16.2.2 Genetic & Neural explanations of Offending Behaviour

• Genetic explanations of offending behaviour revolve around the idea that criminality is inherited and that there may be specific genes which predispose individuals to criminal behaviour
• A genetic explanation of criminality assumes that mutations within specific genes or combinations of genes may be a key contributory factor in determining criminal behaviour in an individual
• Chromosomal variations within the XYY range have been linked to increased testosterone which in turn have been associated with increased aggression (Price et al. 1966)
• One way of investigating a genetic explanation of offending behaviour is to use twin studies in which concordance rates are measured to look for agreement between MZ (identical) and DZ (non-identical) twins in relation to criminality i.e. if one twin has committed a crime how likely is it that the other twin has also committed a crime?
• The main assumption underpinning twin studies is that if criminality is genetic, then there will be a higher concordance rate between MZ twins than between DZ twins as MZ twins share 100% of their DNA
• Some research has suggested that candidate genes such as the MAOA gene (which has been linked to violent, anti-social behaviour by Brunner, 1993) and the CDH13 gene in their mutated forms may predispose an individual to criminal behaviour (Tiihonen et al, 2014)

MZ twins may provide evidence of a genetic explanation of offending behaviour.

• Neural explanations of offending behaviour revolve around the idea that brain structure and/or neurochemistry increase an individual’s propensity to criminal behaviour
• A neural explanation of criminality assumes that specific neurotransmitters may be a key contributory factor in determining criminal behaviour in an individual e.g. heightened levels of dopamine leading to reward-seeking behaviour 
• The neurotransmitter serotonin is thought to regulate mood and impulsivity, so if levels of serotonin are unstable, then this may lead to increased impulsivity and disturbed mood (see Brunner 1993 below)
• Structural differences in the brain may also play a role in offending behaviour, particularly with regard to the limbic system
• The limbic system is the area of the brain that helps to regulate emotional responses, particularly the amygdala which processes emotional information
• Research suggests that a smaller amygdala may be linked to a lack of empathy in offenders, which may explain their lack of guilt and remorse when committing crimes (Shirtcliff et al, 2009) 
• The prefrontal cortex (PFC) is thought to regulate and inhibit  impulsive behaviour and is also associated with offending behaviour e.g. Raine et al. (1997) found, via PET scans, that impulsive murderers did not use the PFC to perform simple cognitive tasks but used the amygdala instead

Key components of the limbic system.

Research which investigates genetic & neural explanations of offending behaviour

• Raine (1993) found a 52% concordance rate for criminality between MZ twins compared to 21% between DZ twins which supports a genetic explanation of offending behaviour
• Brunner (1993) identified a mutation in the MAOA gene which disturbed the levels of key neurotransmitters such as serotonin which he linked to the anti-social behaviour and low IQ of a group of males from one family in the Netherlands

Evaluation of genetic & neural explanations of offending behaviour

Strengths

• There is good supporting evidence for genetic explanations of offending behaviour e.g. Christiansen's  (1977) twin study used a sample of 3,500 twins and found concordance for criminality was higher for MZ twins
• The use of brain imaging techniques such as PET scans provides objective clinical evidence giving it good reliability

Weaknesses

• No single ‘criminality’ gene - or combination of genes - have been identified to date; research evidence so far has been ‘modest’ in its attempts to do so (Morley & Hall, 2003)
• Brain imaging techniques can be unreliable if they are not calibrated properly plus they are very sensitive to temperature and to noise

Link to Approaches:

Genetic and neural explanations clearly fall within the Biological Approach with their emphasis on physiological factors to explain offending behaviours.

Link to Issues & Debates:

The nature side of the nature/nurture debate is part and parcel of genetic and neural explanations. The nature side of the debate assumes that human beings are heavily influenced by innate drives, inherited characteristics and biological mechanisms.