The ‘extreme male brain’ theory of Asperger’s


To what extent is Asperger’s syndrome an ‘extreme male brain’?

Asperger’s syndrome is a condition on the Autistic spectrum, characterised by above average intelligence, difficulty interpreting non-verbal cues, repetitive behaviours and highly focussed interests. It is a reasonably common syndrome, occurring in more than 1% of the UK’s population, notably being fifteen times more common in men than in women.

Although Hans Asperger himself described the syndrome as ‘an extreme form of male intelligence’, it was Simon Baron Cohan (University of Cambridge), who coined the phrase after his experimentation with testosterone. The theory describes two human capabilities- that of systemising and empathising. Systemising describes the human capacity to analyse and construct problems, and has been linked to mathematical aptitude, while empathising is the ability to be aware of other people’s emotions. Stereotypically, males are inherently more talented at systemising while females are more skilled at empathising. The ‘extreme male’ theory stems from people with Asperger’s syndrome who excel at systemising (through consuming knowledge of niche areas of interest and aptitude in problem solving within mathematics and physics), while struggling to empathise with the feelings of others in a situation- in effect, becoming an ‘extreme male’.

Baron Cohen discovered that women injected with testosterone, before completing the Reading the Mind in the Eyes test (a test in which subjects are given photos of people’s facial expression and asked to determine their emotional state), fared far worse at ascertaining the emotions of the people in the photographs than those that were not injected. This also correlated with the more controversial measure of the 2D:4D ratio – the ratio of a person’s length of index (2D) and their fourth fingers(4D). Generally speaking, women have a lower ratio – signifying more even lengths of the fingers – when compared with men, who tend to have longer fourth fingers. Many researchers believe this to be linked to the levels of testosterone in the womb, as the relative finger length is determined by 14 weeks of gestation.  

Recently, researchers have taken this further, discovering that females that had been exposed to an abnormally high amount of testosterone in the womb (due to a genetic disorder), were more inclined to enjoy more male-typical toys, such as building blocks. Furthermore, it was discovered that the quality of relationships with peers, and the ability of a child to empathise was decreased as the level of fetal testosterone increased. Finally, over 200 women who had amniocentesis (the testing of amniotic fluid during pregnancy) completed a survey as to their child’s social, language and repetitive behaviour characteristics. An increased level of testosterone here also correlated to Autism Spectrum related traits. 

That being said, many articles strive to prove that the opposite is true. Obviously, there are women with Asperger’s syndrome, and research suggests that part of the huge difference between male and female numbers of cases may be linked to women camouflaging their ASD* related difficulties.The general population also links Asperger’s to men – meaning that people may not assume to test a woman with Autistic tendencies. 

A study was carried out to show that while it was true that women with Asperger’s had higher than usual testosterone levels, characteristics such as a larger head circumference and more masculine facial features than a neurotypical individual; the opposite was true in men. The men in this study were assessed to have less masculine voice quality and body characteristics than a neurotypical male.Therefore, perhaps it should be said that Asperger’s is a gender defiant syndrome, rather than a characteristically masculine one. Furthermore, it could be deducted that according to the ‘extreme male’ hypothesis, the number of transgender men (female to male) should be higher than transgender women (male to female), whereas in reality, there are significantly more transgender women with Autistic tendencies.

In recent years, researchers have commenced with the exploration of a link between a different hormone and ASD. Oxytocin is best known for its role in lactation, but links between it and the brain are being explored. It is now implicated in a variety of non-social behaviours (eg. learning and anxiety), as well as social ones (eg. attachment and aggression), connecting it  to syndromes such as Autism and schizophrenia. In fact, a study has proven that a nasal spray of oxytocin improves recognition of emotion in Autistic individuals. In addition, oxytocin levels are found to be significantly higher in neurotypical females than males, and has been described as a potential ‘mediator of sex hormones’. This could lead to the conclusion that the ‘extreme male brain’ theory is more correct- the greater female oxytocin levels offset any unusual sex hormone imbalances, explaining why far fewer females are diagnosed than males. Also, ASD male levels of oxytocin are far lower than neurotypical males. Subsequently, expression of testosterone is higher in those with ASD.

The ‘extreme male’ theory of Asperger’s has been criticised as an oversimplification of an organ as complex as the brain, and playing up to outdated stereotypes. However, both the testosterone and oxytocin evidence leans to the theory being more correct than was originally perceived. One can therefore conclude that it is fairly accurate, especially when describing the syndrome in layman’s terms. More research will have to be carried out and it is evident that Asperger’s stems from a combination of factors, both genetic and environmental (eg. conditions of the womb), that affect the accuracy of the term ‘extreme male’ to varying degrees.

*Autism Spectrum Disorder


  1. National Autistic Society (2018) “What is Autism?”
  2.  Ian Community (2010) “The “Extreme Male Brain”
  3. National Autistic Society (2019) “Gender and autism”
  4. Autism Research Centre (2017) “Research Project: Systemizing”
  5. Science Mag (2019), “Study challenges idea that autism is caused by an overly masculine brain”
  6. NCBI (2009) “Fetal testosterone predicts sexually differentiated play types”
  7. NCBI (2016) “Fetal testosterone and empathy”
  8.  Psychology Today (2014) “The X Factor Explains Androgyny in Male Asperger’s”
  9. NCBI (2009) “Oxytocin: the great facilitator of life”
  10.  NCBI (2009) “Intranasal oxytocin improves emotion recognition for people with Asperger’s”
  11.  Clinical Practise (2018) “Sex-Related Differences in Plasma Oxytocin Levels in Humans.”

A helpful link for Internet Safety for those with ASD: Internet Safety Guide


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