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This thesis provides a convergent view of the role of foetal testosterone (fT) on social development during childhood. This has involved the study of the social and emotional development of typically developing children (n = 200 boys and girls, aged 6-9 years) whose mothers underwent routine amniocentesis as part of the Cambridge Child Development Project. Chapters 1 and 2 provide a comprehensive review of literature. Chapters 3, 4, 5 and 6 describe six empirical behavioural studies: a parental report of emphasising abilities; two tasks of emotion recognition; and emotional memory task, an eyegaze detection task and a self-report questionnaire of anxiety traits. All of the measures reveal a specific relationship between task performance and fT level in both boys and girls. Chapter 7 investigates brain activity in the same cohort using MRI during tasks analogous to those completed behaviourally. The results provide the first evidence of a direct link between behaviour, brain activity and fT level. Overall the work allows us to draw the following conclusions: (i) that sexually dimorphic behaviours in typical adults are also present in typically developing children, providing further evidence for the mediation of sex differences by prenatal biology rather than society and culture; (ii) that measures of social development and the occurrence of sexually dimorphic behaviours are related to a child’s level of exposure to fT; (iii) that sexually dimorphic behaviours are underpinned by related variation in brain activity; (iv) that brain activity in associated neural regions are related to levels of fT. Thus, typical ranges of fT exposure modulate ‘normal’ variation on specific measures of social development and brain development. The results have implications for the causes of conditions involving social difficulties, such as autism spectrum conditions. |
