Thursday, 22 September 2016

Heads, I win: big brains lead to bright futures


Some people refer to intelligent persons as “big brains”. They imagine those with bigger brains are more intelligent, a simple idea which is very probably right. School children, who are able to observe how the entire class deal with the same problems they are set, soon work out which children are “brainy”. The general principle that larger brains have greater power holds for many species, not just within humans.

Buried in a recent paper in Molecular Psychiatry (2016), 1–9, which itself contains a full library of publishable findings, is a little gem,:

Infant head circumference

Yes, right at the bottom of this list (and the actual table is much longer) is an indication that infant head circumference is genetically related to later educational attainment.

Here are the results in heat map format:


Infant head circumference heat map


As you can see, the sample sizes are healthy, which gives us reassurance that the findings are very probably real. Infant head circumference shows a link not only to educational attainment but also to verbal-numerical reasoning.

The authors conclude:

For example, the genetic associations between infant head
circumference and intracranial volume with educational
attainment and verbal-numerical reasoning are important in
themselves, as are many other cognitive–mental health and
cognitive–physical health associations. Taken all together, these results provide a resource that advances the study of aetiology in cognitive epidemiology substantially.

For new readers, cognitive epidemiology is a developing field of health research, in which intelligence is measured and evaluated as an explanatory variable in health outcomes. Once included, it turns out to account for sizeable amounts of the variance. In my view, failure to account for intelligence renders much of ordinary epidemiology questionable.

From the point of view of chronology alone, it is likely that having a bigger brain leads to greater ability. For once, the Press paid attention to this finding, and gave it wide publicity. Slowly, genetic research is coming to public attention.

Here is a link to the full paper from which the above section from Table 2 is drawn.

In summary: cognitive epidemiology now has a new problem: it is generating so many interesting results that it is hard to keep up with them. A nice problem to have.


  1. "As you can see ...": not on my screen, doc. (iMac, Safari.) I'm afraid it's a pig's breakfast.

    Meantime, and O/T, have you seen this?

  2. Sorry, got too enthusiastic about the size of the tables. The next post or two will drive them into legibility.Thanks for the link to the excellent blogpost. Good to see the historical record (and to recall that we all knew this stuff, but did not join the dots).

  3. Santoculto piece and love22 September 2016 at 21:23

    Biigger brains = bigger problems**

    1. Santoculto = pinhead

    2. or not, i have a greater forehead, ;)

      in the end, just name-calling is not a argument, it's just a gut-personal opinion.

      you can develop it...i thought.


      ''cognitively smart people [aka, more efficient workers] are invencibly the best''


      ''if the 'smartest ones'' are fantastically superior, the societies they control would just the reflection of their innate and objectively valuable supremacy''

      but not, the societies where ''the smartest'' control usually reflects their high-functioning normalcy or high-functioning lunacy, usually, implicit sociopathy.

  4. For example, the genetic associations between infant head
    circumference and intracranial volume with educational
    attainment and verbal-numerical reasoning. It hardly isn't correlated with intracranial volume, considering it's the Mongolids' strongest cognitive asset

    Why did they say nothing regarding spatial reasoning?

  5. Dr Thompson, I am a rather regular enjoyer of your blog.
    However, you write for Tribe #5 and above.
    It doesn't bother me like the whole course of studies I had to endure in my life which was designed for Tribe #3, but at the end of each entry I am left wishing you had made things for us, 4th-tribers, a little easier.

    I am not requesting to diminish your linguistic tone, nor to remove details. Keep it as detailed and academically-written as it is. I only suggest that, if you added to your posts an explanation of some details (like the meaning of Rg s.e. and P in that table, how to interpret statistic figures, what a phrase like "polygenic score" means: I looked up "polygenic", I presume I know the meaning of "score" but I still can't grasp what a "polygenic score" is ).

    Not to say less, not to say it less simply, but, merely, to add some explanation for us 120-125 IQ dimwits (from your point of view. I know by personal experience it's hard, if not impossible, for you to empathize with us), is what I hope you can do.