BACKGROUND: In animals, fetal testosterone (fT) plays a central role in organizing the brain and in later social behavior. In humans, exposure to atypical levels of prenatal androgens may result in masculine behavior and ability patterns. Normal inter-individual variation in fT levels has also been correlated with later sex-typed behavior. METHODS: In the current study, 38 children (24 male, 14 female), whose fT was analyzed in amniotic fluid, were followed up at age 4. They were asked to describe cartoons with 2 moving triangles whose interactions with each other suggested social relationships and psychological motivations. RESULTS: Females used more mental and affective state terms to describe the cartoons than males. fT was not associated with the frequency of mental or affective state terms. Females also used more intentional propositions than males. fT was negatively correlated with the frequency of intentional propositions, taking sex differences into account. fT was also negatively correlated with the frequency of intentional propositions when males were examined separately. Males used more neutral propositions than females. fT was directly correlated with the frequency of neutral propositions, taking sex differences into account. This relationship was not seen when males and females were examined separately. CONCLUSIONS: These findings implicate fT in human social development. The relevance of our findings to the 'extreme male brain' theory of autism is also discussed.
