Recent research published in autism research suggest that the cognitive changes associated with autism are significantly greater in women than in men. The findings provide evidence that women may require greater biological stimulation to develop autism, which helps explain why autism is diagnosed more often in boys. These insights reveal psychological differences underlying the male-biased prevalence of autism spectrum disorders.
The extreme male brain theory of autism was originally proposed by Cambridge University psychologist Simon Baron Cohen. This theory suggests that autism exaggerates typical male cognitive characteristics. Specifically, it refers to a profile that exhibits relatively low empathy, known as “empathy,” and high interest in analyzing or building rule-based structures, known as “systemizing.”
Empathy involves the ability to recognize and respond to the emotions of others. Systematization is the drive to understand non-social systems such as mathematics, computer code, and mechanical devices. According to the extreme male brain theory, increased exposure to testosterone in utero tends to shift brain development toward this highly organized profile.
Historically, about four men for every woman are diagnosed with autism. Simon Fraser University scientists Cory Sakal and Bernard Crespi wanted to understand whether the extreme male brain theory applies differently to men and women. They also wanted to investigate whether women have a biological resistance to this condition.
Some scientists suspect that a protective effect exists for women. This concept suggests that women require more severe genetic or environmental factors to reach the threshold for being diagnosed with autism. If this protective effect is real, women diagnosed with autism should show far more dramatic cognitive changes than their male peers.
“The main question was how to explain the male bias in autism. The main psychological theory on this issue is Baron-Cohen’s empathy-systemizing theory. However, differences in empathy and systemization between autistics and neurotypicals have never been compared between women and men. We did so using a systematic review and meta-analysis of all published studies,” explained Crespi, professor of biological sciences.
Meta-analysis is a statistical method that combines data from multiple independent studies to identify overall trends. The researchers collected data from 34 previously published studies that measured the traits of empathy and organization.
A total of 1,234,560 participants were included in the analysis, including 757,726 women and 476,834 men. The sample included people with autism and neurotypicals, meaning people whose brains developed according to typical norms. The researchers looked at three specific self-report measures used across these studies.
These scales include the Empathy Quotient, the Systematization Quotient, and the Autism Spectrum Quotient. The empathy index measures a person’s social sensitivity, and the systemization index measures a person’s interest in systems and rules. The Autism Spectrum Quotient assesses the presence of autistic traits in everyday behavior.
Because the 34 studies used different versions of these questionnaires, the researchers standardized the scores. They divided the reported average by the maximum possible score for each particular test. This conversion changed all scores to percentages, making it easier to compare scores across datasets.
Researchers found that the differences in empathy and structuring scores between autistic women and neurotypical women were significantly larger than the disparities between autistic men and neurotypical men. In other words, autistic women exhibit a much greater divergence from the average female cognitive profile than autistic men diverge from the average male cognitive profile. This provides evidence that greater cognitive changes are involved in the development of autism in women.
The data also revealed that the difference in empathy scores between autistics and neurotypicals was significantly larger than the difference in codification scores. On a proportional basis, changes in empathy were three to five times larger than changes in codification. This suggests that reduced empathy may play a larger role in the psychological differences that characterize autism diagnoses.
Additionally, normal gender differences in empathy and structuring are significantly reduced among people with autism. Autistic men and autistic women had similar scores on the Systemizing Index. Regarding the empathy index, we also found that the difference between autistic men and women was very small, with typical gender strains mixed together.
The researchers also examined how strongly these traits predicted overall autistic behavior. They found that changes in empathy and systemization scores had a much stronger impact on overall autism scores in autistic people than in neurotypicals. This data suggests that as empathy decreases and systemization increases, outward signs of autism proliferate much faster for those already on the autism spectrum.
Scientists also discovered an unexpected relationship between empathy and structuring in people with autism. Among neurotypical participants, empathy and systemization scores tend to rise together in a positive correlation. In contrast, individuals with autism showed an inverse relationship, with higher codification scores associated with lower empathy scores.
This inverse relationship indicates a cognitive trade-off in people with autism. Cognitive trade-offs occur when the enhancement of one mental ability interferes with another. For example, excessive focus on rule-based, non-social systems can naturally suppress brain networks used for social and emotional processing.
As with all research, there are limitations that should be considered. The studies included in the analysis were based on self-report questionnaires. Self-reports can reflect how a person wants to be seen or how they hide their characteristics to fit society’s expectations, a behavior known as camouflage.
Autistic women are known to camouflage their characteristics more often than autistic men, often out of a desire to conform to gender norms. They can use their intelligence to mimic social behavior and artificially inflate empathy test scores. Also, participants’ ages were not consistently reported in the data collected, preventing researchers from analyzing how these cognitive traits change over a person’s life.
Another limitation is that the majority of the data came from a small group of researchers. This clustering means that specific testing methods or regional biases can affect the overall results. The scientists recommend that future research investigate the exact cause of the cognitive trade-off observed between empathy and systemization.
Future research should also examine how environmental and genetic factors interact to produce these psychological changes. Understanding these mechanisms may help explain why women seem to have a biological resistance to autism. Diagnostic tools could also be improved to better identify women with autism who are currently overlooked.
The study, “Does the extreme male brain hypothesis of autism apply more to women than men? A systematic and meta-analytic approach” was authored by Cory Szankal and Bernard Crespi.
