Journal of Autism and Developmental Disorders

, Volume 43, Issue 11, pp 2664–2676 | Cite as

A Critical Review of the Research on the Extreme Male Brain Theory and Digit Ratio (2D:4D)

  • Missy L. TeateroEmail author
  • Charles Netley
Original Paper


Boys are more likely than girls to be diagnosed with an autism spectrum disorder (ASD). The extreme male brain (EMB) theory of ASD suggests that fetal testosterone (FT) exposure may underlie sex differences in autistic traits. A link between the organizational effects of FT on the brain and ASD is often drawn based on research using digit ratio (2D:4D), a putative biomarker, without a full survey of the findings. This paper critically and quantitatively reviews the research on the relationship between 2D:4D and ASD as well as autism spectrum, empathizing, and systemizing measures in neurotypical populations. Overall, there is some support for the EMB theory in all four areas, particularly the 2D:4D–ASD relationship. Recommendations for future research are provided.


Extreme male brain Autism spectrum Empathizing Systemizing Digit ratio 2D:4D 


References marked with an asterisk indicate studies included in the meta-analyses

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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Health, Hormones, and Behaviour Laboratory, Department of PsychologyLakehead UniversityThunder BayCanada
  2. 2.Department of PsychologyLakehead UniversityThunder BayCanada

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