genetic theories Flashcards
what is the genetic theory
belief that there is a criminal gene that makes us criminals
cambridge study into delinquent development 1961 by farrington
found that out of 397 families, half of all convictions was within 23 families
twin studies
they focus on identical twins (monozygotic) as they share 100% DNA so if one is a criminal so is the other, can be compared to non-identical twins cause if its a gene more identical twins will both be criminals than non-identical
christiansens twin study
says there’s a 52% chance if one identical twin is a criminal the other is, wereas a 22% chance in non-identical
adoption studies
this tests for genetic cause as they can compare if it’s due to the shared genes of biological parents or shared environment with adoptive parents
mednick et al adoption study
examined data of over 14,000 adopted sons in denmark between 1924 adn 1947 and found they were 20% likely to have a criminal record if one of their birth parents did, and 14.7% likely if adoptive parents did
‘super male syndrome’
some males can get an extra chromosone making them XYY, known as super male syndrome. The males tend to be tall and well built with low intelligence
Jacob et als XYY study 1965
claimed these men tend to be more aggressive and potentially violent making them more suseptible to becoming criminals
effects of brain injuries
some brain injuries linked to criminality like phineas gage who had a metal rod through his prefrontal cortex, survived but he became aggressive and rude after the injury. Some studies say prisoners more likely to have brain damage than non-prisoners.
examples of brain diseases linked to criminality
-1920s epidemic of encephalitus lethargica was linked to criminality being expressed in the kids
-senile dementia, huningtons disease and brain tumours have all been linked to various forms of deviant acts and anti-social behaviour
-charles whitman - murdered several people and upon post mortem a brain tumour was discovered in the part of the brain that regulates aggression and impulses
abnormal brainwave activity and criminality
research showed murderers had an 11% reduction in activity in pre-frontal cortex which is responsible for regulating emotions and behaviour
substance abuse and criminality
research found 80% of family violence includes the misuse of alcohol
low blood sugar levels and criminality
low blood sugar levels have been linked to aggression and especially when alcohol is incloced as it further decreases blood sugar levels
sex hormones and criminality
-high levels of testosterone has been linked to aggression in males and in crimes like murder and rape
-hormone changes in women during menstruation has been linked to criminality especially infanicide (murder of a child)
