A03

• Point: One strength is support for the role of the MAOA gene in aggression.

  Evidence: Mertins (2011) found that men with the low-activity variant of the MAOA gene (MAOA-L) exhibited greater aggression compared to those with the high-activity variant (MAOA-H) during a money-distributing game.

  Explain: In addition, those with the MAOA-H variant were found to be more co-operative.

  Link: Therefore, this suggests a direct link between genetic factors, specifically the MAOA gene, and aggression.
• However, the study by Mertins also showed that non-genetic factors are crucial.

  Mertins (2011) found that participants with the low-activity MAOA variant (MAOA-L) exhibited cooperative behaviour rather than aggression when made aware of cooperative behaviour among others in the study.

  This indicates that environmental factors, such as social norms and awareness of others' behaviour, play a significant role in modulating the expression of aggression.

  Therefore, genes interact with environmental factors to influence aggression, supporting the interactionist approach.
• Point: A strength of the genetic factors is that there is non-human animal studies to support the role of the MAOA gene.

  Evidence: Godar (2014) used the gene deletion technique and found that knocking out the MAOA gene in mice led to increased serotonin and hyper aggression.

  Explain: In addition, when serotonin was blocked by fluoxetine, the mice reverted back to their non-aggressive behaviour.

  Link: Therefore, this adds validity to the genetic role that MAOA gene plays in aggression.
• A further limitation of research into genetic factors is the methods that are used to measure aggression.

  For example, many studies use self-reports, parent/teacher reports and direct observations which may affect whether aggression is accurately measured.

  This is shown in Rhee and Waldman’s (2002) meta-analysis which found that when studies used self-report rather than teacher/parent reports, there was a greater influence of genetic factors found.

  Therefore, this questions the validity of conclusions drawn about the role of genetic factors if they depend on how aggression was measured.