• How does the research support the N.M theory?
• Crockett et al (2008) carried out a repeated measures
experiment on 20 participants. In both conditions the
participants had fasted and were given a protein drink in the
morning before taking part in the study. The difference in the
drink was the difference in the conditions: one drink contained
tryptophan, which the body needs to make serotonin; the other
drink did not contain it. On both days that the study took place
participants played the ultimatum game. In this game one
player poses a way to split a sum of money with a partner. In
the condition where the participants had had the drink that did
not contain tryptophan (so their serotonin levels were low) they
showed increased aggression toward offers they perceived to
Davidson et al (2000) found that violent criminals had
markedly lower levels of serotonin to non-violent criminals.
Mann et al (1990), who manipulated levels of serotonin.
They administered the drug dexfenfluramine known to
deplete serotonin levels, to 35 healthy adults. They then
used a questionnaire to assess hostility and aggression
levels, and found these levels had increased among males
after treatment with the drug.
Potegal et al (1996) researched hamsters and found that
stimulation of the corticomedial amygdala increases
aggression and lesioning of this area reduces aggression in
There are many studies that investigate the role of neural
mechanisms in aggression which use animals and/or
specific types of people (e.g. criminals).
What potential problems could this pose?
Use at least one Psychological term
• Describe and evaluate the role of hormonal mechanisms
• Outline and evaluate research into testosterone and
• Identify the issues of gender bias and determinism in
Starter- On boards
As a spider diagram or a list…
What do you know about hormonal mechanisms in relation
• High testosterone
• High testosterone/low serotonin
• Mismatch effect
An alternative theory is the mismatch effect. This effect also
reflects the view that testosterone links to dominance, so the
higher the testosterone you have, the more dominance or
status you also want.
According to the mismatch effect, testosterone only
becomes important when there is a mismatch between the
level of testosterone in the body and the status of the
If an individual has high status and high testosterone, no
aggression will result, but high testosterone and low status,
or low testosterone and high status, will result in aggression.
Level of Testosterone
Evidence in relation to hormonal mechanisms
• Kreuz & Rose (1972)
• BPS article
• Josephs et al (2006)
Kreuz and Rose (1972)
Kreuz & Rose (1972) studied testosterone levels in a group of 21 young adult
male prisoners and found a correlation between scores on psychological tests
Their testosterone levels did not relate to whether they fought with others
whilst in prison, but it did relate to the nature of the crimes they had committed.
The 10 prisoners with histories of more violent crime such as assault and
armed robbery did have statistically higher levels of testosterone than the 11
prisoners who had committed non-violent crimes.
Ground this to the possible explanations for the role of testosterone on aggression
Any concerns about the research method or sample?
• Read the article from the BPS and answer the questions
at the bottom of the sheet.
Josephs et al (2006)
Josephs et al (2006) conducted an experiment using the saliva
samples of participants and found that men and women high in
testosterone levels reacted negatively after a loss of high status
becoming stressed, confused, and anxious which is a state of
mind that could lead to aggression.
However, men and women with low levels of testosterone who
were put into a position of high status showed the same pattern of
upset which could also lead to aggression.
• Ground this to the possible explanations for the role of
testosterone on aggression
Determinism (vs free will)
• Determinism sees human behaviour of a product of forces
beyond the control of the individual.
• States that people have no control over their actions.
• Determinists would argue that internal and external forces
control a persons behaviour. Two types of determinism are
environmental determinism and biological determinism.
• This means behaviour should be predictable.
• Determinism is a scientific account of behaviour.
Strengths and weaknesses of taking a deterministic view
S = Emphasis on cause and effect= make the world more
understandable and predictable= could be worthwhile in
trying to change certain things in society.
S = Purpose and goal of science= make its more
acceptable to society = scientific basis and objectivity.
W = Does not allow for freewill, freewill is an illusion - we
think we have choice.
W = Can never fully explain behaviour because behaviour
may be too complex.
• How is this relevant?
• How does it link to hormonal mechanisms? (extn- Neural
• Why is this a problem?
(P) All explanations; serotonin, the role of the brain and
testosterone: into aggression have also been criticised by psychologists
for being deterministic.
(E) All theories suggest that aggression is the result of neural and
hormonal mechanisms- biological factors. All theories fail to consider
the role of free will in that we have a choice in how we behave and thus
fails to take into consideration individual differences shaped by
(C) With a lack of individual differences the theory fails to provide a
good explanation into institutional aggression of all individuals. As a
result the external reliability of all theories is weakened.
A pharmaceutical company has introduced a new drug
which suppresses testosterone and claims to lower the
level of aggression in individuals. They are offering this
treatment to the NHS and prison services for service users
displaying aggressive behaviour.
What moral and ethical issues does this raise?
Question- essay plan
• Discuss the role of neural and/or hormonal mechanisms
(8 marks+ 16 marks)
• Bullet point / list a structure of this essay answer