All About IQ

FROM THE LECTURE SERIES: Understanding the Misconceptions of Science

By Don Lincoln, Ph.D., Fermi National Accelerator Laboratory (Fermilab)

IQ, or intelligence quotient, is one of the most misused concepts in discussions of intelligence and the human brain. The IQ test is purported to be a good measure of intelligence. However, it has been frequently politicized in the past, with the differences between certain groups being used to support claims that some groups are inherently superior to other groups.

An IQ meter depicting different scales of intelligence: from below average to genius.
The modern IQ test was first invented in 1904 by Alfred Binet and Théodore Simon.
(Image: Olivier Le Moal/Shutterstock)

The History of the IQ Test

What does IQ mean and can it be changed? It is a very interesting subject. The IQ is a score that is purported to test the intelligence of an individual. The range is from zero at the bottom with no end at the top, although, realistically, everyone is in the 50 to 150 range, with what might be called the normal range at 85 to 115.

A person with average intelligence has an IQ of 100. Though people thought about intelligence and intelligence testing in the 1800s, the modern IQ test was first invented in 1904 by Alfred Binet and Théodore Simon. Binet and Simon were French psychologists and they were asked by the French Ministry of Education to develop a test that would help educators distinguish between what was called at the time ‘mentally retarded individuals’.

It is definitely not politically correct, but it does state, in a nutshell, the point of the effort. And this goal makes a lot of sense. If a person literally does not have the mental capacity to learn complex skills, they would be treated differently to a lazy slacker.

Their test was called the Binet-Simon IQ test, and it tested a number of components, such as reasoning, naming objects, and wordplay. The approach of the first test was to test a large variety of students of all ages. The researchers then determined the average score achieved by students of all ages. Finally, they took the score of an individual child and compared that score with the average for that age.

That was the original meaning of the IQ score. It was just a measure of the ratio of a person’s mental age to their actual age.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, Wondrium.

What Does an IQ Test Mean Today?

An IQ test does not mean the ratio of ages anymore. That ratio thing does not work well for adults, and it is known that it is not always true that people continue to learn more into their adulthood. In fact, most people’s performance on these kinds of tests is stable once they become an adult.

An example of the IQ test where a candidate has to identify the missing ninth pattern using the given eight patterns.
The IQ test is a measure of how an individual scores compared to other people in his or her culture and age group. (Image: Life of Riley/CC BY-SA 3.0/Public domain)

Hence, nowadays, the IQ test is simply a measure of how an individual scores compared to other people in their culture and age group. Here is how it works. Suppose there is a test with 100 questions. A person might get 78 of them right. That is 78%. But that does not mean anything at all from an IQ point of view, at least not directly.

For instance, it could be that you gave an IQ test to a group of people who belonged to the same culture and age group. If the average score of this test was 47, then the person answering 78 questions correctly did better than the average score. Or the average score could have been 82 questions answered correctly, in which case, the test person would be near average, but slightly low.

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The Usage of Bell Curve to Calculate IQ

Different tests use different numbers of questions and all manner of different ways to assess people, so it is important to not use an IQ test score. Instead what researchers do is convert their test to a special kind of curve called a bell curve. Bell curves are also called normal curves or Gaussian distributions after German mathematician and physicist Carl Gauss, who worked out a lot of the curve’s mathematics.

As per the bell curve, an IQ of 100 is normal. Half of the world is higher than that and half is lower. Furthermore, pretty much any IQ in the range of 90-110 is perfectly normal. People scoring in the range of 110-119 are a little above average, while those in the 80-89 range are a little below average, and so it goes.

The geniuses are all in the IQ range 130 and up. In fact, Mensa, which is an organization of people with IQs in the top 2% of the population, requires a Stanford-Binet test of 130 or higher.

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The Misconceptions Regarding IQ

There are so, so, so many IQ misconceptions and misuses that it is jaw-dropping.

One, a person who has an IQ of 140 is twice as smart as a person with an IQ of 70. This is false. IQ is simply a measure of where people stand compared to their peers. It would be much better if the equivalent of IQs were given like many tests given in schools, where the results are just given as where the student is: the 30th percentile, the 70th percentile, or the 99th percentile.

Two, a person can change their IQ by studying and taking tests. This is false. IQ is an innate property held by an individual that is well tested. It is true that a person raised in a neglectful environment might score lower than they otherwise would, as would a person who was ill when they were taking the test. People in those situations would benefit from retaking their test. But if they are taking the test when they were feeling good, it is an accurate assessment of their intrinsic capability.

Three, IQ tests are culturally biased against groups who have historically been economically, socially, and politically disenfranchised. This is false. It once was true, when the tests were entirely based on language back in the early 1900s, but psychometricians have beaten that problem into submission. English IQ tests are validated for any native English speaker. And even for those that are not, there are tests that are entirely non-verbal. These are just three common misconceptions. There are so many more.

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The Misuse of IQ

It can be seen how IQ can be misused through a graph that separates university students into their respective majors and then plots each major’s average IQ on the vertical axis against the percentage of women studying that subject, given on the horizontal axis. A trend can be seen, where majors with a low percentage of females have higher IQs than ones with a high percentage of females.

A graph showing the gender disparity present in high IQ majors.
Despite the disparity in high IQ majors, women do just as well as men in IQ tests. (Image: UNESCO/CC BY-SA 3.0-IGO/Public domain)

And, from there, it’s a short step from making the conclusion that the lower IQs are because there are more women and finally conclude that men are smarter than women.

This is an obvious interpretation of this graph, but it turns out to be wrong. In fact, when IQ tests are given to men and women, the results are, to all intents and purposes, utterly identical. There is no meaningful difference. The underlying cause of this graph is that women tend not to be as interested in the hard sciences as do men. The cause of this is not known, but it is not because men are intrinsically smarter. It may simply be long-standing social pressures that will take time to change.

The Conclusion

The problem is that it is very easy to take a hard number like IQ and manipulate it to support a predetermined message. There was a book published back in 1994 called The Bell Curve, which purported to show racial differences in IQ. Given the touchiness of the subject, there was a firestorm of debate, with some people crying racism and other people crying data. So, what is the truth about that?

In 1994, a group of 52 distinguished psychometricians made a statement that was published in the Wall Street Journal on what is known and not known about intelligence. When they were recently contacted, a few of them claimed that the last 20 years of data further strengthens their statement.

In summary, they claim that IQ is a good, although incomplete, measure of intelligence and that modern tests are reproducible and accurate. They claim that the brain processes that underlie intelligence are not well understood. It is true that different ethnic groups will, on average, score differently on the test, with whites having an average IQ of 100, and Asians and ethnic Jews having a slightly higher average.

They also state that success in life is not determined by IQ, but IQ gives an advantage in a complex and changing environment in which decisions are required. A very interesting claim is the heritability of intelligence. On a scale of 0 to 1, in children the heritability is 0.4, while in adults the heritability is 0.8.

This means that the measured intelligence of children does have a significant environmental contribution, but by adulthood, the genetic connection is stronger.

The statements try very hard to not take any social position and simply state the facts as supported by research. In fact, the last point they make, states: “The research findings neither dictate, nor preclude any particular social policy.”

Common Questions about IQ

Q: What is a higher than average IQ score?

Any IQ score above 110 is considered a higher than average score, but to be called a genius one must score above 135.

Q: How is IQ calculated?

IQ is calculated using the bell curve, which is based on Gaussian distributions formulated by the German mathematician and physicist Carl Gauss.

Q: Can someone change their IQ by studying and taking tests?

No, one can’t change the IQ by studying and taking tests. Although a person raised in a neglectful environment or a person feeling unwell might score lower than they otherwise would.

Q: Do men perform better than women in the IQ tests?

No, men and women are known to perform equally well in their IQ tests.

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