Does IQ measure Intelligence?

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Intelligence beyond IQ; does IQ measure intelligence?

IQ does measure intelligence, but IQ does not fully encompass all the intellectual abilities and skills of cognitive nature humans have. There are many cognitive abilities that present only low to slightly moderate correlations with IQ, whilst others show no correlation at all. Along these lines, not all the subintellectual abilities present a perfect covariance with G or IQ (that is, with general intelligence).

If by intelligence we mean “performance in tasks of intellectual nature”, then IQ is a very good measure of intelligence, but it is not a perfect one; there are some things beyond the span of IQ that influence intellectual performance. And these are:

  1. Cognitive tasks do not generally present a perfect correlation with IQ. Indeed, there are certain mental hacks to boost performance in cognitive tasks regardless of IQ.
  2. Some cognitive aspects are not correlated with IQ at all.
  3. Skill influences performance outside the span of IQ.

If you want to fully understand this article, we recommend you to first read about the differences between G and IQ and the different types of intellectual skills that there are. This way you will finally and fully understand everything about IQ and intelligence, all your doubts will be absolutely cleared!

Keep reading to find out more about what we mean!

How does IQ measure intelligence?

IQ measures intelligence by comparing each test-taker’s performance in a set of intellectual ability tasks with the performance of the entire group of test-takers. This way, IQ is a measure of your intellectual performance relative to the intellectual performance of others. In order to measure/quantify IQ itself, you would need to take an IQ test.

But… what do these intellectual tasks have to do with intelligence? How do we know they measure intelligence?

Good question!

We know they measure intelligence because we can statistically measure so; tests aimed at measuring IQ and intelligence present high reliability and validity. We have explained these two concepts in many other articles, which you can check here:

However, intelligence, outside the technical definition it has in psychology, is a broad concept.

If by intelligence we mean “performance in any sort of task of intellectual nature”, then IQ is not an absolute measure of intelligence; there are things outside the span of IQ that affect intellectual performance. Keep reading.

But…Doesn’t IQ measure intelligence?

IQ measures intelligence, both what we humans define as intelligence in a popular way and what psychology defines as intelligence in a technical way.

The thing is, the brain is very complex, and there are many different types of cognitive tasks it is able to perform.

So many, it is no surprise some of them are not correlated with IQ.

First of all, cognitive has nothing to do with intelligence. Cognitive refers to the different sets of abilities and functions the brain is able to perform, whilst intelligence is the ability to see patterns and learn fast (broadly speaking). In this regard, intelligence would just be something within the sphere of cognitive, a cognitive ability, sort to speak.

Along these lines, there are some abilities or tasks of cognitive nature the brain is in charge of, that do not have anything to do with IQ, and that are uncorrelated.

For instance, think of body coordination and talent for sports. It is the brain what is in charge of everything, yet sports ability does not correlate with IQ.

Social skills are also uncorrelated with IQ.

Some other abilities present low to moderate correlations, meaning there is still a lot of variance in them that is not accounted for by IQ, that is unrelated to it, that escape its influence.

The point here is, that there are abilities that are important in life and that escape to the span of IQ. But the interesting fact is, that even the ones that are correlated with it, also have a certain degree of free variance, that is, part of them is uncorrelated with IQ.

Cognitive tasks do not generally present a perfect correlation with IQ

First of all, we need to understand how G is calculated or what G even is.

G is a construct that arises from the shared variance of several different cognitive/intellectual abilities.

Researchers realized that when giving different tests for different intellectual aptitudes, some test-takers tended to score relatively high in all of them (on average), and others tended to score relatively low or average in all of them (also on average).

These tests aimed at measuring different aspects of intellectual ability, that is, different intellectual aptitudes (numerical ability, spatial intelligence, etc…) were correlated among them.

People who were “smart”, performed well in all of them, people who were “average”, performed “average” in all of them, and so on.

Of course, these correlations were not absolute, they were just a tendency (Eg: there can obviously be people who score high in one thing, whilst lower in other things. The point is that, on average, there is a tendency for “smart” people to score well on everything and vice versa)

This means that there must be a common factor behind all these subintellectual ability tests that is common to all of them, a mental process or set of mental processes that is common to all the different intellectual ability tasks that were being studied.

And this mental factor is what was called G or general intelligence.

As an analogy, think of it as if test-takers were doing sports tests. The results would indicate that those who score well on “running fast” also tend to score well, on average, on “calisthenics”, “playing football”, and so on. This means that there is a factor, a percentage of causality, that is common to all these different skills/tasks: physical fitness.

But, of course, although physical fitness has an important influence on all these different exercises, it does not account for 100% of the participants’ performance in all of them. That is, there are factors outside physical fitness that affect the performance in these subtasks, for instance, when it comes to “running fast”, body size can have an important negative influence, while the same factor can be very helpful when it comes to lifting weights.

The point is, that each of those subtasks has its own unique specificities that impact performance in its own unique way, and which in turn are outside the scope and influence of the general factor common to all of the subtasks; physical fitness.

Same with G and intellectual ability. There is a strong factor, called general intelligence (G), governing the performance of many different intellectual tasks (numerical tasks, spatial tasks, etc…), but at the same time, these intellectual tasks have their own unique specificities/factors outside G affecting performance.

If that was not the case, any measure of any subintellectual task would be a direct measure of general intelligence, just like any measure in any physical activity task would be a direct measure of physical fitness if physical fitness accounted for 100% of the performance.

What psychometricians called “shared variance”, roughly speaking, is the percentage of causality that a variable has over another one (Warning: this is not entirely true, but it is a good simplification in order to ease the explanation).

If they say that “physical fitness accounts for 30% of the variance in football performance”, that means, roughly speaking, that 30% of your results, of your performance, in the said sport, depend on your physical fitness.

Having said that, the point we want to make here is the following one: not all the variance (not all the performance) in these intellectual tasks is accounted for by or depends on G.

This means that, for every particular intellectual task, there are certain factors other than general intelligence that affect performance.

And what this means is that IQ or general intelligence does not account for absolutely all intellectual performance.

G has a strong influence on numerical ability, but numerical ability itself also has its own unique associated mental processes influencing performance in numerical tasks.

Here you can see the most common intellectual tasks that are measured in order to infer IQ or general intelligence along with their correlations with G. (Correlations range from, roughly speaking, 0 to 1, being 1 an absolute correlation and 0 an absolute uncorrelation. As you can see, the ones below 0.7 are probably significantly influenced by factors other than IQ).

Standardized factor loadings for the three-stratum theory of intelligence (from Bickley et al., 1995).

Some cognitive aspects are not correlated with IQ at all

Some functions performed by the brain are uncorrelated with IQ or present only low to moderate correlations. For instance, some studies show that executive functions, a set of mental skills that include working memory, flexible thinking, and self-control (among others), are generally only slightly correlated with IQ.

In other cases,  the correlations with IQ vary as a function of age.

Most importantly, IQ shows very low correlations with all the other psychological personality traits

These personality traits are Openness to experience, Neuroticism, Conscientiousness, Extraversion, and Agreeableness.

These traits are so important they literally define someone’s personality, and they have a great impact on how a person will experience life.

For instance, Neuroticism could be defined as the tendency to experience negative emotion and sensitivity to it.

High levels of neuroticism mean you will have a tendency to experience a lot of negative emotion on a regular basis, which is bad!

It is definitely a trait of cognition, of the human brain, that can significantly impact someone’s life, and thus performance in life as a whole, and that is very lowly correlated with IQ.

For many jobs, neuroticism is a very good predictor of performance, sales contexts are a good example of that.

Skill also influences performance outside the influence of IQ

Skill is built through learning, practice, and experience. All the domains of intellectual nature are affected to a certain extent by IQ (some more than others), but at the same time, they are also affected by the built skill itself.  

Think of, for instance, programming. There is no doubt programming is very g-loaded, but experience and acquired practice also have an important impact on performance. Indeed, they even shape the brain and how it works.

Of course, in very intellectually demanding fields, a high IQ is a necessary entry prerequisite. In others, IQ is important, but it is not everything, building skill and knowledge is. Examples of this would be fields like sales, teaching, or the humanities.



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