Notes · PsychologyUK · A-Levels

Aggression

This optional topic examines the psychology of aggression from several angles: the neural, hormonal and genetic mechanisms that underlie it, the ethological and evolutionary accounts of its origins, the social psychological explanations of human aggression, and aggression in institutions and the influence of the media. It is one of the three choices in the third option block of Paper 3.

5 sections~16 min reading time3 competenciesLevel Advanced 5

T·151515 / 17

Exam profile

AO1 · Describe the neural, hormonal, genetic, ethological, evolutionary and social explanations of aggression and media influencesAO2 · Apply the explanations to novel examples of aggressionAO3 · Evaluate the explanations, including biological determinism and establishing causation for media effects

Operators:describeexplainapplyevaluatediscuss

basic level

This is a full A-Level (A2) optional topic, not part of AS; on Paper 3 students study one topic from this option block (Aggression, Forensic psychology or Addiction).

higher level

The full A-Level requires description, application and evaluation of the biological, ethological, evolutionary and social explanations of aggression, and of institutional and media influences.

Depth

Text

Contents · 5 sections

Aggression

Neural and hormonal mechanisms in aggression#

AdvancedAQA 7182 3.3.8DfE GCE Psychology - neural and hormonal mechanisms in aggression

Brain regions involved in aggression

Fig. 1The amygdala drives threat responses; the orbitofrontal cortex regulates them; serotonin inhibits and testosterone is linked to aggression.

Biological explanations of aggression begin with the brain. The limbic system - especially the amygdala - plays a central role in how we assess and respond to threat: a more reactive amygdala is associated with more aggressive responses, and studies show that stimulating or damaging the amygdala changes aggressive behaviour. The hypothalamus and other limbic structures are also involved, while the orbitofrontal cortex helps to regulate and inhibit aggressive impulses, so reduced activity there can release aggression.

The neurotransmitter serotonin also regulates aggression, but by inhibiting it: serotonin normally has a calming, inhibitory effect on the amygdala and helps the prefrontal cortex control impulses. Low levels of serotonin are therefore associated with greater aggression, because the normal 'brake' on impulsive, aggressive responses is weakened. This is supported by evidence linking low serotonin to impulsive violence.

Hormones, particularly testosterone, are the third mechanism. Testosterone is higher in males and has been linked to aggression: it is thought to act on brain areas involved in aggression, and correlational studies find associations between testosterone levels and aggressive or dominant behaviour. Animal studies (in which castration reduces aggression and testosterone injections restore it) provide stronger, experimental support, though the picture in humans is more complex.

The neural and hormonal explanations are evaluated as having good support but clear limits. Their strengths are converging evidence from brain studies, the serotonin-aggression link and animal research on testosterone, and real-world relevance (e.g. to understanding impulsive violence). Their weaknesses are that much of the human evidence is correlational (high testosterone may be a result of behaving aggressively and winning, not only a cause), that the mechanisms interact rather than acting alone (testosterone, serotonin and brain structures influence one another), and that reducing aggression to biology is reductionist and deterministic, ignoring the social and cognitive factors covered later and raising concerns about excusing violent behaviour.

Worked example

Explaining the serotonin-aggression link

Research links low serotonin to impulsive violent behaviour. Explain the mechanism proposed and one limitation of the evidence.

State serotonin's normal role
Serotonin normally has an inhibitory, calming effect, helping the prefrontal cortex to control impulsive responses from the amygdala.
Explain the effect of low levels
With low serotonin, this inhibitory 'brake' is weakened, so impulsive and aggressive responses are less well controlled and more likely.
Note a limitation
Much of the evidence is correlational, so low serotonin may accompany rather than cause aggression, and other biological and social factors also contribute.

Result: Low serotonin weakens the inhibition of impulsive aggression, though the correlational evidence cannot prove causation.

Typical mistakes

Saying high serotonin causes aggression - it is low serotonin (loss of the inhibitory 'brake') that is linked to aggression.
Treating correlational testosterone findings as proving testosterone causes aggression.

Active revision

Explain how low serotonin levels could lead to increased aggression.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for psychology (Department for Education) · AQA A-level Psychology 7182 specification (AQA)

Genetic factors in aggression, including the MAOA gene#

AdvancedAQA 7182 3.3.8DfE GCE Psychology - genetic factors in aggression

Genetic explanations propose that a tendency towards aggression can be inherited. Twin studies show higher concordance for aggressive behaviour in identical than in non-identical twins, and adoption studies find that adopted children's aggression correlates with that of their biological rather than their adoptive parents - both pointing to a genetic contribution, although concordance well below 100% shows the environment matters too.

The MAOA gene is the specific candidate on the specification. It codes for the enzyme monoamine oxidase A (MAOA), which breaks down neurotransmitters including serotonin after they have acted. A variant of the gene that produces low activity of the enzyme (sometimes called the 'warrior gene') is associated with higher levels of aggression, because reduced breakdown disrupts the regulation of these neurotransmitters. Brunner's study of a Dutch family whose male members showed both a deficiency in MAOA and high levels of violent behaviour is the classic evidence.

Crucially, genes do not act alone. Caspi's research found that the low-activity MAOA variant was associated with antisocial and aggressive behaviour mainly in people who had also been maltreated as children - those with the gene but a normal upbringing were much less affected. This is a clear example of a gene-environment interaction: the genetic vulnerability is expressed as aggression only when combined with an adverse environment, echoing the diathesis-stress logic seen elsewhere.

The genetic explanation is evaluated as supported but incomplete and sensitive. Its strengths are the twin, adoption and MAOA evidence and the compelling gene-environment interaction findings. Its weaknesses are that aggression is a complex behaviour unlikely to be explained by any single gene (it is polygenic and interacts with the environment), that defining and measuring 'aggression' consistently across studies is difficult, and that the research is socially sensitive: linking violence to a gene raises serious concerns about determinism, labelling and the potential misuse of such findings (for example in the criminal justice system), so conclusions must be drawn carefully.

Worked example

Interpreting a gene-environment interaction

A study finds that men with the low-activity MAOA gene are much more likely to be aggressive if they were maltreated as children, but not otherwise. Explain what this shows.

State the two factors
The factors are a genetic vulnerability (the low-activity MAOA variant) and an environmental adversity (childhood maltreatment).
Read the interaction
Aggression was raised only when both factors were present - the gene alone, or maltreatment alone, had a much weaker effect.
Draw the conclusion
This is a gene-environment interaction: the genetic predisposition is expressed as aggression only in an adverse environment, so neither nature nor nurture alone is sufficient.

Result: The gene raises aggression only in combination with maltreatment - a clear gene-environment interaction.

Typical mistakes

Saying the MAOA gene alone causes aggression - it interacts with the environment (e.g. childhood maltreatment).
Treating aggression as controlled by a single gene - it is polygenic and environmentally influenced.

Active revision

Explain how the MAOA gene and childhood experience might interact to influence aggression.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for psychology (Department for Education) · AQA A-level Psychology 7182 specification (AQA)

Ethological and evolutionary explanations#

AdvancedAQA 7182 3.3.8DfE GCE Psychology - ethological and evolutionary explanations

The fixed action pattern

Fig. 2A sign stimulus triggers the innate releasing mechanism, which releases a stereotyped fixed action pattern of aggression.

The ethological explanation studies aggression as an innate, adaptive behaviour by comparing species. It argues that aggression is adaptive because it helps animals establish dominance hierarchies and defend territory and resources, spreading individuals out and reducing actual harm. Lorenz proposed that much aggression is ritualistic - a series of threat displays rather than damaging fights - so that disputes are usually settled without serious injury, and that most species have innate inhibitions preventing them from killing their own kind.

A key ethological concept is the fixed action pattern (FAP): a stereotyped, innate sequence of behaviours that is universal within a species and, once triggered, runs to completion. A FAP is set off by a specific sign stimulus (or releaser) acting on an innate releasing mechanism (IRM) - a neural network that, when the right stimulus appears, releases the fixed action pattern. Tinbergen's classic study of the stickleback showed that males would perform their fixed aggressive display towards any model displaying a red underside (the sign stimulus of a rival male), regardless of its shape.

Evolutionary explanations of human aggression extend this logic to people, arguing that aggressive behaviours were selected because they solved adaptive problems for our ancestors - for example, competing for status and resources, or (in some accounts) sexual jealousy and mate retention (aggression or the threat of it to deter a partner's infidelity, which would have protected a male's reproductive investment). On this view, some human aggression is the legacy of behaviours that once increased reproductive success.

These explanations are evaluated for their evidence and their limits. The ethological account is supported by the cross-species evidence for FAPs and IRMs, but generalising from animals (especially simple species such as sticklebacks) to the complex, culturally shaped aggression of humans is questionable, and human aggression is far more variable than a fixed action pattern implies. The evolutionary account can explain some patterns (such as male-male violence over status) but is criticised as difficult to test, as potentially justifying aggression as 'natural', and as unable to explain why aggression varies so much across cultures - which, again, points to the importance of the social explanations.

Worked example

Applying ethological concepts

A male stickleback attacks any object showing a red underside, even a crude wooden model. Analyse this using ethological concepts.

Identify the sign stimulus
The red underside is the sign stimulus (releaser) that signals a rival male.
The IRM and FAP
The sign stimulus activates the innate releasing mechanism, which releases the stereotyped fixed action pattern of aggressive display.
Explain the crude-model result
Because the FAP is triggered by the specific sign stimulus (red) rather than an accurate image of a fish, even a crude red model sets off the full aggressive pattern - demonstrating that the behaviour is innate and stimulus-driven.

Result: The red belly (sign stimulus) triggers the IRM and the fixed action pattern, so even a crude red model releases the display.

Typical mistakes

Confusing the sign stimulus (the trigger) with the innate releasing mechanism (the neural network) and the fixed action pattern (the behaviour).
Treating human aggression as a fixed action pattern - human aggression is far more variable and culturally shaped.

Active revision

Using the concepts of a sign stimulus and a fixed action pattern, explain the aggressive behaviour of a male stickleback.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for psychology (Department for Education) · AQA A-level Psychology 7182 specification (AQA)

Social psychological explanations: frustration-aggression, SLT and de-individuation#

AdvancedAQA 7182 3.3.8DfE GCE Psychology - social psychological explanations of aggression

The frustration-aggression hypothesis

Fig. 3A blocked goal produces frustration and an aggressive drive; if the source is unavailable, aggression is displaced onto a safer target.

The frustration-aggression hypothesis (Dollard et al.) proposes that aggression is always the result of frustration, and that frustration always leads to aggression. Frustration occurs when our attempt to reach a goal is blocked, which creates an aggressive drive that is released as aggressive behaviour. If the source of the frustration is unavailable, too powerful or likely to punish us, the aggression is displaced onto a weaker, safer substitute target (scapegoating), and the release of the drive was thought to be cathartic (reducing the drive). The hypothesis was later revised (Berkowitz) to say that frustration creates a readiness for aggression that is more likely to be acted on in the presence of aggressive cues (such as a weapon).

Social learning theory applied to aggression argues that aggression is learned by observing and imitating aggressive models, especially when the aggression is seen to be rewarded (vicarious reinforcement). Bandura's Bobo doll studies are the key evidence: children who watched an adult behave aggressively towards the doll imitated that specific aggression, and did so more when the model was rewarded. Learning depends on the mediational processes (attention, retention, reproduction, motivation) and on self-efficacy - the child's belief that they can successfully perform the aggressive act.

De-individuation explains aggression in crowds and groups. It is the psychological state in which a person, as part of a large or anonymous group, loses their sense of individual identity and personal responsibility, and so is more likely to behave in antisocial, aggressive ways they would normally inhibit. Anonymity (e.g. wearing a uniform or mask, being in a large crowd or online) and reduced self-awareness weaken the normal internal controls on behaviour, which is used to explain phenomena such as riots and mob violence.

The social explanations are evaluated as strong but not complete. The frustration-aggression hypothesis is supported but too absolute in its original form (not all frustration leads to aggression, and not all aggression follows frustration), and the idea of catharsis is poorly supported. Social learning theory is well supported and explains cultural and individual variation in aggression (and its transmission), but much of the evidence is from artificial lab studies. De-individuation has support (anonymity does increase aggression in many studies) but not always (anonymity can sometimes increase pro-social behaviour, depending on group norms). Together they show that aggression is heavily shaped by social context, complementing the biological accounts.

Worked example

Applying displacement

An employee is treated unfairly by their powerful boss and later shouts angrily at a family member. Explain this using the frustration-aggression hypothesis.

Identify the frustration
Being treated unfairly blocks the employee's goals, creating frustration and an aggressive drive.
Explain why not the source
The boss is too powerful and could punish the employee, so directing aggression at the source is inhibited.
Explain the displacement
The aggressive drive is displaced onto a weaker, safer substitute target (the family member), which the hypothesis predicts as scapegoating.

Result: Frustration from the boss is displaced onto a safer target at home - the displacement predicted by the hypothesis.

Typical mistakes

Stating the original frustration-aggression hypothesis without the criticism that not all frustration leads to aggression.
Confusing de-individuation (loss of individual identity in a group) with social learning (imitation of models).

Active revision

Explain how de-individuation could account for aggressive behaviour during a riot.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for psychology (Department for Education) · AQA A-level Psychology 7182 specification (AQA)

Institutional aggression and media influences#

AdvancedAQA 7182 3.3.8DfE GCE Psychology - institutional aggression and media influences

How media may influence aggression

Fig. 4Three proposed mechanisms link violent media to aggression: desensitisation, disinhibition and cognitive priming.

Institutional aggression in prisons is explained by two contrasting models. The dispositional (importation) model argues that aggression inside prisons is 'imported' by the prisoners themselves - inmates bring in the aggressive characteristics, values and gang affiliations they had on the outside, so the aggression reflects the kind of people who are imprisoned. The situational (deprivation) model argues instead that aggression is a product of the prison environment - the deprivations of prison life (loss of liberty, autonomy, goods, relationships and security) and factors such as overcrowding and poor management create the stress and tension that lead to violence. Evidence supports both, and an interactionist view (dispositional characteristics interacting with situational pressures) is often taken.

Media influences on aggression concern how exposure to violent media - television, films and especially violent computer games - may affect aggression. The concern is greater for interactive computer games, in which the player actively performs and is rewarded for virtual violence. Research includes experimental studies (measuring aggression after playing a violent game), correlational studies (linking media use to aggression) and longitudinal studies (following people over time), which together give a mixed but somewhat concerning picture.

Three mechanisms are proposed for how media might increase aggression. Desensitisation is the reduction in the normal emotional and physiological response to violence after repeated exposure, so that violence comes to seem less shocking and its consequences less serious, lowering inhibitions against it. Disinhibition is the weakening of the social norms that usually restrain aggression, when media repeatedly portray violence as acceptable, justified or rewarded. Cognitive priming is the activation of aggressive thoughts, scripts and memories by media cues, so that a person primed by violent media is more likely to interpret a situation as hostile and respond aggressively.

The media explanations are evaluated for methodology and effect size. Laboratory experiments can demonstrate short-term increases in aggression but use artificial measures and cannot ethically study serious real-world violence; correlational and longitudinal studies avoid this but cannot establish causation (aggressive people may choose violent media - the direction of the effect is unclear) and are affected by confounds. The effects that are found are often small and short-term, and most people exposed to violent media are not aggressive, so media are best seen as one contributory factor among many rather than a sole cause. This uncertainty - and the difficulty of establishing causation - is the central evaluation point.

Worked example

Evaluating a media-aggression study

A correlational study finds that teenagers who play more violent games report more aggression. Explain why this does not prove the games cause the aggression.

State the finding
There is a positive correlation between violent-game use and self-reported aggression.
Raise the direction problem
The correlation could arise because already-aggressive teenagers choose to play more violent games, rather than the games causing aggression.
Note confounds
Third variables (such as family environment or personality) could influence both, so a correlational design cannot establish that the games cause aggression.

Result: The correlation is consistent with, but does not prove, a causal media effect - direction and confounds are unresolved.

Typical mistakes

Confusing the importation (prisoner characteristics) and deprivation (prison environment) models.
Confusing desensitisation (reduced emotional response), disinhibition (weakened norms) and cognitive priming (activated aggressive thoughts).

Active revision

Discuss whether playing violent computer games causes aggression, referring to at least two of the proposed mechanisms.

Active recall

Recall the key points — then reveal.

Sources: GCE AS and A level subject content for psychology (Department for Education) · AQA A-level Psychology 7182 specification (AQA)

References & sources

Sources

Department for Education

GCE AS and A level subject content for psychology

AQA

AQA A-level Psychology 7182 specification

Aggression

5 sections~16 min reading time3 competenciesLevel Advanced 5

Aggression

Key points

Explaining the serotonin-aggression link

Key points

Interpreting a gene-environment interaction

Key points

Applying ethological concepts

Key points

Applying displacement

Key points

Evaluating a media-aggression study

Sources

Aggression

Key points

Explaining the serotonin-aggression link

Key points

Interpreting a gene-environment interaction

Key points

Applying ethological concepts

Key points

Applying displacement

Key points

Evaluating a media-aggression study

Sources