No evidence to suggest testosterone reduces cognitive empathy, study suggests
The results challenge the notion of autism as reflecting an extreme male brain, researchers say.
There is no evidence to suggest that testosterone reduces cognitive empathy, new research indicates.
The results challenge the notion of autism as reflecting an extreme male brain.
While it has long been understood that autism is far more prevalent in men than women, scientists have not known why.
The primary suspect has been testosterone, as is often the case when something is sharply differentiated by sex, scientists say.
Our results unequivocally show that there is not a linear causal relation between testosterone exposure and cognitive empathy Amos Nadler
But in two randomised controlled studies, which included 643 men, researchers found no evidence of a link with cognitive empathy – the capacity to read the emotions of others.
This is a trait that is characteristically impaired in people with autism.
Amos Nadler of Western University, first author of the study, said: “Several earlier studies have suggested a connection between testosterone and reduced cognitive empathy, but samples were very small, and it’s very difficult to determine a direct link.
“Our results unequivocally show that there is not a linear causal relation between testosterone exposure and cognitive empathy.”
In the study published in the journal Proceedings of the Royal Society B: Biological Sciences, the participants received an application of testosterone gel or a placebo and completed questionnaires and behavioural tasks that measured cognitive empathy.
They 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 – ratio of the length of the participant’s second finger to their fourth finger- measured.
While testosterone gel did increase participants’ levels of the hormone, the researchers found no evidence it affected performance on tests of cognitive empathy.
They also found no relationship between participants’ performance on the tests and their 2D:4D ratio.
We found that there is no evidence to support this effect of testosterone, but that doesn't rule out any possible effects Gideon Nave
Researchers say that prior to this work, the strongest evidence for a link between testosterone exposure and reduced cognitive empathy came in 2011.
A study that found administering testosterone to healthy women reduced their performance on a test of reading emotions.
The results suggested the testosterone impaired their performance.
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 characterised by systemising over empathising.
But the authors of the new study say the previous research was based on a sample size of just 16, and that most other studies relied on correlative rather than causative evidence.
Gideon Nave, assistant professor of marketing in Penn’s Wharton School, said: “The results are plain.
“However, it’s 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 doesn’t 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.”
The extreme male brain theory of autism has received a lot of attention but, Prof Nave adds: “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.”