Is Intelligence Genetic?

February 12, 2017 / Humans / 0 Comments /
is intelligence genetic

Intelligence is the ability to acquire information, apply knowledge, and an ability to engage in abstract thinking (i.e, thinking about times/ places and imagined situations). The intelligence of the general population follows a bell shaped curve (as shown in the image below). From the graph, you can see 50% of the population fall in-between an IQ of 90-100, which is thought of as average. However, there are a very small number of people (2.2%) which have an IP of 70 or less (which are classes as mentally retarded), and an equally small group of people with an if of 130 or more, who are extremely intelligent.iq-bell-curve

If this variance is due to your environment – then you may be able to change your intelligence, which is great! It would also mean you can lose intelligence though…

However, if it is all down to genetics, then it cannot be changed, no matter how hard you try. So, is intelligence genetic, environmental, or a combination of both?

 

Is Intelligence Genetic?

Most tests on the impact of genetics vs environment have shown that genetics make up for 50-80% of intelligence. It is quite a scope because testing the impact of genes vs science is very difficult. The only way to do this with any reliability to to use identical twins. As twins have identical genes, you can eliminate the impact genetics has on what you are measuring (such as IQ).

Identical twins are not particularly common, so studies haven’t been terribly reliable. However, in 2008 a group of researches managed to test 2,602 pairs of twins to identify the impact of genetics vs environment on intelligence. Twins often share the same environments (taught by same teacher etc), but it was not the case with all the twins in the study. This allowed the researches to pick out what was causing the differences in performance. This study is the largest of its type, and so is thought to be the most reliable.

The research concluded that genetics accounts for at least 60% of the variance in intelligence, which agrees with previous studies, but gives a more accurate figure. The remaining 40% is a result of environmental factors. However, although this test clearly highlights the difference in genetic vs environment when it comes to taking academic tests, it doesn’t look at other forms of intelligence.

 

Types of intelligence

Intelligence is can be thought of as either being fluid  or crystallised. 

Fluid intelligence is the ability to solve brand new problems and use logic. It is adaptive, out side the box and on-the-spot intelligence. It would be the intelligence you rely on if you are lost and have to find your way home, or if you are faced with a problem for which there is no solution yet available. This kind of thinking is very common in left handed people, and is what makes them good problem solvers.

Crystallised intelligence is the ability to learn and apply knowledge. For example, memorising the meaning of words in another language and then responding in that language to questions. It is an applied kind of intelligence, which generally, is taught and tested for in schools. ‘Can you remember the name of this bone‘, and ‘what happens if I mix chemical A with chemical B‘ etc.

The study mentioned above only really studies to effects of environment on crystallised intelligence. Perhaps this crystallised intelligence is 60% genetics, and 40% environmental, but what about fluid intelligence?

 

Increasing intelligence

For a long time, improving IQ seemed impossible, which flies in the face of the notion that 40% of intelligence is environmental. However, part of the reason for this is getting reliable data for improving IQ is very difficult. For example, someone who did a test today, might do better on a similar test tomorrow because the kind of questions are more familiar. Does this show an increased IQ? Alternatively, the next test you give them might be a bit harder than the previous, so they may not do as well. Does this mean their IQ has gone down?

You can’t give people the same test, because they will remember the answers, but equally you can’t give people different tests because they are different, and so might be harder/ easier. Then there are other factors to consider which impact performance too. Has a pet recently died? Are they feeling unwell? Have they guessed some the the answers right?

Testing for IQ changes isn’t straight forward, and so many researches claim that because it can’t be tested for, we don’t know if it can actually be done.

However, there is research out there to suggest that fluid intelligence can be improved. Researches have shown that doing n-back tests to improve working memory also improve fluid intelligence significantly, although more research is still needed to know how much. Perhaps this kind of environmental change can improve your intelligence, at least the fluid type.

If you want to give an n-back test a go, you can do the puzzle below.

 

 

 

Aside from this though there is very little research showing that intelligence can be improved, although it is quite possible.

 

Anecdotes for improving intelligence

Many things are claimed to increase your IQ, and they essentially involve being healthy. The list includes cutting out junk food, exercising regularly, doing word/ number puzzles, sleeping at night and reading. Whilst all these things might well improve your quality of life and make you more mentally sharp, the evidence that it can improve your IQ is very vague. It is also suggested that supplements like caffeine and ginkgo biloba help to increase IQ, which is unlikely, but they might improve focus.

 

Summary

The current research shows that genetics account for about 60% of intelligence variation, with the other 40% being environmental. However, this research in this area is still quite limited.

Testing to improve intelligence is very difficult. If 40% of intelligence in non-genetics, then intelligence should be able to be altered to some degree. Research has struggled to show this consistently, and this is in part due to the nature of testing intelligence. So far, it seems that doing n-back tests and similar working memory tests do improve fluid intelligence, and there is reliable research to support this. Additionally, living a generally healthy lifestyle and exercising, eating well and sleeping well are thought to improve intelligence.


Image courtesy of Kevin Dooley