It's a fact: male and female brains are different

post by araneae · 2010-10-07T20:15:19.107Z · LW · GW · Legacy · 8 comments

Contents

  In Which I Present The Opposing Side's Hypothesis and Falsify It
  A Really Long Argument In Which I Argue That Humans Are Not Bisexual
  Introducing the Magic Random Culture Generator
  How could something so obvious be missed?
  You argue that in most cultures women prefer men, but in most cultures women are also dumb.  
  You argument has a flaw!  And that is...
None
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In Which I Present The Opposing Side's Hypothesis and Falsify It

This post is in part in response to a New Scientist article/book review "Fighting back against neurosexism."  And the tagline is "Are differences between men and women hard-wired in the brain? Two new books argue that there's no solid scientific evidence for this popular notion."  

Full disclosure here: I haven't read the books, although I do have a B.S. in neurobiology. But you don't even need to understand anything about neurobiology to falslify their most basic hypothesis: that male and female brains have no hardwired behavioral differences.  

And it's easy to falsify: if male and female brains were the same, all humans would be completely bisexual.  If it's true that female brains, on average, prefer to fuck, date, and marry men, and male brains, on average, prefer to fuck, date, and marry women, then male and female brains are in fact different.

A Really Long Argument In Which I Argue That Humans Are Not Bisexual

The god of the gaps here, is of course, culture.  One could argue that culture makes people straight.  There are number of arguments against this here, such as some famous cases of failed gender reassignment at birth, all the way to gay people, who despite being raised in straight cultures somehow arise anyway.

Yes, some people are bisexual, and the number who are is certainly informed by culture.  Bisexuality has increased to unprecedented levels. What exactly constitutes bisexuality makes decent surveys difficult, but the most generous figure is 15%, and this includes people who identify as straight, have had no experience of the opposite sex, but have had "some same sex attraction."  The null hypothesis predicts 100% bisexuality, and not only that, it predicts a nature of bisexuality which has no preference for either sex.  In our hypothetical situation of identical male and female brains, if 100% of women would choose a man over a woman only 60% of the time, then women still show a preference for men and our hypothesis is falsified.

But the situation is even more dire than that.  It's so dire that some argue that bisexuality doesn't exist at all.  I would not go so far; while I personally do not know any bisexuals that show no gender preference, and quite a few that do show a preference, I am positive there are some out there that would be incredibly angry with me if I didn't acknowledge them (hi guys!).  The question is, how many are there?  If we want to make an argument that true bisexuality is universal, well, larger is better.

If we look at the actual behavior of humans actively engaged in the mate selection process on OkCupid, it's not promising.  The damning evidence?  80% of self-identified bisexuals only contact one gender.  There could be a lot of reasons for this besides "fake" bisexuality, but if we look at how humans behave in our increasingly sex-positive culture, it's not promising.  

So in modern Western cultures where this has been researched, most female brains like men, and most male brains like women.  It still could be cultural; after all, this is only one culture.  What about ancient Greece? In this culture, rich, well educated, mature men by some accounts frequently had sex with pre-pubescent boys.  They would still marry women, which might make them seem like our platonic bisexual.  But sadly for that idea, the mature, post-puberty men weren't having sex with each other.  They were having sex with boys, with smooth skins, that didn't have beards, or an Adam's apple, who were slender and not muscular, without the influence of the increased sexual differentiation between the sexes that happens at puberty.  And the women weren't also bisexual in large numbers, as far as we are aware.  One unusual culture in which one sex has sex with children of the same sex is not terribly promising for the universality of the human brain.  

But it is possible that a truely bisexual culture hasn't arisen yet.

 

Introducing the Magic Random Culture Generator

Some anthropologists do research under the assumption that we can get a good idea of what human behaviors are "natural" or "innate" by surveying a large sample of cultures.  If something is present in a large number of cultures, then it is more likely to be an intrinsic part of human behavior.  It's not a bad strategy to work with.  

However, some people argue that both different regions of the world as well as a sampling of cultures in history represent a random sample of cultures.  Therefore, if something is in the majority of human cultures, it is innate.  But of course, they are not random, because they are not independant. Cultures devoloped from each other, not in a vaccum.  It's possible that cultures are wildly sensitive to inital conditions; that once the first culture declared that women like men and vice versa, all subsequent cultures had to be that way.  

Sadly, we do not have the ability to apply a truely random sample of cultures to sets of people and see how well they take.  

If we did, we could do this experiment.  We could pick a random cultural sexual preference and apply it to the population.  We could create a society in which all men were supposed to fuck, date, and marry only men, and all women were supposed to fuck, date, and marry only women.  It would be similar to many of the cultures across the globe and in our evolutionary past, but with straightness replaced with gayness.  Would it work (propagation issues aside)?  Do you think we could use culture to make almost all men and women gay?

Unless you can believe in all seriousness that it could happen equally easily as our current situation, well, then no amount of lack of evidence about specific sex differences between the brains of human males and females is going to be very convincing.  

 

How could something so obvious be missed?

A lot of the research on innate sex differences have to do with things that people actually find interesting.  It's not interesting that men prefer women on average for intimate relations; this is obvious.  A lot of the research on innate brain differences is done on things such as intelligence.  And so the person that wrote this article extrapolated to claim that if there isn't enough research showing innate differences is these specific areas- where there's a lot of controversy- then that's the case for all differences, even those differences which are so obvious there isn't research to support them.

While the authors are completely incorrect to say there are no innate differences between female and male brains, they are perfectly within their right to claim that there isn't enough evidence for innate differences in specific areas, such as intelligence. 

(Of course, if you don't like an idea, this is a technique that works for every science- to claim there isn't enough evidence to support it.  It's a time-honored trick, one that "intelligent design" proponents pull on macroevolution all the time, exemplified by this futurama clip at 1:15.  I'm not saying this is what these authors did; only that it's something to be wary of when examining any controversial idea.)

 

You argue that in most cultures women prefer men, but in most cultures women are also dumb.  

In this comic Randall Munroe stated he would have more respect for evolutionary psychology if it didn't keep on producing 1950s gender roles.  The reason it does is because a lot of evolutionary psychologists use that anthropological data we talked about earlier.  Most cultures, especially the "primitive" ones, do have something resembling 1950s gender roles, except with more wives (about 2/3 of cultures are at least partially polygynous). Note that I say in my post that that method of research is fundementally flawed; that obviously, we don't have access to a random sample of cultures.  I think in the case of sexuality it's pretty obvious that cultures didn't randomly come to be this way, but it is possible that a more ancestral environment (i.e. one in which women were constantly pregnant or nursing) is the cause of lower intellectual engagment in those societies, not innate brain differences.  In that case, our modern evironment is an experiment, as women have fewer babies, formula exists, men do more paternal care, etc.  And we are seeing female intelligence matching male intelligence.  The difference in intelligence is innate, in a way, because women innately bear the costs of babies, but not innate brainwise.  

So the leap you must make to challenge my overall argument is, are there other innate differences between men and women, not directly related to brain differentiation, that could be responsible for straightness?  That's one avenue with which to challenge my argument.

Another argument in regards to this section heading is that male and female brains don't different in innate intelligence, but in innate drive.  For instance, if women innately love cute things more than men, and this could lead them to pursue careers in veterinary medicine instead of system administration.  Male and female brains could be equally able to perform such duties, but not equally inclined.  In this case, innate differences in the brain do lead to different skills, just through a different mechanism.  

 

You argument has a flaw!  And that is...

Another possible flaw is how I chose my null hypothesis.  When making null hypothesis, scientists have to choose what they think "randomness" in their system looks like.  What data is produced by the lack of a pattern?  There are actually a large number to choose from, and it depends on the nature of what you're studying.  This could be a flaw in any study, and it's not one that people mention much.  

The one I chose, universal bisexuality, assumes sexuality was a continuous trait, a la the Kinsey Scale.  In my null hypothesis, the mean brain was bisexual, but I didn't mention a distribution.  Usually with continuous traits found in nature, the distribution we assume is normal.  In this case, the average person and the mode person would be perfectly bisexual; there would, of course, still be straight and gay people.  They would just be very, very rare.  

However, if the traits "likes males" and "likes females" are discrete, then you would have a different distribution.  In this case, you would expect 50% of both women and men should be gay and 50% of should be straight. If you used my random culture generator, of course you would get some cultures that encouraged more straight people or more gay people; again, this would asymptotically approach a normal distribution with a large number of cultures.  So the mean and mode cultures would have 50% gay/straight ratio, with very few at the tails encouraging being mostly gay or mostly straight.

If my selection of null hypothesis is wrong, does that invalidate my hypothesis?  Well, yes, if those null hypothesis aren't falsified.  I think that they are.  It's clear that human sexuality does follow some sort of pattern sorting along male and female, even if you considered sexuality a discrete trait.  As long as there is some sort of pattern, there's a difference.  

 

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