Genetic Explanations of Offending Behaviour

Genetic Explanation Definition

Genetic explanations investigate the heritability and genetic correlates of offending behaviour. We can investigate the degree to which genes contribute to a trait or behaviour by calculating heritability estimates.

Family studies, including twin and adoption studies, investigate whether genetic similarity is associated with a similarity in behaviour.

However, heritability estimates only tell us how differences in genes account for differences in behaviour on a population level. Just because a trait is highly heritable in the population doesn't necessarily mean we can predict how much genes influence a trait in any specific individual.

Christiansen (1977): Twin Study

One way of studying heritability is by conducting twin studies. Twin studies compare how similar monozygotic and dizygotic twins are on a particular trait. If a trait is heritable, we expect to see a greater similarity among monozygotic twin pairs.

In the late 70s, Karl Christiansen launched a large-scale study of 3,586 twin pairs in Denmark. The aim of the study was to investigate the heritability of criminal behaviour.

• He compared the concordance rates of criminal behaviour among monozygotic (who share 100% of their genes) and dizygotic twins (who share 50% of their genes).

Christiansen found higher concordance rates of criminal behaviour among monozygotic twin pairs compared to dizygotic twin pairs. This suggests that there is an element of heritability to criminal behaviour. However, the concordance rates are relatively low, suggesting that genes are not enough when it comes to offending.

Fig. 2 - One way of studying heritability is by conducting twin studies.

Grove (1990): Study of Twins Reared Apart

Grove (1990) also wanted to investigate the genetic contribution to offending behaviour. To fulfil this aim, he conducted a study of twins who have been separated shortly after birth and grew up in different environments.

• Grove (1990) recruited 32 monozygotic twin pairs that grew up separately for his study.
• The twins were assessed through tests and interviews in terms of alcohol problems, drug problems and symptoms related to antisocial behaviour in childhood and adulthood.

Grove found significant positive correlations between genetic influences and symptoms of childhood antisocial behaviour (0.28) and adulthood antisocial behaviour (0.41).

These results indicate similarity in terms of antisocial behaviour among the twins. However, the correlations are low to moderate, even though the twins shared 100% of the same genes; this again indicates a significant contribution of environmental factors as well.

Mednick et al. (1984) Adoption Study Summary

Mednick et al. (1984) investigated the heritability of offending behaviour using an adoption study design.

They screened 14,427 Danish adoptees to see if they had at least one court conviction and looked at whether their adoptive or biological parents also had any convictions. Those under 15 were excluded.

The study's results suggest that genetic factors may influence criminality, as there was a greater similarity in criminal behaviour between adoptees and their biological families (particularly in sons and biological fathers) compared to their adoptive families.

However, we cannot rule out environmental factors.

Fig. 3 - Mednick et al. (1984) showed that adoptees (sons) are more likely to offend if their biological father has a criminal record.

Neural Explanations of Offending Behaviour

Neural explanations describe behaviour in terms of abnormalities within the brain and the nervous system. One way in which genetics could potentially influence offending behaviour is by causing abnormal monoamine metabolism. One genetic abnormality affecting serotonin metabolism is the MAOA gene.

Brunner et al. (1993) conducted a family study to investigate the effect of the MAOA gene on behaviour. The researchers studied five males within a Dutch family, the members of which had borderline mental retardation and behavioural problems.

The participants had a rare genetic condition, which only affects males and manifests as an inability to control aggressive behaviours. The researchers hypothesised that males in this family had a MAO-A enzyme deficiency due to an abnormal MAOA gene.

The researchers studied the cells of affected males and found negligible amounts of MAO-A activity, which indicated that the metabolism of monoamines in this population was abnormal. This was supported by a decreased concentration of 5-HIAA (a serotonin metabolite) in the participants' urine samples.

It was concluded that the genetic abnormality in the males was linked to their inability to control their aggression.

Role of the Environment in Biological Explanations of Offending Behaviour

Genes can also influence behaviour indirectly through one's environment. Plomin and Asbury (2005) conducted a review that highlighted that, just as environmental research needs to consider the influence of genetics, genetics research needs to consider the role of the environment.

There are several ways through which genes can impact our nurture: these include the passive, the reactive and the active way.

1. Passive way: Biological parents often create the child's early environment.
2. Reactive way: The child's temperament, which develops due to genetics, can influence how others react to them.
3. Active way: Temperament can also impact the person's choices for themselves.

Genetic Explanation: Psychology Evaluation

One strength of the genetic explanation of offending behaviour is that it is based on scientific studies and supported by empirical evidence. However, the quality of methodologies varies, and it might be difficult to separate the influence of genetics and other influences.

The genetic explanation of offending behaviour can be considered to be biologically reductionistic. It looks at aggression as caused by a biological abnormality and doesn't necessarily acknowledge how this may interact with the environment and what other social and environmental factors are related to offending behaviour.

Moreover, the extreme side of this explanation promotes biological determinism. It takes away from people's ability to make free choices about their behaviour and assumes that a genetic predisposition is bound to cause offending.

There are also important social implications to taking that deterministic position. Punishing people will be considered unethical if they offend due to their biology. After all, they were biologically predetermined to commit crimes and had no choice.