What is IQ?

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Podcast Transcript

For ages, people have tried to categorize humans by intelligence. However, it wasn’t until the early 20th century that attempts were made to provide an actual quantifiable measure of intelligence. 

In 1912, a German psychologist by the name of William Stern dubbed a method of scoring intelligence tests called an intelligence quotient. 

Every since there, there has been controversy surrounding the method of scoring and the very idea of scoring intelligence.

Learn more about the intelligence quotient, also known as an IQ score, on this episode of Everything Everywhere Daily.


The concept of intelligence is one that everyone is familiar with. We all know people who are intelligent, and we know people who are probably not so intelligent. 

However, while everyone is familiar with it, it is a very slippery concept and one that is very hard to nail down. It is an especially hard concept to quantify.

The fact that it was hard didn’t stop people from trying. 

In the 19th century, the English statistician Francis Galton tried to show that intelligence was a hereditary trait, like other physical attributes, but he couldn’t find any statistical evidence for his claims. 

The first real step towards quantifying intelligence came in 1905 when French psychologists Alfred Binet and Théodore Simon published the Binet-Simon test. 

The test was only a test of verbal abilities, and it was primarily targeted toward children to evaluate their development. In particular, it wasn’t designed to test for gifted children but rather for children who were on the extreme other end of the spectrum.  

The test took a normalized score for children of different ages and then compared that to a score from an individual child’s test to compare where they were against the average. 

You would take the intellectual age of the child and divide that by the chronological age, to get a quotient or a score. 

For example, if a 10-year-old took the test and was found to have the intellectual age of a 15-year-old, you would divide 15 by 10 and multiply by 100 to get a score of 150. 

As I mentioned in the introduction, this score was dubbed by the German psychologist William Stern as the Intelligenzquotient, or IQ for short. 

This name stuck, even though IQ tests today no longer use this method. 

The point which should be stressed is that early IQ tests were only for children. 

If you have ever read an article or come across a reference to someone who was supposedly the “smartest person in the world,” it usually has to do with an IQ test taken when they were a child. 

If a child is a prodigy and has the intelligence of a 12-year-old at the age of 6, they would have an IQ of 200, which is incredibly high.

If you were average and had the same intellectual age as your chronological age, you would score a 100. 

However, you can probably see that this system doesn’t really work for adults, nor was it ever intended to work for adults. The concept of mental age doesn’t make sense after a point, as test results for adults of all ages will flatline after a certain age. 

The Binet-Simon test was eventually adapted for use in the United States by Lewis Terman at Stanford University in 1916, and that version became known as the Stanford-Binet Test. 

The test has undergone five different revisions over the years, and it is still used today. 

The test developed by Alfred Binet was, by his own admission, intended to be very limited in scope. It was only designed to test a certain group for a certain purpose. 

Once the idea of testing and quantifying intelligence came into being, it began being used for darker purposes. 

One of the early proponents of the Stanford-Binet test was the American psychologist Henry Goddard.

Goddard developed a version of the test that the United States Army administered during World War I. It was administered to 1.7 million soldiers, which was the first time a written intelligence test was administered en masse. 

The problem with the test is that the results were pretty much useless. The test itself was more a test of American culture, and there was incredible variation in the administration of the test around the country.

Goddard was still a big believer and became one of the lead proponents of the eugenics movement. He believed if we could identify people he saw as being “feeble-minded”, we could take them out of the breeding pool, and their traits wouldn’t be passed along. 

He developed a scale with what we now consider pejorative terms, which you’ve probably heard before, but never realized they were used clinically. 


Someone with an IQ of 51 to 70 he classified as a “moron.” Someone with an IQ between 26 and 50 he classified as an “imbecile,” and anyone with an IQ below 26 would clinically be an “idiot.”

Goddard’s intelligence tests were used by eugenicists to forcibly sterilize over 60,000 people in the United States, and his testing was copied for similar purposes in Nazi Germany.

Intelligence testing eventually became more sophisticated. 

American psychologist David Wechsler introduced the Wechsler Adult Intelligence Scale in 1939. This test did away with the concept of intellectual age that the Binet-Simon Test introduced. 

Wechsler simply normalized all scores around an average of 100, which allowed for similar comparisons to the Stanford-Binet-Simon test, which also had an average of 100. 

The Wechsler test did away with a quotient, but the term IQ was so ingrained by this point that it stuck, even though the “Q” in IQ no longer existed.

At this point, you might be thinking that there is something entirely wrong with this entire system of trying to encapsulate intelligence into a single number.

There are different types of intelligence. Someone might be good at math but not good at playing an instrument. Someone might be a good writer but a poor painter. 

The theory of intelligence and general human cognition began to incorporate more of these elements. 

The first person to tackle this was the psychologist Raymond Cattell who in 1941 theorized that there were two types of intelligence: Fluid intelligence and Crystalized Intelligence. 

Fluid intelligence would be your ability to solve a novel problem. Crystallized Intelligence would be things you know based on your upbringing, education, and cultural background. 

In 1966 one of Cattell’s students, John Horn, expanded this into even more categories. He outlined aspects of intelligence that covered: crystallized, fluid, visual, auditory, quantitative, processing speed, Long-term storage and retrieval, and short-term acquisition and retrieval. 

This theory was further advanced in 1993 by the psychologist John Carroll who created a three-layer theory of intelligence. On the top level was general intelligence, below that was Horn’s categories of intelligence, and below those were narrow intelligence aptitudes.

That final category encompassed a whole host of things, including spelling, reading comprehension, reading speed, ability to identify musical pitch, and originality. 

Today this is known as the Cattell-Horn-Carroll theory of Human Cognition. 

There are an enormous number of IQ tests that are given today. All of them test for different things, including spacial intelligence, logic, mathematical ability, and verbal intelligence. If you took different tests, the odds are that you would get different scores, if even just slightly different, on different tests. 

What almost all IQ tests have in common is how they are scored. The system of normalizing to 100 that Wechsler developed is still used today. 

So an IQ of 100 is by definition defined to be average. 

One standard deviation is 15 IQ points. That means that approximately 68% of the population has an IQ between 85 and 115. 

At two standard deviations, you encompass approximately 95% of the population. 


An IQ of 130, or two standard deviations above the mean, is the cut-off for membership in Mensa, which is an international high IQ society. 

The Triple Nine Society is for those who can score at three standard deviations above the mean or an IQ of 145. 

There are also other high IQ societies above that, but to be honest, they are mostly mutual admiration societies because tests have no meaningful way to measure anything beyond that point. 

I mentioned that an IQ score is normalized around 100, so no matter how everyone in society performs on an IQ test, the average is always going to be 100.

But what if everyone did start doing better on IQ tests? How would we know? 

Well, that exact thing has been happening. 

A New Zealand intelligence researcher by the name of James Flynn discovered that when people took the exact same version of older IQ tests, raw scores increased over time. 

For example, a test known as the Raven’s Progressive Matrices has been given to British Children for decades. The raw scores increased by 14 points from 1942 to 2008. 

This phenomenon has been dubbed the Flynn Effect, and it has been found all over the world, in country after country, even with completely different cultures. It has been found on every major IQ test, in every age and ability range. 

In the United States, it has been going up an average of 3 points per decade. If you normalized IQ scores based on 1997 data, the average American in 1932 would have had an IQ of just 80. 

This has been one of the biggest areas of debate and research in the human cognition community over the last few decades. 

No one is really sure why this is happening. Theories include better schooling, better nutrition, fewer diseases, and more stimulating environments with computers. 

It has also called into question the entire premise behind IQ tests and that it might not be testing for intelligence at all but rather a general test-taking ability. 

There is one final thing that some of you might be wondering. What about this Emotional Intelligence that you’ve heard about, also known as EQ (even though there is no “q” in emotional intelligence).

Emotional intelligence came from a popular science book by journalist Daniel Goleman in 1995. 

While the concept of measuring intelligence is full of problems, it is much more straightforward than the concept of emotional intelligence, which is a very fuzzy definition. 

Emotional intelligence is usually just defined as being aware of your own emotions and those of others and being able to react accordingly. 

There actually is an emotional intelligence test called the Mayer-Salovey-Caruso Emotional Intelligence Test. However, it is radically different from any general intelligence test. 

In a normal IQ test, you are given a set of questions, and you are tested on how many of them you got correct. In an emotional intelligence test, you are tested on how well your answers fit social norms. There is no right or wrong. The more average you are, the better.

So emotional intelligence is certainly an active field of research, but I don’t think I would equate an EQ score as being equivalent to an IQ score. 

There are, of course, certain types of intelligence that simply cannot be measured with a test. A great example of this is with elite athletes. 

In the 1970s, researchers began studying elite chess players to see how they could memorize so many past games of chess. There are videos online right now where people have presented the World Champion Magnus Carlsen with positions on a chessboard, and he could recall which games those positions came from, even if the game occurred decades ago. 

Sports science researchers took this up and found the same behaviors in athletes. 

As a homework assignment, do a search for “Lebron James memory.” You will find dozens of videos of him doing post-game press interviews where he can recall almost every play of the game he was just in from memory. Not just that, but he can recall almost every game he has ever played in, in his entire life. 

Many coaches and teammates have called him a basketball savant. 

I was a very competitive academic debater in college and competed at the top national levels of competition. One of the guys on my team had this ability. He could recall any debate round he ever had. I’ve never met anyone before or since who had that ability. 

Researchers call this domain-specific intelligence. While Magnus Carlsen and Lebron James both certainly have high general intelligence, there is no indication that this particular ability to recall previous games or matches carries over into every other aspect of their lives. 

Both James and Carlsen have basically wired their brains for a very specific task. The enormous database of past games they carry around with them is one of the things which makes them great. 

This sort of intelligence can’t really be tested. The only way to test it, is through competition. 

Human intelligence is multi-faceted. There is no one type of intelligence, and IQ tests that try to distill everything down to a single number is a very crude measure. 

Perhaps the last word on IQ tests and IQ scores should be left to one of the greatest minds of the last century, Stephen Hawking. 

When he was asked what his IQ score was, he replied, “I have no idea. People who boast about their IQ are losers.”


Everything Everywhere Daily is an Airwave Media Podcast. 

The executive producer is Darcy Adams.

The associate producers are Thor Thomsen and Peter Bennett.

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