Here’s a definition of intelligence that lots of psychologists can get behind:

Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings-“catching on,” “making sense” of things, or “figuring out” what to do […] Intelligence, so defined, can be measured, and intelligence tests measure it well.

Intelligence sounds pretty great. Who doesn’t want to “catch on” and “make sense”? Hell, “figuring out” what to do is pretty much all of life!

Naturally, people with more of this mental horsepower must live happier lives. When they encounter a problem, they should use their superior problem-solving ability to solve it. Smarter people should do a better job making plans and getting what they want, and they should learn more from their mistakes and subsequently make fewer of them. All of this should add up to a life that makes smart people go “this life rules!"

So smarter people are happier, right? 

Well, this meta-analysis says no. Another says maybe a teeny tiny bit. This large, nationally-representative study from the UK finds that people who score the lowest on an intelligence test are a little less happy than everyone else, but that’s pretty much it. 

I also pulled data from the General Social Survey, which includes (a) a short vocabulary test that seems to correlate reasonably well with longer intelligence tests (you can try it here), and (b) a simple measure of happiness: "Taken all together, how would you say things are these days—would you say that you are very happy, pretty happy, or not too happy?" Across 50 years of data and 30,346 people, the folks who scored higher on the vocab test were a tiny bit less happy (r = -.06, p < .001).

WHAT’S GOING ON HERE?

Maybe our tests are bad. The psychological study of intelligence has a long, bleak history of racism and prejudice against poor people (“three generations of imbeciles are enough”), so we should be skeptical coming in. Psychologists have been trying to construct bias-free tests for a long time, but it’s hard. Plus, people score higher on IQ tests when you pay them for performance, so what looks like a test of intelligence may in part be a test of how hard you’re willing to try. 

But even if intelligence tests only measure something like “ability to succeed in an unfair society” or “willingness to try hard,” it only deepens the mystery. Shouldn’t those people end up with happier lives, however unfair that may be?

And the tests likely do tap something more than just privilege and effort. There’s plenty of skepticism toward intelligence tests in psychology, but even the biggest skeptics agree that IQ can predict things like how well you do in school and what kind of job you get, even accounting for all the criticisms. So why doesn’t it also predict living a life that you like?

SPEARING SPEARMAN

I think there’s one guy to blame for this big mystery, and his name is Charles Spearman.

Way back in 1904, Spearman noticed something weird: the same kids who did well in one subject in school tended to do well in other subjects, too. The correlations were never perfect, of course, but they were pretty darn high, even across subjects that seemed pretty different from each other, like French and math. How come?

Spearman figured there must be some general mental ability that humans use to solve all kinds of problems. He later wrote:

This continued tendency to success of the same person throughout all variations of both form and subject-matter—that is to say throughout all conscious aspects of cognition whatever—appears only explicable by some factor lying deeper than the phenomena of consciousness.

Helpfully, he also drew us a picture:

This is, I think, exactly where everything went wrong with the study of intelligence for the next 119 years. It’s not that Spearman’s results were inaccurate—in fact, they’ve been replicated over and over. At this point, pretty much every paper on intelligence has to start out like this review from 2006:

In the study of intelligence, one empirical phenomenon is well established: Test scores on cognitive tasks show a positive manifold, that is, they are invariably positively intercorrelated, albeit to varying degrees. This implies that people who score well on one cognitive test are likely to score well on other cognitive tests. The positive manifold is a robust phenomenon.

Spearman’s stats were sound, but his interpretation was wrong. He did not, as he claimed, observe a “continued tendency to success throughout all variations of both form and subject-matter,” nor has anybody else. It merely looks as if we’ve varied all the forms and the subject-matters because we have the wrong theory about what makes them different. 

We think tests of math, vocabulary, French, music, etc. are all different because some are about words and others are about numbers and others are about sounds. But psychology, like all sciences, is all about discovering the differences between seemingly similar things, and discovering the similarities between seemingly different things. If psychologists ever had to march into battle, a good candidate for our crests may be the famous Müller-Lyer illusion, the two lines that look like they’re different lengths but aren't:

Just like those lines, I think all of our various tests of intelligence aren’t as different as they seem. They’re all full of problems that have a few important things in common:

• There are stable relationships between the variables.

• There’s no disagreement about whether the problems are problems, or whether they’ve been solved.

• There have clear boundaries; there is a finite amount of relevant information and possible actions.

• The problems are repeatable. Although the details may change, the process for solving the problems does not.

I think a good name for problems like these is well-defined. Well-defined problems can be very difficult, but they aren’t mystical. You can write down instructions for solving them. And you can put them on a test. In fact, standardized tests items must be well-defined problems, because they require indisputable answers. Matching a word to its synonym, finding the area of a trapezoid, putting pictures in the correct order—all common tasks on IQ tests—are well-defined problems.

Spearman was right that people differ in their ability to solve well-defined problems. But he was wrong that well-defined problems are the only kind of problems. “Why can’t I find someone to spend my life with?” “Should I be a dentist or a dancer?” and “How do I get my child to stop crying?” are all important but poorly defined problems. “How can we all get along?” is not a multiple-choice question. Neither is “What do I do when my parents get old?” And getting better at rotating shapes or remembering state capitals is not going to help you solve them.

We all share some blame with Spearman, of course, because everybody talks about smarts as if they’re one thing. Google “smartest people in the world” and most of the results will be physicists, mathematicians, computer scientists, and chess masters. These are all difficult problems, but they are well-defined, and that makes it easy to rank people. The best chess player in the world is the one who can beat everybody else. The best mathematician is the one who can solve the problems that nobody else could solve. That makes it seem like the best chess players and mathematicians are not just the smartest in their fields, but the smartest in the whole world.

THE POORLY DEFINED PROBLEM OF BEING ALIVE

There is, unfortunately no good word for “skill at solving poorly defined problems.” Insight, creativity, agency, self-knowledge—they’re all part of it, but not all of it. Wisdom comes the closest, but it suggests a certain fustiness and grandeur, and poorly defined problems aren’t just dramatic questions like “how do you live a good life”; they're also everyday questions like “how do you host a good party” and “how do you figure out what to do today." 

One way to spot people who are good at solving poorly defined problems is to look for people who feel good about their lives; “how do I live a life I like” is a humdinger of a poorly defined problem. The rules aren’t stable: what makes you happy may make me miserable. The boundaries aren’t clear: literally anything I do could make me more happy or less happy. The problems are not repeatable: what made me happy when I was 21 may not make me happy when I’m 31. Nobody else can be completely sure whether I’m happy or not, and sometimes I’m not even sure. In fact, some people might claim that I’m not really happy, no matter what I say, unless I accept Jesus into my heart or reach nirvana or fall in love—if I think I’m happy before all that, I’m simply mistaken about what happiness is!

This is why the people who score well on intelligence tests and win lots of chess games are no happier than the people who flunk the tests and lose at chess: well-defined and poorly defined problems require completely different problem-solving skills. Life ain’t chess! Nobody agrees on the rules, the pieces do whatever they want, and the board covers the whole globe, as well as the inside of your head and possibly several metaphysical planes as well.

IF YOU’RE SO SMART, WHY ARE YOU SO DUMB?

Here’s another way of looking at it.

Say you want to test people’s math ability. You design a test, administer it to a bunch of people, do all your psychometrics, etc. You’re feeling pretty good about your math test. And then you find that some of the people who ace your test later say things like “two plus two is 19” and “88 is the biggest number.” You’d feel pretty embarrassed about your math test because it’s clearly not measuring mathematical ability, if it’s measuring anything at all.

This is exactly the situation we’re in with tests that claim to measure people’s “reasoning” and “problem-solving ability.” Christopher Langan, a guy who can score eye-popping numbers on IQ tests, believes that 9/11 was an inside job meant specifically to distract the public from his theories, and he claims that banks won’t give him a loan because he’s white. John Sununu supposedly has IQ of 176, but he still had to resign from being George H.W. Bush’s chief of staff because he flew to his dentist appointments using military jets. Bobby Fischer is one of the greatest chess players of all time, but he also claimed that Hitler was a good dude, the Holocaust didn’t happen, and "Jews murder Christian children for their blood and they’re doing it even today." Then there's the ever-lengthening list of professors at elite universities who have been disciplined or dismissed for doing things like sexually harassing colleagues and students or completely making up data or hanging out with a known pedophile. These are supposed to be some of the smartest people in the world, endowed with exceptional problem-solving abilities. And yet they’re still unable to solve basic but poorly defined problems like “maintain a basic grip on reality” and “be a good person” and “don't make any life-altering blunders.”

GAZE UPON OUR WORKS AND DESPAIR

And here's another way of looking at it.

Over the last generation, we have solved tons of well-defined problems. We eradicated smallpox and polio. We landed on the moon. We built better cars, refrigerators, and televisions. We even got ~15 IQ points smarter! And how did our incredible success make us feel? 

Well:

All that progress didn’t make us a bit happier. I think there’s an important lesson here: if solving a bunch of well-defined problems did not make our predecessors happier, it probably won’t make us happier, either. The barrier between you and everlasting bliss is probably not the size of your television, nor your ability to solve Raven’s Progressive Matrices. 

(To be clear, I still think it’s good we did all this. Polio sucks and going to the moon is awesome.)

I wish we knew more about how to make that bright green line go up, but we just haven’t yet defined the problem of “living a happy life”. We know that if you’re starving, lonely, or in pain, you’ll probably get happier if you get food, friends, and relief. After that, the returns diminish very quickly. You could read all the positive psychology you want, take the online version of The Science of Wellbeing ("Yale’s Most Popular Course Ever!”), read my post on hacking the hedonic treadmill, meditate, exercise, and keep a gratitude journal—and after all that, maybe you’ll be a smidge happier. Whatever else you think will put a big, permanent smile on your face, you’re probably wrong.

So if you’re really looking for a transformative change in your happiness, you might be better off reading something ancient. The great thinkers of the distant past seemed obsessed with figuring out how to live good lives: Socrates, Plato, Aristotle, Epicurus, Buddha, Confucius, Jesus, Marcus Aurelius, St. Augustine, even up through Thoreau and Vivekananda. But at some point, this kind of stuff apparently fell out of fashion. 

And hey, maybe that’s because there’s just no more progress to make on the poorly defined problem of “how do we live." But most well-defined problems were once defined poorly. For example, “how do we land on the moon” was a hopelessly poorly defined problem for most of human history. It only makes sense if you know that the moon is a big rock you can land on and not, say, a god floating in the sky. We slowly put some definitions around that problem, and then one day we sent an actual dude to the moon and he walked around and was like “I’m on the moon now.” If we can do that, maybe we can also figure out how to live good lives. It certainly seems worth it to keep trying.

BUT AREN’T THERE MULTIPLE INTELLIGENCES?

I’m not the first to propose that “general" intelligence is more than one thing. Pretty much as soon as Spearman started claiming that intelligence is mainly one thing, other people started saying that intelligence is actually many things. (That’s science, baby!) Today, the most popular version of this theory claims there’s something like  eight intelligences, ranging from “visual-spatial” to “bodily-kinesthetic.” I’m sympathetic to this take because it tries to account for all the different weird and wonderful things that humans can do. But it’s got two big problems. 

Problem #1: People very rarely try to find any evidence for it. And when they do, they find that the people who score high on one of the many intelligences tend to score high on the others, too, just as Spearman would’ve predicted a hundred years ago. 

Problem #2: When you label every human activity as its own intelligence, you give up any hope of understanding anything about the structure of problems in the world or how people solve them. We can make up whatever categories we want; they aren’t given by God. The only reason to use some categories and not others is that some categories are useful and others aren’t.

For instance, we could have created a periodic table that organized the elements alphabetically, or by color, or by how good they taste. Instead we organize them by atomic number, not because it's their “true” order, but because it’s useful. It helps us realize things like, “Hey, we’ve got a number 62 and a number 64—I wonder if there’s a number 63 out there. We should go looking for it."

So we should pick the way of categorizing intelligence that gives us the most bang for our buck. “Intelligence is many things” can’t explain why people perform similarly across supposedly different tests, and “intelligence is mostly one thing” can’t answer a basic question like "why smart people aren’t happier?” But we can handle both of those challenges when we split intelligence into skill at solving well-defined and poorly defined problems.

And that’s not all we can do.

OH BOY HERE COMES THE PART ABOUT AI

People think of AI as a big glob of problem-solving ability. If you make the glob bigger, it can solve harder problems. That’s certainly been true so far: gigantic globs of AI can now drive cars, defeat our greatest chess players, and predict how proteins will fold. 

All this has happened very quickly, which may make it seem like we’re careening toward a “general” artificial intelligence that can do all the things humans can. But if you split problems into well-defined and poorly defined, you’ll notice that all of AI's progress has been on defined problems. That’s what artificial intelligence does. In order to get AI to solve a problem, we have to give it data to learn from, and picking that data requires defining the problem.

That doesn’t mean the problems AI has solved so far are stupid or trivial. They’re really important and interesting! They’re just all well-defined problems. And we should expect that pattern to continue: for any well-defined problem, AI will eventually outperform humans. But for poorly defined problems, AI is hopeless. To solve those, we need humans running around doing weird human stuff.

"What about GPT-3—it can write movie scripts! And what about DALLE-2—it can paint pictures!" These AIs perform a clever trick: they make it seem like they’re solving poorly defined problems when, under the hood, they’re really solving well-defined problems. GPT-3 doesn’t actually write movie scripts; it predicts what words should come next. DALLE-2 doesn’t actually paint pictures; it matches words to images. These problems aren’t easy to solve—that’s why you need such a big glob of AI. But they obey clear, unchanging rules, they have bright boundaries, and you know precisely when you’ve solved them. They are well-defined problems. (This is also why AI art isn’t art).

If you booted up a super-smart AI in ancient Greece, fed it all human knowledge, and asked it how to land on the moon, it would respond “You can’t land on the moon. The moon is a god floating in the sky.” How would you get it to realize the moon is actually a big rock? That’s a great, poorly defined problem, and I don’t expect AI to solve it anytime soon.

SHOUTOUT TO MY GRANDMA

Here’s one last advantage of dividing intelligence into well-defined problem-solving and poorly defined problem-solving: it reminds us to give some respect where respect is due.

We’ve got no problem fawning over people who are good at solving well-defined problems. They get to be called “professor” and “doctor.” We pay them lots of money to teach us stuff. They get to join exclusive clubs like Mensa and the Prometheus Society. (By the way, Mensa’s page explaining IQ doesn’t mention anything about the dark history of using intelligence tests to hurt people, and you might expect a bunch of smarty-pantses to, you know, use their brains to discuss things with a bit more nuance. But what do I know, I’m just a big dummy.)

People who are good at solving poorly defined problems don't get the same kind of kudos. They don’t get any special titles or clubs. There is no test they can take that will spit out a big, honking number that will make everybody respect them.

And that’s a shame. My grandma does not know how to use the “input” button on her TV’s remote control, but she does know how to raise a family full of good people who love each other, how to carry on through a tragedy, and how to make the perfect pumpkin pie. We sometimes condescendingly refer to this kind of wisdom as “folksy” or “homespun,” as if answering multiple-choice questions is real intelligence, and living a good, full life is just some down-home, gee-whiz, cutesy thing that little old ladies do.

Excluding this kind of intelligence from our definitions doesn’t just hurt our grandmas—it hurts us too. If you don’t value the ability to solve poorly defined problems, you’ll never get more of it. You won’t seek out people who have that ability and try to learn from them, nor will you listen to them when they have something important to say. You’ll spend your whole life trying to solve problems with cleverness when what you really need is wisdom. And you’ll wonder why it never really seems to work. All of your optimizing, your straining to achieve and advance, your ruthless crusade to eliminate all of the well-defined problems from your life—it doesn’t actually seem make your life any better. 

If you’re stuck trying to solve poorly defined problems with your slick, well-defined problem-solving skills and you’re lucky enough to have a grandma like mine still on this Earth, my god, go see her. Shut up and listen to her for a while. And once you’ve learned something, maybe ask her if she needs help with her TV.