Book Review: Intelligence (2015) by Stuart Ritchie

August 12, 2015

Stuart Ritchie


An Uphill Battle

It’s no easy task to explain why intelligence is so important. The reason for this is oddly enough that many highly intelligent people insist it’s not important at all. While their arguments are weak, their eloquence, learned references, and general cleverness, charisma etc, often conceal this, at least to the unsuspecting part of the reading public.

To show what he is up against the author, psychologist Stuart Ritchie, begins with a quote from the late left-wing intellectual Christopher Hitchens,

“There is…an unusually high and consistent correlation between the stupidity of a given person and [their] propensity to be impressed by the measurement of IQ.”

As some of you may have noticed, this is an illogical statement. Correlation, as Hitchens no doubt knew, is a mathematical measure of the linear relationship between two variables. So to speak of a correlation between stupidity and something else implies that he relies on some measure or estimate of stupidity – which would be a reversed IQ test – to make the point that such tests are useless.

Or as the author says, “Smart people don’t like the idea of intelligence.” Strictly speaking this isn’t true. It’s mostly Western, left-leaning intellectuals who don’t like this concept, but they have been the most vocal and influential in the debate. Their critique is of course political rather than scientific in nature and they have made pretty ugly straw men out of proponents of IQ tests and research.

The Factual Psychologist?

So what do you do if you’re already cast as the Villain before having spoken your first line? Like the “factual feminist” Christina Hoff Sommers, Ritchie’s strategy seems to be to counter politically biased and emotional arguments with plain facts. The facts being that intelligence, as measured by IQ tests, is highly heritable, stable across the lifespan and linked to a number of life outcomes most of us find very important, like level of education, work performance, income, crime, health etc. Critics dismiss this by saying that IQ tests simply measure the socio-economic status which these correlates reflect. But high heritability and stability makes a strong case for causality going in the other direction. We’re born with a certain amount of intelligence and differences in this regard will explain later differences in terms of education, health etc. And if you think these correlates are important, you’re simply forced to agree that the intelligence that contributes to them is important too.

This is not to say that intelligence is “all that matters,” as it says on the cover of the book (referring to the name of the series the book is a part of and not the title). Leadership effectiveness, for instance, correlates a modest 0.35 with IQ. And there are “facts” in this book that can be contested. Like the link between IQ and socially liberal attitudes, which has a more sizable correlation of 0.45. This is possibly due to the fact that most research is done in the West where these attitudes are popular, especially among politically correct university students who make up the common “convenience” samples. A similar case can be made against the inverse relation between IQ and religious belief, a weak correlation of 0.25 to begin with, but even weaker if you look at the research behind it, something I have covered in more detail in an earlier post here.

That said, I haven’t found much to remark on in this book. And besides facts relevant to the importance of intelligence and to the critique against the concept, Ritchie also presents lots of other interesting stuff, explaining the basics of intelligence research and how it relates to subjects like behavioural genetics, evolution, neuroscience etc. And the book is so well-written I doubt anyone without prior knowledge will have a problem understanding it.

The Norwegian Enigma

One of the most interesting studies the author mentions is one that suggest a case for environmental influence, and a pretty hefty one too. It concerns the addition of two additional school hours in Norway which took place in the 1960s. This reform appears to have added on average 3.7 IQ points per year, which is a very big effect. This is in line with a global trend of increasing test scores over the recent century, called the Flynn Effect – which coincides with more children going to school all over the world.

According to the author there is no current theory that explains this boost, or the larger Flynn Effect. It could be simply that training a skill will improve it. Like a naturally muscular person will be stronger than the average but even more so if he works out in a gym frequently. While this study may hold a clue to how we can boost intelligence, the author also mentions that similar projects (of which there have been many) have given short-term increases with no lasting impact on the adult person. The Norwegian IQ tests that showed this effect come from the military so it’s young adults who were in school not long ago. Still, it’s intriguing, given the big effect. I would have liked some more space devoted to this study, what other researcher say about it, if there have been follow-up studies later in life or anything else to corroborate the test results.

The Controversy

In the last chapter, Ritchie returns to the controversial aspects of intelligence research that he mentioned briefly in the beginning of the book. Presumably because at this point readers now armed with the facts will be less likely to have their brains hijacked by their emotions. This seems like a good strategy, although even better would have been to keep presenting the facts and simply put the critics in the historical overview at the beginning. After all, most of the prominent opponents of intelligence testing are now dead or very close to death (no offense, we’re all headed there). That way he could have ended the book by highlighting interesting research areas and discuss future directions.

Instead the author tries to reason, coax, and negotiate with the critics, which to me implies that the facts somehow don’t hold up on their own (which they do). For instance, he mentions that Nazi doctors discovered the link between smoking and lung cancer, and that this finding is valid and useful regardless of who uncovered it. True, but in the very next sentence he goes on to say, “Also, it should be remembered that not all of the history of intelligence testing is tainted by eugenics,” thus undermining the point he just made. Or he tries to be nice by saying that differences in intelligence “might be influenced in part by biology,” when he has already stated that heritability trends toward 0.8 in adults.

Adopting the emotional arguments of your opponents on an issue like this is just a terrible idea. Even if Ritchie should win that game (and to his credit he doesn’t), it invalidates the research that shows intelligence to be an important concept, which was the reason the book was written in the first place. Evidence is the only currency of science. Responding to emotional arguments by appealing to those emotions is to short-change yourself to intellectual bankruptcy.


That said, my overall view of this book is very positive. Although I disagree with how the author deals with critics, he is at least trying to push things in the right direction (towards what the evidence tells us). He also packs a lot of interesting information into just over 100 pages without making the text feel crammed; in fact the book is so clearly written it almost reads itself. And Ritchie is a great teacher who knows how to explain things to a wider audience without becoming too technical or dumbing it down. In short, I doubt you can find a smoother ride to basic literacy on the subject of intelligence than this.

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