You've probably heard a lot of claims

made about intelligence and [music] IQ.

Well, we wanted to check what's actually

true. So, we ran a giant study involving

3,691 [music]

people and 62 distinct intelligence

related tasks. So, are the claims made

by influencers, academics, and critics

of IQ actually right? Does IQ actually

measure anything at all or is it BS? And

if it does measure something, do people

with higher IQs actually achieve more?

and are they happier or less happy? In a

moment, we'll find out the answer to

these questions and others. [music]

But first, we have to address a more

fundamental question. What actually is

IQ? IQ is a measure of a person's

ability in whatever it is that

intelligence tests have in common. For

example, in our study, we had 62

distinct intelligence related tasks,

including all sorts of things like

memorization, spelling, math,

vocabulary, mental rotations, puzzle

solving, game playing, predicting

patterns, and so on. Suppose that you've

been given a random assortment of these

tasks, and the goal is to assign a

single number to your performance so

that we can best predict how you'll do

on the rest of the tasks that you

haven't yet tried. IQ is precisely this

number. It reflects the mathematical

estimate of how you'll perform on

average across a wide range of

intelligence tasks. The higher a

person's IQ, the better you'd expect

them to perform if you were to give them

a random intelligence related task they

hadn't seen yet. This doesn't imply that

IQ captures everything about a person's

intelligence. It's just that IQ is

designed to be the most accurate single

number across a wide range of tasks.

With that in mind, let's jump into the

claims. Claim one, IQ follows a normal

distribution. You may have heard about

the idea of a normal distribution,

sometimes called a bell curve because it

looks like the shape of a bell. It's a

distribution where most of the data

points fall near the average with fewer

and fewer as you go toward the edges. A

common claim made about IQ is that it

naturally follows a normal distribution

with most people having an IQ close to

average which is defined to be 100 and a

moderate number of people having an IQ

above 115 or below 85 and few having an

IQ above 130 or below 70. Other people

dispute this. [music] They say that IQ

only has a normal distribution because

it's purposely transformed to have this

shape. In fact, you can find long

discussion threads of people on the

internet arguing that the bell curve is

artificially created based on the way

the test is defined. So, who's right?

Well, it is true that in some data sets,

they force a bell curve on the data. But

we can look at what happens without

that. In our US general population

sample, we did indeed find that IQ has a

normal distribution naturally. We did

not define it to have a bell curve

shape. This is simply what emerged from

the data. Claim two, if you're good at

one intelligence task, it increases the

chance you'll be good at a different

one. There's a common sense notion a lot

of people have that you're either more

of a math and science person or more of

a language and arts person. You may find

that you tend to do well in physics

class or that you tend to do well in

English class. This would suggest that

skill at math and skill at vocabulary

would be negatively correlated. Being

good at one makes you less likely to be

good at the other. Is that what we find?

No, it's not. This image shows the

correlation between performance on each

pair of our 62 [music] intelligence

tasks. We can see the correlation

between how well people did at task

[music] seven and task 13. In this

rectangle here, we use blue to indicate

a positive correlation, white to

indicate no correlation, and red to

indicate a negative correlation. Notice

how almost the entire thing is blue, and

there's almost no red. That's because

doing well at one intelligence task was

almost always positively correlated with

doing well at other intelligence tasks.

This is a strange thing to observe, but

it closely matches other studies on IQ.

It's sometimes referred to as the

positive manifold, the idea that scores

on almost all cognitive tasks are

positively correlated to each other. It

doesn't mean that there aren't some

people who are better at math and others

who are better at vocabulary. There's a

lot of individual variability and each

person will have personal strengths and

weaknesses. What this does show though

is that people who are better at math

tend to actually be better at

vocabulary, not worse on average. Claim

[music] three, IQ captures everything

there is to know about a person's

intelligence. Sometimes when people

discuss IQ, they make it sound like it's

the full accounting of intelligence. End

of story. But is this really true? Well,

let's take a look at the data from our

study. The tall blue bar represents IQ.

What this chart shows is that IQ

accounts for about 45% of the variance

of people's performance across the 62

distinct intelligence tasks. 45% is a

lot to account for with just a single

number. But on the other hand, that

means that 55% of the variability in

performance is left unaccounted for by

IQ, which is even more. So what's in

this 55% of variability that IQ doesn't

account for? Well, first of all, there's

random noise. Someone might accidentally

click on the wrong answer, have a bad

night's sleep before taking a test, or

just get a lucky guess on one of the

answers. IQ can't account for these

random factors. But there's more than

just random noise in this unexplained

55%. Another aspect not explained by IQ

is that people differ in the skills that

they've learned through practice. If you

spend a lot of time doing mental math

problems, you'll get better at mental

math, and this will improve your ability

at any related task, even if it doesn't

change your IQ. Additionally, people

differ in their non-IQ related

aptitudes. [music]

If you take two children with identical

IQs, you'll find that they are not

equally good at different things. One

child may have more natural aptitude at

visualizing, for example, and another

may have more natural aptitude at

solving puzzles. It's also worth taking

into account that studies on IQ,

including ours, typically only include

intelligence related tasks that can

easily be measured in a short amount of

time on a computer or in a laboratory.

It's less clear if IQ would successfully

capture other types of intelligence such

as social intelligence or the natural

intelligence of hunter gatherers. IQ

captures a meaningful chunk of what we

mean by intelligence, but it doesn't

capture all of it. Claim four, people

with higher IQs have greater

achievements. If IQ is a measure of

people's ability at a wide range of

intelligence tasks, you might think that

people with higher IQs tend to have

greater achievements in life. Is that

true, though? Yes, we confirmed this in

our study. While the effects were not

always strong, we did find a positive

link between higher IQ and a variety of

forms of achievement. This includes

education, grade point average in high

school, income, and self-reported job

performance. IQ is not necessarily

relevant to all forms of achievement

that people care about, but we did find

that it positively correlates with a

number of forms of achievement. Claim

five, higher IQ people are happier. It

may seem obvious that higher IQ people

must be happier because as we've seen,

people with higher IQs tend to have

greater achievements, but some people

actually claim that the opposite is

true. That higher IQ people must be more

miserable because they struggle to fit

in or because they refuse to believe

pleasing falsehoods. So, what does our

data actually say? Well, we found no

relationship at all between IQ and

happiness, neither positive nor

negative. We even tried measuring

happiness in multiple ways. Regardless

of whether we asked in our study at this

very moment, how happy or unhappy do you

feel? Or if we asked a long series of

questions about how satisfied they are

with their life, neither method produced

a link between IQ and happiness. While

there are some studies to find a link

between IQ and happiness, it typically

is either very small or non-existent.

Claim six, IQ is just a measure of

privilege. It's certainly true that some

terrible childhood experiences can

impact IQ, such as severe lead poisoning

and brain damage from head trauma, but

some people go beyond this and say that

IQ is merely a measure of a person's

privilege or social class. Is this true?

In our data, the answer is no. We looked

at this in a variety of ways. First, we

tallied up how many adverse childhood

experiences each study participant

reported, sometimes known as the

person's ACES score. This includes

questions about whether they were swear

at, abused, or hit as a child, among

other things. We found no link between

AC's score and IQ. Additionally, we

asked participants about what their

level of wealth and social class was as

a child. We found [music] extremely weak

relationships between each of these and

IQ. Interestingly, our data is not in

line with some other studies [music]

which did find a link between IQ and

averse childhood experiences and between

IQ and childhood socioeconomic status.

It's unclear why our data contradicts

these prior studies. IQ is not merely a

measure of social privilege. If it were,

we would have expected to find a strong

correlation with these variables.

However, it may well be meaningfully

linked to a number of aspects of the

childhood home environment, as there

have been other studies that have found

this. My hope is [music] that more

research on this topic will be

conducted. Claim seven, people can

actually estimate what their IQs are. On

the one hand, you might think it's

relatively easy to figure out your own

IQ because it will impact how well you

do at a wide range of intelligence tasks

such as tests and homework assignments

in school. On the other hand, I think

most of us have met someone who thinks

they are much smarter or much less smart

than they really are. To test what's

true, we asked people to estimate their

own IQs before we measured them. It

turns out people only have a weak idea

of what their IQs are. They are better

at guessing their IQs than if they were

completely guessing at random, but they

aren't all that much better.

Interestingly, the people that

overestimated their IQs the most tended

to be the people with the lowest IQs.

This is compatible with the so-called

Dunning Krueger effect. People higher in

narcissism were also more likely to

overestimate their IQ. Claim eight.

Higher IQ people are more introverted.

We've all heard the stereotype of the

smart but introverted nerd who spends

time solving math problems and playing

on their computer instead of

socializing. But are higher IQ people

actually more introverted? In our data,

they were, but only vary slightly. Some

studies find a small negative link

between extraversion and IQ, whereas

others actually find none at all. A

somewhat stronger effect we found in our

data was a negative link between IQ and

self-reported charisma. So maybe the

stereotypes of socially awkward,

intelligent people are not totally

false. It would be interesting to see if

other studies replicate this lack of

charisma effect. Claim nine. Women and

men are good at different types of

intelligence tasks. You may have heard

that women and men have different sorts

of brains and therefore are good at

different sorts of things. Is this

really true? In our data, we did find

slight differences in average

performance between men and women in

some intelligence tasks. For instance,

we found that women outperformed tasks

that require you to come up with words,

such as listing as many words as you can

quickly that meet certain criteria. On

the other hand, we found that men

outperformed women on average on tasks

related to spatial visualization, such

as mental rotation of objects. Sometimes

people claim that men and women differ

in their processing speed, but we found

no difference between men and women in

processing speed tasks. [music]

Importantly, even though we found that

women and men differed a bit in their

average performance on some tasks, the

distributions are heavily overlapping.

It's not accurate to say men are good at

X and women are good at Y. It's more

accurate to say on average, men are a

little bit better at one type of task

and women are a little bit better at

another. Furthermore, it's important to

keep in mind that we shouldn't jump to

conclusions about the causes of

differences like these. We can't tell

from a study like ours where these

differences arise from. For instance,

whether they're cultural, genetic, or

environmental. Today, we've done a

speedrun through nine different claims

about IQ. If you want to learn more

about how your own mind works, you can

take our cognitive assessment at

clearerinking.org. You can also dig into

our full report, which investigates a

full 40 different claims about

intelligence. If you found this video

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