The Flynn Effect Puzzle

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From a BBC article.

Richard Lynn notes that measures of infants’ mental development increased in the UK and US at rates correlated to the increasing IQs of slightly older children. It’s difficult to see how Flynn’s theories are enough to explain this. “Are infants thinking more scientifically today?” he asks rhetorically.

Pointer from Neerav Kingsland, who writes,

For gains in IQ, I wonder whether changes in the method of harnessing energy caused IQ gains (our brains adapted to the needs of the new economy), or whether gains in IQ led to the development of new ways of harnessing energy (we got smarter and invented new ways of doing things).

My guess is that, for the transition from farming to industry, it’s the former.

Or to put it another way: humans developed the IQ we needed.

In Sapiens, Yuval Noah Hariri argues that foragers need more intelligence than farmers. Foragers need to know much more about their environment, including information about many varieties of plants. Farmers just need to know a routine for raising a staple crop.

One can argue that ordinary workers in the early stages of the industrial revolution did not need to know much, either. More recently, the skill demands of jobs have gone up, so that we may be reverting to forager-level intelligence.

But what is the mechanism by which “humans developed the IQ we needed.” For foragers, the mechanism is Darwinian. If you cannot remember which plants are edible, you die without passing on your genes. By the same token, farming is dysgenic. It allows more intellectually weak people to survive.

But does that mean that we should seek a eugenic explanation for the Flynn effect? That is, for the past hundred years, has the trend within a given country been for the proportion of children born of less-intelligent parents to decline? Researchers, including Lynn, seem to prefer nurture-based explanation.

20 thoughts on “The Flynn Effect Puzzle”

  1. Hey Arnold. I’m still working through this, but I’m not sure you need evolutionary selection to explain recent IQ gains.

    My point is that external environments (work, technology, society, etc.) lead to different IQ levels without changes in brain capacity starting points.

    In other words, a random person born in 1900 would see an IQ increase just by being born in 1980.

    • I probably should have used words other than “adapted” and “developed” … they were misleading for recent gains. Humans “utilize” the IQ we need might be a better way to say it; that being said, what there is to utilize could be affected by long-term genetic pressures, I just don’t know if this is true in recent times for the reasons you point out.

  2. It seems to me that the argument concerning foragers being more intelligent than farmers has some flaws. To show this, compare chimpanzees to non-mechanized rice farmers, or cotton farmers from the United States before the civil war. If farming required less intelligence, I would expect to see more chimpanzees engaged in farming.

    In fact I would expect to see more baboons, etc. farming if in fact farming required less intelligence than foraging.

    • Probably true. Remembering which plants are edible/poisonous is a matter of memory, not raw intelligence. Those are two different things.

      Hunting is what requires intelligence. For a slow biped with no claws or fangs, like us, our big brains and ability to cooperate are our only weapons. But that doesn’t change the basic question about moderns vs. hunter-gatherers.

    • Yeah, that was my first reaction, too: Farmers are, at their core, problem solvers.

      Of course, my experience is with modern farmers and Little House on the Prairie: I don’t know what the earliest farmers were like and I don’t know what forager life was like beyond some long ago National Geographic specials that I wasn’t watching with an eye towards how complicated their day to day lives are compared to farming.

      So until I read the book, I’m going to give Yuval Noah Hariri the benefit of the doubt and assume he researched the issue and came to a reasonable conclusion.

  3. “In Sapiens, Yuval Noah Hariri argues that foragers need more intelligence than farmers.”

    This makes me think that the Yuval overestimates what he thinks he knows about foraging and farming.

  4. “has the trend within a given country been for the proportion of children born of less-intelligent parents to decline” — A genetic explanation for the Flynn effect is not feasible because it’s happening too quickly. The population mean of the trait is shifting by a full standard deviation every few generations! Assuming that this is occuring due to selection, and that IQ has a heritability of 0.5, and using the breeder’s equation, this implies a selection coefficient of around 1. In other words, people with IQ that is one standard deviation higher have twice as many kids on average. This is not plausible.

  5. Jared Diamond made a similar claim in Guns, Germs, and Steel, and this sounds like a mere repetition of that claim, but Gregory Cochran has argued persuasively against it.

    Let’s consider those peoples who were most recently living as foragers – without farming or large-scale civilization – prior to their encounters with foreigners from more advanced cultures. The most extreme cases are those uncontacted small tribal groups in the Amazon basin, and the Papua New Guinea highlanders, where there were over a million people who were not ‘discovered’ until the 20th century! And you could also go back and look at many similar tales of contact with foragers in human history, and see what happened. What about the Native Americans? What about the Maoris?

    Under the Hariri / Diamond theory, you would expect these folks and their current descendants to be some of the of the most cognitively gifted people in the world, doing great in school with high test scores, and easily punching well above their weight in all sorts of intellectual pursuits, or at least in the those areas where the hypothetical forager intelligence provides a comparative advantage versus those dull farmers. If, for example, they really need such a phenomenal memory to remember all those plants, then we should see that many of their descendants have exceptions memories and succeed in careers that leverage that special talent.

    But not only do we not see this, we see exactly the opposite.

    Furthermore, one would expect to see some correlation between cognitive ability and the duration in which some culture has engaged in agriculture (at least absent Social Darwinism and the kind of eugenically-Malthusian economic and procreative conditions that Gregory Clark described in A Farewell to Alms).

    But we see no such correlation either, most evidently in Africa and the Americas, where foragers lived in relatively close proximity with closely-related tribes who had been engaging in low-scale civilization farmers for a long time. There doesn’t seem to be a significant cognitive difference between their descendants.

    So this theory doesn’t really meet the smell test, and the question is why is it nevertheless so seductive?

    • Yes, an agronomist friend was telling me that cattle will eat a little of weed and if it is poison they will remember and not eat it again. (He said cattle eating poison weeds is a problem when you move them to a new environment). Cattle are not that smart so i would conclude the remembering what is edible and what is not is not so impressive.

        • Bet you could. It’s called the “Garcia effect”–anything that has made you sick before makes you feel sick when you just think about eating it. This is not a rational process and requires little intelligence AFAICT; just basic pattern recognition of the sort that all mammals do. This is why so many folks can’t touch the first alcohol they got drunk on, and I still get ill just thinking about a particular sort of creme caramel I ate just before coming down with stomach flu when I was eight.

  7. But does that mean that we should seek a eugenic explanation for the Flynn effect? That is, for the past hundred years, has the trend within a given country been for the proportion of children born of less-intelligent parents to decline?

    IMHO the idiocracy people ignore that few really low IQ men reproduce. Many of those single mothers where charmed by a fairly intelligent player.

  9. What we define as intelligence is, to a large extent, the ability to make and understand abstractions.
    One can quibble over whether that is the greatest part of intelligence, but that is most of what IQ tests quantify.
    Abstraction is a much larger part of ones life born in the last 20 years vs 100 years ago.
    I think that and the fact that we are now exposed to infinitely more “factoids” is most of the Flynn Effect.
    I think it’s better to call it firing into modern society more than getting smarter.

  10. This post made me think about the whole “lead exposure caused the big spike in crime in the second half of the twentieth century theory.” Since lead poisoning has a well known deleterious effect on IQ, I would think that if it were really common enough to cause a dramatic spike in crime, it ought to show up in IQ and other standardized test score from that period. I wonder if anyone pushing the lead/crime theory has looked into that.

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