What is IQ?
IQ (Intellectual quotient) is a psychometric construct that serves as a quantification of a person’s intellectual ability. In order to quantify/measure intelligence, IQ tests are used. If you would like to see what an IQ test looks like and practice for a real one, it is possible to take a free IQ test here.
These tests give participants an IQ score by comparing the test-taker’s performance in the test with the performance of all the other sample of test-takers that was used to develop the test. This sample should be representative of the normal/overall population.
The score you get will be your IQ, and it will be given in the form of a percentile, which indicates where you stand in comparison to all the other test-takers. The full IQ range/scale spans from 55 (close to the 0th percentile) to 160+ (99.9th percentile). For instance, if you get a score in the 90th percentile, that means you are smarter than 90% of the population.
IQ should not be confounded with general intelligence or G, although they are almost the same and they are usually used interchangeably.
What is the difference between IQ and G? IQ vs G
IQ is the total quantitative result (that is, the number; the score) of a test aimed at measuring intelligence. If a test consists of 5 different subtests, IQ will be the total composite score of all of them.
On the other hand, G (general intelligence) is a psychometric construct that represents the variance shared by all the different tests measuring different mental abilities (or in other words; the variance shared by all the different existing intellectual abilities, such as spatial intelligence, working memory, etc…).
Let’s explain everything in Layman’s terms.
It turns out that all the different mental abilities are correlated to a certain degree.
What this means is that smarter people (people with more G) tend to score higher in all the tests measuring these different existing mental abilities, while “less smart people” tend to score lower in all of them.
In other words, “smarter” people are better “at everything” (have better spatial intelligence, better working memory, etc…), whilst the opposite is also true for “less smart” people.
This correlation is obviously not perfect, that is, someone who gets a score of 120 on a spatial intelligence test won’t necessarily get the same score on a working memory test, there is some degree of variability, and some people could score high in some mental abilities while average or even low in others.
This tendency, this correlation, is not perfect, but it is there, it exists.
If people who are smarter get better scores in all the different mental ability tests and the same is true for “less smart” people, then that means that there must be an intellectual ability that is above all the others, there must be some mental process common to all these subintellectual abilities.
Think about it, if on average, people who are good at running 100m athletics races are also good at running 400m ones, then that means there must be some factor/ability that is common to both types of races (eg: speed, the ability to run fast).
Similarly, if people who are good at spatial intelligence are also good at working memory, that means that these mental processes share one mental process in common, which is above both of them.
This mental process can be measured through psychometric procedures, and it is what is known as G.
G is the mental process or set of processes that account for the shared variance in all of these types of intellectual tasks/tests.
In Layman’s terms again, G is the general mental process/ability that powers people’s specific mental abilities. It is a general mental factor that increases (or the lack thereof, decreases) the other specific mental abilities (like spatial intelligence).
If you have ever played RPG videogames, you might remember that there used to be some that gave you a finite set of points say 100, and you had to distribute them across the different skills of your character. For instance, you could add 30 points to your defense, 40 points to your magic resistance, and then 30 to your mana.
Characters with an overall of 50 points distributed across all these abilities were obviously “less strong” than characters with 100 points, but that didn’t mean that they could be better or worse at very specific abilities.
However, when comparing a character with 500 points against a character with 50 points, the stronger character will probably be better at every single specific ability.
Think of G as something similar.
IQ is just the total score given by a test with a set of different subtests (aiming to measure different mental abilities), and this score is supposed to measure G (or at least, to be an approximation of it).
In the light of above, we can conclude that general intelligence (G) is the mental process or the set of mental processes that manifest themselves in each specific intellectual task. IQ is just an attempt to measure G, it is just the score given by a test composed of different subtests, which aims to be a good approximation of G.
If you think you are finally understanding everything, you must know this matter is actually much more complex than what has been explained here. Keep reading.
What types of intelligence does IQ measure?
IQ aims to measure a person’s reasoning ability. Broadly speaking, IQ attempts to measure G (general intelligence) (this is not entirely correct though), usually by administering test-takers with a set of test batteries, each aimed at measuring different cognitive abilities. These different cognitive abilities, that is, these different “intelligences” IQ measures are:
- Spatial Intelligence
- Fluid Reasoning
- Comprehensive Knowledge
- Processing Speed
- Working Memory
Remember that the cognitive abilities they measure are correlated among them, which means they are, to a certain extent, the same thing (that is, they involve one mental process that is common to all of them, which is G, also called general intelligence).
Remember that, as we explained before, G and IQ could overall be defined as someone’s reasoning ability and learning potential.
We would also like to warn you about something; there is a common popular opinion that says that IQ does not measure all intelligences or that IQ “only measures one aspect of intelligence”. It is very likely you have heard things like “there are more intelligences other than IQ, judging a fish by its ability to climb a tree is obviously a wrong approach”.
Indeed, when someone asks “what types of intelligence does IQ measure”, what they might also be wondering is whether there are more types of intelligence other than IQ.
Well, such statements are scientifically wrong.
No, there aren’t “multiple intelligences” in the sense they have in mind, there is only one intelligence, and what IQ measures is that absolute intelligence.
What people who make such statements really mean is that “There are skills that are not correlated with IQ, and this means you can be competent, even to the level of being a genius, without needing to score high on IQ tests”.
And guess what, they are right. Skill is not a synonym for IQ and vice versa.
Who would be better at mechanical engineering, someone who is very smart, or someone who has been working in that field all his life?
However, keep in mind that as long as the skills required are of cognitive nature, IQ will matter; people with higher IQs will have the advantage that they will learn them faster and better. But of course, not all the skills that are important are of cognitive nature, and not all the fields require skills of cognitive nature either.
Anyway, the point is, people can excel and be very competent, irrespectively of their IQs (depending on the field). But that does not mean that these other skills constitute other forms of intelligence, or as popular opinion calls it, “that there is another intelligence or that IQ does not exist”).
What it means is that there are other abilities and skills that have nothing to do with or that can be acquired regardless of IQ.
Calling these other skills “intelligences” is technically wrong. Remember that the psychological definition of intelligence (which is the one we all implicitly hold as well) is that it is “someone’s mental reasoning ability”.
You can say that someone who is very good at football is “smart” because he is very good at football, but the truth is, as you can imagine, being good at football has little to do with “reasoning ability”.
In this case, either that person would be wrong, or that person would be making up his own definition of intelligence.
Imagine I said I am a millionaire when in reality I just have $2000 in my bank account. I would be either lying or creating and using my own definition of “millionaire”.
Even if the definition of millionaire changed and now it only applied to citizens who have $2000 or more, that would not change the fact that I just have $2000.
Same if we all agreed to change the definition of intelligence and now we used it as a synonym for skill, that would not change the objective fact that people who score better in reasoning ability tests have higher reasoning abilities.
Muhammad Ovais is Ph.D. from Chinese Academy of Sciences (CAS), National Center for Nanoscience and Technology of China. His research interests are in Neurodegenerative diseases, Nanomedicines and Biomaterials. He is the recipient of over 30 international awards including, 2019 Outstanding International Researcher by the Ministry of Education, China and 2019 Premium Award for Best Research Paper by IET-Institution of Engineering and Technology, UK. He owns to his credit over 60 scientific articles including research studies, reviews, editorials and book chapters in peer-reviewed journals/publishers such as, Advanced Materials-Wiley, NanoToday-Elsevier, Nanomedicine-Future Medicine, with h-index of 30. He is the co-founder of Synthon Nanotech, a Netherlands based Startup Company developing peptides and also working as a Tech Ethicist for a US based company GenoEmote; that is developing novel Brain-Computer Interface technologies.