Bigger brains are smarter, but not by much | Hacker News Reader

Bigger brains are smarter, but not by much

medicalxpress.com

61 pointsdnetesn31 comments

> 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?

Apparently this seems to be popular topic among academics and general consensus is small but significant correlation as per this Wikipedia article:

https://en.m.wikipedia.org/wiki/Height_and_intelligence

We already know good nutrition makes you taller and smarter. I thought this was basically settled, hence the implicit knowledge of the researchers of the height/intelligence link and not much discussion about it.

Could height be correlated with better nutrition, which itself could be correlated with better mental development?

Whether tall people are considered more attractive will almost certainly depend on local culture, and fashion, but I think I read about a study showing that in one particular European city taller women tended to marry someone from a higher social class.

However you define "social class", you'll probably find higher social class is associated with higher intelligence, however you define "intelligence".

There are loads of research papers on "height" and "social class", though perhaps they are mostly concerned with nutrition rather than genetics.

Height and intelligence are only correlated in the general population, not within families. The current hypothesis is there is not a direct genetic connection, but it is due to assortive mating.

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

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

I'm surprised by his, too. All intelligent people I've ever met are average or below average in height.

Nobel prize winners seem to be average in height.

Sounds like confirmation biased anecdata.

ALL, really?

> Interesting. I couldn’t initially think of any plausible explanation for why height would cause intelligence.

Science is no longer interested in explanations, correlation is enough to assume causal "contribution."

I honestly think that taller people could be smarter simply because they're more often looking down at the person they're asking for an explanation from. It's a lot easier to ignore or brush off someone who is looking up at you.

edit: I also had a little sister (14 years younger) who was very tall as a child, although by adulthood she fell back closer to the norm (she's only about 5'10" now.) It was amusing to our family how carefully strangers explained concepts to her that were well beyond her age level to understand; because her height made her look older, it also made her look stupid for her age, and invited special attention from people who didn't realize how young she was. We use height as a proxy for age, and put pressure on taller people to be smarter earlier.

> Science is no longer interested in explanations, correlation is enough to assume causal "contribution."

Cite? Some journalism about science, perhaps, but your brush is broad enough to be absurd at best.

Science has a significant reproducibility problem.

Maybe it's a bit much to say it's no longer interested in explanations, but there's a lot of bad science being published.

> 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?

> 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 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.

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.

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.

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

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

We need to widen the vagina

Grow babies in large jars, remove all cranial size limits.

This actually happened to my wife. Our daughters head was too big to fit through the birth canal and when she came out (c-section) her head was in the 90th percentile for size.

Looks like we can circumvent that bottleneck with modern medicine but then we run the risk of introducing new problems (faulty immune systems and risk to the mother for example)

Yes, large brains are obviously very important.

The article says the maximum difference is 100 cm³ while the largest brains are about 1500 cm³, so on average 7% larger means 2% smarter.

But I think a couple of things come into play - one is that our genes might be optimised for a certain size and it's not simple to scale, but requires reprogramming. At least in some species, larger brains just means larger neurons, not more of them.

> We evolved to have big brains

Neanderthals had the bigger brain, (1600 cm³ vs 1300 cm³ according to wikipedia) and we still extincted them so it doesn't appear to be an ultimate evolutionary advantage.

Well not completely we didn't. Many of us still carry Neanderthal DNA.

But not the genes coding for big brain, so these were not resulting in a significant advantage in the vehicle to ensure their own longevity.

"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.

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.

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

> 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?

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.

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