Biological Evidence

Wise

Rats were so motivated to seek pleasure through electrical stimulation that they were willing to starve rather than stop doing so (a recent version of Olds and Milner)

Olds and Milner

Enabled rats to give themselves a pleasurable electric shock by pressing a lever would return so many times that they would ignore other sources of pleasure such as food, like drug addicts

Mazur

Reported a marked increase in fighting between young males during puberty, when they become sexually active

Daly and Wilson

Male sexual jealousy was the leading issue in social conflict homicides in Detroit in 1972, supports the idea that aggression is used to secure a mate to have better chances of passing on their genes

Dabbs et al

Higher levels of testosterone were found in the saliva of rapists and violent offenders compared to burglars and thieves in both male and female offenders. They were highest in cases of unprovoked violence but lowest when violence was defensive

Downer

Found that removing the amygdala of monkeys made them calmer and more placid when facing a threat

Raine

Used PET scans to measure the glucose metabolism of murderers’ brains compared to non-violent individuals

Beeman

Castrating male rodents, therefore stopping the production of testosterone, decreased aggressive behaviour in a threatening situation to a little or none. Injecting testosterone back into them returns their aggressive tendencies

Verona and Sullivan

Participants who reacted in an aggressive way to frustration caused in an experiment had a reduced heart rate than those who didn’t act that way. Validates idea of cathartic release

Freud

Based his theories on in depth case studies of middle class women living in Vienna

Gossop and Strand

Compared the withdrawal responses of methadone and heroine addicts during a ten-day in-patient detoxification programme. The methadone group had more severe withdrawal symptoms during the programme

Charles Whitman

brain tumour on amygdala caused murder of family and others

Eisenegger et al

women given a dose of testosterone behaved more generously and sociably in a negotiating game