and taste are processed, in other words, where external stimulation (other than smell) is processed.
Another point uncovered during brain imaging studies was that the neuro-pathways most used by extroverts are activated by dopamine. Those participants with an ability to process a higher amount of external stimuli and a novelty seeking personality (extreme extroverts) were less sensitive to dopamine.
So how do they get the dopamine their neuro-pathways need? They enlist the help of adrenaline, which is released in the sympathetic nervous system, to make more dopamine. The more active the extrovert is the more adrenaline is produced and dopamine increases.
Extroverts feel good when they have places to go and people to see. — Dr. Marti Olsen Laney, The Introvert Advantage
The introverted brain
Introverts’ brains work differently than extroverts’. For one thing, introverts have more blood flow to their brains than extroverts. According to Marti Olsen Laney, that indicates more internal
stimulation and sensitivity. The blood in an introvert’s brain travels longer, more complicated pathways and focuses on parts of the brain involved with internal experiences like remembering, solving problems and planning.
Introverts’ brains still use dopamine but are more sensitive to it and too much of it will cause over-stimulation. The more dominant neurotransmitter found in the introvert’s neuro-pathways is acetylcholine. Acetylcholine affects attention and learning, influences the ability to stay calm and alert, utilizes long-term memory and activates voluntary movement. Not surprisingly, acetylcholine stimulates a good feeling when we think and feel.
Acetylcholine acts as an inhibitory neurotransmitter when it activates our parasympathetic nervous system, which helps us calm down and conserve energy when stimulated. The sympathetic nervous system (fight or flight) has the opposite effect. It is characterized by activity and mobility and employed more by the extroverted brain.
The science geek in me ponders this…
The recent studies regarding dopamine as a seeking and searching chemical versus a reward chemical makes me wonder about the introvert’s sensitivity to it. The fact that it stimulates curiosity (seeking and searching) about ideas and information (which seems like internal work) makes it seem like the ideal and probable chemical behind our love of internet surfing and research. Could this be an introvert’s way of mitigating and applying dopamine (being active?) without over-stimulating ourselves? Could our brain chemistry/physiology be changing because of the internet? Just a couple of questions that came up as I did the research.
Thank you for allowing me to entertain my science mind. I’ve always had a fascination with neuroscience, biology and anatomy.
Have you noticed your penchant as an introvert to ‘throttle down’ more than ‘rev up the engine’? Do you prefer more active tasks or more reflective? What did you learn from this post?
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