Testosterone does not reduce capacity to read emotions, a trait impaired in people with autism: Study
The results of the new study challenge the notion of autism as reflecting an ‘extreme male brain’; in the largest study of its kind, researchers found no evidence that testosterone administration affected performance on tests of cognitive empathy.
Testosterone does not reduce cognitive empathy - the capacity to read the emotions of others, a trait that is characteristically impaired in people with autism, according to a new study. The findings challenge the controversial theory that characterizes autism as the result of an “extreme male brain.”
It has long been known that autism is far more prevalent in males than in females, the reason behind which is not well understood. Several studies have suggested a connection between testosterone and decreased cognitive empathy, but the sample size of these studies was very small, and it is tough to determine a direct link, says the research team from the University of Pennsylvania’s Wharton School, who conducted the current study.
The new study - led by Gideon Nave, an assistant professor of marketing in Penn’s Wharton School - involved two randomized controlled studies of testosterone administration, which were the largest of their kind and included over 600 men. The researchers found no evidence of a link with cognitive empathy. The findings have been published in the journal Proceedings of the Royal Society B: Biological Sciences.
“Our results unequivocally show that there is not a linear causal relation between testosterone exposure and cognitive empathy", says Amos Nadler of Western University, the first author of the study.
What is the extreme male brain theory?
There are two long-standing psychological theories: the empathizing-systemizing theory of sex differences and the extreme male brain theory of autism.
The empathizing-systemizing theory predicts that women, on average, will score higher than men on tests of empathy, the ability to recognize what another person is thinking or feeling and to respond to their state of mind with an appropriate emotion. Similarly, it predicts that men, on average, will score higher on tests of systemizing, the drive to analyze or build rule-based systems.
The extreme male brain theory predicts that autistic people, on average, will show a “masculinized shift” on these two dimensions: which implies that they will score lower than the typical population on tests of empathy and will score the same, if not higher than the average population on tests of systemizing. The extreme male brain hypothesis was proposed by Simon Baron-Cohen, director of the Autism Research Centre (ARC) in Cambridge, UK, to explain why boys are four times more likely than girls to be diagnosed with an autism spectrum disorder.
Why the current study?
Before this work, says the research team, the strongest evidence for a link between testosterone exposure and reduced cognitive empathy came in 2011 in a study, which said that giving testosterone to healthy women reduced their performance on a test of reading emotions. The results suggested the testosterone impaired their performance.
“Moreover, the work pointed to the ratio of the length of the participant’s second finger to their fourth finger, known as the 2D:4D ratio, as a proxy for sensitivity to testosterone. Some believe that the ratio declines with increased in utero exposure to testosterone, though evidence for that connection is mixed,” say the researchers.
The authors of the 2011 study had stated that their findings supported the idea that prenatal testosterone exposure created a more “masculinized brain that less readily inferred the emotional state of others.”
“The study was used as support for the extreme male brain hypothesis of autism, which contends that autism is an exaggeration of “male” tendencies toward a cognitive style characterized by systemizing over empathizing", say researchers of the current study.
The 2011 investigation, says the research team, however, relied on a sample size of 16 subjects. “Most other research investigating the idea that testosterone is linked to reduced cognitive empathy had relied on ‘correlative’ rather than ‘causative’ evidence and had also resulted in inconclusive findings,” the team adds.
Accordingly, to get a more rigorous data on the connection, the researchers conducted two randomized controlled studies in which 643 healthy men received an application of testosterone gel or a placebo and completed questionnaires and behavioral tasks that measured cognitive empathy. Participants were then shown a photo of an actor’s eyes and asked to select the emotional state that best described their expression. All participants also had their 2D:4D ratio measured.
While the testosterone gel did increase participants’ levels of the hormone, the researchers found no evidence that testosterone administration affected performance on tests of cognitive empathy. They also found no relationship between participants’ performance on the tests and their 2D:4D ratio.
“The results are plain. However, it is important to note that the absence of evidence is not evidence of absence. We found that there is no evidence to support this effect of testosterone, but that does not rule out any possible effects. From what we know, though, it seems that if testosterone does have an influence, the effect is complex, not linear. Reality is typically not that simple,” says Nave.
“Of course, the primary suspect when we have something that is sharply differentiated by sex is testosterone. The extreme male brain theory of autism has received a lot of attention, but, if you look at the literature carefully, there is still not really strong support for it. For now, I think we have to embrace our ignorance on this,” adds Nave.
According to Nadler, while the 2011 study included women and the current one included men, one would still expect to find differences if the effect of testosterone were real, “especially since men were exposed to more testosterone prenatally, which would presumably amplify the effects of administration.”