Attenuation but Persistence of Normative Sex Differences in Empathizing, Systemizing, and Autistic Traits in 800 High-Functioning Adults with Autism: A Big-Data Test of the ‘Extreme Male Brain' Theory

Background: Sex differences have been reported in autistic traits, empathizing and systemizing among typical individuals. In individuals with autism, these cognitive-behavioural profiles correspond to predictions from the ‘extreme male brain’ (EMB) theory of autism. Sex differences within autism, however, have been under-investigated.

Objectives:  This study aims to examine sex differences using self-report measures of empathizing, systemizing and autistic traits in a large sample of individuals with autism, in order to have sufficient power to test if sex differences exist within autism and if these are attenuated as would be predicted by the EMB theory

Methods: n = 811 adults (454 females) with autism were compared with 3,906 age-matched typically developing adults (2,562 females). Participants completed the Empathy Quotient (EQ), the Revised Systemizing Quotient (SQ-R) and the Autism Spectrum Quotient (AQ) online. The discrepancy between standardized EQ and SQ-R scores (the ‘D-score’) was also used to classify individuals into different cognitive-behavioral profiles (‘brain types’).

Results:  Typical females on average scored higher on the EQ, and typical males scored higher on the SQ-R and AQ, confirming earlier studies. Both males and females with autism showed a shift toward the extreme of the ‘male profile’ on these measures and in the distribution of ‘brain types’. There were sex differences in the autism group on the AQ, EQ, SQ-R and D scores, though smaller compared to those observed in the typically developing group, all evidenced by a significant ordinal sex-by-diagnosis interaction.  Normative patterns of sex differences were preserved in the autism group for all the measures, evidenced by significant differences between males and females with autism.

Conclusions:  In a large sample of high-functioning adults with autism, both males and females cognitive-behavioural profiles of empathizing, systemizing, and autistic traits show a shift towards and beyond the typical male range of scores. However, normative sex differences were preserved in individuals with autism, highlighting significant differences between males and females with autism. This exemplifies that the presence of autism attenuates but does not eliminate typical sex differences in these aspects of cognitive-behavioral traits.