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Neural and Hormonal Mechanisms

1. Nerotransmitters

   • Chemicals that enable impulses in the brain to be transmitted from one area of the brain to another. There is evidence that serotonin and dopamine are linked to aggressive behaviour
   • Serotonin
     • Thought to reduce aggression by inhibiting responses to emotional stimuli that may lead to an aggressive response
     • Low levels in the brain are linked to an increase in impulsive behaviour, aggression and even violent suicide
     • Some drugs can alter levels and increase aggressive behaviour.
       • Mann et al
         • Gave 35 healthy PPs a drug known to alter levels and used a questionnaire to assess hostility and aggression levels.
         • Found treatment was associated with an increase of hostility and aggression scores in men only
   • Dopamine
     • Link between high dopamine levels and aggression is not well established but there is some evidence to suggest the link exists
     • Lavine
       • Increases in activity via amphetamines have also been associated with aggressive behaviour
     • Buitelaar
       • Antipsychotics which reduce the levels, have been shown to reduce aggressive behaviour in violent delinquents

2. Evaluation

   • Serotonine
     • Evidence from Non-Human Studies
       • Raleigh et al
         • Found people fed on diets high on trytophan exhibited decreased levels of aggression.
         • Those fed on low tryptophan diets showed increased levels of aggression suggesting that the difference in aggression could be down to their serotonin levels
       • Popova et al
         • Animals are selectively bred for domestication and for increasingly docile temperaments, there is a corresponding increase over generations in brain concentrations of serotonin
     • Evidence from Antidepressants
       • Bond
         • Low levels are associated with low impulse control and agg. drugs that raise levels should produce concurrent lowering in agg. Clinical studies of anti-depressant drugs do reduce irritability and impulsive aggression
   • Dopamine