biological explanations:Genetic and neural explanations Flashcards
(10 cards)
intro
Genetic explanations for crime suggest that would-be offenders inherit a gene, or combination of genes, that predispose them to commit crime.
Twin and adoption studies
The importance of genes is illustrated by twin studies. For example, Karl Christiansen (1977) studied over 3500 twin pairs in Denmark, and found concordance rates for offender behaviour of 35% for identical twin (MZ) males and 13% for non-identical twin (DZ) males (with slightly lower rates for females).
This included all twins born between 1880 and 1910 in a region of Denmark.
Offender behaviour was checked against Danish police records. This data indicates that it is not just the behaviour that might be inherited but the underlying predisposing traits.
Raymond Crowe (1972) found that adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by the age of 18, whereas adopted children whose biological mother didn’t have a criminal record only had a 5% risk.
candidate genes
A genetic analysis of almost 800 Finnish offenders by Jari Tihonen et al. (2015) suggested that two genes (MAOA and CDH13) may be associated with violent crime. The MAOA gene regulates serotonin in the brain and has been linked to aggressive behaviour (see page 294) and the CDH13 gene has been linked to substance abuse and attention deficit hyperactivity disorder). The analysis found that about 5-10% of all severe violent crime in Finland is attributable to the MAOA and CDH13 genotypes.
diathesis stress model
If genetics do have some influence on offending, it seems likely that this is at least partly moderated by the effects of the environment. Elsewhere, we have seen how the diathesis-stress model has been applied to schizophrenia (see page 214). A tendency towards offending behaviour may come about through the combination of genetic predisposition and biological or psychological trigger - for example, being raised in a dysfunctional environment or having criminal role models.
neural explanation-prefrontal cortex
Evidence suggests there may be neural differences in the brains of offenders and non-offenders. Much of the evidence in this area has involved individuals diagnosed with antisocial personality disorder (formerly referred to as psychopathy). APD is associated with reduced emotional responses, a lack of empathy for the feelings of others, and is a condition that characterises many convicted offenders.
Prefrontal cortex/
Adrian Raine has conducted many studies of the APD brain, reporting that there are several dozen brain-imaging studies demonstrating that individuals with antisocial personalities have reduced activity in the prefrontal cortex, the part of the brain that regulates emotional behaviour. Alongside this, Raine and his colleagues (2000) found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to controls.
neural explanations-mirror neurons
Recent research suggests that offenders with APD can experience empathy but they do so more sporadically than the rest of us. Christian Keysers (2011) found that only when offenders were asked to empathise (with a person depicted on film experiencing pain) did their empathy reaction (controlled by mirror neurons in the brain) activate. This suggests that APD individuals are not totally without empathy, but may have a neural ‘switch’ that can be turned on and off, unlike the ‘normal’ brain which has the empathy switch permanently on. (Mirror neurons are also discussed on page 190.)
s-support for diathesis stress model
One strength is support for the diathesis-stress model of offending.
A study of 13,000 Danish adoptees was conducted by Sarnoff Mednick et al. (1984). When neither the biological nor adoptive parents had convictions, the percentage of adoptees that did was 13.5% (which is quite high). This figure rose to 20% when either of the biological parents had convictions, and 24.5% when both adoptive and biological parents had convictions.
This shows that genetic inheritance plays an important role in offending but environmental influence is clearly also important, providing support for the diathesis-stress model of crime.
L-adoption and twin studies
One limitation with using twin studies as genetic evidence is the assumption of equal environments. it is assumed by researchers studying twins that environmental factors are held constant because twins are brought up together and therefore must experience similar environments. However, this’ shared environment assumption’ may apply much more to MZ twins than DZ twins because MZ twins look identical and people (especially parents) tend to treat them more similarly which, in turn, affects their behaviour.
Therefore higher concordance rates for Ms in twin studies may simply be because they are treated much more similarly than DZ twins.
s-neural explanations-brain evidence
One strength of the neural explanation is support for the link between crime and the frontal lobe.
Elizabeth Kandel and David Freed (1989) reviewed evidence of frontal lobe damage (including the prefrontal cortex) and antisocial behaviour. People with such damage tended to show impulsive behaviour, emotional instability and an inability to learn from their mistakes. The frontal lobe is associated with planning behaviour.
This supports the idea that brain damage may be a causal factor in offending behaviour.
l-neural explanation-intervening variables
One limitation is the link between neural differences and APD may be complex.
Other factors may contribute to APD, and ultimately to offending. David Farrington et al. (2006, see page 334) studied a group of men who scored high on psychopathy (APD). These individuals had experienced various risk factors during childhood, such as being raised by a convicted parent and being physically neglected. It could be that these early childhood experiences caused APD and also some of the neural differences associated with it - such as reduced activity in the frontal lobe due to trauma (Rauch et al. 2006).
This suggests that the relationship between neural differences, APD and offending is complex and there may be other intervening variables that have an impact.
