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Is there a correlation between height and IQ?

It is well-known both anecdotally and statistically that taller people generally have it better in life. They have higher levels of self-esteem, they get paid more and they are more likely to have successful relationships. But incredibly, there is also evidence to suggest that taller people also have an intelligence advantage. Almost all large-sample surveys have found a small but consistent correlation between height and IQ, a fact which presents a number of questions. Firstly, what is it about tall people that makes them smarter and secondly how does this effect what we understand about height and intelligence independently?

Explaining the correlation

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There are two alternate explanations for why taller people tend to be smarter, and it is indeed possible that both theories are correct in some way at explaining the phenomenon. The first theory presents that intelligence in tall people is directly related to health: height is one of the best intergenerational indicators of health and health can have a massive effect on intelligence.

Nutritional deficiencies, poor living conditions and other factors can start affecting your IQ even before you are born. As poor health can impair growth as well as intelligence, many think this has caused a correlation between the two factors over time. The second theory is more complicated but in a way more interesting.

Satoshi Kanazawa from Psychology Today has theorised that because women are generally attracted to both tall men and successful men (intelligence often being a prerequisite for success), this over generations has caused a plethora of people who have inherited both height and intelligence.

The Gender Gap

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An interesting place where height and IQ have actually had an effect is how we understand differences concerning intelligence and gender.

While past studies have usually found little difference in the average IQ of men and women, more recent analysis has actually found that men on average are slightly smarter than their female counterparts (by an average of 3-5 IQ points). Yet that is not the true shock: several analysts have posited that the difference in IQ between men and women has nothing to do with the fact they are male and female; instead it is actually to do with their height.

Because men on average are taller than women, they statistically show up as smarter than women. However once the variable for height is factored out, women are generally smarter than men by the same margin (a 5ft 6” woman is likely to be smarter by 3-5 IQ points than a 5ft 6’ man).

But what does it all mean?

The correlation between height and intelligence is statistically significant, but at the same time it is also rather small. This means that it is completely possible to have small people with large IQs just as one can find tall people with small IQs. There is no causation between the two factors: we are not tall because we are smart or smart because we are tall. Instead they are just two beneficial genetic traits which have a habit of going together.

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