The terms introversion and extroversion were introduced by Swiss psychiatrist and psychoanalyst Carl Jung, although both their current understanding and usage vary.

"In general, introverts work things out in their heads, and extroverts work things out in the world," Dr. Laurie Helgoe told Bored Panda. "This has all kinds of implications. When presented with a question, an introvert will bring the query into their private laboratory, work it through and then offer a response. This takes time and focus. By contrast, extroverts will work things out in the interaction, thinking out loud or bouncing ideas back and forth."

"Introvert preferences: writing, one-on-one conversations, solitude for reflection. Extrovert preferences: talking, fast-paced interactions, social feedback."

Helgoe said "our current understanding is that introversion and extroversion exist on a continuum, with introversion on one end, extroversion on the other, and 'ambiversion' at the midpoint."

"Most of us are somewhere in the middle, leaning one way or the other. And, yes, there are complex combinations, such as the social introvert who gravitates toward people, but becomes overstimulated and needs to refuel with solitude. Or the shy extrovert, who is self-conscious around people but is oriented to engage externally," the psychologist explained.

Most likely, introverts develop due to a combination of nature and nurture. The way that the human body's physiology responds to the outside environment plays a critical role in determining the level of our extroversion and introversion.

On a physiological level, a network of neurons located in the brainstem known as the reticular activating system (RAS) regulates arousal levels, including wakefulness and transitions between sleeping and waking.

The RAS also plays a role in controlling how much information we take in while we're awake. When confronted by potential threats in the environment, the RAS increases arousal levels so we can be alert and ready to deal with danger.

Each person has a basic set point in terms of arousal level. But while some naturally have a high set point, others have a much lower set point.

Psychologist Hans Eysenck suggested that these arousal levels could be thought of as a continuum. According to his arousal theory of extroversion:

• 15% of people have a minimal set point, meaning they naturally have low arousal levels;
• 15% of people have a high set point, meaning they naturally tend to be more aroused;
• 70% of people lie somewhere in the middle of the continuum.

According to Eysenck, introverts have high levels of arousal. Because of that, they tend to seek activities and environments where they can escape from overstimulation. Alone time gives them the opportunity to process and reflect on their experiences.

"Because introverts go out less frequently than extroverts, they often have higher expectations of social situations," Thea Orozco, the author of The Introvert's Guide to the Workplace, explained to Bored Panda.

However, that doesn't mean introverts have to come out of their shell.

"Oftentimes they feel a need to act like an extrovert at parties, or talk to half the people at a networking event. Instead, introverts should think about what they actually want from socializing. For instance, the goal for going to a party might be to have one interesting conversation, or for a networking event it might be meeting two people you want to keep in touch with."

Orozco highlighted that introversion is neither inferior to extroversion nor a synonym for shyness.

"Shyness is the fear of being judged by others, while introversion describes how a person recharges their energy," she said. "They might look the same on the outside, but they have different motivations on the inside. Shy extroverts do exist!"