Genetic & Neural Explanations

• Genetic explanations suggest that offenders inherit a gene or combination of genes that predispose them to committing a crime
• Twin studies demonstrate genetic explanations e.g. Christiansen
• Christiansen studied over 3500 danish twin pairs and found that concordance rates of offender behaviour were 35% in monozygotic twins and 13% in dizygotic twins
• Adoption studies demonstrate genetic explanations e.g. Crowe
• Crowe found that adopted children with criminal biological mothers had a 50% chance of becoming a criminal by 18 compared to a 5% risk for non-criminal biological mothers
• Candidate genes demonstrate genetic explanations e.g. MAOA, CDH13
• The MAOA gene regulates serotonin in the brain and the low activity version has been linked to aggressive behaviour
• The CDH13 gene is linked to substance abuse and ADHD
• Tiihonen et.al found that 5-10% of all severe violent crime in Finland is attributable to MAOA & CDH13 genotypes
• The Diathesis-Stress Model suggests a tendency towards offending may come about through a combination of genetic predisposition and a psychological trigger
• There is evidence to support the diathesis-stress model e.g. Mednick
• Mednick studied 13,000 Danish adoptees and found that when neither sets of parents had a conviction 13.5% of adoptees did, when biological parents did 20% of adoptees did, and when both sets of parents did 24.5% of adoptees did
• A limitation of twin studies is the assumption of equal environments as there may be higher concordance rates for identical twins due to being treated more similarly
• A limitation of adoption studies is confounding variables as many adoptions take place at a later age or may maintain contact with biological parents
• Neural explanations suggest there may be neural differences in the brains of offenders and non-offenders
• Differences in the pre-frontal cortex demonstrate neural explanations e.g. Raine et.al.
• Raine et.al conducted PET scans on 41 murderers who has pleaded not guilty by reason of insanity (APD) and compared them to an age & gender matched control group
• Raine et.al. found reduced brain activity in the pre-frontal cortex and corpus callosum, and abnormalities in the activity of the limbic system e.g. amygdala & hypothalamus
• Antisocial Personality Disorder (APD) is associated with a reduced emotional response and lack of empathy
• Raine et.al found an 11% reduction in volume of grey matter in the pre-frontal cortex of APD offenders
• Mirror Neurons have been shown to control the empathy reaction in APD brains e.g. Keyers
• Keyers found that only when participants were asked to empathise with a film character in pain did their empathy reaction 'switch on'
• Dopamine has been linked to addiction and substance abuse due to the dopaminergic pathway which results in pleasure, therefore indirectly linked to criminal behaviour