# The Flynn Effect Clarified

I said in [my review of WEIRDest
People](https://www.lesswrong.com/posts/kYJ6RvS9zJ3WrGP7o/book-review-weirdest-people)
that the Flynn effect seems like a natural consequence of thinking
styles that became more analytical, abstract, reductionist, and
numerical.

I\'ll expand here on some questions which I swept under the rug, so that
I could keep that review focused on the book\'s most important aspects.

### Cultural Bias

After reading WEIRDest People, I find that the goal of a culture-neutral
IQ test looks strange (and, of course, WEIRD). At least as strange as
trying to fix basketball to stop favoring tall people.

I found after writing that review that Muthukrishna and Henrich discuss
IQ in [Innovation in the collective
brain](https://royalsocietypublishing.org/doi/10.1098/rstb.2015.0192)
(hereinafter referred to as MH2016), saying roughly what I inferred from
WEIRDest People.

MH2016 says: \"IQ measures the abilities that are useful at school and
work in these societies.\"

There\'s a good case to be made for removing accidental cultural bias.
Doing so will increase the test\'s ability to detect cognitive patterns
that are oriented toward science and technology.

Similar cultural biases pervade psychology. E.g. there are real cultural
differences about the wisdom of conformism, which lead me to doubt
there\'s a culture-neutral rule for what the correct answer is in the
Asch conformity test.

Strong cultural biases are built into the central ideas behind what we
call science. E.g. it\'s somewhat WEIRD to believe that we should seek
universal laws of nature, rather than expecting valuable knowledge to be
context-dependent knowledge.

Could a genuinely culture-neutral IQ test be developed? I presume it\'s
possible to shift the emphasis so that it measures holistic reasoning
more, and analytical reasoning less. But what would be a neutral mix of
those two? You could average over all humans currently alive, but that
would produce a rather different result than if you\'d taken that
average 1000 years ago.

Changes of this nature seem likely to reduce the value of IQ tests at
satisfying the original goals behind testing, without satisfying
critics.

If I really wanted to develop a culture-neutral IQ test, I\'d start with
the research that has been done on measuring cognitive abilities of
[nonhuman animals and
software](http://www.bayesianinvestor.com/blog/index.php/2017/03/31/the-measure-of-all-minds/).
I suspect that that research has so far remained an obscure niche due to
confusion about whether it ought to measure something more universal
than the skills needed in current high-status jobs.

### Timing

The rise of WEIRD culture happened over many centuries. WEIRDest People
doesn\'t provide a lot of evidence that Western culture became more
WEIRD during the 20th century, which is most of when the Flynn effect
has been measured. Does this mean we\'re just measuring the tail end of
an effect that was stronger in prior centuries?

I\'m pretty sure it started centuries before 1900, but it seems somewhat
likely that the most dramatic effects happened after 1900.

A casual reading of the book might lead you to imagine culture spread
fairly uniformly throughout a population. Yet I see hints that the book
focuses more than Henrich admits on people in the most knowledge
intensive professions.

The median man in 1900 needed muscle power much more than he needed
brain power, but that shifted fairly steadily toward mostly needing
brain power by 2000. To the extent which people optimize their cognitive
abilities for their needs, I\'d expect the median IQ to have risen
mainly in the 20th century, even when some parts of the population
experienced important IQ rises much earlier.

Some of the culture changes depended on reading in early childhood. I
presume that practice spread fairly slowly, and didn\'t reach
diminishing returns until well after 1900. From MH2016:

> \[Tsimane\] Children and adolescents with access to schooling showed a
> strong linear effect of age on IQ score (R\^2 = 0.519), compared with
> no effect of age in those with no access to schooling (R\^2 = 0.008).
> These results suggest that IQ increases with age not because of
> maturation, but because of the influences of a particular WEIRD
> cultural institution: formal schooling.

Also, nothing that Henrich says implies that changes in culture have
slowed down. I presume he omitted discussion of most 20th century trends
due to lack of time and/or space.

### Nutrition

Henrich also points to evidence that the Flynn effect might be partly
due to better nutrition, particularly better childhood nutrition.

Henrich cites [Precocious albion: A new interpretation of the British
Industrial
Revolution](https://www.annualreviews.org/doi/abs/10.1146/annurev-economics-080213-041042),
which argues that better human capital was a key driver of the
industrial revolution, and nutrition contributed to that via improved
health.

Diets had more meat, and several hundred more calories per day, in
England than France in the late 1700s. English heights were 5
centimeters taller than French heights. Height is correlated with both
nutrition and IQ.

That paper also shows evidence that English workers were more productive
at standard common tasks such as reaping and threshing, and suggests
this was due to health differences.

[Is Childhood Meat Eating Associated with better later Adulthood
Cognition in a Developing
Population?](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903695/)
suggests that meat improves cognition, at least compared to being too
poor to afford meat (i.e. there\'s some wealth related benefit, but
it\'s hard to say whether meat was a cause or a symptom).

[Killing Me Softly: The Fetal Origins
Hypothesis](https://www.aeaweb.org/articles?id=10.1257/jep.25.3.153) by
Almond and Currie (nominative determinism alert!) summarizes evidence
related to the earliest stage of nutrition: IQ was apparently not
affected by the 1945 Dutch hunger winter, and there seem to be no
studies directly showing that fetal nutrition affects IQ.

Yet they point to some studies saying something close to that. E.g.
[Health Capital and the Prenatal
Environment](https://www.nber.org/papers/w14428):

> the occurrence of Ramadan early in pregnancy nearly doubles the
> likelihood of a disability related to diminished cognitive function.

[Iodine
supplementation](https://econpapers.repec.org/article/oupjeurec/v_3a15_3ay_3a2017_3ai_3a2_3ap_3a355-387..htm)
\"can explain roughly one decade's worth of the upward trend in IQ in
the United States\".

Fogel argues that [the biggest gains in
nutrition](http://www.bayesianinvestor.com/blog/index.php/2004/12/16/hunger/)
started around 1900.

So I\'m inferring from this somewhat sketchy evidence that there was a
weak nutrition-led Flynn effect starting before 1800, which accelerated
around 1900, and has been diminishing or maybe even reversing in
developed countries more recently. But I\'m guessing, based on the
weakness of the evidence, that it\'s not the primary cause of the Flynn
effect.

### Conclusion

These IQ differences are easy to confuse with genetic effects. Parental
culture influences child culture, if only via influencing what community
the child lives in. Maternal nutrition influences child nutrition. So
the effects are somewhat inherited, even if not via genes, and partly
have life-long effects.

Flynn
[explained](http://www.bayesianinvestor.com/blog/index.php/2007/10/08/flynn-effect-explained/%22)
the Flynn effect as a shift in how people view the world, from
pre-scientific spectacles to post-scientific spectacles. That continues
to look mostly right. Henrich mainly provides a richer description of
that shift, and clarifies that it wasn\'t a free lunch (it involved some
loss of social bonds).

Have I learned anything about how IQ will change in the future? I
certainly have a deeper understanding of why it\'s hard to predict.

Our affluence has given many of us the luxury to return somewhat to a
more forager-like culture, to which we\'re more adapted.

But I still see a bit of pressure toward the kind of abstract thought
and universal rules that have enabled cooperation within large
populations.

An [Age of Em](http://ageofem.com) might dramatically increase the
returns to IQ-oriented cognitive styles, or an AI-run garden of Eden
might enable a larger shift back toward forager cognitive styles.

I\'ll weakly predict a trend of increasing IQ, but with large sectors of
the population that decide to opt out and let their IQ slide.