Book Review: Intelligence (2015) by Stuart Ritchie

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.

28 Responses to Book Review: Intelligence (2015) by Stuart Ritchie

  1. Sisyphean says:

    People who complain about people who are interested in IQ tests are an interesting breed. I was one of those people when I was younger though having accepted the facts for what you are I now reserve my most vociferous complaints for pretentious people. For me it boils down to social intelligence those with higher social acumen, perhaps more empathy, will cringe when others discuss subjects that are likely to make others feel inferior. And there’s also HBD chicks out bred universal thinking to consider, it may be that if you have the core belief that all beings are the same, facts that clearly contradict that belief are to be attacked at all costs.

    • Staffan says:

      It’s certainly those genius-pesky Northwest Europeans who complain. My guess (inspired by HBD Chick, Peter Frost and others) is that, for whatever reason, a process of outbreeding widened the circle of empathy which in turn led to universal thinking, economic success etc.

      If there is a core in that emerging cluster of traits, beliefs etc, I think it’s the core of what’s called dignity culture – the inalienable worth of all individuals. I heard a woman of this culture who was untypically against gay marriage responding to LGBT claims that not being able to marry deprive gay people of dignity. She said something like “you already have dignity, it’s nothing the government can bestow on anyone.” (Quoting from memory.)

      That often translates to the idea that we’re all the same because it seems to justify the idea of inalienable worth. And IQ tests then become a both unscientific and immoral.

  2. Margott says:

    Staffan, it’s a messy issue and a consistent terminology would help, especially to those like I, who haven’t read those books. One can’t use interchangeably the ‘Intelligence’ and the ‘IQ Test’. Correlation between health and intelligence? Health, or the way one takes care of it?..different. ….and in general, haven’t read those books, but many others, and can promise – a correct terminology is the ‘must’ in scientific writings. This not because any writing must be scientific, but to avoid a misunderstanding. In general I have to say I am very impressed by your site and majority of the articles.

  3. Staffan says:

    It’s true that there isn’t any exact definition of intelligence, but it’s equally true that we have a rough idea. All kinds of problem solving tests tend to correlate to some extent, making the case for a general intelligence along side the special talents. It’s this general intelligence that is simply referred to as intelligence.

    As for health, it’s not been established why this is so strongly linked to intelligence. Health behaviors are a part of it. People with low intelligence get into accidents, but that’s not all of it. Many believe intelligence is a measure of how efficient our entire bodies are. We know that intelligent populations with unhealthy behaviors, like the Japanese for instance, live longer than others. Similarly individuals who are obese but of high intelligence have the same mortality as skinny individuals of high intelligence.

    It’s a fascinating subject, sadly misrepresented.

  4. Santoculto says:

    Hitchens is not wrong when he said that those who are excessively concerned with their own scores on cognitive tests tend to be in some perspective, more stupid than others who do not, but as often happens with liberals, they tend to do some good insights, sorrounded by a bleak desert of healthy, independent and coherent thought.

    As I always said here and how I will always speak. I’ll keep pushing it.

    I do not deny and never denied any of the statements made among hbds bloggers on intelligence, which is measured by IQ tests.

    Yes, IQ measures somehow not very complete, but effective, what we call intelligence. The school system was not invented from nothing, but in my view, it seems obvious that it can not be summarized just that.

    Yes, IQ is related to better social indicators. On the surface, discard a number of environmental factors such as the tendency of people to favor with the same political or ideological convictions (or ”life philosophy) to occupy certain positions. That means playing some of the most valuable traits to off the boat, such as honesty, real rational thinking ability of long-term or systematic ….

    But as I have always said and will always say, it is complicated and lazy conclude that ” those with the highest scores are smarter about those with other levels of scores ”. Perhaps to IQ tests in the same manner as the top chess players will be more intelligent to play chess than others. Of course, this hierarchy, the cognitive tests approach the real concept, completeness and correctness of intelligence than chess game. Still, it is not enough because it is not completely intelligence.

    Cognitive tests should be treated as great ways of measuring part, more technical, the intelligence, than as if it were intelligence. To measure human intelligence, we must embrace the complexity of our behavior.

    From this complexity, I thought of some ways to simplify this reality, deconstructing certain popular certainties.

    For example, ” the smartest people from scores on cognitive tests, are smarter empathically ”.

    Very complicated, we all have our individual intelligence and stupidity load (like, Antoine is 75% rationally smart and 25% rationally stupid, 80% empathetically smart and 20% empathetically stupid….). The most talented of cognitive polymaths have weaknesses, such as the ability to be empathetic. Yes, our personality is part of our cognition, is not conceptually different, because it belongs to the same physiology.

    This is a way to break this (old) attempt to create a hierarchy of values ​​really arbitrary where a minority because of their scores on cognitive tests (and not for their personal achievements, from short to long term) will be identified and treated as ” smarter ”, as if all that did, had resulted in a conceptually clever product, it seems clear, does not consist in the full reality of the facts.

    While we continue to deny the cognitive diversity of human beings, we will continue to put the wrong people in the wrong jobs.

    tell me what you think about the idea of genius and psychopathological predispositions ** Do you believe that is just a popular myth, ancient and anecdotal **

    Tell me about your thoughts regarding the work of Lewis Terman.

    • Staffan says:

      Nice to hear your voice again : )

      I think the basic issue is terminology. In natural language the word “intelligence” is vague and refers to all sorts of skills. In science you need to define and measure things more precisely. For this reason psychologists have chosen to use this word in a more narrow sense.

      This is not to say that other abilities aren’t important. Judgment, empathy, curiosity, creativity etc, are all interesting traits and that are being researched under separately – because they are separate entities.

      There is some evidence of the link between creativity and psychopathology, especially bipolar disorder, but also schizotypy. This seems distinct from intelligence (as mesasure with IQ tests), although I’ve no doubt it helps a creative person to also be intelligent in order to be more productive. Terman illustrated this distinction in that his longitudinal study showed high IQ children became successful, but not very creative, adults.

      • Santoculto says:

        Yes, I think two lines of thought should be taken into consideration. Treating the most important psychological characteristics as separate conceptual entities, but also see them as part of a complex physiology where they all interact. For example, why I’m here talking to you about controversial issues and continue to expose myself to hate people to think differently and even critically different **

        Because I’m conscientious and truth lover, perceive as a psychological aspect, conceptually separate technical cognition or intelligence, profoundly affects my actions **

        I totally agree that the term intelligence is very vague, precisely why I have preferred for wisdom, because in my understanding, this seems to be cleaner, it seems to be a more pure form of intelligence, to seek philosophizing or harmonize the wisdom It consists in this capacity.

        I try to understand this form of intelligence metaphorically speaking as understanding reality or truth, objective or direct, directly observable, and the realidadeo u truth subjective or abstract, the increase of objective truth. We see what is before us and we can extrapolate non-obvious scenarios or abstractions of this communion of observable variables. Harmony is undoubtedly better than chaos, wisdom always leans towards balance.

        I’m attending a psychologist. I tried the diagnosis of broader autism spectrum to be able to retire and parasitize the semi-slave system that consists of Brazilian society, the Brazilian system for now, she just found what I concluded, I am the only real normal (rational, natural and empathetic) among the people around me, the most ”normal” of all. Could this not come within the criteria of mental illness psychology ** I am, statistically speaking, a crazy person.

        my body is cold, my mind is hot.

        Yes, iq tests measure the capacity of convergent thinking style, in a relative superficial way, but most people don’t know apply their higher scores in verbal (semantic) analogies in the real world.

        Creativity clearly is a divergent thinking or a capacity to produce novel and useful analogies, look the ”object-idea” in a different perspectives, in a different angles.

      • Staffan says:

        Wisdom is probably as hard to define and measure as intelligence. It’s certainly found among a high number of autistic people who won’t compromise truth for nothing. But what you can do is to make compromises when interacting with other people. We all play a game to get along. The difference is that for some the game becomes a second nature. And when that happens wisdom is lost and balance too.

        The trick is to know and accept that social interaction is a game. That’s not you, that’s the intersection between you and other people. Only if you start thinking about your persona as your identity will you lose yourself. I think some autists have this urge to speak the truth regardless of whether anyone asked for it or not may come from a fear of getting compromised. But they are probably the ones who have the least risk of that.

      • Santoculto says:

        I disagree in part of you, because I see, at least in the wrong planet, that the percentage of autistic all strains who define themselves as liberal, is very high, almost as high as that of a student body of students of history, more near to you.

        I know and live with many liberals, and if there is something that seems to be missing in their minds is precisely the wisdom, although it is surprising to note that many of them are close moderately to be half wise. My concept of wisdom is to understand the world the way it is, first, an action that looks simple but is very difficult, tell me about a society where people have not childish beliefs about reality. In all human societies there are allegorical gods.

        When you peel all the layers of onion that is the matrix called ” human society ”, you will find the wisdom and along with it, melancholy. It seems that both go hand in hand.

        The more mundane side and anti-social wisdom what would be called as’ ‘a little wisdom’ or astuteness, the ability to understand the context or big picture, and use it to your advantage, selfishly. Genuine wise can also understand the context, but will use it unselfishly, to harmonize their environment of experiences and interactions.

        Still, the wise people are very rare. Autistic, or most of them, seem to me to end up falling on the same mental mechanisms of hyper-rationalization that depresses coherent or rational thinking skills among many of the liberals, liberalism is the practice of Taoist philosophy in complete disregard for human nature and therefore the nature of all creatures of sexual reproduction where the strongest survives.

        The storm encapsulates and denigrates the calm, just as the most dominant shift the less dominant and potentially more cooperative.

        Nietzsche said that Buddhism, in general, consists in performing, in real-time practice of all metaphysics and hypocritical nonsense that is characterized Christianity, it is the practice of Christianity, literally. So you have a lot of good people who have a focused mind in the individual analysis, trying to overthrow all natural and progressively artificial barriers that have been made by man, believing that with such naive attitudes will change the world in the promised paradise.

        All the teachings of good conduct as well as intelligent attitudes in everyday life we ​​see on Facebook or other social media, it basically consists of wisdom.

        The vast majority of intelligent human beings end up failing in some essential aspect of harmonic existence, and the wise would be one who commit mistakes less and learn more from your mistakes.

        We are not seeing any observable angle that people, a lot of them, are learning from their mistakes or trying to avoid them, we are **

        Self knowledge is an essential tool for wisdom, because when you analyze the world, you’re not making a neutral analysis, but directly biased from their own psychological idiosyncrasies. Therefore, it is important to know first so that we can counteract excesses by his personal observations and see the world as it really is first.

        It is also important to know, be recognized as an individual, that has unique features and fight for their rights, we lived in semi-slavery societies. We are also corrupting the time to get him out of much of the common people, the mentally handicapped psychopaths in power, as is the custom, do everything wrong.

        The school and the psychology has caused a succession of cognitive suffering large-scale in the population, to treat them as pieces that should fit in general and surface molds of society.

        Sorry, it was an extremely long comment.

      • Staffan says:

        Yes, I may have to get back to you on this. For now, I just like to point out that autism is a fashionable diagnosis, and liberals are fashionable people – in clothes, hairstyles, diet, and even in imagined psychopathology.

  5. If we switched to another word besides “intelligence” it would not clear up the discussion. People go through enormous evasions to insist that “IQ isn’t the same thing, no, not at all, perish the thought. IQ is just, er…something. Something that may be related to intelligence in a teensy, weensy way, but it’s all just so artificial and clumsy that we just can’t talk like that.”

    All that is just an evasion. The motives are various, I imagine. The one listed above, that socially aware people don’t like to have public discussions about topics that make people uncomfortable, is likely important, as is the desire to show one’s “just folks” bonafides by downplaying the importance.

    It is a straw man to claim that any people consider IQ and intelligence interchangeable terms, and then spend so much time and effort showing how they Aren’t Exactly The Same. Of course they aren’t. But we do have a fairly clear idea of what intelligence is and can illustrate it cross-culturally. IQ measures that moderately well. IQ doesn’t measure diligence, charm, reliability, decisiveness, or a dozen other important life-virtues very well at all. It doesn’t pretend to.

    It’s rather like claiming that height isn’t a valid measurement because it doesn’t fully capture the concept of Size, or Reach, or basketball skill. It doesn’t claim to. IQ measures some cognitive abilities very well, and they show real-world application and results.

    • Staffan says:

      I think it all comes back to the dignity culture of Northwest Euros (aka guilt culture). There is a threat to this tenet of every person’s inherent worth. No one illustrates this error more clearly than SJ Gould in his book The Mismeasure of Man. Once you have the idea that IQ is inherent worth, then post hoc rationalization dictates that IQ tests must be bogus.

  6. Santoculto says:


    scandinavian men tend to be more introverted than scandinavian women**

  7. Santoculto says:

    autistics are people with masculinized brain, caused by higher testosterone exposure in the womb and lower circulatory&general testosterone levels, on average. My impression about it.
    Autistic mothers tend to have lower testosterone and autistic men tend to have lower ones, but of course, averages.

    It explain why autistics tend to unfit with normatized genre patterns but also with hyper-masculinized trends about its cognition.

    But, aspies tend to have/score higher verbal iq than non-verbal. Verbal intelligence is a slight/relative femminine trait.

    Higher testosterone exposures but the nature of this sexual hormones, autistics have higher exposure of mutational testosterone.

    • Staffan says:

      Well, you could argue that they have masculine-typ cognition, but men who are the opposite are typically considered way more masculine. That’s my issue with this idea. They are not seen as sexy because they are not seen as masculine.

      • Santoculto says:

        I think the ”sexiest ones” are a ”favourable” mix between feminine and masculine traits, for example, the capacity to read emotions and intentions of other, is extremely important during ”game dates”, ”flirts”. Supposedly, very feminine woman prototype will tend to be very socially-oriented.

        But, what do you think about ”my” hypothesis??

        Generally, autistics have lower circulatory and total testosterone levels but with masculinized brains caused by testosterone exposure in the womb?? It is possible?

      • Staffan says:

        I agree that androgynous is sexy, but regarding the idea of testosterone I’m not convinced. Is there evidence of this? The prenatal testosterone has to come from either the mother or possibly a twin (lots of pregnancies start as twins as you may know). This means a close relative with high levels of this hormone which, since it’s heritable, should make low levels in the child post-natally unlikely.

        A simpler explanation would be that autism is just the extreme end of certain personality traits. It has been noted that relatives are similar but at a sub-clinical level.

  8. Santoculto says:

    Yes, the idea being an extreme personality spectrum.

    But what I’m saying is

    ” You can have a man who had a large exposure to prenatal testosterone and born with low levels of testosterone ” ??

    That is, the testosterone ” masculinize ” your brain, but that does not reverberate in higher levels during the life ??

    That would explain androgyny in autistic men.

    About androgyny in neurotypicals, I did not mean in the literal sense that we understand androgyny, but for example, almost imperceptible mixtures of female behavioral characteristics in classic heterosexual men.

    The type nerd, especially that within the autistic spectrum often very literal, while women tend to excel by their cognitive bias for ambiguity.

    • Staffan says:

      It’s possible. I haven’t heard anything about that. But I guess you could look for evidence. HBD chick certainly found plenty to back up her theory of broad-sense clannishness and there isn’t anything similar in Academia. I imagine lots of interesting ideas are ignored.

  9. santoculto says:

    Culture loaded iq subtests have higher ”heritability” (twins heritability, whatever that means ) than less culture iq subtests ”because” long-term memory on general knowledge while culturally purified iq subtests seems depend on environmental circumstances where people are doing this test. Purified cultural iq tests are based on ”quasi-exclusive use of cognitive faculties” (concentration, ”clean” the head to focus on activity which is being required). Higher-iq people are the best for emulate a computer behaviour. (it still not all about intelligence).

    East asians (and higher-iq non-east asians) are much better for concentration or ”neutralize the effects of personality influence on cognition” ( general knowledge have greater influence on verbal-semantic intelligence, is not*).

    Iq tests measured also (and/or) fundamentally concentration capacity or isolate personality effects on cognition during (specifically scholastic or mechanic-repetitive) ”cognitive activities”.

  10. Santoculto says:

    why people say that ”creative people ARE MORE adaptative” ***

    The most important proxy for adaptation is fertility and creative ones tend to produce few kids or NONE. Maybe creative people will be one of the least adaptative people and not the MOST, specially in the ”civilization context”.

    Creativity is not a complete synonyms for adaptability, just for evolutive creative behaviour, a unusual way to be ”succesfull” in society and produce greater families, 😉

    • Staffan says:

      I wouldn’t say that. If we talk about adaptive in an evo sens you should keep in mind that there is both fertility and mortality. Africa had a stable population before colonization reduced mortality.

      Right now, most of the world is hitching a ride on the Western creativity express, but I think we can agree that is a weak strategy as it relies on help from others. Doing so can only give you as much fitness as your host, so to speak.

      (This is also a bit off-topic, as IQ isn’t creativity.)

      • Santoculto says:

        Yes but i’m talking at individual level. Creative achievements are fundamentally important, no doubt about it. But the problem is when people say ”creative people are the most adaptative”. Adaptation in crude words mean higher reproduction/fertility, capacity to adapt TO produce many kids or produce a balance of good environment and kids number (a malthusian approach).

        Individually speaking, creative ones tend to be the least adaptative because they tend to be socially nonconformist and nonconformism tend to result in lower fertility, not all, i see utilitarian creatives people who produce things for daily life the more adapted among them.

        Other thing, we can have a individual with greater adaptative potential (evolutive creativity) but without advantages in environmental circumstances and even bio-circumstances for example, to be assexual.

        Some people are adaptable but adaptation in social contexts don’t valorize individual gift BUT just the capacity to fit in social norms, work and have kids.

        Of course poorer people today have more kids than middle and upper classes because we are living in a final stage of star/civilization and because there are a friction between K and R reproduction-social contexts.

        The idea of creativity AND adaptation is logical and explain why so many people make this analogy. But seems in real world, real adaptation obey natural guidelines while human creativity, most part of time, to do the otherwise, desire change what is pragmatically logical/obvious.

        Mentalistic geniuses seems to be those with higher adaptability via creativity.

  11. I mentioned you in a post this evening, with a request for opinions from people who know more than I do. Please consider reading this post and those following and commenting.

    • Staffan says:

      Thanks for the tip, I haven’t been very active recently but I’m hoping to fix that. I think you’re onto something. When I’ve bumped into American tourists in Stockholm, I’ve never encountered anyone bragging about America. Very loud and extraverted, yes, but not boastful.

  12. Plz come back says:


    Have you considered using Patreon or pay pal for receiving payments?

    I’d love to see much more about blogs like this.

    • Staffan says:

      The blog is dormant for various reasons, but I have PayPal, it’s under Donations. I’m hoping to get started on it again this year, at least a few reviews.

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