hormones

• hormones are chemical messengers that transmit information around the body
• unlike neurotransmitters, hormones are carried in the blood and operate all around the body
• hormones take longer to work than neuro transmitters and tend to be used to effect longer-term changes
• Hormones are excreted by glands through the system of glands called the endocrine system
• endocrine system


  the system of glands that secrete hormone messages around the body using the circulatory system
• pituitary gland


  the small organ at the base of the brain that produces hormones that control the growth and development of the body
• androgen


  a chemical that develops or maintains male characteristics
• Hormones affect behaviour and cause physical changes in the body
• oxytocin: a hormone released by the pituitary gland that has been shown to increase trust between people
• testosterone is and androgen. Everyone has testosterone in their bodies but it is present in a much greater degree in males
• Antenatal exposure to testosterone has an organising effect on the developing brain, leading to increased spatial ability and competitive aggression
• castration stops the production of testosterone
• the behaviour of castrated rodents and control rodents will be compared to determine if the behavioural changes are due to the hormones
• castrated rodents show little to no aggression, but if their testosterone is replaced by injection they will show typical aggressive behaviour
• Edwards (1968)


  injecting neonatal female rodents with testosterone makes them act much more aggressively when given testosterone as adults compared to control females. This supports the idea that testosterone is implicated in aggressive behaviour.
• human studies generally support the link between testosterone and aggression
• D'Andrade (1966)


  Boys are on average more aggressive than girls; boys have higher exposure to testosterone both prenatally and postnatally
• Mazur (1983)


  Testosterone levels increase during early teens and around this time there is a strong positive correlation with aggressive behaviour and inter-male fighting
• Hawke (1951)


  Cases where convicted sex offenders have been castrated leads to a removal of aggression and loss of sex drive
• some studies supporting the hypothesis that testosterone is influential in aggressive behaviour lack appropriate scientific rigor such as having a control group and fully objective measures of aggression: current ethical standards would prevent such studies taking place
• reciprocal model - testosterone is and effect of dominance and not the cause of it suggesting that aggression could be the cause of raised levels of testosterone
• basal model - a model that suggests that testosterone is assumed to be a persistent trait that influences behaviour
• research using animals is limited in how far it can be generalised to people