Discuss genetic explanations of aggression

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Discuss genetic explanations of aggression:

The genetic explanation of aggression suggests that aggressive behaviour is hereditary and is passed on through a person’s genes, which would cause aggression to run in families. Similarly your genes could cause you to have a vulnerability or predisposition to aggressive behaviour. Studies on this could be grouped into two types, twin studies and adoption studies. Twin studies compare the difference in concordance rates (likelihood of both twins being aggressive) for MZ and DZ twins. For example, McGuffin and Gottesmann (1985) found a concordance rate of 87% for aggressive and antisocial behaviour for MZ twins, compared with 72% for DZ twins. Adoption studies look at aggressive behaviour in children who have been brought up and influenced by adoptive parents not their biological parents. For instance Hutchings and Mednick (1973) reviewed over 14,000 adoptions in Denmark. They found a significant positive correlation between the number of convictions for criminal violence among the biological parents and the number of convictions for criminal violence among their adoptive sons.

In addition, researchers have identified a number of ‘candidate genes’, genes that are thought to contribute to an increased risk of engaging in antisocial and aggressive behaviour. For instance, dysfunctions of serotonin and dopamine are known to increase aggressiveness; therefore, genes that are associated with the expression of these neurotransmitters are also considered to influence the aggressive behaviour indirectly. A meta-analysis by Farone et al (2001) of studies gene for the dopamine receptor D4 found a modest association between the variants of this gene and ADHD. The relationship between ADHD and aggressive behaviour has been consistently demonstrated in research. Other studies have concentrated on the gene for the dopamine receptor D3. Retz et al (2003) found an association between a variant of the DRD3 gene and both impulsivity and ADHD symptoms in violent offenders. Researchers have also found that the gene for MAOA may also be associated with individual differences in aggressive behaviour. MAOA breaks down neurotransmitters such as noradrenaline and dopamine after they have transmitted an impulse from one cell nerve to another. Research by Brunner et al has demonstrated the link between MAOA and aggressive behaviour. Brunner et al (1993) studied a family in the Netherlands, many of whose male members behaved in a particularly violent and aggressive manner. These violent individuals were found to have abnormally low levels of MAOA in their bodies.

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The genetic explanations of aggression are arguably reductionist. The explanation focuses purely on one biological factor, genetics. In doing so it overlooks many other important factors, for instance deindividuation. Studies such as Mullen (1986) offer support that deindividuation can lead to aggression and therefore by not taking it into account, the genetic explanations are shown to be reductionist. Mullen analysed newspaper reports of 60 lynchings that had taken place in the first half of the 20th century. It was found the more people there were in the lynch mob, the more the deindividuation and the greater the savagery with which members of the crowd killed their victims. This therefore demonstrated support for the deindividuation theory of aggression. In addition, the twin study carried out by McGuffin and Gottessman

(1985) only found a concordance rate of 87% for aggressive and antisocial behaviour for MZ pairs. Considering MZ twins have identical genes, the concordance rate should have been 100% if genetics alone caused aggression. Therefore as the concordance rate was not 100% this indicates that there must be other factors involved, therefore making the genetic explanations of aggression reductionist as they fail to take these into account. Yet it could be argued that the genetic explanations of aggression are made slightly less reductionist due to the fact they acknowledge the influence of the neurotransmitters serotonin and dopamine and therefore don’t overlook neural mechanisms and their involvement in aggressive behaviour.

The genetic explanations of aggression are, as made obvious by the name, heavily nature based. The explanation focuses on aggression being genetic and it being passed down in families, which clearly makes it on the nature side of the nature vs. nurture debate. Studies such as Hutchings and Mednick (1973) demonstrate this further. Hutchings and Mednick (1973) reviewed over 14,000 adoptions in Denmark. They found a significant positive correlation between the number of convictions for criminal violence among the biological parents and the number of convictions for criminal violence among their adoptive sons. These findings are very compelling evidence that the genetic explanations are nature based as it was their biological parents that had an effect on whether they were aggressive or not as opposed to their adoptive parents who nurtured and raised them. However, Twin studies such Mcguffin and Gottesman could potentially demonstrate that the genetic explanations of aggression are slightly nurture based. Twins are arguably raised in the same way and exposed to similar things when growing up, especially MZ twins. This could therefore account for the concordance rates in this study both being so high, 87% MZ and 72% DZ. Aggressive behaviour could be learnt by both of the twins from the media or peers or alternatively aggressive behaviour by one twin could be mimicked by the other. Therefore this could demonstrate that the genetic explanations are partly nurture based, however for the large part, they are nature based.

The genetic explanation of aggression is arguably deterministic. It suggests that if a person has these ‘aggressive’ genes then they will inevitably be aggressive and that a person does not have the power to control it. Some legal experts have questioned the assumption that a violent offender can still exercise free will despite possessing a genetic predisposition to violent crime. For example in 2009 an Italian judge decided to reduce the prison sentence of a person convicted of murder because he was found to be the carrier of genetic variants thought to be associated with a predisposition to aggressiveness (Forzano et al 2010). This supports the idea that a person genetically predisposed to aggression cannot exercise free will as to whether they will be aggressive or not, making the genetic explanation of aggression deterministic. However, Hines and Malley-Morrison (2005) claim that the finding that aggressive behaviour might be genetically influenced simple means that some people, as a result of their genotype are more likely to commit aggressive acts than people without the genotype. Therefore instead of being deterministic, the genetic explanation could be probabilistic.