Neural and Hormonal factors in Aggression

A01 and A02 included. Dopamine, serotonin, testosterone but no cortisol.

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Neural and hormonal mechanisms in aggression
These are chemicals that enable impulses to be transmitted from one side of the brain to the other. Low
serotonin and high dopamine are associated with aggression in humans and animals.
Serotonin- In normal levels, serotonin has a calming, inhibitory effect on neuronal firing in the brain. It is
thought to lower aggression by inhibiting responses to emotional stimuli which could otherwise lead to an
aggressive response therefore lowering serotonin would cause aggression.
Mann et al. 35 healthy adults were given dexfenfluramine (known to deplete serotonin). A questionnaire was
used to assess hostility and aggression levels. They found increased hostility and aggression in males after
treatment with the drug suggesting lower serotonin levels caused the higher aggression.
Dopamine- Some evidence links higher dopamine levels to aggression.
Lavine (1997) Using amphetamines to increase dopamine activity, they found that there was an increase in
aggressive behaviour but this is an association.
Couppis et al (2008) Research suggests that individuals seek out aggressive encounters because of the
resulting high dopamine levels giving a rewarding sensation. Therefore dopamine plays a reinforcing role in
Supporting study for dopamine and serotonin: Ferrari et al
The experiment involved allowing a rat to fight for 10 days to build aggressive behaviour and disallowing it to
do so on the 11th day. On this day, serotonin and dopamine were measured in the brain and they found low
serotonin and high dopamine. This suggests that the aggressive behaviour was consistent with the hormone
levels because the rat was anticipating a fight.
Use of rats in the experiment- The findings cannot be applied to humans because we function
differently compared to rats and the release of hormones may be different to humans.
Difficult to establish a link- between dopamine and aggression. Couppis et al conducted a study
with mice where they `turned off' dopamine in the brain making the rats movement difficult. The restriction
of movement can be applied to this study as this may have made it difficult for the rats to respond to

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These are chemicals that control and regulate bodily functions. They initiate responses to external threats
etc... High testosterone and low cortisol levels are associated with aggression.
Testosterone- A hormone produced by both males and females but in smaller amounts in females. It
produces male characteristics.
Olweus et al They compared institutionalised male students with non-delinquent male students. Delinquent
students, who had a history of violent crimes, had slightly higher testosterone levels compared to those with
a history of non-violent offences.…read more


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