Biological explanations: Genetic and neural Flashcards
what does the genetic explanation suggest?
Genetic explanations for crime suggest that would-be offenders inherit a gene, or combination of genes, that predispose them to crime.
who conducted twin and adoption studies?
Christiansen (1977) - twin
Crowe (1972) - adoption
Twin and adoption studies
The importance of genes is demonstrated in twin studies.
Christiansen (1977) studied over 3500 twin pairs in Denmark and found concordance rates for offender behaviour of 35% for MZ male twins and 13% for DZ male twins. 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.
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 mother didn’t have a criminal record only had a 5% risk.
Candidate genes
A genetic analysis of almost 800 Finnish offenders by Tiihonen et al (2015) suggested that two genes may be associated with violent crime. The MAOA gene regulates serotonin in the brain and has been linked to aggressive behaviour. 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 DCH13 genotypes.
Diathesis-stress model of offending
If genetics do have some influence on offending, it seems likely that this is at least partly moderated by the effects of the environment. A tendency towards offending behaviour may come about through the combination of genetic predisposition and biological or psychological trigger.
Evaluation of genetic explanations (brief)
weakness - assumption of equal environments
strength - support for diathesis-stress model
weakness of genetic explanations
one limitation with using twin studies as genetic evidence is the assumption of equal environments. It is assumed by researchers studying twin 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 tend to treat them more similarly which in turn affects their behaviour. Therefore, high concordance rates between MZ twins may simply because they are treated more similarly than DZ twins.
strength of genetic explanations
there is support for the diathesis-stress model of offending. A study of 13,000 Danish adoptees was conducted by Mednick et al (1984). When neither the biological nor adoptive parents had convictions, the percentage of adoptees that did was 13.5%. The 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.
what does the neural explanation suggest?
Evidence suggests there may be neural differences in the brains of offenders and non-offenders.
APD
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
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 prefrontal cortex is the part of the brain that regulates emotional behaviour. Raine and his colleagues found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to controls.
mirror neurons
Recent research suggests that people with APD can experience empathy but more sporadically than the rest of us. Keysers (2011) found that only when offenders were asked to empathise did their empathy reaction activate. The empathy reaction is controlled by mirror neurons. 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 empathy permanently switched on.
Evaluation of neural explanations (brief)
strength - link between crime and frontal lobe
weakness - link between neural differences and APD complex
strength of neural explanations
there is support for the link between crime and the frontal lobe. Kandel and Freed (1989) reviewed evidence of frontal lobe damage 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.
weakness of neural explanations
one limitation is the link between neural differences and APD may be complex. Other factors may contribute to APD, and ultimately offending. Farrington et al (2006) studied a group of men who scored high on psychopathy. These individuals had experienced various risk factors during childhood. It could be that those 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. This suggests that the relationship between neural differences, APD and offending is complex and there may be other intervening variables that have an impact.
