What is aggression?
Aggression is any behaviour meant to harm another person who wants to avoid that harm. An accident is not aggression, because there is no intent.
- Hostile (reactive) aggression: hot, angry, a reply to a threat or insult.
- Instrumental (proactive) aggression: cold, planned, used to get something, such as money or status.
- It can be physical (hitting) or verbal and relational (insults, spreading rumours, leaving someone out).
Neural, hormonal and genetic factors
Neural (brain) factors
The limbic system, especially the amygdala, reacts fast to threats. The orbitofrontal / prefrontal cortex controls impulses. Brain scans of some violent people show a very active amygdala and a less active prefrontal cortex. Serotonin is a calming chemical; low serotonin weakens self-control.
Hormonal factors
Testosterone is linked to dominance and aggression, though the link in humans is weaker than in animals. The dual-hormone idea says testosterone raises aggression mainly when cortisol (a stress hormone) is low.
Genetic factors
Twin studies compare identical (MZ) and non-identical (DZ) twins; MZ twins are more alike in aggression, so genes play a part. Adoption studies separate genes from upbringing. The MAOA gene controls an enzyme that breaks down serotonin; the low-activity version (MAOA-L) is linked to aggression, especially with childhood abuse. This is a gene-environment interaction (diathesis-stress).
Limits: correlation is not cause; much research is on animals or men only; biology ignores free will and social setting.
Ethological and evolutionary explanations
Ethology (animal behaviour)
Ethologists study animals in their natural home. They say aggression is adaptive: it protects territory and food. Many species use ritual signals (displays, growls) so fights rarely end in death. An innate releasing mechanism in the brain is triggered by a sign stimulus (such as a red belly) and sets off a fixed action pattern: the same sequence, every time, run to the end.
Evolutionary psychology
Behaviours that helped our ancestors survive and reproduce were passed on. Mate retention: males may use jealousy and guarding to avoid raising another man's child (paternity certainty). Aggression can also win status in a group.
Limits: human aggression varies hugely between cultures, so it cannot be only instinct; ideas are hard to test because we cannot see the past.
Social psychological explanations
Frustration-aggression hypothesis
When a goal is blocked, we feel frustration, which builds an aggressive drive. Letting it out is called catharsis, but research shows venting often increases anger. A later version adds aggressive cues: anger is more likely to become aggression if a cue, such as a weapon, is nearby (the weapons effect).
Social learning theory
Children learn aggression by watching models. If the model is rewarded (vicarious reinforcement), the child is more likely to copy. Four steps: attention, retention, reproduction, motivation. Self-efficacy is the belief that you can do it.
Deindividuation
In a crowd, wearing a uniform or being anonymous online, people feel less personally responsible and less self-aware, so normal rules weaken. Trolling online is a modern example.
Institutional aggression in prisons
Institutional aggression happens within a setting such as a prison, a hospital or a school, and is shaped by that setting.
- Dispositional (importation) model: inmates bring in their own traits, values and gang links. Aggression would happen anywhere.
- Situational (deprivation) model: the pains of prison (loss of freedom, goods, safety, privacy, relationships) cause stress and aggression. Crowding, heat and poor staff control make it worse.
Most researchers now combine the two: the person and the place work together.
Media influences: films, TV and computer games
Research methods include lab experiments, correlation studies and meta-analyses (combining many studies). Results show a small link between violent media and aggressive thoughts and behaviour, but it is debated.
- Desensitisation: seeing lots of violence makes it feel normal; the body reacts less.
- Disinhibition: media can make violence seem acceptable, so normal restraints weaken.
- Cognitive priming: violent images prepare aggressive ideas in the mind, ready to be used.
Limits: lab measures of aggression (like noise blasts) are artificial; aggressive people may simply choose violent games (direction of cause); many other factors, like family and peers, matter more.
Key formulas and definitions
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Worked examples
1. Classify: (a) a boxer hits an opponent within the rules to win; (b) a person punches someone who insulted them; (c) a student spreads a cruel rumour about a classmate.
(a) Not hostile aggression in the usual sense: it is within agreed rules (sport), though it is instrumental in aim. (b) Hostile (reactive) aggression: hot anger after a provocation. (c) Relational (verbal) aggression: it aims to damage the person's friendships and reputation.
2. A study finds that men with the MAOA-L gene who were abused as children are much more violent than those with only one of the two. Which idea does this support?
Step 1: gene alone gave a small effect. Step 2: abuse alone gave a small effect. Step 3: both together gave a big effect. This is a gene-environment interaction (diathesis-stress model): biology loads the gun, environment pulls the trigger.
3. Explain a riot in which ordinary people smash shop windows, using one social explanation.
Deindividuation: in a large, noisy crowd at night, each person feels anonymous and less responsible. Self-awareness drops, so personal standards are not checked. Group norms ('everyone is doing it') take over, and people act in ways they never would alone.
4. A prison reduces violence by moving inmates to single cells, adding education and visits. Which model does the success support, and why might the other still matter?
It supports the deprivation (situational) model: reducing the pains of prison lowered aggression. But some inmates may still be violent because of traits and gang links they brought in (importation), so a full plan addresses both.
Common mistakes
- Calling any harm aggression. Without intent to harm (an accident) it is not aggression.
- Saying 'the aggression gene causes violence'. MAOA-L only raises risk, mostly together with harsh experiences.
- Thinking venting anger (catharsis) is good. Hitting a pillow or shouting usually keeps anger going.
- Claiming violent games definitely cause violence. Research shows a small, debated link, and correlation is not cause.