NEUROBIOLOGY

The brain, caught between science and ideology

Catherine Vidal, neurobiologist and Research Director at the Institut Pasteur (FR), does not limit her activities to her fundamental work, in particular on pain, memory and neurodegenerative ailments. This brain specialist also devotes her time to popularising science and to the relations between science and society.

Catherine Vidal – “As it develops, the brain integrates outside elements associated with its owner’s personal history.” © CNRS
Catherine Vidal – “As it develops, the brain integrates outside elements associated with its owner’s personal history.” © CNRS
©Shutterstock
©Shutterstock

Let’s start with a very direct question: is the brain sexed?

The scientific answer is, paradoxically, yes and no. Yes, because the brain controls the reproductive functions. Male and female brains are not identical, in every species, including our own, because sexual reproduction involves different hormone systems and sexual behaviours, which are controlled by the brain.

But the answer is also no, because when we look at the cognitive functions, it is cerebral diversity which reigns, independently of gender. For thought to emerge, the brain needs to be stimulated by its environment. At birth, just 10 % of our 100 billion neurons are inter-connected. The 90 % of remaining connections will be constructed progressively depending on the influence of the family, education, culture and society. In this way, during its development, the brain integrates external elements associated with its owner’s personal history. We call this cerebral plasticity; which is why we all have different brains. And the differences between individuals of one and the same gender are so great as to outweigh any differences between the genders.

In fact, behind your question is the fundamental problem of the degree to which behaviour is innate and to which it is acquired – an essential question that philosophers and scientists have been debating for centuries. This remains an ideologically-charged subject, which the media adore.

Absolutely. The media often echo works that argue that cerebral specialisation differs between male and female. They say, for example, that language functions are undertaken by both hemispheres only in women’s brains. What do you say?

The theories on the hemispheric differences between the sexes in language appeared over thirty years ago. They have not been confirmed by recent brain imaging studies which allow us to see the living brain at work. These theories are often based on observations carried out on very small samples – often a dozen people. People continue to quote these studies whereas contemporary scientific reality is very different. Meta-analyses, which draw conclusions from all the experiments published in scientific literature and cover several hundred men and women, show that there is no statistically signi ficant difference between the sexes in the hemis pheric distribution of language zones. This is explained by the fact that the location of these language zones differs considerably from one individual to the next, with this variability being more important than a possible variability between the sexes.

Another proposed idea is that the male brain is more suited to abstract reasoning, in particular mathematics.

These conceptions have no biological foundation. This is illustrated by two major studies that were published last year in Science. A first investigation took place in 1990 in the United States, involving a sample of 10 million pupils. Statistically speaking, boys did better than girls in maths tests. Certain people interpreted this as a sign of the inaptitude of the female brain in this field. The same study, commissioned in 2008 (1), this time shows girls scoring as well as boys. It’s hard to imagine that in less than two decades there has been a genetic mutation to increase their aptitude in maths! These results are due simply to the development of the teaching of science and the growing gender mix of scientific fields. Another study (2) carried out in 2008 on 300 000 adolescents, in 40 countries, has shown that the more the socio-cultural environment is favourable to male-female equality, the better the girls score in maths tests. In Norway and Sweden, the results are comparable. In Iceland the girls beat the boys, while the boys outperform the girls in Turkey and Korea.

One argument that is frequently advanced to explain unequal performances in maths is that men succeed better in three-dimensional geometric-type tasks. What is this idea based on?

Experimental psychology does indeed show that men often perform better on tests on the mental representation of three-dimensional objects. But one forgets to mention the influence of the context in which these performance differences take place. If, before carrying out this test in a classroom, pupils are told that this is a geometry exercise, the boys will generally get better results. But if the same group is told that this is a drawing test, the girls will perform as well as the boys. These experiments clearly show that self-esteem and the internalisation of gender stereotypes play a decisive role in the scores obtained in this type of test.

In the end, what are the challenges for research on the differences between men’s and women’s brains?

It is fascinating to look for the origins of these differences beyond the simple description of them. These origins are to be found in biology, but in particular in history, culture and society. One major advance of neurobiological research has been a revaluation of the extraordinary plastic capacity of the brain. It is not justifiable to invoke biological differences between the sexes to justify the different distribution between men and women in society.

But this ‘biologising’ vision continues to satisfy people as providing a sort of scientific justification for the existence of manifest inequalities. In this way people use the theory of evolution to explain that men find their bearings better in space because, in prehistoric times, they went hunting mammoths while the women remained in the cave looking after the children. This scenario is totally speculative – no one was there to see whether it really happened like that. Any prehistory specialists will tell you that no document – fossils, cave paintings, graves, or the like – reveals any details of the kind on the social organisation and division of labour among our ancestors.

How do you explain the renewed interest in these questions over the past 20 or so years?

First of all by the fact that these studies are easily taken up by the media – an aspect to which the publi shers of scientific journals, including the most prestigious, are unfortunately sensitive. Second, by the development of cerebral imaging technologies which initially gave new life to the old theories on the inequality between men and women explained by the differences in their brains. But the more cerebral imagery progresses the more we observe, as I said, the major role of the plasticity of the brain and the variability of its functioning from one individual to another, independent of gender.

I find it regrettable that studies of doubtful scientific value continue to be so widely echoed. But other things are there to make me optimistic. The fact that the 2008 Nobel Prize in physiology and medicine rewarding the discovery of the AIDS virus was awarded jointly to Luc Montagnier and his main female collaborator, Françoise Barré-Sionoussi shows that mentalities are changing. Formerly only the head of the laboratory was rewarded… Think back here to Rosalind Franklin, the British biophysicist who played a key role in elucidating the double-helix structure of DNA and whose work was taken over by James Watson and Francis Crick, the winners of the Nobel Prize in physiology and medicine in 1962. We are seeing a real awareness of women’s role in research. But this evolution is slow. And belief in change is, alas, stronger than change itself…


Interview by Mikhaïl Stein

  1. C.Guiso et al., Culture, Gender and Math, Science (2008), 320: 1164-1165.
  2. J.S. Hude et al., Gender Similarities Characterize Math Performance, Science (2008), 321 : 494-495.

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Find out more

    Selected publications by Catherine Vidal
  • Sexe et pouvoir, with Dorothée Benoit-Browaeys, Paris, Belin, 2005. Translated into Italian, Japanese and Portuguese.

  • Féminin/Masculin: mythes et idéologie, Paris, Belin, 2006.

  • Hommes, femmes: avons-nous le même cerveau?, Paris, Le Pommier, 2007.

  • Cerveau, sexe et liberté, DVD Gallimard/ CNRS, col. «La recherche nous est contée», Paris, 2007.