High levels of testosterone in utero may be at the root of some aspects of autism spectrum disorder (ASD). This concept, called Extreme Male Brain (EMB) theory, could explain why four times as many males are diagnosed with ASD than females. Researchers at the University of Western Australia (UWA) and Telethon Kids Institute recently investigated whether the EMB theory held up against a competing paradigm: the androgyny theory, or the idea that people with ASD are less gender typical than their peers. The results supported EMB theory. The findings may help researchers understand the causes of ASD.
EMB theory posits that males with ASD exhibit hyper-masculinization and females exhibit defeminization. The core of EMB theory is that individuals with ASD are exposed to higher levels of testosterone in utero. The researchers were able to test EMB theory by looking for other traits impacted by testosterone: faces and voices.
For the study, male and female undergraduate students (with a mean age of 17 to 18 years) had their faces photographed and their voices recorded. The researchers assessed the participants using the Autism Quotient (AQ) questionnaire to determine their levels of autistic-like traits. Thirty students rated the participants’ faces and voices for masculinity or femininity. Then, the researchers evaluated the results against participants’ AQ scores.
Males with a high AQ score were rated more masculine-sounding than males with a low AQ score. Females with a high AQ score were rated less feminine-looking than females with a low AQ score. For both sexes, a high AQ score correlated to a hyper-masculinization.
“The results of our study provided support for the extreme male brain theory,” stated Diana Tan, a PhD student in psychology at UWA. “EMB theory seems to describe the physical features of the high-AQ participants better than the androgyny theory.”
The study authors state that more research is required to understand the relationship between facial and vocal features, ASD, and elevated testosterone levels.
This research is published in the journal PLoS One.
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