hormonal mechanisms

• what is the main hormone in aggression?

  testosterone
• what is testosterone?

  it is an androgen (male sex hormone) secreted by the testes
• evaluation

  experiments with animals have consistently demonstrated a link between testosterone and aggression. Wagner castrated male mice and found that aggression was reduced. he later injected the mice with testosterone which re-established their aggression. this is supported by Giammanco who found that increasing testosterone had the opposite effect, further supporting the role of testosterone in aggression. castration has long been used as a method for making domestic and farm animals more manageable.
• evaluation - Dabbs

  they measured testosterone in the saliva of 692 adult male prisoners and found higher levels in violent offenders than in non-violent offenders, suggesting that aggression is increased when testosterone is high. Dabbs also found a similar effect in women prisoners. testosterone was higher in those that had committed an unprovoked act of violence compared to those whose violence had been an act of self defence
• evaluation

  not all research has supported this link. Carre's dual-hormone hypothesis claims that high levels of testosterone lead to aggressive behaviour only when levels of cortisol is low. when cortisol is high, testosterones influence on aggression is blocked. this suggests that the link between testosterone and aggression is more complex than some studies have suggested.
• evaluation

  further evidence for the role of testosterone being a complex one, comes from the studies that show that testosterone doesn't necessarily increase aggression but increases status-seeking behaviour in animal species, which is not intended to cause actual harm. aggression is only one type of status-seeking behaviour. this lends support to the idea that testosterone does not directly increase aggression, but produces status-seeking behaviour