biological explinations for criminal behaviour

there is a link between brain injury and offending. 

analysed data from 196 inmates from 1 uk prison. 

found that 60% recalled history of head injury. 

analysed data from the swedish population register. 

examined the association between BI and violent crime. 

8.8% of brain injured people had commited a violent crime compared to only 3% of the control group.

abnormalities in the size or structure of the amygdala correlate with increased aggression making criminal behaviour more likely. 

conducted an experiment on 1795 3-year-olds.

electrodes were placed on their fingers and 2 different sounds were played. 

one was followed by a loud bang and the other was followed by silence.

two decades later those children who had gone on to commit crime were more likely to be thise who diddnt show a fear resonse to the loud noise. this was explained by abnormal functioning of the amygdala, illistrated by the lack of fear at 3 years old. 

conducted neuro scanning on a group of 26 year old men. 

they were then divided into groups on the basis of if they had a normal sized amygdala or if they had reduxed amygdala volume. 

3 years later- the men with reduced amygdala volume were three times more likely to be aggressive and violent than the people who had a normal sized amygdala. 

1 in 1000 men have this. 

it is where they are born with an extra y chromosome which means that some physical and behavioural factors are affected such as: 

- height (taller) 

-lower intellegence 

-more impulsive

-experience behavioural difficulties

conducted a chromosome survey of male patients in a state hospital in scotland. 

found that men with an extra y chromosome were more likely to be in prison: 
15/1000 compared to 1/1000

a weakness of the xyy explination. 

birkhoff stated that xyy syndrome is explained better by social explinations, as xyy characteristics make it harder for the men to socialise, find work and involve themselves in society which is why the crime rates for men with this syndrome are higher.