Large randomized trials find no clear link between testosterone and cognitive empathy
Summary: New randomized controlled trials challenge the idea that testosterone levels reduce cognitive empathy, a trait often impaired in autism.
Source: University of Pennsylvania
Background: Autism is diagnosed more frequently in males than in females, and scientists have long investigated biological explanations for that disparity. Because sex differences often point to sex hormones, testosterone has been a primary hypothesis for influencing traits related to autism, including cognitive empathy—the ability to recognize and interpret other people’s emotions.
Gideon Nave, an assistant professor of marketing at the Wharton School of the University of Pennsylvania, led a new set of studies that tested this hypothesis directly. In two randomized controlled experiments involving nearly 650 healthy men, Nave and colleagues found no reliable evidence that administering testosterone impairs cognitive empathy.
The research appears in the journal Proceedings of the Royal Society B: Biological Sciences.
Amos Nadler of Western University, the study’s first author, emphasized the strength of the new data compared with earlier work. “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,” he said. “Our results unequivocally show that there is not a linear causal relation between testosterone exposure and cognitive empathy.”
Why this question matters
Previous influential work from 2011 reported that giving testosterone to healthy women reduced their performance on tasks that require reading emotions from eye expressions. That study also used the 2D:4D ratio—the relative lengths of the second and fourth fingers—as a putative marker of prenatal testosterone exposure. The 2011 findings were interpreted by some as supporting the “extreme male brain” theory of autism, which proposes that prenatal masculinizing influences lead to a cognitive style characterized by systematizing rather than empathizing.
However, the earlier study’s small sample size (only 16 participants) and reliance on correlational measures limited the strength of its conclusions. Subsequent investigations produced mixed and inconclusive results, leaving the field without a definitive causal test.
What the new studies did
To obtain more definitive causal evidence, Nave, Nadler, and their collaborators conducted two randomized, placebo-controlled trials including a total of 643 men. Participants received either testosterone gel or a placebo, then completed behavioral tasks and questionnaires designed to measure cognitive empathy. One key measure showed participants a photo of an actor’s eyes and asked them to select the emotional state that best matched the expression. Researchers also measured participants’ 2D:4D finger ratios.
Although the testosterone gel reliably elevated circulating hormone levels, the researchers found no measurable effect of testosterone administration on performance in the emotion-recognition tasks. Likewise, participants’ 2D:4D ratios did not predict performance on the cognitive empathy measures.
“The results are plain,” Nave said. He also cautioned that absence of evidence is not necessarily 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.”
Nadler noted an important methodological point: the 2011 experiment tested women while the new trials tested men. Given that males generally have higher prenatal testosterone exposure, a true causal effect would likely be detectable in men as well. The much larger sample size in the new research—almost two orders of magnitude greater than the 2011 study—adds confidence to the null findings.
Implications and caveats
The new findings do not conclusively disprove any role for hormones in shaping empathy or autism risk, but they do challenge a straightforward, linear model in which higher testosterone exposure directly reduces cognitive empathy. Nave and his colleagues argue that if hormonal effects exist, they are likely to be more intricate—possibly interacting with genetic, developmental, and environmental factors rather than acting alone.
The study authors also point out that the broad literature on the so-called extreme male brain hypothesis remains mixed. “If you look at the literature carefully, there is still not really strong support for it,” Nave said. “For now, I think we have to embrace our ignorance on this.”
Authors and funding
Gideon Nave coauthored the study with Amos Nadler (Western University), Colin F. Camerer (California Institute of Technology), David Zava (ZRT Laboratory), Triana L. Ortiz and Justin M. Carré (Nipissing University), and Neil V. Watson (Simon Fraser University).
Funding: The research received support from Caltech, the Ivey Business School, IFREE, the Russell Sage Foundation, the University of Southern California, INSEAD, the Stockholm School of Economics, the Wharton Neuroscience Initiative, the Natural Sciences and Engineering Research Council of Canada, and the Northern Ontario Heritage Fund Corporation.
Source:
University of Pennsylvania
Media Contacts:
Katherine Unger Baillie – University of Pennsylvania
Original Research: The study will be published in Proceedings of the Royal Society B.