Role of Neural and Hormonal Influences on Aggression.

Notes outlining the role of neural and hormonal influences on aggression, focusing on serotonin and testosterone. With relevant research examples and evaluative points.

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  • Created on: 15-06-11 10:45
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Aggression -
Role of neural and hormonal influences:
Biological explanations view aggression as having internal physiological
causes rather than external social or environmental ones. Research has
concentrated on several biological areas, including genetics, hormones,
neurotransmitters and brain structures themselves. Biological factors can be
perceived as sole causes of aggression or as working in conjunction with other
external factors.
Neurotransmitters and hormones play an important role in many areas of
human functioning, and the neurotransmitter serotonin, along with hormones
such as testosterone, adrenaline and the female hormones oestrogen and
progesterone, have been identified as having links to aggressive behaviour.
Serotonin has been linked with various bodily effects, such as sleep, but low
levels of the neurotransmitter have been particularly associated with
increased levels of aggression.
Delville et al (1997) found that drugs increasing serotonin production
lead to reduced levels of aggression, suggesting that high levels of
serotonin are linked to increased aggression.
Linnoila and Virkunen (1992) found a relationship between low levels of
serotonin and highly explosive violent behaviours, suggesting that a
lack of serotonin is linked to aggression.
Lidberg et al (1985) compared serotonin levels of violent criminals with
non-violent controls, finding the lowest levels of serotonin among the
violent criminals.
Higley et al (1996) set up an island colony of forty-nine infant male
monkeys, regularly measuring their serotonin levels and observing their
behaviour. After four years, eleven of the monkeys were dead or missing,
46% of which had very low levels of serotonin and regularly exhibited
aggressive behaviour. Not one monkey with high levels of serotonin
was dead or missing. Those with high levels stayed in close proximity to
each other, indulging in a lot of social grooming. This suggests that

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Various drugs, approved by clinicians, have been associated with
reducing serotonin and increasing aggressive behaviour. Penttinen
(1995) reported that cholesterol-lowering drugs and appetite suppressors
produce such effects. Some drugs have been withdrawn from medical
practice because of their potent anti-serotonergic effects.
The fact that alterations in serotonergic activity can induce profound
changes in behaviour have been used in positive ways, such as the
introduction of Prozac, which works by enhancing serotonin activity and
has been used to treat depression.…read more

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Bermond et al (1982) found that testosterone only affects certain
types of aggression in animals, such as inter-male aggression as a
defensive response to intruders, while predatory aggression is not
Albert et al (1993) found that raising testosterone levels in female rats
elicited aggressive behaviour in the presence of certain environmental
events, such as competition, suggesting that testosterone alone is not
responsible for aggression as it requires certain environmental
triggers.…read more


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