genetic factors in aggression

• P: an advantage of MAOA gene research is that it offers an explanation for the uneven rates of violence for males and females

  E: Nelhoff suggests this may be a consequence of the differential genetic vulnerability that males and females have to the MAOA gene.

  E: MAOA gene is liked to the x chromosome . women have 2 x chromosomes whereas males have one . when men inherit and x linked gene from their mothers, they are more likely to be affected by it whereas women inheriting the same gene are generally unaffected.
• link for nelhoff


  L: this could explain why males typically show more aggressive behaviour than females.
• link for tihonen 


  L: however, critics argue that although these genes may make it harder for some people to control violent urges, they do not predetermine violent behaviour.
• P: in many countries, the majority of all violent crime is committed by a small group persistent offenders, a recent study in finland has added research support that the MAOA gene is implicated in sever violent behaviours such as murder

  E: Tihonen studied finnish prisoners, revealing that the MAOA low activity genotype (MAOA-L) in combination with another gene (CDH13) was associated with extremely violent behaviour. There was no substantial evidence for either of these genes among non violent offenders, indicating that this combination of genes was specific for violent offending only
• P: It is difficult to establish genetic contributions to aggressive behaviour for the following reasons:

  • E: more than one gene usually contributes to a given behaviour
  • as well as genetic factors, there are many non-genetic influences on the manifestation of aggressive behaviour
  • these influences may interact with eachother. genetic factors may affect which environmental factors have an influence, and vice versa

  L: the last point is demonstrated in the study by casp and highlights the problem of identifying the specific contribution of genetic factors to aggressive behaviour.