Here’s what really makes someone an introvert — and how your own personality might be shaped.
Introverts are finally having our moment in the spotlight. There are more websites, books, and communities for introverts than ever before — enough that young introverts can grow up understanding their introversion instead of feeling “wrong,” like I did as a kid. But there’s still no shortage of people who don’t get it. Anytime I mention I’m an introvert, someone suggests something like, “Why can’t you just learn to be social like everyone else?”
That perspective is outdated, but it does raise an interesting question: Do people “learn” to be introverts as they grow up, or are we introverts from birth? In other words, what makes someone an introvert — your genes, your upbringing, or a mix of both?
The Science of Young Introverts
To explore this question, I turned to Dr. Marti Olsen Laney’s book The Hidden Gifts of the Introverted Child: Helping Your Child Thrive in an Extroverted World. Laney provides a detailed overview of what we know about young introverts, including the key factors that shape their introversion.
Like most debates about nature versus nurture, Laney explains that the answer is a bit of both:
“Yes, children are born with an innate temperament. And yes, parents are vitally important to how that temperament is nurtured.”
However, she emphasizes that introverts are (mostly) born that way. Specifically:
- The degree to which you are introverted or extroverted is influenced by genetics.
- Among personality traits, introversion/extroversion is one of the most strongly hereditary.
- That said, environmental factors — like how you’re raised — play a role too.
These aren’t just guesses. Laney uses brain research to show how genetics strongly shape your temperament — and how certain experiences can sometimes change your natural tendencies.
The Genetic Basis for Introversion
According to Laney, introversion is rooted in our brain chemistry. Human brains use over 60 neurotransmitters — chemicals that control how the brain works. While everyone has the same basic chemicals, the exact “recipe” varies slightly from person to person. This unique mix is determined by your genes and is present from birth. It influences many traits, including whether you’re more introverted or extroverted.
Laney explains that this connection is so strong, children might show signs of being introverted or extroverted from the moment they’re born.
One of the most important neurotransmitters is dopamine, which motivates us to chase rewards. Introverts’ brains are less influenced by dopamine. We might not get the same buzz from it as extroverts do, so we naturally seek less external stimulation.
This sensitivity to dopamine is an example of how our neurotransmitters shape us — and it’s all decided by our DNA.
How Genetic ‘Set Points’ Make You Flexible
Introversion isn’t entirely genetic. It’s shaped by your environment, especially when you’re young, and your genes allow some flexibility. This flexibility works through “set points,” which are the upper and lower limits of how much social stimulation your brain can handle.
Laney compares set points to a thermostat. Imagine you set your thermostat to keep the house between 68 and 74 degrees Fahrenheit. Within that range, everything feels comfortable, and no adjustments are needed. But if it gets too cold or too hot, the heater or AC kicks on, using energy to bring things back to the comfort zone.
Your brain works the same way. As an introvert, you might crave more social time one day and less the next. As long as you stay within your set points, you’re fine. But if you go past your upper limit — like attending a loud, crowded birthday party — you’ll likely feel drained and need time to recharge.
This explains why two introverts with similar genetics can act quite differently. One might prefer staying near the high-stimulation end of their comfort zone, while the other sticks closer to the low-stimulation side. These tendencies are shaped by experience. For example, a child with positive social experiences may enjoy pushing their limits, even as an introvert. Meanwhile, a child with negative experiences might develop quieter, more reclusive habits.
A Portrait of Three Kids
To understand how set points work, let’s look at three hypothetical children. All three are introverts, but they’re not the same:
Jen and Amanda are identical twins with the same DNA and similar brains at birth. Both show signs of introversion, but their set points are pretty wide, allowing them to act more social or more introverted depending on the day.
Matthew is also introverted, but his brain has much narrower set points than Jen and Amanda’s.
Even though they’re all introverts, their personalities develop very differently:
Jen has early experiences that reward being social. Since she’s a few hours older than Amanda, adults often ask if she’s the “leader” of the two. When she does something bold or outgoing, people laugh and cheer. This positive feedback makes socializing fun for her, so she spends more time at the high end of her set point range and becomes a social introvert.
Amanda has a different experience. When she tries to be outgoing, adults dismiss her efforts, saying she’s just copying Jen. She doesn’t find it rewarding to come out of her shell. By preschool, she’s less excited about making friends than Jen. When other kids stare at the twins, Amanda feels self-conscious and takes the attention as negative. She’s happier staying near her lower set point and is seen as the shy one.
Matthew grows up as an only child. His parents notice his introversion early and encourage him gently. They take him to playgrounds, join playgroups, and enroll him in a private preschool that values creativity.
Even with this supportive environment, Matthew remains deeply introverted. His set points are so narrow that even positive social experiences leave him tired or cranky. While he’s socially well-adjusted, he prefers quiet, imaginative activities over spending time with people.
Want to feel more at ease in social situations?
Discover the secrets to enjoying fun, meaningful conversations. Know exactly what to say, even if you’re introverted, shy, or anxious. Feel less drained and have more energy while socializing. Click here to secure your spot in Jenn Granneman’s upcoming course, Easy Conversation.
So, Are You Born an Introvert or Not?
These kids are imaginary, but their stories match patterns many of us have experienced in real life. Your genes give you a “range” of introversion. If your range is wide, your upbringing can influence how social or introverted you become. But if your range is narrow, your upbringing won’t change you as much. That’s why Laney’s answer to the nature vs. nurture debate is, “Yes… and yes.” Your genes set the limits, but they also allow for some flexibility.
What’s clear is that your introversion or extroversion preference is decided early on. Laney says that most children stick to the tendencies they showed in their first four months of life, even as their experiences shape them over time.
I can see how my own life experiences helped solidify my introvert tendencies — like feeling like a misfit at school. I also wonder if I have a “narrow” range of set points, more like Matthew than Jen or Amanda, since I can happily go days without any social interaction. 
