Psychological explanations of criminal behaviour
If criminal behaviour has a physiological cause it is controlled genetically, so it's a product of evolucion
Lombrose found that prisoners had similar features, so it maybe it comes down to natural selection
Criminal body types
1- Ectomorphic = thin/fragile
2- Mesomorphic = muscular/hard (most likely to be a criminal
3- Endomorphic = fat/soft
Modern physiological explanations for genes and criminality may be down to hereditary factors making it more likely that someone will be a criminal
Jacobs found that XYY men were more aggressive than XY men, and XYY men make up 1.5% of prisoners, they are also less intelligent generally
Osborn and West found that only 13% of non-criminal sons had convictions, but 40% sons with criminal fathers also had convictions, which suggests genes may be partly responsible for crime
Twin studies
MZ's share 100% genes, while DZ share 50% genes
Lyons found that MZ's are not more likely to be both be jailed than DZ's, which means environment is important in early criminal behaviour
Adoption studies
Hard to separate genetic effects in environment in twin studies, in adoption the 2 factors can be explored independently
There are similarities between adoptive parents and kids, showing that environment is important
Having biological parents with criminal records increases the risk of sons doing the same, showing how genes influence crime
Adoptive parents with criminal records also had increased chance of their sons doing the same = supporting environmental influences
Non-physiological explanations of criminal behaviour
Kids could imitate criminal behaviour from parents, parents are high status models, which influence offspring a lot, same sex models are even more effective
Trzensniewski found that adolescents with low self esteem are more likely to engage in criminal activity