Neural mechanisms
A01
- Aggression is hostile behaviour that is intended to cause physical or
psychological harm.
- Proactive aggression - ‘cold-blooded’ aggression, a method of getting what you
want
- Reactive aggression - hot blooded aggression accompanied by physiological
arousal
- Limbic system consists of sub cortical structures in the brain
- Paper and Maclean linked the Limbic system to emotional behaviours
Defined as the hypothalamus, amygdala, parts of the hippocampus
- Reactivity of the amygdala is an important predictor of aggressive behaviour –
how humans assess and respond to env threats
- Serotonin is a neurotransmitter that has inhibitory effects in the brain
- Normal levels of serotonin in the OFC are linked with reduced firing neurons –
associated with greater behaviour self control
Decreased distrusts this mechanism - reducing self control and leading to
impulsive behaviour
A03
L - Other brain structures
P - One limitation of the limbic explanation is that research has produced
contradictory evidence about which brain structures are actually responsible for
aggression, undermining the clarity of the explanation.
E - For example, although the amygdala is central to limbic system accounts, research
shows it functions in conjunction with the OFC, which is not part of the limbic system.
Coccaro et al found that people with aggressive psychiatric disorders showed reduced
OFC activity, demonstrating that aggression cannot be explained by limbic structures
alone.
E - This OFC activity weakens the brain’s impulse-control capabilities, meaning
individuals struggle to regulate emotional responses triggered by the amygdala. This
suggests that aggression arises from dysfunctional neural networks, not a single
structure, indicating that limbic-only explanations overlook essential components of
emotional regulation.
L - it shows that aggression is governed by a broader and more interconnected neural
system than limbic explanations propose.
By oversimplifying the neural basis of aggression, limbic-only accounts lack internal
validity, as they fail to accurately represent the complexity of neural regulation
,S - Drugs and serotonin
P - One strength of the serotonin explanation is that there is strong experimental
evidence supporting the causal role of serotonin in reducing aggression.
E - Berman et al administered either a placebo or paroxetine (a serotonin-enhancing
SSRI) before ppts took part in a provocation task involving electric shocks.
Ppts who received paroxetine delivered fewer and less intense shocks than the placebo
group, demonstrating a measurable reduction in aggression.
E - suggests that increasing serotonin levels improves impulse control and reduces
aggressive responses by promoting greater inhibition of neural circuits linked to
emotional overarousal.
Because the study used a placebo-controlled design, it allows researchers to isolate
serotonin’s specific effects, strengthening confidence in a cause-and-effect
relationship between serotonin functioning and aggression.
L - This is a strength because controlled, replicable drug studies provide highly reliable
evidence: similar procedures are likely to produce similar results.
The careful use of blinding and placebo conditions also improves internal validity,
ensuring that the observed reduction in aggression is attributable to serotonin
modulation alone.
C - However, drug studies may not reflect real-life aggression because laboratory
provocation tasks lack real consequences. This can limit the ecological validity,
meaning results may not generalise to genuine aggressive encounters
L - Neural factors may be direct or indirect
P - Nonetheless, a further issue is the ongoing debate over whether neural factors
influence aggression directly or only indirectly, through interactions with psychological
and social factors.
E - Gospic et al found heightened amygdala activity during aggressive responses, and
benzodiazepines reduced both amygdala reactivity and aggression.
Serotonin is also known to reduce aggression by inhibiting neuronal activity.
However, Denson et al showed that serotonin’s link to aggression is mediated by social
and cognitive variables, suggesting it is not a simple direct cause.
E - implies that low serotonin may impair OFC function, making people more
impulsive, but whether that impulsivity becomes aggression depends on situational
cues, stress, social learning, and individual differences in cognitive control.
The explanation therefore becomes interactionist, showing that neural activity alone
cannot fully determine aggressive behaviour.
L - highlights that purely bio explanations are reductionist, oversimplifying aggression
by ignoring how environment, cognition, and learning interact with brain function. A
,more holistic approach would provide a fuller and more realistic account of
aggression.
C - However, identifying biological predispositions remains useful, as it helps explain
why some individuals are more vulnerable to aggression when exposed to particular
environments, supporting a diathesis-stress perspective
Hormonal mechanisms
A01
- Aggression is hostile behaviour that is intended to cause physical or
psychological harm.
- Proactive aggression - ‘cold-blooded’ aggression, a method of getting what you
want
- Reactive aggression - hot blooded aggression accompanied by physiological
arousal
- There is evidence that progesterone (a female hormone) plays an important role
in aggression in women
- Levels of progesterone vary during the ovulation cycle and are lowest during and
just after menstruation
- Ziomkiewicz et al found a negative correlation between progesterone levels and
self-reported aggression
- Testosterone is an androgen responsible for the development of masculine
features - It is thought to be linked to aggressive behaviour.
- Daly and Wilson - Men become more aggressive towards other men at a time in
development (after 20yrs old) when testosterone levels are peaked
- Dolan et al found a positive correlation between testosterone levels and
aggressive behaviours in 60 male offenders (UK maximum security hospitals)
- These men had personality disorders (psychopathy) and a history of impulsive
violent behaviour.
A03
S - animal research
P - One strength hormonal explanations of aggression is the strong animal research
evidence demonstrating the role of testosterone in regulating aggressive behaviour.
E - Giammanco et al reviewed numerous animal studies and found consistent
evidence that testosterone levels correlate positively with aggression. Male rhesus
macaque monkeys, for example, show marked increases in both testosterone and
aggressive behaviour during mating seasons, when competition for mates is highest.
, E - This suggests that testosterone plays a fundamental, evolutionarily conserved role
in preparing males for intrasexual competition. The fact that similar hormonal
mechanisms drive aggression in animals and
humans supports the view that aggression is a biologically adaptive response shaped
by natural selection to enhance reproductive success.
L - Therefore, this is a strength because cross-species consistency enhances the
evolutionary validity of hormonal explanations. If testosterone regulates aggression in
multiple species, it implies that this hormonal mechanism is biologically ingrained and
has been naturally selected for its survival and reproductive advantages.
C - However, although animal studies reveal important biological patterns, they may
oversimplify human aggression because animals lack the complex cognitive and social
influences that shape aggressive behaviour in humans
L - dual hormone hypothesis
P - One limitation of testosterone-based explanations is that human research provides
contradictory findings, questioning whether testosterone alone predicts aggression.
E - Carré and Mehta proposed the dual-hormone hypothesis, which states that
testosterone increases aggressive behaviour only when cortisol levels are low. When
cortisol is high (a hormone associated with stress) testosterone’s influence is blocked,
meaning aggression does not increase even when testosterone is elevated.
E - This suggests that aggression results from a complex interaction between multiple
hormonal systems rather than testosterone acting independently. Cortisol appears to
moderate the expression of testosterone-driven aggression, highlighting the
involvement of broader physiological mechanisms that regulate behavioural responses
depending on stress and situational demands.
L - This is a limitation because, it undermines the internal validity of single-hormone
explanations. If aggression depends on testosterone and cortisol levels, then
attributing aggressive behaviour solely to testosterone oversimplifies hormonal
influences and misrepresents the true biological processes involved
S - animal research may aid in understanding human aggression
P - Nonetheless hormonal mechanisms governing aggression in humans and animals
are likely to be broadly similar, because both groups share key structures within the
endocrine system, including the testes, which produce testosterone.
E - For example, Giammanco et al. found a clear testosterone–aggression link in
macaque monkeys, supporting the idea that testosterone facilitates competitive
behaviour. However, human aggression is more complex. Carré and Mehta’s dual-
hormone findings apply specifically to humans, showing that cortisol moderates
A01
- Aggression is hostile behaviour that is intended to cause physical or
psychological harm.
- Proactive aggression - ‘cold-blooded’ aggression, a method of getting what you
want
- Reactive aggression - hot blooded aggression accompanied by physiological
arousal
- Limbic system consists of sub cortical structures in the brain
- Paper and Maclean linked the Limbic system to emotional behaviours
Defined as the hypothalamus, amygdala, parts of the hippocampus
- Reactivity of the amygdala is an important predictor of aggressive behaviour –
how humans assess and respond to env threats
- Serotonin is a neurotransmitter that has inhibitory effects in the brain
- Normal levels of serotonin in the OFC are linked with reduced firing neurons –
associated with greater behaviour self control
Decreased distrusts this mechanism - reducing self control and leading to
impulsive behaviour
A03
L - Other brain structures
P - One limitation of the limbic explanation is that research has produced
contradictory evidence about which brain structures are actually responsible for
aggression, undermining the clarity of the explanation.
E - For example, although the amygdala is central to limbic system accounts, research
shows it functions in conjunction with the OFC, which is not part of the limbic system.
Coccaro et al found that people with aggressive psychiatric disorders showed reduced
OFC activity, demonstrating that aggression cannot be explained by limbic structures
alone.
E - This OFC activity weakens the brain’s impulse-control capabilities, meaning
individuals struggle to regulate emotional responses triggered by the amygdala. This
suggests that aggression arises from dysfunctional neural networks, not a single
structure, indicating that limbic-only explanations overlook essential components of
emotional regulation.
L - it shows that aggression is governed by a broader and more interconnected neural
system than limbic explanations propose.
By oversimplifying the neural basis of aggression, limbic-only accounts lack internal
validity, as they fail to accurately represent the complexity of neural regulation
,S - Drugs and serotonin
P - One strength of the serotonin explanation is that there is strong experimental
evidence supporting the causal role of serotonin in reducing aggression.
E - Berman et al administered either a placebo or paroxetine (a serotonin-enhancing
SSRI) before ppts took part in a provocation task involving electric shocks.
Ppts who received paroxetine delivered fewer and less intense shocks than the placebo
group, demonstrating a measurable reduction in aggression.
E - suggests that increasing serotonin levels improves impulse control and reduces
aggressive responses by promoting greater inhibition of neural circuits linked to
emotional overarousal.
Because the study used a placebo-controlled design, it allows researchers to isolate
serotonin’s specific effects, strengthening confidence in a cause-and-effect
relationship between serotonin functioning and aggression.
L - This is a strength because controlled, replicable drug studies provide highly reliable
evidence: similar procedures are likely to produce similar results.
The careful use of blinding and placebo conditions also improves internal validity,
ensuring that the observed reduction in aggression is attributable to serotonin
modulation alone.
C - However, drug studies may not reflect real-life aggression because laboratory
provocation tasks lack real consequences. This can limit the ecological validity,
meaning results may not generalise to genuine aggressive encounters
L - Neural factors may be direct or indirect
P - Nonetheless, a further issue is the ongoing debate over whether neural factors
influence aggression directly or only indirectly, through interactions with psychological
and social factors.
E - Gospic et al found heightened amygdala activity during aggressive responses, and
benzodiazepines reduced both amygdala reactivity and aggression.
Serotonin is also known to reduce aggression by inhibiting neuronal activity.
However, Denson et al showed that serotonin’s link to aggression is mediated by social
and cognitive variables, suggesting it is not a simple direct cause.
E - implies that low serotonin may impair OFC function, making people more
impulsive, but whether that impulsivity becomes aggression depends on situational
cues, stress, social learning, and individual differences in cognitive control.
The explanation therefore becomes interactionist, showing that neural activity alone
cannot fully determine aggressive behaviour.
L - highlights that purely bio explanations are reductionist, oversimplifying aggression
by ignoring how environment, cognition, and learning interact with brain function. A
,more holistic approach would provide a fuller and more realistic account of
aggression.
C - However, identifying biological predispositions remains useful, as it helps explain
why some individuals are more vulnerable to aggression when exposed to particular
environments, supporting a diathesis-stress perspective
Hormonal mechanisms
A01
- Aggression is hostile behaviour that is intended to cause physical or
psychological harm.
- Proactive aggression - ‘cold-blooded’ aggression, a method of getting what you
want
- Reactive aggression - hot blooded aggression accompanied by physiological
arousal
- There is evidence that progesterone (a female hormone) plays an important role
in aggression in women
- Levels of progesterone vary during the ovulation cycle and are lowest during and
just after menstruation
- Ziomkiewicz et al found a negative correlation between progesterone levels and
self-reported aggression
- Testosterone is an androgen responsible for the development of masculine
features - It is thought to be linked to aggressive behaviour.
- Daly and Wilson - Men become more aggressive towards other men at a time in
development (after 20yrs old) when testosterone levels are peaked
- Dolan et al found a positive correlation between testosterone levels and
aggressive behaviours in 60 male offenders (UK maximum security hospitals)
- These men had personality disorders (psychopathy) and a history of impulsive
violent behaviour.
A03
S - animal research
P - One strength hormonal explanations of aggression is the strong animal research
evidence demonstrating the role of testosterone in regulating aggressive behaviour.
E - Giammanco et al reviewed numerous animal studies and found consistent
evidence that testosterone levels correlate positively with aggression. Male rhesus
macaque monkeys, for example, show marked increases in both testosterone and
aggressive behaviour during mating seasons, when competition for mates is highest.
, E - This suggests that testosterone plays a fundamental, evolutionarily conserved role
in preparing males for intrasexual competition. The fact that similar hormonal
mechanisms drive aggression in animals and
humans supports the view that aggression is a biologically adaptive response shaped
by natural selection to enhance reproductive success.
L - Therefore, this is a strength because cross-species consistency enhances the
evolutionary validity of hormonal explanations. If testosterone regulates aggression in
multiple species, it implies that this hormonal mechanism is biologically ingrained and
has been naturally selected for its survival and reproductive advantages.
C - However, although animal studies reveal important biological patterns, they may
oversimplify human aggression because animals lack the complex cognitive and social
influences that shape aggressive behaviour in humans
L - dual hormone hypothesis
P - One limitation of testosterone-based explanations is that human research provides
contradictory findings, questioning whether testosterone alone predicts aggression.
E - Carré and Mehta proposed the dual-hormone hypothesis, which states that
testosterone increases aggressive behaviour only when cortisol levels are low. When
cortisol is high (a hormone associated with stress) testosterone’s influence is blocked,
meaning aggression does not increase even when testosterone is elevated.
E - This suggests that aggression results from a complex interaction between multiple
hormonal systems rather than testosterone acting independently. Cortisol appears to
moderate the expression of testosterone-driven aggression, highlighting the
involvement of broader physiological mechanisms that regulate behavioural responses
depending on stress and situational demands.
L - This is a limitation because, it undermines the internal validity of single-hormone
explanations. If aggression depends on testosterone and cortisol levels, then
attributing aggressive behaviour solely to testosterone oversimplifies hormonal
influences and misrepresents the true biological processes involved
S - animal research may aid in understanding human aggression
P - Nonetheless hormonal mechanisms governing aggression in humans and animals
are likely to be broadly similar, because both groups share key structures within the
endocrine system, including the testes, which produce testosterone.
E - For example, Giammanco et al. found a clear testosterone–aggression link in
macaque monkeys, supporting the idea that testosterone facilitates competitive
behaviour. However, human aggression is more complex. Carré and Mehta’s dual-
hormone findings apply specifically to humans, showing that cortisol moderates
