Biological explanation

• The biological explanation is split into

  genetic and neural
• Tiihonen 2015 


  Genetically analysed 800 Finnish offenders finding the MAOA and CDH13 genes that attributed to 5-10% of severe violent crimes in Finland
• MAOA

  A gene that regulates serotonin , low levels of this gene cause aggression
• CDH13


  A gene linked to substance abuse and ADHD
• Diathesis stress model

  Genetic vulnerability + Stressor = Crime or affect of the genes
• Christiansen 1977


  Studied >3500 twins in Denmark. 35% concordance rate of criminality in MZ twins and 13% concordance rate of criminality in DZ twins supporting the stress diathesis model
• Crowe 1972


  Children adopted from a criminal mother were 50% likely to commit a crime compared to children adopted from a non criminal mother who were 5% likely
• AO3 genetics + / x

  + Research support - Mednick 1984 studied 13,000 Danish adoptees

  No convictions in bio or adopted parents = 13.5% criminality

  Convicted bio parents = 20%

  Convicted bio and adopted parents = 24.5%

  Supports diathesis stress

  x Assumptions - MZ look more alike than DZ twins so are treated more similarly so scientists assume their environment is the same however it may not be offering a difference explanation to concordance rates.
• amygdala

  Integrative centre for emotions , emotional behaviour and motivation
• Prefrontal cortex


  responsible for regulating behaviour
• Raine 2000


  Measured the grey matter in 21 people with APD with an MRI and monitored autonomic behaviour when talking about their faults. Compared to a control group they had only 11% grey matter show up and a reduced autonomic response.
• Mirror neurons

  Offenders with APD have a neural switch to turn their empathy on / off that people without APD do not have as their mirror neurons ( the mimic other behaviour ) are always on
• Keyser 2011


  Only when asked would offenders with APD empathise with a video containing someone in pain. empathy reaction activated
• AO3 neural + / x


  + Supporting research - Kandel and Freed 1989 found that people with frontal lobe damage were more likely to display impulsive behaviour , emotional instability. So the frontal lobe must be associated with planning behaviour so must be a causal factor of offending behaviour

  x Intervening variables - Farnington 2006 Studied a group of men scoring high on an APD test. They had all been exposed to risk factors for crime as children. These experiences may have caused APD and neural differences or reduced activity in the frontal lobe.