testosterone

• chromosomes, hormones and reproductive systems that develop will influence the development of the brain - size of the sexually dimorphic nucleus (SDN)
• what's the SDN in the brain?

  an area associated with our psychological gender identity
• testosterone is associated with masculinisation of the brain, such as the development of brain areas linked with spatial skills
• GORSKI et al injected female rats with testosterone prior to birth. The rats developed ambiguous genitalia and their SDN resembled those of male rats. Their behaviour was masculinised; attempted to mount on other female rats
• GORSKI finds the SDN the most visible structural difference in the brains of male and female mammals

  • demonstrating that hormones released pre and postnatally affect brain structure, which in turn affects our gender behaviour, male-associated behaviour in particular
• testosterone has been widely linked to aggressive behaviour in males

  • VAN DER POL report that lab studies with animals show that testosterone leads to increased aggression
  • male rats show more aggression than female rats
  • castrated males show reduced aggression
  • aggression increases with injections of testosterone
• testosterone has been widely linked to aggressive behaviour in males

  • MONEY and EHRHARDT reported on a sample of girls whose mothers took drugs containing testosterone during pregnancy. The girls exhibited male type behaviours and an absence of female type behaviours
• further evidence comes from studies of CAH (Congenital Adrenal Hyperplasia)
• CAH?

  a rare genetic order that causes high levels of prenatal levels of male hormones
• BERENBAUM and BAILEY found that CAH females are often described in their family as tomboys, exhibit higher levels of aggression than other girls and show preference for typical 'male' toys
• studies with men taking body building steroids show they have higher than normal aggression scores on questionnaires further linking testosterone to aggressive behaviour