hormones

• Sex hormones


  Hormones produced in different quantities by males and females
• Sex hormones


  • Affect the development and functioning of various bodily organs
  • Affect behaviour, explaining some differences between males and females
• Differences in verbal and spatial abilities, memory & aggression


  Linked to differences in hormone secretions between males and females
• Hormonal imprinting


  gender identity is influenced by "hormonal imprinting" before birth
• Prenatal androgenisation, exposure to high levels of testosterone before birth


  May lead to a more masculinised brain and behaviour
• Testosterone


  produced in greater quantities by males than females
• Testosterone


  • Affects several 'typically male' behaviours such as dominance, aggression
  • Produced by the testes
  • Influences the development of external genitalia, brain and behaviour
• Testosterone levels


  influence of teststerone on sexual differentation of a foetus occurs around 8 weeks into pregnancy, once the gonads have developed. Male foetus' have higher levels of testosterone than females 8-24 weeks gestation.
• Testosterone


  • a surge of testicular hormones after birth makes testosterone increase in boys than in girls for the first 6 months. Testosterone also stimulates secondary sex characteristics in puberty
• Violent offenders


  • Had higher testosterone levels than non-violent offenders (Dabbs et al., 1995)
• Female rats - (Young, 1966)


  • male hormones given to female rats. They exhibited male-type behaviours, like mounting others, the effect was irreversible. This suggests that testosterone may alter SDN in the brain resulting in masculisation. Also suggests hormones key role in determaining behaviour.
• Girls whose mothers took drugs containing testosterone during pregnancy - (Money and Ehrhardt, 1972)


  • Exhibited male-type behaviours (playing energetic sports) and an absence of female-type behaviours
• Testosterone


  Acts on the hypothalamus, without this the brain develops as a female type. it is associated with masculinisation of the brain such as the development of brain areas linked to spatial skills and male-type behaviours like competitiveness and aggressiveness
• Swabb - The Sexually Dimorphic Nucleus (SDN) in the brain is 2x larger in males than females, supporting that testoterone is involved in enlargment of SDN
• The Batista Family


  • Four children born with external female genitalia and raised as girls even though they had XY chromosomes
  • When they reached puberty, the surge in testosterone levels led to masculinisation, causing male genitalia to appear externally
  • They accepted their new male role without difficulty - explained by socialisation being overridden by bio factors - testosterone had pre programmed masculinity into their brains and also cultrual differences of gender fulidity
• Oestrogen


  Promotes the development and maintenance of female characteristics, regulates menstruation
• Oestrogen


  • Has psychological and behavioural effects such as premenstrual tension
  • Plays a role in feminising the brain, promoting neural interconnections for a more 'distributed' female brain
• Removing ovaries from female rats 16 days after birth - (Fitch and Denenberg, 1998)

  • Led to changes in the corpus callosum area and affected connectivity between hemispheres. Suggesting oestrogen is involved in the feminising of the brain even after birth - referred to as the 'sensitive period' for oestrogen's feminisation of the brain compared to testosterone regulated masculinsation
• Oxytocin


  The 'love hormone' produced in (and outside of) the brain by both males and females to control key aspects of the reproductive system
• Oxytocin


  • Action is greater in females as it combines with oestrogen to enhance each other's effect
  • Helps to facilitate childbirth and breastfeeding - increases during sex, with males levels dropping immediately after orgasm
  • Affects female social behaviour such as mate selection, 'nesting' behaviour, monogamy and pair bonding, as well as the nurturing, acceptance and protection of offspring
• Injecting an antagonist of oxytocin into female rats shortly after birth - (Van Leengoed et al., 1987)


  • Delayed maternal behaviours such as picking up and grooming their pups when effects wore off normal maternal behaviours were seen, supports oxytocins role in maternal behaviour
• see evaluation for both chromosomes and hormones