Delusions of Gender

by Cordelia Fine

  But in all the excitement of having found a neurological explanation for male inconsiderateness and female underrepresentation in the Faculty of Mental Rotation, people failed to notice that the empirical ground had shifted beneath their feet. And they also forgot to ask a very important question: Why should a localised brain create a spotlight mind good at certain masculine tasks? And why should a global, interconnected brain create a floodlight mind better at feminine activities?29 And this brings us to the second problem with interpreting sex differences in the brain: what do they actually mean for differences in the mind?

  Seeing that the average brain-weight of women is about five ounces less than that of men, on merely anatomical grounds we should be prepared to expect a marked inferiority of intellectual power in the former. Moreover, as the general physique of women is less robust than that of men – and therefore less able to sustain the fatigue of serious or prolonged brain action – we should also on physiological grounds be prepared to entertain a similar anticipation. In actual fact we find that the inferiority displays itself most conspicuously in a comparative absence of originality, and this more especially in the higher levels of intellectual work.

  —George J. Romanes, evolutionary biologist and physiologist (1887)1

  It’s always pleasant when data confirm predictions. But did George Romanes never once consider whether an African Grey parrot (with a brain weight of less than half an ounce) might outsmart a cow with a brain more than thirty times heavier? Did he really know not a single weedy intellectual, nor one muscular chump, to provoke him to wonder whether physical strength really was correlated with tenacity of ‘brain action’? Perhaps it was only natural that the brain scientists who meticulously measured men’s and women’s head dimensions, skull volume and brain weight should try to relate their findings to psychological differences between the sexes. But with the benefit of hindsight we can see that it was not just neuroscientific understanding they lacked, but humility. ‘Optimistic’ is the only kind word to use to describe their confident assertions that differences in the engine power of male and female minds were being probed by tape measures, sacks of millet grain and sets of scales.

  Today, we are no less interested in pinning our more sophisticatedly obtained sex differences in the brain onto the mind. ‘[H]ope springs eternal’, Fausto-Sterling wryly notes. ‘Is it now possible that finally, with really new, really modern approaches, we can demonstrate the biological basis of sexual or racial inequality?’2 And, as neuroendocrinologist Geert De Vries has pointed out, it is intuitive to assume that males and females have different brains so that they can behave differently. With the discovery of differences in hormone receptors, or neuronal density, or corpus callosum size, or different proportions of grey and white matter, or brain region size, the instinct is to look for a psychological difference to pin it on. But the counterintuitive possibility that always needs to be considered is that sex differences in the brain may also ‘just as well do the exact opposite, that is, they may prevent sex differences in overt functions and behavior by compensating for sex differences in physiology.’3 For example, a smaller number of neurons in a particular brain region can be compensated for by greater neurotransmitter production per neuron.4

  One very striking example of the principle that brain difference can yield behavioural similarity, discussed by De Vries, comes from the prairie vole. In this species, males and females contribute equally to parenting (excepting, of course, nursing). In female prairie voles, parenting behaviour is primed by the hormonal changes of pregnancy. But this leaves a mystery. How do father voles, which experience none of these hormonal changes, come to show paternal behaviour? The answer turns out to lie in a part of a region of the brain called the lateral septum, which is involved in the triggering of paternal behaviour. This part of the brain is very different in males and females, being much more richly endowed with receptors for the hormone vasopressin in the male, yet this striking sex difference in the brain enables male and female prairie voles to behave the same. We can’t assume that even quite substantial sex differences in the brain imply sex differences in the mind. As Celia Moore has pointed out, ‘Some neural differences are inconsequential, because they are offset by other compensatory differences. Other neural differences are alternative pathways to the same behavioral end.’5

  In humans, one indisputable physiological difference between males and females is size – including the brain. Although there is overlap, men on average have larger brains than do women, and a large brain is not simply a smaller brain scaled up. Larger brains create different sorts of engineering problems and so – to minimise energy demands, wiring costs and communication times – there are physical reasons for different arrangements in differently sized brains.6 From this perspective, ‘men and women confront similar cognitive challenges using differently sized neural machinery.’7 The brain can get to the same outcome in more than one way. And in line with this, recent studies of brain structure have argued that it is not that women have larger corpora callosa, or a more generous serving of grey matter, relative to brain volume. Rather, it is people with small brains, male or female, who show this quality. As one group put it: ‘brain size matters more than sex.’8 If this principle proves to be correct – there’s currently no agreed way of controlling for absolute brain size – then, unless we’re happy to start comparing the spatial or empathising skills of big-headed men and women with those of their pin-headed counterparts, we may have to abandon the idea that we will find the answers to psychological gender differences in grey matter, white matter, corpus callosum size or any other alleged sex difference in brain structure that turns out to have more to do with size than sex.

  This, one would think, would secretly be a relief. This is not just because those gender differences can wax and wane, depending on the time, place and context. But also the very idea of trying to relate these kinds of structural differences to psychological function is fantastically ambitious, given that, as neuroscientist Jay Giedd and colleagues have put it, ‘most brain functions arise from distributed neural networks and that within any given region lies a daunting complexity of connections, neurotransmitter systems, and synaptic functions’.9

  Yet sometimes the temptation is too much to resist.

  Twenty years ago, my mother proposed a neuroscientific model to explain why some brains have an extraordinary capacity for deeply focused thought. Her hypothesis was that ‘[a]ll the blood in your brain rushes to the really clever bits and there’s none left over to warm up the roots.’10 My mother, by the way, is a novelist. Yet her idea, coined as an acerbic marital insult in a work of fiction, shares an important flaw with a suggestion made in a prestigious journal of science. Simon Baron-Cohen and his colleagues, as mentioned earlier, suggested in Science that a brain skewed towards local connectivity is ‘compatible with strong systemizing, because systemizing involves a narrow attentional focus to local information, in order to understand each part of a system.’11 Likewise, in the recent book Why Aren’t More Women in Science? neuroscientists Ruben and Raquel Gur conjecture that ‘the greater facility of women with interhemispheric communications may attract them to disciplines that require integration rather than detailed scrutiny of narrowly characterised processes.’12

  But why, we might ask, should shorter circuits in the brain allow narrower focus in the mind? As McGill University philosopher of science Ian Gold has said, ‘[m] ay as well say hairier body so fuzzier thinker. Or that human beings are capable of fixing fuses because the brain uses electricity.’13 Consider what’s involved in zooming in your attention on, say, a small aspect of the process of photosynthesis. Does only a little bit of the brain get involved because only a little detail is being processed? Or is there – as seems far more likely – activity all over the brain as distracting information is suppressed, the inner voice formulates ideas and poses questions, visual stimuli are processed, motion is imagined and information is retrieved from memory?14

  In tru
th, if it was the male brain that seemed to be more long-range, we could easily concoct a plausible hypothesis to explain why this enhances their systemising skills. And this is the problem: the obscurity of the relationship between brain structure and psychological function means that just-so stories can be all too easily written and rewritten. Do you find that your male participants are actually less lateralised on a spatial problem? Not to worry! As the contradictory data come in, researchers can draw on both the hypothesis that men are better at mental rotation because they use just one hemisphere, as well as the completely contrary hypothesis that men are better at mental rotation because they use both hemispheres. So flexible is the theoretical arrangement that researchers can even present these opposing hypotheses, quite without embarrassment, within the very same article.15

  Likewise, Gur and his colleagues happily tinker with the longstanding idea that it is males’ more lateralised spatial processing that underlies their superiority on mental rotation tasks. They found that performance on two spatial tasks correlated with the volume of interconnecting white matter in the brain.16 White matter is made up of the axons, insulated for speed of travel of the electrical signal by the white fat myelin, which communicate between distant brain regions. ‘When we looked at the top performers for spatial tasks in our study … there were nine men and only one woman,’ Gur explained for the Science Daily news release. ‘Of these nine men, seven [actually, it was six] had greater white-matter volumes than any of the women in the study.’17 Now, we’re talking about ten people here – hardly a sample size on which to base sweeping generalisations about the sexes. It’s also, as psychologists well know, dangerous to assume that correlation means causation. Further, in the scientific article itself, Gur cautions that the ‘correlations could be spurious and should be interpreted with extreme caution.’18 And they really could be spurious, given that 1 in 20 ‘significant’ results occur by chance, and the researchers tested for thirty-six relationships. Of course, we don’t know who decided that this caveat was not worth mentioning in the report designed for public consumption. But despite all this, Gur goes on to suggest to Science Daily that ‘in order to be a super performer in that area, one needs more white matter than exists in most female brains.’ Following up this line of argument in their chapter in Why Aren’t More Women in Science? the Gurs conjecture that ‘[t]he requirement of large volume of WM [white matter] for complex spatial processing may be an obstacle in some branches of mathematics and physics.’19 This, they suggest, is because men’s greater white matter volumes enable better within-hemisphere processing.

  But meanwhile, back in the functional neuroimaging lab, the Gurs and their colleagues have found that in some regions of the brain men show more bilateral activation than women while performing spatial tasks. They therefore suggest a ‘reformulation’ of the spotlight hypothesis, namely, ‘that optimal performance requires both unilateral activation in primary regions, left for verbal and right for spatial tasks, and bilateral activation in associated regions.’20 Well, maybe they are right to now emphasise the importance of participation from both hemispheres. Interestingly, researchers who study people with exceptional talent in mathematics argue that enhanced interaction between the hemispheres – supposedly a female brain characteristic – is a special feature of the mathematically gifted brain.21 But maybe, just until such a time as we have a somewhat firmer grasp of how the structural properties of the brain relate to complex cognition, the Gurs should stick to the lower-maintenance hypothesis that optimal performance requires whatever features of the brain happen to be observed in males.22

  This kind of theoretical U-turn has always beset the neuroscience of sex differences. For example, in the nineteenth century, when the seat of the intellect was thought to reside in the frontal lobes, careful observation of male and female brains revealed that this region appeared both larger and more complexly structured in males, while the parietal lobes were better developed in women. Yet when scientific thought came to the opinion that it was instead the parietal lobes that furnished powers of abstract intellectual thought, subsequent observations revealed that the parietal lobes were more developed in the male, after all.23 With startling insight, Havelock Ellis, the author of a comprehensive late-nineteenth-century review of sexual science, described these earlier erroneous observations as ‘inevitable’:

  It was firmly believed that the frontal region is the seat of all the highest and most abstract intellectual processes, and if on examining a dozen or two brains an anatomist found himself landed in the conclusion that the frontal region is relatively larger in women, the probability is that he would feel he had reached a conclusion that was absurd. It may, indeed, be said that it is only since it has become known that the frontal region of the brain is of greater relative extent in the ape than it is in Man, and has no special connection with the higher intellectual processes, that it has become possible to recognise the fact that that region is relatively more extensive in women.24

  Of course, there’s nothing wrong with changing your mind in the light of new evidence about the sexes. But those who are tempted to play this game, by claiming that sex differences in the structure of the brain yield essentially different kinds of minds, should be aware that this sort of flipping seems to be a common part of the process. And, with the benefit of hindsight, it never looks good.

  No less care is required when it comes to interpreting differences between the sexes in brain activity. No doubt about it, functional neuroimaging technologies have brought the fresh, modern zing of neuroscience to old stereotypes. Allan and Barbara Pease, for example, purport to demonstrate in their book Why Men Don’t Listen and Women Can’t Read Maps the striking sex differences in the sheer volume of brain devoted to emotion processing. A brain diagram of ‘Emotion in men’ shows two blobs in the right hemisphere. As the text explains, emotion in men is highly compartmentalised, meaning that ‘a man can argue logic and words (left brain) and then switch to spatial solutions (right front brain) without becoming emotional about the issue. It’s as if emotion is in a little room of its own’. But in the illustration of ‘Emotion in women’ there are more than a dozen blobs scattered across both hemispheres of the brain. What this means, according to the Peases, is that ‘women’s emotions can switch on simultaneously with most other brain functions’. Or, to call a spade a spade, emotion can cloud all and any of a woman’s mental activities.25

  These emotion maps of the male and female brain, the Peases inform readers, are based on fMRI research by neuroscientist Sandra Witelson. In order ‘to locate the position of emotion in the brain’, she used ‘emotionally-charged images that were shown first to the right hemisphere via the left eye and ear and then to the left hemisphere via the right eye and ear.’26 Should readers have both the time and the resources to check out the six Witelson references in the book’s bibliography, they will find only two studies published after functional neuroimaging techniques first began to be substantively put to use by cognitive neuroscientists in the 1980s. One study did not involve brain research (it is a survey of handedness in gay men and women). The other is a comparison of corpus callosum size in right- and mixed-handed people.27 It might also be worth mentioning that it was a postmortem study. Possibly Sandra Witelson really did present her samples of dead brain tissue with emotionally charged images – but if she did, it’s not mentioned in the published report.

  It may be that the Peases were referring to functional neuroimaging research published by Sandra Witelson and colleagues in 2004.28 It’s hard to know: this study used PET rather than fMRI; stimuli were presented in the normal two-eyed, two-eared fashion; and the male/female blob tallies and locations are dissimilar to those presented by the Peases. However, this study did at least look at brain activity while men and women performed one of two emotion-matching tasks. The easier task involved deciding which of two faces match the emotion of a third, target, face. The harder task involved deciding which of two faces match the emotion expressed
in a voice. According to Susan Pinker’s summary of Witelson’s results, ‘[w]hen women looked at pictures of people’s facial expressions, both cerebral hemispheres were activated and there was greater activity in the amygdala, the almond-shaped seat of emotion buried deep in the brain. In men, perception of emotion was usually localised in one hemisphere’. Pinker then goes on to suggest that since research also shows that women have a thicker corpus callosum, allowing speedy interhemispheric transmission of information (a claim that, as you will recall from the previous chapter, is under serious scientific dispute), ‘the hardware for women’s processing of emotion seems to take up more space and have a more efficient transportation grid than men’s. Scientists infer that this allows women to process emotion with dispatch.’29

  In fact, the researchers found no differences in how quickly men and women performed the tasks. It’s also worth noting that although the statement ‘both cerebral hemispheres were activated’ in women might conjure up an image much like that presented by the Peases, with activity over a generous portion of the female brain, this is not the case. Rather – and take a deep breath before reading on – in the easy task women showed greater activation than men in left fusiform gyrus, right amygdala and left inferior frontal gyrus. In the hard task they showed greater activity in left thalamus, right fusiform gyrus and left anterior cingulate. Men, meanwhile, showed greater activity than women in right medial frontal gyrus and right superior occipital gyrus for the easy task, and in left inferior frontal gyrus and left inferior parietal gyrus for the hard task. Or, rather less technically, women always had two left blobs and one right blob, while men had either two right blobs or two left blobs, depending on the task – painting a rather less striking image of contrast. (Bear in mind, too, that blobs represent differences in brain activity, not brain activity per se. If a search for regions activated more in men yields a blob-free left hemisphere, for example, that doesn’t mean that that hemisphere is switched off in men. Rather, it means that the researchers didn’t find any regions in the hemisphere that were activated more in men than in women.)30