This Is How Your Brain Judges Others’ Personalities

Our personalities define us. They’re the sum of what we think, feel, and do in different situations. They’re what make us unique. After about a century of research, personality psychologists now have a good grasp of what distinguishes one personality type from another—things like how extroverted, emotionally stable, ambitious, or inquisitive we are relative to the general population. These dimensions are to our minds what height, weight, and skin color are to our bodies.

But while scientists study those features using carefully designed tests, the rest of us evaluate one another’s personalities all the time.

Always Sizing Up
Because we assess others’ personalities quickly and intuitively, many of the judgments we make about them remain unconscious. That reality has been shown to factor into workplace interactions in ways we’re only just beginning to realize and respond to.

Other times we devote a great deal of thinking to try to figure someone out—whether he’s trustworthy, smart, sincere, what makes him tick. Needless to say, not everyone’s willing to admit they actually do this, since we don’t want to be seen as prejudiced or narrow-minded. But multiple studies have shown that whenever we interact with people, we adjust our behaviors according to our implicit attitudes toward them. We’re behaving like amateur psychological profilers pretty much all the time, whether we realize it or not.

Getting It Right
A key question, then, is how accurate our judgments of others’ personalities actually are. Of course, our evaluations don’t need to be accurate in order to impact the ways we react. You might be wrong thinking I’m stupid, but if you really believe it, you’ll probably treat me as though I am.

But that doesn’t mean all of the judgments we make are totally baseless all the time—some personality stereotypes do have a kernel of truth to them. Indeed, the average correlation between scores on validated personality tests and intuitive inferences by others is statistically significant (at around 0.30 to 0.40). In other words, we’re accurate enough about the judgments we make at least enough of the time to keep making them.

That correlation gets stronger the more familiar two people are, but only up to a point. For example, our work colleagues and friends can describe us better than strangers, and so can our partners and closest friends and family members. We base some of our inferences purely on appearance, but—especially as we get to know someone—we also consider what they say, feel, and do in different circumstances.

In fact, studies also show that other people’s views of our personality are often better predictors of our future behaviors than our own views about ourselves are—in part because we tend to think of ourselves a little more favorably than others see us.

Getting It Wrong, Or Just Not Getting It
Not everybody is equally legible, though. Extroverts tend to be easier to read. In fact, that very fact may be one of the biggest disadvantages of being extroverted. It makes you unwittingly leak information about your character, even when you don’t want to.

Still, not everyone is equally good at reading others’ personalities. Those with better social skills and more experience interacting with people make more accurate personality judges than those with lower emotional intelligence. It’s also been found that introverts tend to read one another better than extroverts can read them, perhaps because extroverts aren’t as focused on themselves. They’re busy being the center of attention and sometimes miss out on information about those around them as a result.

A Room With A View
Sometimes we give other clues to our personality when we aren’t even present. Studies show that our possessions and habitats—whether it’s our office space, living space, or bedroom—reveal reliable information about our character. So much so that strangers can make accurate assessments about us based just on those spaces.

We leave traces of our personality wherever we go and whatever we do. The environments we inhabit don’t look different for random reasons, but because they reflect the choices we make and the preferences we have—both of which are clear indicators of our personality. That’s why when you visit someone’s home for the first time, you’re unlikely to be totally surprised by what you find there. (The handful of things you hadn’t counted on are usually the result of how we behave differently in public and private.)

The Eye of the “We-Holder”
Finally, there’s the power of collective thinking. Small groups tend to be more accurate in their judgments than individuals. If you ask a group of observers to assess someone’s personality, then take the average of their evaluations, it’s likely to be more accurate than the judgment of any individual observer in the group.

In that sense, our personalities are in the eye of the “we-holder,” not the beholder. Accurate assessments can be crowdsourced the way IMDb does film trivia, TripAdvisor does hotel features, and Uber does driver ratings. It would therefore be pretty useful to learn what most people think of us, even though strangers and friends alike aren’t always likely to weigh in objectively.

Our brains have evolved to gather information about the people around us all the time. Which means that in the realm of human interaction, there’s no second chance for a good first impression.

This article originally appeared in Fast Company.