Philosophy, Film, Politics, Etc.

Thursday, September 25, 2014

Sexism, Gender and Neuroscience

A recent Guardian article by Robin McKie attempts to undermine an allegedly sexist tendency plaguing the field of neuroscience.  I have no idea how widely or deeply sexism flows through the annals of neuroscientific research, but I'm willing to assume it's pretty wide and pretty deep.  That's not a jab at neuroscience per se.  There's compelling evidence that sexism is virtually everywhere, so why not neuroscience?

The alleged manifestation of sexism in McKie's sights is the idea that there is such a thing as a genetically determined male or female brain.  McKie's thesis is this:  Men and women think and act differently because they have been raised to think and act differently, and not because they are genetically predisposed to think and act differently.  She accuses the field of neuroscience of engaging in a cover-up: Intentionally or not, neuroscientists have been misleading us about the real causes of gender difference:  The culprit is cultural bias, not biological determinism.

Most biologists will tell you that nature and nurture go hand in hand.  All behaviours and cognitive capacities should be considered the result of both environmental factors and genetic predispositions. You would be very hard-pressed to find a neuroscientist who denied that cultural factors played any role at all in neurological development.  The question is, how much of a role does culture play?  Are there some behaviours or capacities which women or men are genetically more likely to express?

McKie's answer is clear:  There are no cognitive capacities or behaviors which men or women are genetically more likely to express.  (Obviously she's not including things like ovulation or breast-feeding.  She's talking about behaviors which are not forced or limited by our reproductive organs.)

McKie's thesis is politically attractive:  It can seem like a useful weapon to wage in the war against sexism.  However, it is not supported by the science and it runs counter to common sense.  Common sense tells us that men and women have all sorts of genetically determined differences, so why shouldn't we think there are important neurological differences as well?  It would be more than a little surprising if it turned out that of all the genetically gendered parts of our bodies, our brains were not one of them.

McKie makes two mistakes which are worth highlighting.  The first is that she falls for the line-drawing fallacy. She approvingly quotes Professor Dorothy Bishop, of Oxford University:

"They talk as if there is a typical male and a typical female brain – they even provide a diagram – but they ignore the fact that there is a great deal of variation within the sexes in terms of brain structure. You simply cannot say there is a male brain and a female brain."
Consider an analogy:  There is no such thing as a typical hurricane or a typical tropical storm.  There is a great deal of variation within hurricanes and tropical storms, in terms of wind speed, precipitation and threats to various ecosystems.  Therefore, you simply cannot say there is a hurricane and a tropical storm.

The fact that there is variation within groups, or even that there is not always a clear, dividing line between them, does not mean that there is no sense in recognizing the groups at all.  Vagueness is not always hopeless.  While Professor Bishop is surely right about the variety within male and female brains, we should not jump to the conclusion that these categories are useless--especially since there is scientific research which indicates significant differences between them.

Perhaps McKie has a point, however:  Perhaps neuroscientists are jumping to conclusions about male and female brains.  What scientific evidence is McKie discussing?  This takes us to her second error.  She is discussing a new study by a team led by Professor Ragini Verma:
Verma's results showed that the neuronal connectivity differences between the sexes increased with the age of her subjects. Such a finding is entirely consistent with the idea that cultural factors are driving changes in the brain's wiring. The longer we live, the more our intellectual biases are exaggerated and intensified by our culture, with cumulative effects on our neurons. In other words, the intellectual differences we observe between the sexes are not the result of different genetic birthrights but are a consequence of what we expect a boy or a girl to be.
There are three points to consider here.  First, the fact that a finding is consistent with McKie's view does not mean it entails her view.  There may be an entirely genetic reason why neuronal connectivity differences between the sexes increase during development.  In fact, developmental differences between genders is very often the result of delayed gene-expression.  Just as puberty is genetically determined to occur at a particular time in life, so too may neuronal differences be genetically determined to kick in at various stages of development.

Second, McKie has given a somewhat misleading presentation of the results of Verma's study.  Verma's conclusion is about key stages in neurological development, not about how the brain changes "the longer we live."  Unsurprisingly, most of the differences that Verma's team have observed appear during puberty. Verma's conclusion is that this research suggests a biologically optimized gender difference in neuroanatomical development.  That appears to be a valid conclusion.

The third point to consider is that McKie is promoting a false dilemma.  Even if we say that cultural factors lead to a greater divergence between male and female brains, there may be a genetic explanation for that.  It's not necessarily EITHER genes OR culture.  It could be genes AND culture.  It may be that men and women are genetically disposed to have brains which are different, and these differences are statistically likely to produce cultural institutions which reinforce those differences, leading to an even greater divergence between male and female neuroanatomy.  Alternately, it may be that genes are not ultimately responsible for many of the observed differences between male and female brains, but they still may be responsible for some, or even most, of them.

McKie ends by giving us a scientific basis for questioning Professor Verma's findings.  That is in the spirit of good science, but what conclusions should we draw?

The lesson I take from this situation is not that men will be men and women will be women.  Rather, it is that we don't yet know what men will be, or why, or what women will be, or why.  Not knowing is liberating.  It means nobody can tell women what they will be, and nobody can tell men what they will be.  We can enjoy not knowing, and we can stop pretending like we have more answers than we really do.

Update:  It's also worth pointing out that we should look out for the naturalistic fallacy here.  The fact that we are genetically determined to be a certain way doesn't mean we should be that way.  We can (and often do) resist genetically determined differences if we don't like them.