A observation of many animals has found that aggression in more common in males than females. Over 80% of homicides are committed by men. The sex difference in aggression has lead to consider the role of the hormonal mechanisms in aggression, specifically the androgen's i.e. male sex hormones. The main androgen looked at is testosterone.
Testosterone is created in the adrenal cortex and the testes. It is argued that because males produce more testosterone (due to the testes), they are more aggressive. Wagner et al showed that male mice that are castrated are less aggressive. When the castrated mice were injected with testosterone, there was elevated aggression.
Dabbs et al (1995) measured testosterone in the saliva of 692 male prisoners and found testosterone levels were higher in more violent criminals (e.g. ******) and lower in less violent criminals (e.g. burglars.).
In a study, using the double blind procedure, young males were either injected with testosterone or a placebo and were told to push a button. They were told that there was another person in the room next door, and the person who pushed the button the most would receive more money. Those injected with testosterone pushed the button significantly more times.
(AO2) The double blind procedure removes demand characteristics and allows testosterone to be said that it effects aggression. However, the long term effects of injecting testosterone (if any) are unknown.
Testosterone - Studies evaluation (AO2)
Wagner et al - Castration has been common for domestic animals, as it makes them more manageable. However, the study was conducted on mice, and not humans. Social factors may lead the aggression in humans. The problem is that there is ethical to castrating humans to see if aggression change as the level of testosterone changes.
Dabbs et al (1995) - The study used a large, male sample, even though women have less testosterone, the effects are assumed to be the same. Also, only a correlation between testosterone and aggression is established, not cause and effect.
Simpson (2001) argues that testosterone is only on factor that influences aggression. Environmental factors, like temperature, noise and overcrowding have also been shown to increase aggression.
Neural mechanism in aggression
Damage to the frontal lobes can effect aggression. The frontal lobe controls inappropriate actions, so only socially acceptable actions can be used.
In 1848, Phineas Gage worked on the railroads, one day a tamping iron was propelled through his skull. He was left with damage to his frontal lobes, but he survived. He was described to have become more aggressive, obstinate, impatient and impulsive.
The research doe suggest that damage to the frontal lobes can increase aggression, however, the exact damage to Gage's brain is unknown. The damage can only be estimated with experiments. And it is only a single case, therefore it cannot be generalised.
Frontal lobe damage - serial killers
Serial killers have also been found to have damage to the frontal lobe.
Albert Fish was a **********, torturer, murderer and cannibal. In the 1920s USA he ate children. He was found to have suffered frontal lobe damage as a child.
Fred West sadistic, serial killer between 1960 - 1980, he tortured and dismembered his victims (one was his daughter). He suffered frontal lobe damage after a motorbike accident, and further frontal lobe damage when he fell off a fire escape.
However, this theory is seen to be reductionist, as the damage is to other parts of the brain, as well as the frontal lobe. Also, serial killers have experienced abusive childhoods. Albert Fish was left in a orphanage at a early age and witnessed beatings daily and Fred West was abused by his father.
Freewill vs Determinism (AO3)
Biological psychologists view the brain as a machine, therefore there is no freewill. The brain is a very complex machine, but it is still a machine. It can be seen as reductionist and deterministic. If the brain is just like a machine and just processes information, then moral responsibility becomes irrelevant.
However, we still believe that people make choices and must face the consequences of those choices. If the biological processes have overridden 'freewill' then a person should not be responsible for their actions.