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Biological explanations of
aggression
Brain functioning as an explanation of
aggression
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Essentially the argument is
……Brain abnormalities……
..... are associated with aggression
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Which other brain structures are involved
in aggressive behaviour?
• Rat lesion studies suggest
that different types of
aggression may be
controlled by different
subsets of brain structures.
– Limbic sites: (amygdala,
septum and hypothalamus)
Amygdala
•
Rabies is caused by a virus that damages the temporal lobe. Rabid
animals are violently aggressive.
•
Autopsies of Charles Whitman who carried out a sniper attack from
the University Tower at Texas in 1966, showed he had a tumour
pressing on his amygdala. He left a note begging for his brain to be
studied.
http://www.learner.org/resources/series142.html?pop=yes&pid=1593
The Role of the Amygdala
• Kluver-Bucy syndrome – taming
effect found in rhesus monkeys
by removing part of the
temporal lobes and therefore
destroying the amygdala.
• Narabyashi et al (1972) – 43 / 51
patients whose amygdala was
destroyed through
psychosurgery showed reduced
aggression afterwards.
• Mark & Ervin (1970) – case study of
female patient behaviour following
electrical stimulation of amygdala.
• She exhibited facial grimacing,
became very angry and flung herself
at the wall.
• Ashford (1980) – temporal lobe
epileptics often become aggressive,
attacking furniture and people.
• Wong et al (1997) – criminals with violent tendencies
have reduced size amygdala
• Van Elst et al (2000) aggressive patients with temporal
lobe epilepsy, amygdala had lost 20% of its volume.
•The exact role of the
amygdala in aggression is
unclear, but it is certainly a
significant one.
•Research suggests an
interaction between the
amygdala and the pre-frontal
cortex.
The Role of the Prefrontal Cortex
• Regulates the emotional responses driven by the
amygdala.
• Damage to prefrontal cortex results in impulsivity,
immaturity and loss of control.
• Anderson et al (1999) – damage during infancy
related to aggressive behaviour as adults.
• Case studies comparing early onset damage with
adult onset damage to frontal lobes. Early onset
patients also performed poorly on tests of moral
and pro-social reasoning.
• Raine et al (1997) –
investigated brain activity of
41 murderers using PET
scans.
• Found reduced glucose
metabolism in prefrontal
cortex, suggesting this brain
area is less active than in
normal controls.
• Volkow et al (1995) found
violent psychiatric patients
had reduced cerebral blood
flow to prefrontal cortex.
•http://www.youtube.com/
watch?v=_0aNILW6ILk&featu
re=related
•During the 1940s, frontal lobe
lobotomies were performed with
startling regularity ; partly because
of the ‘calming’ effect on patients
with a range of mental health
problems – from depression to
ADHD to OCD.
Raine et al (1997) Brain abnormalities
in murderers by positron emission
tomograpghy
• Raine et al., (2000) found that the
(prefrontal cortex, which inhibits aggressive
behaviour), was 14% less active than
normal in non-abused murderers &15%
smaller in antisocial males.
THIS IS YOUR CLASSIC STUDY
• http://www.learner.org/resources/series142.html#
Evidence:
Phineas Gage
• Railroad Accident – Sept. 1848
• Leveling land with Dynamite
• 3 foot inch thick tamping rod was
projected in to his brain
• Entered via cheek, left Eye and into the
frontal lobes
• Driven by other workers in a ox-cart to
Doctor’s office
• The rod damaged the pre-frontal
cortex. This region is implicated in
personality changes and
aggression/violence.
What
happened?
• Lost conscious and had convulsion immediately, but awoke quickly and was
talking and walking soon afterwards
• Never showed any impairment of movement or speech
• Memory was intact, and was capable of learning new things
• However, within months his personality had changed dramatically
– He became extravagant and anti-social, a foul mouth liar with bad manners,
frequently got into fights and assaults.
– could no longer hold a job or plan his future
• According to friends “Gage was no longer Gage”, he died 13 years later
– A penniless, epileptic
Issues and Debates
• The exam requires you to develop an
appreciation of issues and debates in
psychology that are relevant to the particular
topic.
• What issues/debates are relevant in the
Aggression topic?
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Reductionism in Psychology
• Reductionism is a scientific approach that tries
to explain phenomena in terms of basic
elements.
• For example, a psychobiologist investigates
behaviour by looking at brain activity – this is
a reductionist approach as it ignores
psychological and cultural variables
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Reductionism in Psychology (con)
• The types of reductionism in psychology of
most interest to us are:
1. Evolutionary reductionism = attempts to
explain behaviour in terms of evolutionary
theory and may ignore the fact that
cultures/societies develop in ways that may
not involve evolutionary processes.
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Reductionism in Psychology (con)
2. Methodological reductionism = relates to the
scientific approach in psychology involving
controlled experiments. Human behaviour has
so many variables they cannot all be identified
and operationalised.
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Task
• Look through the section on Aggression and
identify at least three examples of
reductionism
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AO2
Support for brain function impacting aggression:
• Individuals prone to aggression are more likely
to drink & become aggressive while drunk. –
(Alcohol effects the brain).
4 in 10 violent crimes committed by people
who’ve been drinking.
• Surveys of rapists--over half report they were
drinking before committing the rape.
• Alcohol – reduces self-awareness & disinhibits
(deindividuates). It also ‘switches off the frontal
areas leaving the aggressive ‘limbic’ areas
without cognitive control!
AO2 clarification needed
• Need to distinguish between aggression &
dominance
• Issue relates to the internal validity if the
research as studies may be measuring
different things, making comparison of results
difficult
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AO2 issues
• Gender bias evident as most research done on
males (animals and humans) whereas it is
known that there are differences between the
genders in androgens
• Also cultural bias as most research conducted
in western countries
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AO2 debates
• Physiologically reductionistic to just consider
role of biochemistry alone
• Also need to consider genetic factors
• Also need to consider the contribution of
environmental factors such as situational cues,
temperature, noise, overcrowding, and the
role of learning
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AO2 application
• Clearly a very important & useful area of
biopsychological research and theory as aggression
associated with many anti-social phenomena in society,
eg. numerous forms of crime, violence
• If the role of biochemistry can be understood it can
perhaps be treated or managed
• Although there would be ethical issues associated with
giving people drugs simply to alleviate aggression (ie.
for social control) , or male castration, even if it may be
in the interests of multiple parties
• Could perhaps be treated more ethically through diet
(tryptophan) and exercise
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