Aggression in both animals and humans has been associated with low levels of serotonin and high levels of dopamine. Serotonin appears to stop aggression. So it is harder to stop aggression for those people with low levels of serotonin. David et al suggests that serotonin levels found in criminals are lower than in non-violent criminals. It has also been found that reducing serotonin levels in Vervet monkeys increases their aggressive behaviour, and increasing serotonin levels reduces aggressiveness.
Support that serotonin leads to aggressive behaviour has been found, as human and animal research suggest that serotonin levels influence aggression and violent behaviour. There seems to be a negative correlation as low levels of serotonin, increase aggressive behaviour. Although we cannot determine a causal link as the cause of aggression cannot be attributed solely to serotonin. The link between dopamine and aggression is not as clear as with serotonin. Although there does seem to be a relationship between high levels of dopamine and aggression. Dopamine is produced in response to rewarding stimuli such as food, sex and recreational drugs. Research suggests that some individuals try to find aggressive encounters because of the rewarding sensations it brings, caused by increases in dopamine. Researchers have also suggested that people can become addicted to aggression, in the same way that they become addicted to food, gambling, etc.
Ferrari et al. made a rat fight for 10 consecutive days. On the 11th day it was not allowed to fight. Researchers found that in anticipation of the fight the rat’s dopamine levels had raised and serotonin levels had decreased. This shows that experience had altered the rat’s brain chemistry, gearing it up for a fight. This supports the idea that both neurotransmitters are involved in aggressive behaviour and suggests a possible cognitive element in aggression i.e. the anticipation the rats experienced seemed to altar the levels...
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