Role of hormones in explaining aggression

• Men have 10 times more testosterone

  Giamanco et al - experimental increase in testosterone are related to more aggressive behaviour in several male species
• Cortisol produced by adrenal glands control stress level

  vikkunen reported low levels of cortisol in violent offenders
• Edwards and Roffi - found rats that can’t produce testosterone and injected with testosterone aggression reemerges.

  demonstrates very simple cause and effect relationship

  However castrated newborn rats do not demonstrate more aggression when injected with testosterone it takes 10 days for rats to reach normal levels of aggression

  Cause an effect only occurs at certain ages
• Dabbs et al - measured testosterone levels in saliva of male and female prisoners

  Males have higher levels violent offenders compared to burglars

  Females high levels, unprovoked violence compared to defensive violence

  Weakness - not ethical to test on humans - cause of trauma
• Popma et al - increase levels of testosterone = physical aggressive behaviour when cortisol levels low

  When cortisol levels high testosterone influence of aggression is blocked

  Combined activity of both maybe better prediction of human aggression
• Animal studies strength

  Disease in animals treated the same

  Biologically similar to rats 89% DNA

  unethical to test on humans
• Animal studies weaknesses

  Animals aren’t the same same as humans

  Behaviour/thoughts

  Eugenics, some people are biologically inferior
• Dual hormone hypothesis - High levels of testosterone lead to aggressive behaviour only when levels of cortisol are low