Intelligence is a powerful thing. It can be a major predictor of academic and financial success, giving people with it a significant advantage over those without it.

It’s also obvious that human intelligence has made us the dominant species on the planet.

So you would think that intelligence would be easy to spot. But actually, it can be surprisingly difficult.

Some people will actively hide how intelligent they are. Others simply don’t feel a  need to show it off. And if you don’t know the signs to look for, it’s easy to underestimate the intelligence of the people around you.

However, a powerful mind is bound to show itself sooner or later.

Keep an eye out for these traits that will show you someone is highly intelligent.

1) They are curious

Recently, I started sharing my home with two kittens. Cats are famous for their curiosity anyway, but that’s even more true when they are young. It’s impossible to keep these adorable creatures out of anything.

Part of the reason is that their brains are developing, so they seek out new experiences to learn new things.

Humans do the exact same thing, which is why kids can drive you crazy, asking hundreds of questions every day. And those who keep this curiosity into their adulthood are often more intelligent.

Check out this study, which found that kids with a higher IQ at the age of 11 remained more open and curious at the age of 50 than those with lower IQs.

It makes sense when you think about it. Being curious about the world around you helps you to learn more and helps your brain make new connections. So maybe it’s not so surprising that more curious people are more intelligent.

2) They are observant

Part of being curious about the world means observing it closely. So you can often tell an intelligent person by how much they notice about what’s going on around them.

Intelligent people pay attention to what other people say. They also pay attention to what they don’t say, using body language and gestures to reveal more about the state of mind of those they are talking to.

They also pay attention to the world around them. Weather patterns or the movements of animals can all tell you something interesting if you are willing to notice them.

Often, people with high intelligence seem to notice more than other people. That’s because their powerful minds are always seeking out new information.

3) They have good self-control

Having self-control means thinking before you speak or act. And it’s a trait that intelligent people often show, which can make them much more successful.

Think about it. Those who are prone to emotional outbursts tend to act in irrational ways. They will follow their feelings, even when it is detrimental to their long-term plans, and often become their own worst enemy.

Smart people, on the other hand, know that it’s always a good idea to think before you act. That way, you can determine the best course of action and make sure you are acting in a way that is consistent with your values and goals.

For example, it’s often been noted that people with high intelligence tend to be in better physical shape. A study established to find out why demonstrated that more intelligent people have greater self-control.

That means they are more likely to make themselves exercise and less likely to indulge in unhealthy habits.

4) They know their limits

Given how highly intelligence is prized and how big an effect that can have on life success, you might think intelligent people would be arrogant. But often, the opposite is true.

Part of being smart means knowing there are limits to your intelligence. And because intelligent people tend to be curious, they investigate their knowledge and soon discover that no matter how smart you are, there’s always someone smarter. There’s always more to know about the world.

This often gives highly intelligent people a great sense of humility. After all, being intelligent doesn’t necessarily make you a better person, and the truly intelligent are well aware of this.

5) They read

Is it that smart people read more, or is it that reading more makes you more intelligent?

That’s an open question. Certainly, reading in childhood can have a positive effect on brain development.

But it’s also true that reading more, even as an adult, can expand your base of knowledge and experience, which can make you seem more intelligent.

What is undeniable is that some of the world’s most successful people are voracious readers.

Reading, whether it’s fiction or nonfiction, provides an incredible workout for your brain. It can increase knowledge, focus, concentration, and even your sense of empathy.

So if you know someone who reads a lot, chances are they are more intelligent than most.

6) They are passionate about their interests

The curiosity of highly intelligent people means they often develop a broad range of interests. Still, it’s also true that they often pick a few special subjects and get incredibly passionate about them.

Partly, that’s because a powerful mind needs something to work on. Getting caught up in a passionate pursuit, whether its history, languages, music, or anything else, gives an intelligent person an outlet for the restless energy of their brain.

“[Intelligent people] are able to admit when they aren’t familiar with a particular concept or if something falls outside of their realm of knowledge, and are willing to learn what they don’t know,” writes clinical psychologist Holly Schiff.”

“Their intellectual curiosity will lend itself to wanting to self-educate and read anything they can get their hands on.”

7) They listen

There are lots of different ways for an intelligent person to give their brain the exercise it craves. Reading is a great one. But also, simply listening to other people gives the highly intelligent a way to learn more about the world from the viewpoint of others.

Perhaps even more importantly, they ask questions.

“Someone must have said this often-quoted line: ‘Knowledge is having the right answer. Intelligence is asking the right question,’” says Andi Simon, author of Rethink: Smashing the Myths of Women in Business.

“Intelligent people recognize that others have information and insights that through a shared conversation will help both grow and expand their wisdom and enhance their intellect.”

8) They are open-minded

On the other hand, all the listening in the world won’t do you any good if you don’t have an open mind.

That’s why intelligent people tend to be more open to the viewpoints of others in the hope of learning something new.

Intelligent people tend not to believe anything until they have some evidence for it. This means they are less stuck in their own viewpoints and more willing to adopt the views of others – if they can be convinced those views are correct.

9) They like to spend time alone

Finally, one of the more subtle signs of someone of high intelligence is that they like to spend more time alone.

This is demonstrated by the savanna theory of happiness, which shows that social interaction is usually good for people, increasing their level of happiness and life satisfaction.

However, for intelligent people, the reverse is true. The more time they spend socializing, the less happy they are.

There are lots of reasons for this.

One may be that for intelligent people, it’s harder to have more social relationships because fewer people are on the same level of intelligence. Get beyond around 30 points of IQ, and meaningful communication becomes almost impossible.

Also, highly intelligent people always have something on their minds. Often, their thoughts are best worked out alone, without interruptions caused by other people.

Combine that with the fact that intelligent people often prefer solitary pursuits like reading, and it’s no wonder that those who like to spend time alone are often more intelligent.

Spotting intelligence

Movies and TV have trained us to think that intelligent people are nerdy geniuses scrawling math equations in the steam condensed on the bathroom mirror.

But in reality, intelligent people are all around us, and they may not be as visible as you might think.

Keep an eye out for these traits that can point you toward someone with a powerful intellect. Combine a few of these, and it’s a dead giveaway that you’re dealing with someone with a first-rate mind.