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Neurons and hormones
Biological explanations of aggression assume that the propensity for aggressive behaviour lies in an
individual's biological constitution. A number of biological factors have been identified.
For example, the male sex hormone testosterone is thought to influence aggression in both males and
females. Evidence for this association comes from a number of sources involving both violent and
nonviolent populations.
It has been suggested however, that we should make a distinction between aggression and dominance.
High levels of testosterone have been associated with dominance behaviour and occasionally, this
takes the form of aggression. However, in humans, dominance is likely to be expressed in more varied
and subtle ways than simple aggression (e.g. through statusstriving behaviour assertiveness,
competitiveness, etc.).
The basal model of testosterone suggests that testosterone causes a change in a person's dominance.
Alternatively, the reciprocal model of testosterone agrees with the fact that testosterone levels vary
with the person's dominance. However, it proposes that levels of testosterone are the effect of, and
not the cause of, dominance. Evidence for this model comes from longitudinal and experimental
Significance for this explanation comes from Dabbs et al. who supports the influence of
testosterone on aggression. (1987). the findings suggest an association between high levels of
testosterone and a history of violent crimes. This evidence implies that the sex hormone testosterone
has an effect on the levels of aggression displayed, increasing the credibility of this explanation.
However a limitation of this study is that it only found Correlation not causation because most of the
research in this area offers, at best, an association between biological factors and aggression therefore
cause and effect cannot be established. The study doesn't explain what their testosterone levels were
before the crime, so the direction of causality is at question, as what happened first the crime then high
testosterone or high levels then crime? So this decreases the validity of the study which consequently
affects the applicability of the findings, and therefore the hormonal mechanism explanation.
Other chemicals, such as neurotransmitters, have also been associated with aggression. There is some
evidence that at least two of these neurotransmitters, serotonin and dopamine, are involved.
Evidence from research, conducted with human and n0nhuman animals, has supported the claim that
low levels of serotonin in the brain increases susceptibility to aggression. Furthermore, researchers had
found a gene associated with aggressive behaviour. This gene is involved in the production if the
protein MAOA (monoamine oxidase A), which in turn regulates the levels of serotonin in the brain.
In addition evidence, derived from studies on the consumption of both licit and illicit drugs known to
influence levels of dopamine, suggests that increased levels of dopamine are linked to increased
aggressive behaviour although the link between high levels of dopamine and aggressive behaviour is
not as well established as with serotonin.
Supporting evidence for this explanation of licit and illicit drugs effecting levels of dopamine comes
from (Lavine, 1997). Who found an association between increased aggressive behaviour and the use
of amphetamines, which increase dopamine activity. his shows that there is a correlation between high

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However, this study is low in temporal validity because it was conducted in 1997 and since then the
world has developed medically, so the readings may differ from now and may be more accurate now
than then, therefore this decreases the applicability of the findings and therefore also decreases the
explanation that it supports.
However these explanations adhere to the biological approach as it suggests that our genetic makeup
and bio chemicals lead to aggression, which is passed through our genes/hormones/neurotransmitters.…read more


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