neural and hormonal influence

• P: duke provided support for the serotonin deficiency hypothesis as an explanation for aggressive behaviour in human beings.

  E: carried out a meta-analysis of 175 studies. analysis found a small relationship between serotonin levels and aggression. also found magnitude of the relationship varied with methods, used to assess serotonin functioning, with self-reported versus other reported aggression - only other-reported aggression was positively correlated to serotonin functioning

  L: This suggests that the relationship between serotonin and aggression is more complex than origionally thought
• P: raine provided support for the role of the hippocampus in aggressive behaviour in their study of violent offenders.

  E: studied 2 groups of violent criminals who faced conviction and some who had evaded the law (successful). Latter group considered to be 'cold' criminals whereas former group acted more impulsively, which is why they were caught. MRI revealed asymmetries in hippocampus in the 'unsuccessful' group. Hippocampus in either hemisphere of brain differed in size, an imbalance presumed to have risen in early brain development.
• link for raine 


  L: researchers suggested asymmetry might impair the ability of the hippocampus and amygdala to work together - emotional info is not processed correctly, leading to inappropriate verbal and physical responses as a result.
• P: pardini found that reduced amygdala volume can predict the development of persistent aggression

  E: longitudinal study of male participants from childhood to adulthood - some 56 of participants with varying histories of violence were subjected to brain MRI at 26. results showed participants with lower amygdala volumes showed higher levels of aggression and violence - relationship between amygdala volume and aggressive behaviour remained even after confounding variables controlled
• link for pardini


  L: this suggests the amygdala plays an important role in evaluating the emotional importance of sensory info and that lower amygdala volume compromises this ability and makes a violent response more likely.