At the risk of everyone wanting my head on a pike:
A. We don't really know what introversion and extroversion are.
B. The higher the IQ, the more likely they are to qualify for the label "introvert."
So in at least some cases, it's possible smart people just give up on trying to connect socially because they get a lot of negative feedback from other people and it's mostly downside for them, so they stop bothering.
Most people marry people within about 10 IQ points of themselves. If you are "introverted" because talking at most people is an extremely negative experience due to you having a high IQ, it's not unrealistic to shoot for finding a means to connect with someone of similar IQ in hopes of establishing a relationship. If your IQ is high enough, odds are good they will also be labeled "an introvert" by the world.
Please note this is not saying "introversion indicates high IQ." That's not what it says at all.
My completely unscientific experience (n=1) of having a major mental health breakthrough and “becoming” and extrovert after years testing as an introvert tells me a few things.
1. For a variety of reasons, some people have extreme difficulty making mutually supportive connections and/or have no service familial attachments
2. There are compensating structures in the form of small safe groups that are lower risk or share a common yet outsider connection (obscure music, complex systems, historical or obsolete collections etc…) that lend themselves to a different “pace.”
3. In some cases, a combination of factors, mental health issues, lifestyle and life issues etc… mask a self love that can represent as something shameful in being expressive and thus after perceived or real rejection or failure many people just give up trying to put the effort in and become comfortable in that lifestyle.
That’s in the best case however, and assumes you can find an affinity group. Unfortunately it’s getting harder to get people together cause everyone’s just trying to survive they don’t feel like they have time to spend building community.
I knew someone with a very high IQ who was an extrovert and became an introvert after an abusive middle school experience.
I also know of a case of a bright child who consciously chose to stop playing to the crowd after they started school because it didn't go good places.
People act like extroversion and introversion are some kind of hard wired internal set point and seem oblivious to the myriad ways humans get taught to be one thing or another and that some people change in reaction to outside influences.
My personal anecdote is when I was younger. I took things very seriously. I took people very seriously. I came off as a smart ass.
Later I learned if I want to be part of the party. I needed to check my brain in a lock box and not let it out until the social event is over. A social event is about meeting people and good feelings.
Bitcoin. Investing in Beanie Babies. Selling your house and becoming a digital nomad? That’s wonderful. You are living the dream. Other platitudes.
I suspect introversion is correlated with my IQ because high IQ people enjoy thinking, and thinking is easier when you're by yourself without distractions.
I did volunteer work eons ago for tagfam.org and I test as a middle-of-the-road extrovert but spend a lot of time in geeky circles where most people are basically painfully shy and many people interpret my middle-of-the-road extroversion as "God, what a ridiculous attention monger!!!!!"
I've gotten enough negative feedback over it, I spend less time on forums than I used to. I'm not an introvert but even I eventually give up on bothering if it's mostly downside.
It can be isolating when one has thoughts and ideas that the people around one simply cannot follow or understand.
Of course it’s also often the case that introverts are simply low social status and thus find social interaction generally unrewarding. In that case pretensions of high intelligence are usually just a coping mechanism.
You can also just be labeled as a weirdo and become the target of bullying for sharing your ideas which aren’t well understood by your peers, and therefore you just keep your mouth shut and become an introvert.
Another aspect is that the IQ grades a very specific set of capabilities. I usually get a result between an armchair and a fly (I am not particularly proud of that, but it does not exactly reflects my capcities :))
It may be tha introvert people, rather calm in their heads, are better at analyzing the patterns you typically find in these tests (wildly guessing)
However, while introverts are a minority group in society, they form the majority of gifted people. Moreover, it appears that introversion increases with intelligence so that more than 75% of people with an IQ above 160 are introverted.
A. We don't really know what introversion and extroversion are.
B. The higher the IQ, the more likely they are to qualify for the label "introvert."
So in at least some cases, it's possible smart people just give up on trying to connect socially because they get a lot of negative feedback from other people and it's mostly downside for them, so they stop bothering.
Most people marry people within about 10 IQ points of themselves. If you are "introverted" because talking at most people is an extremely negative experience due to you having a high IQ, it's not unrealistic to shoot for finding a means to connect with someone of similar IQ in hopes of establishing a relationship. If your IQ is high enough, odds are good they will also be labeled "an introvert" by the world.
Please note this is not saying "introversion indicates high IQ." That's not what it says at all.