Testing the Empathizing–Systemizing theory of sex differences and the Extreme Male Brain theory of autism in half a million people

David M Greenberg,Varun Warrier,Carrie Allison,Simon Baron-Cohen

doi:10.1073/pnas.1811032115

David M Greenberg, Varun Warrier + Show 2 more

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https://doi.org/10.1073/pnas.1811032115

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Abstract

The Empathizing-Systemizing (E-S) theory of typical sex differences suggests that individuals may be classified based on empathy and systemizing. An extension of the E-S theory, the Extreme Male Brain (EMB) theory suggests that autistic people on average have a shift towards a more masculinized brain along the E-S dimensions. Both theories have been investigated in small sample sizes, limiting their generalizability. Here we leverage two large datasets (discovery n = 671,606, including 36,648 autistic individuals primarily; and validation n = 14,354, including 226 autistic individuals) to investigate 10 predictions of the E-S and the EMB theories. In the discovery dataset, typical females on average showed higher scores on short forms of the Empathy Quotient (EQ) and Sensory Perception Quotient (SPQ), and typical males on average showed higher scores on short forms of the Autism Spectrum Quotient (AQ) and Systemizing Quotient (SQ). Typical sex differences in these measures were attenuated in autistic individuals. Analysis of "brain types" revealed that typical females on average were more likely to be Type E (EQ > SQ) or Extreme Type E and that typical males on average were more likely to be Type S (SQ > EQ) or Extreme Type S. In both datasets, autistic individuals, regardless of their reported sex, on average were "masculinized." Finally, we demonstrate that D-scores (difference between EQ and SQ) account for 19 times more of the variance in autistic traits (43%) than do other demographic variables including sex. Our results provide robust evidence in support of both the E-S and EMB theories.

Highlights

The Empathizing–Systemizing (E-S) theory of typical sex differences suggests that individuals may be classified based on empathy and systemizing
The Extreme Male Brain (EMB) makes four further predictions: (vii) that more autistic than typical people will have an Extreme Type S brain; (viii) that autistic traits are better predicted by D-score than by sex; (ix) that males on average will have a higher number of autistic traits than will females; and (x) that those working in science, technology, engineering, and math (STEM) will have a higher number of autistic traits than those working in non-STEM occupations
Effect sizes of sex differences were significantly attenuated for the Autism Spectrum Quotient (AQ), the Empathy Quotient (EQ), and the Systemizing Quotient (SQ) in cases compared with controls (SI Appendix, Table S1), in line with previous results [10]

Summary

Introduction

The Empathizing–Systemizing (E-S) theory of typical sex differences suggests that individuals may be classified based on empathy and systemizing. The Empathizing–Systemizing (E-S) theory [1, 2] of sex differences suggests that individuals can be classified on the basis of two dimensions: empathy, defined as the ability to recognize another person’s mental state (“cognitive empathy”) and the drive to respond to it with an appropriate emotion (“affective empathy”) [3], and systemizing, defined as the drive to analyze or build a rule-based system [4]. Both of these dimensions are normally distributed in the general population, with well-established biological factors [e.g., prenatal testosterone [5, 6] and common genetic variants [7, 8]] contributing to a proportion of the variance

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