genetic and neural explanation

genes

genes produce instructions for physical features eg eye colour or neurotransmitter levels which can impact psychological features, genes are inherited

genetic explanations

suggest criminals inherit one or more genes that make them more likely to commit crimes, this is called a predisposition

genetic explanations- Christiansen (1977) twin studies

• studied over 3500 twin pairs in Denmark, including all twins born between 1880 and 1910 in one region

• collated criminality data from police records

• found concordance rates for criminality as 35% in MZ males and 13% in DZ males (slightly lower rates for females)

• supports a genetic component in offending

genetic explanations- Crowe (1972)

• adopted children with a criminal biological mother had a 50% risk of criminality by age 18 (having a criminal record)

• adopted children with non criminal biological mother only had 5% risk

• suggests genetics have more of an impact on criminality than upbringing

candiate genes- Tiihonen et al. (2015)

genetic analysis of around 800 Finnish offenders, identified 2 genes associated with violent crime:

1. MAOA gene- regulates serotonin in the brain, linked to aggressive behaviour

2. CDH13 gene- linked to ADHD and substance abuse

• study found 5-10% of all severe violent crime in Finland was carried out by those with MAOA and CDH13 genes

diathesis stress model

• if genetics explained all criminality, we’d expect concordance rates to be 100% in MZ twins, relatively low rates of 35% suggests other factors play a role

• diathesis stress model suggests a genetic predisposition to criminality may be inherited, a biological trigger then ‘activates’ the criminal behaviour

• having the MAOA gene and being raised in a dysfunctional environment could trigger later criminality, genetic predisposition triggered by biological or psychological stressor

neural explanations

• any explanation of behaviour and disorders in terms of (dis)functions of the brain and nervous system, includes the activity of brain structures and neurotransmitters

• evidence from people diagnosed with antisocial personality disorder (psychopathy) suggests there are neural differences in offenders, APD associated with reduced emotional response and lack of empathy, commonly seen in convicted offenders, especially serial killers

role of prefrontal cortex

• Adrian Raine conducted many studies on APD brains, found many brain imaging studies suggesting APD individuals have reduced activity in the prefrontal cortex, PFC regulates emotional behaviour, less activity = less regulation

• Raine et al. (2000) found reduced activity and an 11% reduction in the volume of grey matter in the PFC of people with APD

role of mirror neurons

• mirror neurons control our ability to empathise, take others perspectives and perceive others intentions, affected in autism

• APD is associated with a lack of empathy, but research suggests they can show empathy, just more sporadically than us

Keysers (2011) mirror neuron research

• presented offenders with a film showing someone experiencing pain

• only when offenders were asked to empathise, they could activate their empathy response controlled by mirror neurons

• suggests APD individuals may have a neural switch that can turn their empathy on and off, whereas neurotypical brain has the empathy switch permanently on

limitation- twin studies is assuming equal environments

• often assumed that environmental factors are the same for MZ and DZ twins because they experience similar environments

• however, because MZ twins look identical, people (especially parents) tend to treat them more similarly, which affects their behaviour

• so higher concordance rates for MZs may be because they are treated more similarly than DZs suggesting conclusions lack validity

strength- evidence to support diathesis stress model of offending

• Mednick et al. (1984) studied 13000 Danish adoptees having at least one court conviction

• conviction rates 13.5% when biological or adoptive parents had no convictions, 20% if one biological parent had convictions, 24.5% when both biological and adoptive parents had convictions

• suggests both genetic inheritance and environment influence criminality, supporting the diathesis stress model of crime

evaluation- nature vs nurture

• twin adoption studies separate nature and nurture, similarities due to biological parents can only be genetic

• however, many adoptions occur when children are older and many adoptees maintain contact with biological family, so still environmental influences

• suggests adoption studies cant fully separate nature and nurture

strength- support for the link between crime and frontal lobe

• Kandel + Freed (1989) researched people with frontal lobe damage, including the prefrontal cortex and antisocial behaviour

• found evidence this damage is associated with impulsive behaviour, emotional instability and inability to learn from mistakes, frontal lobe associated with planning

• supports the idea that structural abnormalities in the brain are a causal factor in offending behaviour

limitation- link between neural differences and APD is complex

• Farrington et al. (1981) studied adult males with high APD scores, they were raised by a convicted parent and physically neglected

• these early experiences may have caused APD and associated neural differences eg reduced activity in the frontal lobe due to trauma

• suggests the link between neural differences, APD and offending is complex, and there may be intervening variables

limitation- biological determinism

• the biological approach suggests offending behaviour is determined by factors which cant be controlled, genes, so no responsibility for criminals

• however, justice system is based on individual responsibility, the identification of possible biological biological precursors to crime complicates this principle

• suggests we should ‘excuse’ some people, insanity defence, but ultimately this isn’t possible as then many could claim no responsibility