Genetic and neural explanations of crime Flashcards
Genetic theory
one or more genes predispose individuals to criminal behaviour (evidence from twin studies)
- some men are born with a chromosomal abnormality where they have 2 Y chromosomes, these ‘supermales’ are thought to be more aggressive and less intelligent – leading to criminal behaviour
Raine (1993)
reviewed research (meta-analysis of 13 studies) on the criminal behaviour of twins
-found a 52% concordance rate for MZ twins and a 21% concordance rate for DZ twins
Raine evaluation
- MZ twins are not 100% so can’t be fully down to genetics, however concordance rates higher in MZ than DZ so must partially be down to genetics
The warrior gene (MAOA)
- enzyme
- its function is to break down neurotransmitters in the synapses so that they can be reabsorbed and reused
- the production of this enzyme is determined by the MAOA gene
- one variation of this gene leads to less MAOA being produced, which affects the levels of serotonin in the brain
- around a third of men have this variation
Brunner et al. (1983)
Studied a large Dutch family whose male members were consistently involved in impulsively aggressive, violent criminal behaviours such as rape, attempted murder and physical assault
- found these men had abnormally low levels of MAOA in their brains and had the warrior gene variation
Brunner et al. evaluation
- correlational (offending may run int he family as the behaviour has been learnt not due to the genetics)
- SLT (family members may be viewed as role models)
- nature/nurture debate
State the neurotransmitters linked to criminal behaviour
- noradrenaline (fight or flight, high levels are linked to violence and aggression)
- serotonin (regulated mood and impulse control, associated with higher impulsivity)
- dopamine (linked to addiction, high levels linked to addiction to drugs and other crimes)
Higley et al. (1996)
- studied rhesus monkeys
- found that low levels of serotonin were associated with extreme aggression
- low serotonin levels also negatively correlated with risk taking and impulsive behaviour
- monkeys had more scars
Evaluation of Higley et al.
- only correlational (can’t establish cause and effect)
- can’t generalise the findings (studies on animals can’t be generalised to humans)
Positive evaluation of neurotransmitters as an explanation of crime
- research support (Brunner, Higley)
- scientific
Negative evaluation of neurotransmitters as an explanation of crime
- link between neurochemicals and crime may be indirect (they clearly do affect mood, impulsivity, aggression and mental illness which could all affect crime, but can be hard to establish
- studies conducted on animals (can’t generalise)
- reductionist (oversimplifying very complex behaviour with many influences down to the level of a single chemical, lots of other factors could be involved)
Brain physiology
- the size and functioning of certain parts of the brain itself has been suggested as a cause of criminal behaviour
- the limbic system processes emotion and over activity in this region and lower activity in the cerebral cortex could explain many crimes
Charles Whitman
Had a tumour on his amygdala (limbic system) and shot dead 16 people from the University of Texas tower
Raine et al. (1997)
- compared brain function of murderers and non-murderers using PET scans
- found less activity in the pre-frontal cortex in murders (an area associated with impulse control)
- found higher activity in parts of the limbic system
Raine et al. (2000)
- went onto suggest that the pre-frontal cortex acts as a ‘brake’ to stop people committing immoral or anti-social behaviours
- found that people with anti-social personality behaviour have reduced frontal lobe volume compared to controls
- both structural & functional differences between criminals & non-criminal
