
Bigger brains are smarter, but not by much - dnetesn
https://medicalxpress.com/news/2018-11-bigger-brains-smarter.html
======
baddox
> Yet the connection has remained hazy and fraught, with many studies failing
> to account for confounding variables, such as height and socioeconomic
> status.

> Height is correlated with higher better cognitive performance, for example,
> but also with bigger brain size, so their study attempted to zero in on the
> contribution of brain size by itself.

Interesting. I couldn’t initially think of any plausible explanation for why
height would _cause_ intelligence. Perhaps taller people on average are
considered more attractive or given higher social status, which could provide
developmental advantages. Or perhaps there is another confounding variable
here, like health/nutrition or nationality.

I can’t seem to find any studies on height and intelligence. Anyone have any
ideas or links?

~~~
enkid
Being taller may mean they had better nutrition as a child. Which I imagine
would also lead to increased intelligence.

~~~
toasterlovin
This would only apply in certain contexts. Height is 80% genetic in the
developed world.

------
baddox
> Their analyses also systematically controlled for sex, age, height,
> socioeconomic status, and population structure, measured using the
> participant's genetics.

I’m a woefully unqualified armchair researcher/statistician, but I always
enjoy speculating on potential confounding variables that _weren’t_ controlled
for.

As the article mentions, there is an obvious naive candidate explanation for
why people with larger brains would be smarter (more computing hardware). But
I find it fun to guess at reasons there might _not_ be a causal relationship.

It’s nice to see the researcher doing the same exercise:

> "However, things could be much more complex in reality. For example,
> consider the possibility that a bigger brain, which is highly heritable, is
> associated with being a better parent. In this case, the association between
> a bigger brain and test performance may simply reflect the influence of
> parenting on cognition. We won't be able to get to the bottom of this
> without more research."

I wonder what exactly is meant there. Is he speculating that a larger brain
directly provides better parenting ability? Or that perhaps generations ago a
family with a useless gene that causes large brains also happened to have
another unrelated gene that gave them better parenting abilities, and thus
both genes ended up being reproduced a lot? How would you even control for
this? Maybe adopted children?

~~~
smoll
> I wonder what exactly is meant there. Is he speculating that a larger brain
> directly provides better parenting ability? Or that perhaps generations ago
> a family with a useless gene that causes large brains also happened to have
> another unrelated gene that gave them better parenting abilities, and thus
> both genes ended up being reproduced a lot?

My guess is something closer to the former, that the two sets of genes are
linked
[https://en.m.wikipedia.org/wiki/Genetic_linkage](https://en.m.wikipedia.org/wiki/Genetic_linkage)
and there’s a direct causal relationship between the two. Therefore, it’s
actually the “better parental ability” trait is the one that produces the
positive result and not the “bigger brain” trait. So yes, adopted children
could help falsify this hypothesis.

------
krzat
We evolved to have big brains so it must be important. I don't think 2%
improvement would be worth extra energy needed for bigger brain.

~~~
waterhouse
From what I've heard, we've run into the (semi-literal) bottleneck of infants
having heads that just barely, or that don't, fit through a birth canal.

~~~
paavoova
If infants can develop brain mass in the womb, why can't they once born?

~~~
TomMarius
Brain actually does develop until you're adult, but bones need to calcify and
that limits how much it can grow

------
xenadu02
"The authors underscore that the overarching correlation between brain volume
and "braininess" was a weak one; no one should be measuring job candidates'
head sizes during the hiring process, Nave jokes. Indeed, what stands out from
the analysis is how little brain volume seems to explain. Factors such as
parenting style, education, nutrition, stress, and others are likely major
contributors that were not specifically tested in the study"

The tl;dr is their research found that 2% of cognitive differences can be
attributed to brain volume, indicating intelligence is influenced primarily by
other factors.

They also found that though male and female brains differed in size that
didn't produce a statistically significant difference in outcomes, but the
study didn't tackle this specific issue so they couldn't say much else
definitive about it (the cortex construction speculation notwithstanding).

I applaud them for pre-publishing their methodology and their commitment to
publish regardless of the results.

~~~
mdorazio
I've read previously that it's not absolute brain size that matters, but
rather brain size relative to body size, hence the lack of difference in
intelligence between genders. This makes sense as well since we don't see
hyper intelligent whales or elephants building space ships.

~~~
vkou
Does this explain why short, skinny people are smarter then overweight, tall
people? /s

------
bryananderson
> They pre-registered the study, meaning they published their methods and
> committed to publishing ahead of time so they couldn't simply bury the
> results if the findings appeared to be insignificant.

Am I crazy for thinking that this should be mandatory for all peer-reviewed
research?

------
Lerc
Once upon a time I had half an idea to leaverage this fact for a story
involving genetically engineered pygmy marmosets. They were modified to have
human brain structure but retaining their size. Ideal crew for space missions.
Fast forward to a time when they dominate space and seek independence.

