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Image by Yogendra Singh





Neural mechanisms

Limbic system, amygdala

Overactive amygdala = higher levels of aggression

Gospic (2011) - ultimatum game - BZ decreased ANS and less aggressive

Reduced serotonin in OFC - Virkkunen (1994) low levels in violent offenders compared to non-violent offenders


Support for OFC: Coccaro (2007)

- Correlational research

+ Drug research: Berman (2009)




Adaptive functions - forces move of territory and dominance hierarchy (mating rights)

Ritualistic signalling (Lorenz 1966) - intraspecies appeasement display

Innate releasing mechanism - biological structure, triggered

Fixed action patterns - stereotyped, universal, ballistic

Tinbergen - red belly on wooden shapes create FAP in sticklebacks


- Jane Goodall - chimpanzees displayed intra species aggression

- FAPs may change with learning

- Ignores culture: North-South divide in USA for homicide

- Issues with animal extrapolation

Social Learning



Direct learning through operant conditioning -+ve reinforcement

Indirect learning through observing & imitating role models

Vicarious reinforcement

Mediational processes (ARMM)

Importance of self-efficacy

Bandura's Bobo Doll study


+ Evidence - aggressive boys befriend similar boys (Boivin)

- This finding was only for proactive not reactive aggression

+ Real life application: observe calm behaviour instead

- Ignores biological factors

Media influences on aggression


Excessive TV watching = increases aggression (Robertson)

Violent films = increases aggression (Bobo Doll replication)

Mixed evidence: meta-analysis 200+ studies showed increase

but accounted for 1-10% variance

Computer games have a powerful effect due to active player and being directly rewarded

Lab experiments use Taylor Competitive Reaction Time

Batholow & Anderson (2002) ppts playing Mortal Kombat higher white noise then golf game 


Operationalisation of violent behaviour is hard = low reliability

Meta-analyses often include poor methodological studies

+ SLT can easily explain the link

- Correlation does not equal causation




Aggression is highest in males 20+ years old when testosterone peaks

Dolan (2001) +ve correlation in impulsive violent offenders

Castrated male animals are less aggressive but injecting it restores the aggression (Giammanco)

Ziomkiewicz found -ve correlation between progesterone and aggression in females


+/- Animal studies

- Dual hormone hypothesis (Carre & Mehta 2011)

+ Mehta & Josephs (2006) - rechallenge in competitive game




Sexual jealousy

Anti-cuckoldry behaviours are adaptive

Mate retention strategies: direct guarding & -ve inducements

Wilson (1995) in IPV more mate retention strategies used

Bullying may be seen as adaptive: warn off rivals & access to more females

Female bullying is seen more within a relationships to secure a partners fidelity


+ Ignores the role of socialisation

Cultural differences e.g. !Kung San not aggressive = not universal

+ Real life application: anti-bullying strategies

- Too deterministic



Le Bon (1895) when in a crowd = lose personal responsibility

Zimbardo (1969) can lead to aggression as disinhibited

Anonymity is a major factor

Self-awareness is reduced, both private and public (Prentice-Dunn & Rogers, 1982)

Dodd (1985) student deindividuation - 36% chose anti-social behaviour 


+ Evidence - most aggression online messages are anonymous

- Anonymity sometimes leads to intimate behaviour not aggressive

- Retains group norms not go against social norms

- Males more aggressive when deindividuated (beta bias) 

Desensitisation, disinhibition & priming


Desensitisation = reduced sympathetic NS activity & psychological response

Disinhibition = exposure to violent media reduces social constraints

Strengthened by OC

Cognitive priming = script learnt on how to behave to aggressive cues

Aggressive song lyrics can increase aggressive towards women (Fischer & Greitemeyer)


+ (Desensitisation) Krahe - exposure reduced NS arousal & blasted higher white noise

- (Desensitisation) Cannot explain all aggression (e.g. cathartic)

+ (Disinhibition) Berkowitz & Alioto watching vengeful film = + shocks

+ (Disinhibition) Can explain cartoon aggression which is unrealistic  (unlike SLT)

+ (Cognitive priming) Real world application to challenge cognitive scripts

- (Cognitive priming) Complexity of computer games is a confounding variable (Zendle 2018)




Twin studies - Coccaro (1997) - physical 50% MZ, 19% DZ & verbal aggression 28% MZ, 7% DZ

Adoption studies - Rhee & Waldman (2002) meta-analysis showed genes 41% of variance

MAOA 'Warrior' Gene - MAOA-L variant = low MOA-A enzyme = high aggression, 56% Maori men

Brunner (1993) - 28 men from Dutch violent family had MAOA-L variant

GxE interactions (Diathesis-Stress Model) Frazetto (2007) MAOA-L & trauma in 1st 15yrs


+ Supportive evidence: McDermott (2009) - money allocation

Stuart (2014) - IPV - 5HTT gene

Sampling issues - crimes

- Methodologies = low reliability

Frustration-aggression Hypothesis


Dollard (1939) when a goal is blocked = frustration

Frustration always leads to aggression

Aggression is cathartic as it reduces the aggressive drive

Aggression sometimes has to be displaced e.g. if angry at an abstract concept

Berkowitz & LePage (1967) - weapons effect, frustration merely creates a readiness for aggression

Geen (1968) - impossible puzzle


- Aggression may not be cathartic (Bushman)

- Frustration does not always lead to aggression (too deterministic)

+ Berkowitz updated it to the 'negative effect theory' 

+ Supportive meta-analysis evidence for displaced anger (Marcus-Newhall)




Dispositional explanation: importation model

Irwin & Cressey (1962) inmates bring in a subculture of criminality

Characteristics establish power, status & resources

DeLisi (2011) juvenile delinquents who imported trauma, drug abuse etc. more likely to self harm and be aggressive

Situational explanation:

deprivation model

Clemmer (1958) prison conditions cause stress = aggression

Psychological and physical factors

Steiner (2009) 512 US prison = higher aggression when female staff & overcrowding


+ (importation model) Camp & Gaes - no significant increase in aggression in low or high control

- (importation model) Poorly managed prisons have the highest aggression (Dilulio) 

+ (deprivation model) Cunningham - higher inmate homicide in Texas when 'boundaries' were crossed

- (deprivation model) No less aggression in prison allowed conjugal visits


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