A Role for Fetal Testosterone in Human Sex Differences

Abstract

Autism spectrum conditions (ASCs) may be an extreme manifestation of specific male-typical characteristics. Evidence for this theory is provided by the empathizing--systemizing (E--S) theory of sex-typical behavior, which suggests ASCs as an extreme form of the male brain (EMB). In this chapter, we review the evidence supporting EMB theory and examine the effect of hormones on the development of sex differences related to ASCs. An important candidate mechanism for the development of sex-typical behavior is the effect of fetal testosterone (f{\thinspace}T) during pregnancy. Evidence that elevated levels of f{\thinspace}T may be a risk factor for ASC is also discussed. Many neurodevelopmental conditions occur in males more often than females, including autism, dyslexia, attention-deficit hyperactivity disorder (ADHD), and early onset persistent antisocial behavior [1]). Autism in particular has been described as an extreme manifestation of some sexually dimorphic traits or an ``extreme male brain'' [2]. In this chapter, we review the reasons why this condition in particular has been viewed in this light and the evidence related to it.