The genetics of intelligent radio

BBC Radio 4 has just concluded an excellent three-part series on the controversies over the genetics of intelligence and it’s one of the best and most nuanced discussions you’ll hear about the topic for many years.

The series is called Intelligence: Born Smart, Born Equal, Born Different and it’s carefully put together, wide in scope and doesn’t shy away from either tough science or difficult issues.

The only point I’d make about is one of context: most of the discussions apply to Western populations. This is not a point about race but one about environment.

Calculating heritability for a particular trait, in this case for cognitive function, involves working out how much of the difference between people is accounted for by genetics and the environment. But the result only holds for similar populations in similar environments.

For example, malnutrition, disease and high levels of environmental neurotoxins (e.g mercury from illegal gold mining) have a massive impact on cognitive function in kids and are clearly all environmental, rather than genetic, contributors to cognitive function.

But when most of these studies are done, these serious environmental effects have been screened out either explicitly (for example, by not including people who have pre-existing damage through neurotoxins in the study) or implicitly (because, for example, malnutrition barely exists where most heritability of intelligence studies are done).

The qualified conclusion is that general cognitive function is largely heritable when the most significant environmental effects on cognitive function have already been removed. This would be true for many European kids, for example, but much less so for kids from, let’s say, South Sudan.

The programme doesn’t claim otherwise, and lucidly describes how heritability is population specific, but it’s worth bearing in mind how much of the subsequent discussion addresses issues more relevant to the developed world than the one fifth of the world’s population who live in extreme poverty.

Either way, if you want to get up to speed on the debate about intelligence, cognitive function and genetics, the BBC Radio series is an excellent place to start and you’ll come away much smarter as a result.
 

Link to ‘Intelligence: Born Smart, Born Equal, Born Different’
Link to podcast page for the series.

3 Comments

  1. Posted May 15, 2014 at 3:13 am | Permalink

    Amusing the gyrations people go through to not sound racist.

  2. Posted May 15, 2014 at 2:18 pm | Permalink

    I haven’t heard the podcast yet, but I am very much looking forward to it.

    Have you ever read the book Selfish Reasons to Have More Kids? It goes a lot into the genetics of intelligence. There’s also a Freakonomics podcast.

    There’s lots of interesting research out there on the nature vs. nurture debate.

  3. Guido Biele
    Posted May 26, 2014 at 1:34 pm | Permalink

    You write:

    “The qualified conclusion is that general cognitive function is largely heritable when the most significant environmental effects on cognitive function have already been removed. This would be true for many European kids, for example, but much less so for kids from, let’s say, South Sudan.

    The program doesn’t claim otherwise, and lucidly describes how heritability is population specific,…”

    However, after having heard the series, I cannot agree with this statement.

    While I remember limitations of twin studies being briefly mentioned and the role of the environment being discussed, statements in which the main speaker (who thankfully repeated several times that he is a geneticist) or one of the interviewees states that intelligence is largely heritable, without offering any qualifiers, are much more frequent.

    I think it is good to keep three things in mind:
    1) Studies of twins living with their biological parents assume that the extent to which monozygotic and dizygotic twins share a shared environment is the same (the twins, parents, and the environment treat monozygotic and dizygotic twins equally equal). This assumption seems implausible, and I cannot remember having seen any test of this assumption.
    2) This problem can be circumvented in studies of adopted twins. However, given strict standards for adoptive parents, this means that even the environment of adopted twins living apart likely relatively similar (parents typically having a good SES), thus amplifying effects of genes compared to environmental effects.
    3) There is an intellectual leap starting at high heritability estimates from twin studies to “genetic diagnostics” that totally glosses over the so-called “hertitablility gap”, the effect that nowadays genes explain much less variance in intelligence than they should, given the high heritability estimates from twin studies. [for the nerd: Newer methods as genome-wide complex trait associations suffer seriously from over fitting problems because of an unfavorable (to say it friendly …) ratio of model parameters to number of subjects, which seems to be rarely controlled through out of sample cross validations].

    I think that thes ideas (and the idea that finding genes that explain differences within groups (English children) tells us little about genetic reasons for between group differences (english and chinese children)) should have been expresses more clearly and prominently in the show, instead of focusing on a pendulum that swings back and forth between a societal and biological explanation. This antagonistic view might make a good story line, but it does not work well in communicating the inherent complexity of the research field.

    In sum, my impression is that while the series gives some room to those skeptical about the size of the effect genes have on intelligence, the naïve listener will overestimate the role of genes after having heard this series.


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