Bad news: Your husband’s brain is bigger than yours. Good news: it DEFINITELY doesn’t mean he’s cleverer
Professor David Dexter peels the lid off a white plastic container to reveal a fresh human brain. Professor Dexter runs the Parkinson’s UK Tissue Bank in London, where the charity’s scientists study people’s donated organs in its quest to cure the disease.
‘We do play a guessing game about the donor’s gender,’ he says, with a spark of dark humour. ‘Generally, female brains are smaller,’ he adds with a twinkle, at which point his colleague, Kirsten Goldring, interjects: ‘He means “more compact and better organised”.’
Joking apart, most people are convinced men’s and women’s brains are very different organs. After all, we are surrounded by ‘Men are from Mars and Women are from Venus’ pop psychology about our roles and instincts.
Anyone who has been around small children knows girls tend to like dolls, and boys toy guns; their preferences dictated by the organ between their ears. They may not be colourcoded pink or blue but most people assume men and women’s brains are as distinctive as their choice of underwear.
Well, apparently not. It is that sort of thinking that dropped the London science Museum into a row about whether our brains can actually be categorised as ‘male’ or ‘female’.
earlier this month, scientists lambasted the museum over its ‘sex-o-meter’ exhibit; a game claiming to reveal whether your brain is male or female after a series of tests involving logic and spatial awareness. Answers determine whether an arrow points to a blue or pink section.
The test claims that men can see things better in three dimensions and are more able to imagine how things rotate, while women’s brains have better visual memories and can distinguish more easily between subtle details.
However, Dr Joseph Devlin, the head of experimental psychology at University College London, said last week that he was ‘surprised’ at the exhibit: ‘Claiming that there are “male” or “female” brains is disingenuous and grossly oversimplifies a complex topic.’
The museum now acknowledges that some of the scientific research used in the display is more than a decade old, and is planning an update in the coming months ‘to reflect the latest scientific evidence’. Getting away from the idea that our brains are either pink or blue will not be easy, however, because scientists across the globe are discovering ever greater complexities in the nature of our brains, along with astounding levels of similarities between the sexes. so, is there really such thing as a male or female brain?
WHY SIZE DOESN’T MATTER
OVER the past two centuries, many scientists argued that as men’s brains are bigger they must be more powerful. new research confirms men’s brains are about 10 per cent bigger but it is simplistic to assume a direct link between size and intelligence.
A study last october found no significant relationship between brain size and performance in IQ tests. The quality of the connections between brain cells is the important factor in how bright someone is, says psychologist Dr Jakob Pietschnig, of the University of Vienna: ‘Brain structure and integrity appear to be more important as a biological foundation of IQ.’
LITTLE PINK, BLUE AND GREY CELLS
InsTeAD of having a brain full of ‘all-male’ or ‘all-female’ components, some experts argue that our heads contain a ‘mosaic’ of regions that may be a jumble of male and female characteristics as unique as a fingerprint.
Last november a team led by Professor Daphna Joel, a behavioural neuroscientist at Tel Aviv University, studied brain scans of more than 1,400 people. she measured grey matter (sometimes called ‘thinking matter’) and white matter (nerve fibres that transmit signals) in 116 parts of the brain to find out which areas had the biggest sex differences. These areas were scored as more characteristically female, male or somewhere in between.
They reported, in the Proceedings of the national Academy of sciences, that about five per cent of the brains studied were consistently a single sex. Most had a mix of features that varied widely from person to person.
The team found some structural differences between men and women. for example, the left hippocampus, an area of the brain associated with memory, was usually larger in men.
However, there was significant overlap; some women had a larger or more male left hippocampus, while some men’s was smaller than the average woman’s. ‘Human brains do not belong to one of two distinct categories,’ she argues.
BRING ON THE BRAIN TEASERS
oTHer scientists vehemently disagree, however. Dr Adam Chekroud, a British psychologist at Yale University, subjected Professor Joel’s results to computer analysis and claimed he could predict with 95 per cent accuracy whether the brains were from women or men.
Professor Joel said that Dr Chekroud included head-size measurements in his analysis and that removing them dropped his accuracy to 65 per cent — which is not much better than guessing. Professor Marek Glezerman, the president of the International society for Gender Medicine, is another critic: ‘functionally, the brains of women and men are indeed different. not better, not worse, neither more nor less sophisticated, just different.’ Glezerman, author of new book, Gender Medicine: The Groundbreaking new science of Gender- and sex-related Diagnosis and Treatment, says that even the cells in our brain differ by sex because they have different chromosomes, the structures that contain our DnA. He adds that men and women differ widely in the nature of the illnesses they suffer, such as heart attacks and strokes, and argues: ‘Most of the functional differences of our bodily systems are controlled by our functionally different brains and yes, there is a female and a male brain.’ If Men’s and women’s brains do have inbuilt design differences, then we must surely be born with them and their structures will be like that for life. right?
no. new research by scientists studying people undergoing sexchanges shows brains can change their ‘sex-typical’ characteristics depending on the hormones they are exposed to.
for example, when spanish psychologists scanned the brains of 15 women and 14 men undergoing hormonal therapy to change their genders, they found that testosterone and oestrogen had opposite effects on brain structure.
Dr Leire Zubiaurre-elorza, a psychiatrist at Barcelona University, says that when women changing into men are given testosterone, the thickness of a brain area called the cerebral cortex, responsible for intelligence, language and memory, tends to increase.
she says that when men changing into women are given oestrogen, their cortexes often become thinner.
The relationship between thickness (thicker cortexes are typically seen in men, thinner in women) and intelligence is not fully understood. However, as individuals, men and women have very widely differing levels of testosterone and oestrogen.
These hormone levels change significantly during our lives. Men’s testosterone wanes after their 30s.
Women’s oestrogen plummets after the menopause but their ovaries continue to secrete such male hormones as testosterone.
Likewise our cortexes are also known to change thickness over time. In effect, our brains are not necessarily ‘gender-stable’ throughout our lives.
BATHED IN A SOUP OF HORMONES
MIND-BOGGLING QUESTIONS
If Men and women’s brains are so similar then, how is it that they can show such differing personality traits?
The answer, says simon Baron-Cohen, a leading British expert in this field, and a professor of developmental psychopathology at Cambridge University, is that very often they don’t.
‘There is no such thing as a “male” brain or a “female” brain in cognitive terms,’ he says.
‘In some tests, more males score in one way and more females score in another, but there are always overlaps.’
‘one cannot infer anything about what kind of mind or brain type a person will have from their sex, since an individual may be typical or atypical for their gender.’
rather than being born with brains stamped ‘male’ or ‘female’, he says they are shaped by a hugely complex interreaction between the genes and sex hormones that we inherit and develop, and the social experiences we have in our early and later lives.
‘Institutions such as the science Museum have a duty to explain this science in a nuanced and cautious way,’ he says.
It sounds like the institution’s pink-and-blue brain-testing machine may be headed for a museum of outdated science gimmicks.