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

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.



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

Why Do Left-Handers Exist?

March 27, 2016 / Humans / 0 Comments /
Why do left handed people exist?

I’ve got nothing against left handed people – I am one. But the existence of left handed people defies the evolutionary logic that if a trait is favourable, it will become persistent throughout the entire population. Unfavourable traits get lost pretty quickly, and even neutral traits can fade out in the gene pool. A great example of this is a giraffe. The long neck trait is very desirable because it allows you to reach food that is harder to get. This meant that the longer necked giraffes are more likely to survive and bread/ pass on the long neck genes, and before you know it, all giraffes will have long necks. There is no small population of giraffes with short necks.

Being right handed is clearly be the most favourable trait, with about 90% of the population being right handed. You would expect the left handed genes to fade away many thousands of years ago, but it hasn’t. In fact, left handers have consistently made up around 10% of the population for as long as we know, right back to the earliest humans, so there must be a reason for left handed people to exist.


What makes a person left handed?

There are 2 reasons why people can become left handed. The first is genetic. You can see from the table below that left handed parents are more likely to have left handed off spring, and right handed parents are more likely to have right handed off spring.  The genetics are not particularly straightforward because there are thought to be a number of genes involved in making someone left handed, and no one really knows which.

Graph showing that being left handed is linked to genes.

The second reason is that trauma or stress at birth such as oxygen deprivation to the brain can cause damage to the left hemisphere of the brain and cause dominance to shift. Research has shown that birth complications like this result in an increased number of left handers.

There is no way of determining the cause for an individuals left handedness, but the fact that there is a genetic link is very interesting, and suggests that there is so advantage to being left handed.


Left VS Right

lets look at the key differences between left handed people and right handed people:

They think differentlyEvidence published in the American Journal of Psychology showed that left handed people were much better at tasks which required divergent thinking, which requires creative thinking and exploring different solutions. This shows that left handed people are often better at problem solving than right handed people, and this is supported by the fact that left handed people tend to pursue careers in science, art and technology. All of which require a large amount of creativity and problem solving. The study showed that there was no difference in convergent thinking (required no creativity), suggesting that left handers may be better thinkers. However, other research has shown that left-handers are not so good with language and communication skills.


Better at sports – It is a well acknowledged fact that the left handed people are over represented in professional sports, particularly ones where you are in direct competition with another player like boxing or tennis. In 2015 left handed tennis players made up 40% of the top players, which is 4 times more than the proportion of lefties in the general population. The advantage is so well known that some top tennis were taught from a young age to play left handed even though it wasn’t their dominant hand, and this is something Rafael Nadal is famous for.

This is thought to be because left handed people are so uncommon, most players will practice against a right handed player. Right handed players practice against right handed players, and left handed players practice against right handed player. Everyone knows how to read and play against a right handed opponent, but everyone has very little experience playing against a left handed opponent. This is supported by research published in the British Journal of Psychology which showed that novices and experts alike find right handed shots much easier to predict than left handed ones.


Increased risk of mental disorders – It has been observed that the risk of developing mental disorders such as schizophrenia and autism increases with left handedness. This could very well be due to the mental trauma at birth that causes some people to become left handed.

Other differences of note include left handed people are often shorter in height, live slightly shorter lives but earn about 4% more than their right handed counterparts.


Why Do Left-Handers Exist?

We have ascertained that there are some significant differences between left handed people and right handed people, and that being left handed is at least in part an inherited trait. Despite being apparently the lesser of the 2 traits, it has remained throughout the gene pool – why?

Despite the potential health risks (shorter lives and association with metal disorders) being left handed is an advantage in a population which is right handed dominant, and this is why it has not become an extinct trait.

Historically left handed people would have had the upper hand in a fight, which would increase their chance of survival, and are able to ‘think outside the box’, which would allow them to tackle problems that their tribe would otherwise struggle with.


Why is left handedness not dominant?

On the surface, the pros of being left handed seem to outweigh the cons (after all, not all lefties suffer from autism), but left handed people only have an advantage in a right handed population. A right handed person would enjoy all the same benefits in a left handed population, and more. They would not only be better at fighting, but bigger too, making them formidable and make the right handed trait much more favourable. Right handed people would dominate left handers to the point that the left handed trait is rare, at which point it become an advantage. This is the state we find ourselves in today- a working equilibrium of handedness.



Left handed people differ from right handed people in a number of ways, but the most notable is their creativity and dominance in sport.These advantages only exist because the population is predominantly right handed, and this is why the left handed trait has remained a minority trait, but not become extinct. The fewer the left handed people there are, the more advantage they have, but if the trait becomes too abundant, the have less of an advantage, and the trait declines in the population.


Image courtesy of beezart

This Youtube video will give an overview of the information found on the article tab. If you want to know more about the topic, or want to see where the information came from, have a read of the article after you watch the video.

Left handed people exist as a minority because their only advantage is as a minority. They are smaller, and think differently, to right handed people, which makes them difficult to fight (or play against in sports) and approach problems differently. 

If left handed people were the majority of the population, these benefits would vanish, because they would be common.