
Greater male than female variability in regional brain structure (Paper) - vackosar
https://www.biorxiv.org/content/10.1101/2020.02.17.952010v1
======
pubby
Related theory:
[https://en.wikipedia.org/wiki/Variability_hypothesis](https://en.wikipedia.org/wiki/Variability_hypothesis)

I first heard of this when researching chess. Men rank ~200 ELO points higher
than women at chess, which is a fairly significant amount. Men also seem to do
better at several other non-physical competitions like Go, video games, and
Jeopardy. Plus, the history of math and science is dominated by men at the
top.

It seems like men are not smarter on average, but they do peak higher (and
valley lower).

~~~
commandlinefan
> and valley lower

Yeah - there are also a lot more men than women in prison.

~~~
Grustaf
Surely that is more due to testosterone than stupidity.

~~~
belorn
Modern research says no.

There has been a lot of research on this topic. You can not measure the
testosterone in a group and make a prediction about who is going to commit a
crime. If you measure testosterone on criminals, you can't make any prediction
about what kind of crime they did.

There are weak associations such as risk taking (possible facilitated through
increased dopamine transmitters), but there are much stronger links between
criminals. To mention a few: Social economical status, social support
structure, and childhood trauma is much better predictors than high
testosterone.

Hormones are a terrible explanation for crime, even if they often have a weak
association. Did you know that women are much more likely to have committed a
crime during pms? The crime statistics support the link, but ask a researcher
and they will list multiple reason why such correlation make for very weak
association rather than strong evidence of a link between hormones and crime.

~~~
Grustaf
> You can not measure the testosterone in a group and make a prediction about
> who is going to commit a crime.

Well, if the group is mixed, with both men and women, then you can predict
that 95% of the violent crimes will be committed by people with higher
testosterone (i.e. men). Surely in that sense it's about testosterone, not
genitalia?.

That's why it's very surprising to hear that the _level_ of testosterone among
men has no predictive power.

~~~
belorn
Nope, higher testosterone is not an predicting factor for violent crimes. If
you measure a mixed group what you get is the same correlation as you would
get with any other sex trait.

Many research papers has been written on the topic of testosterone and
violence, including meta studies. The general conclusions is... there is a
weak link between testosterone and violence. No cause and effect, but there is
a small amplification of existing behavior, a common finding among endogenous
studies.

The full reason is complex, but a simplification is that testosterone increase
preexisting behavior in relation to social status hierarchy. It makes
individuals spend more energy in defending their place on the ladder (spending
more time looking at faces to recognize threat, increased response to
threatening faces, more suspicion against ambiguous faces). This in turn has a
link towards violence, but only in cultures where status is given as an reward
for violence.

But there is an additional complexity that should be mentioned. A lot of the
effects of hormones such as testosterone only happen as a result of changing
levels of hormones rather than absolute values. The absolute value has less of
a predictive effect then changes over a short time frame.

~~~
lliamander
Interesting. So, my understanding is that most male violence is committed by
males between the ages of 15 and 25 (roughly). That is also generally the
period of highest testosterone levels in men. What would cause the spike in
violence if not the elevated testosterone levels?

I have a couple guesses:

1\. This may be a period in which men experience the greatest status
_uncertainty_ and so may resort to violence in an attempt to solidify their
place in a social hierarchy.

2\. This is generally the age range during which many disorders that are more
prevalent or severe in men (such as schizophrenia, bi-polar, etc.) begin to
manifest.

~~~
belorn
15 to roughly 25 is the period when the frontal cortex is maturing, and also
the period where peer influence has the most impact on development. The
frontal cortex is highly involved in silencing the fear response, and in
determining the socially correct response to threats, particularly threats
towards a person's social position (a common theme for studies around
violence).

1) I have not read any study however that looked at periods of social
uncertainty, but it sounds plausible.

2) My guess would go towards the relation of frontal cortex maturation. Before
fully maturation, other parts of the brain "step in" and handle some of the
frontal cortex' role, but by around age 25 they stop doing that.

~~~
lliamander
> My guess would go towards the relation of frontal cortex maturation. Before
> fully maturation, other parts of the brain "step in" and handle some of the
> frontal cortex' role, but by around age 25 they stop doing that.

So, do you mean that such disorders originate from the frontal cortex, and
that the reason they manifest by 25 or so is because it is at that point that
the frontal cortex is no longer "supported" by other parts of the brain and
it's flaws become apparent? Interesting if so.

------
jmpman
A president of Harvard, Lawrence Summers, was forced to step down after a 2005
speech in which he suggested that the under-representation of women in science
and engineering could be due to a "different availability of aptitude at the
high end".

Could this regional brain structure account for the higher variance in male
intelligence?

~~~
octokatt
May I suggest you read the paper before (re)commenting this trope?

~~~
gizmo686
What part of the paper are you refering to?

The paper assumes a prior of males having greater variance in a diverse set of
traits, and frames itself as exploring the cause of such variance.

It proceeds to empirically study brain structure, and found that "results
confirmed the hypothesis of greater male variability in brain structure.".

Parent's question, while relevent, is much broader than what the paper
attampted to answer. I see no discussion in the paper that would render the
question moot.

~~~
octokatt
Correct. The question OP asked is much broader than what the paper's subject
matter, and does not support evidence for the conjecture.

Instead of asking again "maybe men just outcompete women because they have an
inherent advantage", can we please just not do this. Again.

It's become really disheartening to see this question being asked, because of
a long history of infantilizing women and misusing science to prove it.

Even if we're talking about population-level differences. I'm asking for
empathy here, because every time a gender study comes up, it seems like
someone again needs to ask if women really deserve an equal role at the table,
as historical leaders or scientists, as part of humanity.

~~~
jmpman
“For many traits, males show greater variability than females” - first
sentence in the paper’s abstract.

What “many traits” do you think are being referenced?

I’ve worked with many female engineers who are unquestionably smarter than I
am. I’m married to one. Of course we are talking population-level differences,
and I’m not suggesting that women shouldn’t be included in any table based
upon meritocracy.

That doesn’t negate the fact that a president of Harvard was forced to step
down for having a hypothesis that there could possibly be a gender difference
explained by variance. Now that his hypothesis has a glimmer of possibly being
supported by research, again, it continues to be vilified.

I’m asking for a world where a scientist can freely propose a hypothesis and
not be forced to step down. Anything else is driving the anti-enlightenment.

Lawrence Summers is the Galileo of our time.

~~~
fiihddzfg
1\. Summers is not a neuroscientist. He is an economist, and he is ill
equipped to make any meaningful claims about this.

2\. Proposing a hypothesis is not doing science. Science would involve
actually testing a hypothesis by applying rigorous and reliable methods that
suit the phenomenon being investigated, verifying the validity of results,
interpreting the results and having the results reviewed by peer experts.

3\. Summers’ remarks were merely pulled out of his ass and we’re in no way
informed by any scientific process.

4\. He has crucially undermined the work of countless women working as
scientists at Harvard, and therefore failed in his duties as leader of that
world class institution.

4\. He resigned as a result of a no-confidence vote from the faculty (i.e. all
the smart people who work at Harvard), which underscores how shitty he was at
his job and how dumb his remarks were.

> Lawrence Summers is the Galileo of our time.

5\. lol

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RocketSyntax
Females don't have chromosome Y, they have two chromosome X's.

Therefore they don't get any Y stuff. And a mutation in one chromosome X can
be mitigated by a non-mutation in the other chromosome X.

~~~
prlambert
But they get two different X chromosomes with (hopefully) no correlation
between them. Mutation interactions are complex.

~~~
RocketSyntax
Look into zygosity. Variants are either heterozygous or homozygous. A
heterozygous variant is far less worse than a homozygous variant because the
correct protein can still be produced to a certain extent.

------
lliamander
That is a lot of authors on a paper.

As a layman reading the paper, my understanding is that greater male
variability has already been observed in "personality, coginitive abilities,
and school achievement". The question here whether and to what extent that
variability is due to "early life genetic or gene-environment interaction
mechanisms". The implication of this paper seems to be that since pervasive
brain-structure differences in variability can be observed throughout the
lifespan of individuals, the variability in high-level traits are likely to
have strong genetic component.

The introduction in the paper focuses on the "downside" of high-variability in
males (their propensity for neurological disorders). Unless I've missed it,
any "upside" to high-variability was left unstated.

~~~
lunias
Intuitively to me (I'm a layman as well) it seems that this male variability
stems from increased competition amongst males. Historically, but certainly
not necessarily, men have played the active role in society while women have
been much more passive. It makes sense to me that without constant new
stimuli, women have settled into a "best fit" position; while men are still
rolling the dice (so to speak) looking for a big win.

~~~
Pyxl101
Point of consideration: supremely fit men in history (in a Darwinian sense)
could have hundreds or thousands of children. Big wins can have big genetic
payoffs. Supposedly Genghis Khan has millions of living descendants today,
with perhaps as many as 1 in 200 men being direct descendants [1]. Supremely
fit women can only have a limited number of children. This difference likely
has some kind of effect on reproductive strategies, and what kinds of
variation are selected for.

[1] [https://www.discovermagazine.com/the-
sciences/1-in-200-men-d...](https://www.discovermagazine.com/the-
sciences/1-in-200-men-direct-descendants-of-genghis-khan)

------
DaniFong
measure this versus age in different cultures and we'll _finally_ have some
evidence on nurture versus nature.

it's nurture + nature + serious amounts of work that makes extraordinary
levels of talent; you can't get away with anything less.

imho, schools and the popular culture cause brain damage, so who knows what
the actual situation is.

I know the article doesn't do this specifically, but since people _will_ and
_do_ cite results like these as prescriptive facts which guide the people are
waaay too complex and adaptable for helping us guide our lives.

also interesting: explore similarities in background between structural brain
outliers.

~~~
rajansaini
Out of curiosity, what about schools and the popular culture do you think
cause brain damage? What would your idea of an ideal education be?

~~~
marto1
Not OP, but how about we start from far away and not assume education is
necessary.

There is a strong correlation throughout human history between a discipline
not being taken seriously and the same discipline growing by leaps and bounds.
It is of course usually unintentionally or intentionally covered up by
academics of various sorts. One major example is medicine - most of the
ridiculously useful developments we got come from people experimenting and
discovering without much formal constraints. Leonardo Da Vinci comes from a
"guild of arts and medicine", the discovery of the nicotine patch came from
the scientist almost killing himself with concentrated nicotine, incredible
discoveries from WW1 till the end of WW2.

Just my 2c.

~~~
lliamander
I would say that education is definitely necessary, but it need not take the
shape of putting kids in desks for 6-8 hours a day for 12 years, nor need it
involve a peer-dominated social environment entirely separate from the world
of adults.

~~~
Grustaf
Well, the main purpose of school is to socialise children and prepare them for
spending 8 hours a day behind a desk doing things that they often don't find
very interesting. So schools seem pretty apt preparation for real life.

~~~
lliamander
Socialization is good, but that doesn't mean the way schools provide it is
optimal. A peer-dominated social environment all too often results in a _Lord
of the Flies_ scenario of children playing petty power games. And when the
_only_ interaction with adults is as impersonal authority figures, children
are left unprepared for the world of adult interaction.

Something I've seen actually work really well for socialization is
homeschooling, where children are exposed both to children of a variety of
ages (younger and older) and the interactions with adults are more personable.
They also more often get to see adults interacting with each other as adults.

I suspect there is probably a profound benefit to children who have adult
figures in their own lives (aside from their parents) that they can look up to
as a models of successful behavior - as opposed to merely having pop culture
and other kids to model themselves after.

~~~
Grustaf
Few things in this world are optimal... But homeschooling seems very
suboptimal for socialization purposes, just meeting your family all the time
seems like an extremely bad idea. Or what did you have in mind?

~~~
AnimalMuppet
Most homeschooled children _don 't_ just meet with their own family all the
time.

Say you have the typical dad-works-and-mom-stays-home setup. Mom's got to go
to the grocery store? Kids go, too, and practice their arithmetic in real-
world environments. They also interact with at least the cashier, and probably
a number of other adults.

It's a nice day? They go to the park, and look at wildlife and plants. Along
the way, they interact with a number of other people at the park. And so it
goes. They interact with non-family-members _all over the place_.

But if that's not enough for socialization, well... when we got concerned
about socialization, we grabbed the kids, dragged them into the bathroom, and
beat them up for their lunch money. You know, so that they got socialized the
way that public school kids did.

~~~
lliamander
> But if that's not enough for socialization, well... when we got concerned
> about socialization, we grabbed the kids, dragged them into the bathroom,
> and beat them up for their lunch money. You know, so that they got
> socialized the way that public school kids did.

We just put ours in a drab room with an uncomfortable chair and a video of an
adult droning on for several hours.

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tossAfterUsing
I thought everybody had exactly the same brain structure.

