Are short people less intelligent?
Well, it's complicated.
Some research has found that a correlation does indeed exist between height and IQ.
This goes all the way back to the late 19th century, when WT Porter’s exceptionally-titled study ‘The physical basis of precocity and dullness’ posited, based on a 33,500-strong sample of students, that, in the same age group, the taller ones outperformed the shorter ones.
But coincidence is not the same as causation. And it is only a very slight correlation. A piece in Discover Magazine notes that when you control for age across different studies, correlations between growth and intelligence mostly range between 0.10 and 0.30, with the average coming in around 0.20. (It’s also the same article that notes paedophiles tend to be shorter than average, but let’s leave that one for now.)
Analysis of 6,815 people pulled from a Scottish study into family health found a 0.16 correlation between height and general intelligence, a “modest” effect by the author’s own admission.
Geography doesn’t seem to matter either when it comes to the strength of the correlation. Developed and developing countries exhibit similar patterns, as do different regions within developed countries, and the correlations are never so strong that we can definitively say that no-one below 5’5’’ is mentally fit to be a chief executive, say. (See previous chapters).
But is the height income gap really best explained by the idea that shorter people are dumber? There have been plenty of below-average-height geniuses, from Beethoven (5’3’’) to Isaac Newton (5’6’’).
According to a study authored by Mark Pearce and others at the Institute of Health and Society, Newcastle University, in 2005, which made it into the International Journal of Epidemiology, when you control for social class, data from the Newcastle Thousand Families Study shows that children with a higher IQ at age 11 were the same ones who were taller at the age of 9 or 13. This could show that taller children are smarter but, more likely, it is the result of socio-economic factors that would improve educational and physical development in wealthier-than-average households.
Researchers have noted that a variety of countries have exhibited continual growth in average IQ as the average height of their populations have increased. But again, this is not necessarily a causal link. Particularly in the developing world, height increase can be the product of better nutrition, the result of economic growth, allowing an improvement in both the quality and availability of education; children did not miraculously grow smarter just because they were an inch and a half further from the ground.
Some studies do argue that smarter people are smarter because - among other things - they are taller. The British National Health Examination Survey, for example, has hinted that the link between height and IQ is not due to family size or income alone.
But the overwhelming body of research suggests that it is socio-economic factors like education, household conditions, educational attainment of parents, and family wealth that determine IQ, rather than height per se.
If you’re the kind of family that can provide quality nutrition and a comfortable physical surrounding, you are probably, but not necessarily, also the kind of family to turn out with higher intelligence. You will also probably turn out taller because of the nutrition and the rest of your privileged environment,
Because of how those environmental elements filter down to height, and also into income and economic prospects, you could easily make the argument that the socio-economic height gap is a self-fulfilling prophecy that culminates in a vicious downward spiral. A short generation of a family would, statistically speaking, end up earning less, meaning future generations are likely to be shorter too, because they will be provided with less favourable environments and struggle more throughout the school system.
As a prime example of how this can work in practice, data from the Newcastle Thousand Families Study has linked poor housing, air pollution, and other “neighbourhood” factors as significant in determining both height and IQ.
More intelligent children have a better chance of being taller in late adulthood, according to one study, while there was also a slight correlation between how intelligent someone is in late adulthood with how tall the individual was at childhood. It’s simply access to better conditions to grow up in, biologically speaking, that means the brain develops as it does. Or it could be that taller children command more attention in the classroom, and naturally improve their intelligence above their shorter peers who have less physical presence. (Again, see previous chapters).
What we do know is that it’s not about how quickly you grow in puberty that’s responsible for any difference in your ability to be smart.
“Among 2177 children studied longitudinally in the National Health Examination Survey of the 1960s, change in relative height between the ages of 8 and 13 years was not related to change in score on tests of intelligence or academic achievement,” psychology professor Catharine Gale wrote in a 2005 commentary on where we were at with research on the link between height and IQ.
“Years of cumulative height-biased expectations may explain the association,” she posits.
There may well be some truth in that: children are naturally primed to try to live up to the stereotypes society places on them. They see tall people being dominant, more successful in the world of work, and more popular with their peers. They will naturally assume that is the kind of person they are supposed to be, and are entitled to be.
And as we discovered in my first chapter, shortness is a highly heritable trait; some 80 to 90 per cent of height is linked to genetic factors which are passed down generations. By studying 30,111 pairs of twins, researchers were able to isolate the rest as environmental factors.
In contrast, the heritability of intelligence has been estimated to be far lower, even down to the 40 per cent mark, but that is still a degree of correlation that can persist over multiple generations if we wanted to look at how reduced height could then impact on future IQs and therefore generational economic exclusion.
It is entirely possible that the genetic markers that code for both height and intelligence just happen to coincide in many cases. They are both attractive factors in sexual selection, meaning individuals falling into both groups will naturally gravitate towards each other. In fact, this is what a 2013 study in the Plos Genetics journal uncovered; pleiotropy (the same gene impacting different traits) was found to “contribute significantly” to the correlation between height and intelligence.
Yet there also doesn’t appear to be definitive proof that any one gene is strongly correlated to intelligence, so even if a “tall gene” was so linked, we wouldn’t be able to show that it alone was the cause of above-average IQ.
It’s certainly not as simple as saying that an extra inch in height will automatically result in an extra X per cent increase in how smart you are, but if the genes coexist in similar samples, they logically do not exist in others. Those family groups will unfortunately continue to fall behind.
Analysing some 65 million youngsters, drawing on data from more than 2000 studies across 4 decades, a 2019 study published in Lancet showed a major cause of the 7.9’’ gulf between the average height in taller and short countries is the diets of school-age children. Poor diets, it goes without saying, are linked to lower socio-economic status. Yes, genetics plays a part, but the researchers say nutrition is a key pillar in forming children’s height and weight.
Having a pop at someone for their height, or looking unfavourably on them for employment opportunities, like any other trait, if you think about it logically, would only be fair if it was both a choice, and one that impacted negatively on their output. It would hardly be fair to judge someone on the basis of something that has been forced on them, nor to relegate them for a decision that impacts no one but them.
I think we could already have safely scratched the negative impact justification. There is nothing to suggest taller CEOs perform better. In fact, the reverse might even be true. In an albeit unscientific study of entrepreneurial success, Inc Magazine columnist John Warrillow calculated the average height of a handful of the top Fortune 500 chief executives who had their metrics available online.
The average in the handful he got a good reading on was 6’2’’, including the likes of Apple boss Tim Cook, at 6’3’’ and General Electric’s Jeffrey Immelt at 6’4’’.
Comparing that figure to some of most successful innovators of recent years - Google co-founder Sergey Brin, 5’8’’ and Facebook’s Mark Zuckerberg, for example - the mean was 5’10’’.
The link between IQ and height is far more likely to be explained by family upbringing that tallness itself. But now we can basically scratch the choice one too, given the extent to which height is dictated by socio-economic factors outside of a child’s control. Otherwise your argument is essentially “what a shame it was that you were born into a family without the means or education to feed you properly, a totally avoidable outcome you really should have rectified as a toddler”.
Subtly, height becomes an indicator of the kind of upbringing you had, the kind of stock you come from and therefore respectability for a competitive position.
The impact of tallness on personal and professional outcomes is so severe that there is even a public policy recommendation in the Lancet paper.
Imperial College London’s Dr Andrea Rodriguez, co-lead researcher, says that because healthy height has such key benefits for wellbeing that last a lifetime, government should take on “policies that increase the availability and reduce the cost of nutritious foods, as this will help children grow taller without gaining excess weight for their height”.
Examples include giving low-income families food vouchers to be spent on nutritious food and free healthy school meals.
In my own little bubble of privilege, it is particularly galling to see height come into the equation specifically at times when I’m doing that little bit extra when it comes to getting the job done.
I recall taking to Twitter one Friday to inform my relatively-limited audience that I had planned a day off. Then something cropped up, as it so often does for us journalists, and I posted again a few minutes later regarding a breaking story I had set to work on.
One of my followers kindly advised me to switch my phone off. Another hypothesised the reason I hadn’t been able to was that I couldn’t reach it with my short arms.
My feelings about said comment were a mixture of bafflement and disappointment. Bafflement because I didn’t actually get the joke. I hate to bring logical consistency to matters of humour, but if I couldn’t reach my phone, how could I have posted the message on Twitter in the first place? Disappointment because, yet again, my height cropped up in a professional capacity for little apparent reason.
I was at an event once, where a former colleague placed her elbow onto my shoulder, leaned into it a little, and with a smile on her face told me that I was the perfect height armrest. I was her direct line manager at the time, and am still amazed she thought that behaviour was appropriate. Clearly, my use as a leaning post outweighed the potential downsides of making a potentially demeaning remark to the person with the ability to fire her.
I am a journalist and an editor. I am also 5'2''. I feel like the latter defines me in a way nothing in my professional life possible could. It must have done, otherwise I wouldn’t have been patted on the head at conferences before. I would also not have had a colleague - again someone who I directly managed at the time - quip that I must have grown since I last saw her if I really was 5’2’’.
I was once told I don’t “look like an editor” in regards to the seniority of my position managing a team of nine at the time. I am a white, middle class, southern male, so I’m quite surprised I didn’t slot into that stereotype quite neatly.
Being charitable, I would say it is because I am indeed younger than most people in my position. But I can’t help thinking the other trait that I do not share with senior managers - height - is a more significant one, and what was really on that individual’s mind that day.