Limbic System

  • Limbic system (subcortical structures in the brain that incl. amygdala , thalamus, hypothalamus) has been linked to aggression as the limbic system is involved in regulating emotions. 
  • Papez-Maclean Limbic theory suggests that structures such as the amygdala and hypothalamus are implicated in reactive aggression.
  • Gospic (2011) found p. who had received unfair offers in a social co-operation game involving sharing money displayed increased activity in they anygdalae during fMRI scans. P. that were given benzodiazepine (BZs) before the game displayed reduced activity and were less likely to reject unfair offers. This shows the relationship between reactive aggression and amygdala activity.
  • Zagrodzka (1998): damage to the central nucleus of the amygdala in cats led to predator-like attacks.
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  • Serotonin is an inhibitory neurotransmitter in the brain - increased serotonin levels decresases neurons from firing.
  • Denson (2012) suggested that decreased serontonin levels in the orbito-frontal cortex leads to reduced self control and increased impulsivity.
  • Ferrari (2003): placed an intruder rat in the living area of resident rats at the same time for 10 days. He witnessed increases in dopamine and decreases in serotonin. This response was also observed on the 11th day, when an intruder rat was not introduced, suggesting that the rats had been conditioned to have this response - behaviour can modify neurochemical functioning.
  • Virkkunen (1994): compard serotonin by-products in impulsive and non-impulsive violent offenders. He found significantly lower levels of serotonin by-products and more sleep irregularites in impulsive offenders.
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  • Testosterone is an androgen that exerts an influence on social behaviour incl. aggresion.
  • The basal model of testosterone: assumes that increases in the level of testosterone leads to increased competitiveness and dominance.
  • Wagner (1979): reported that levels of aggression in mice (shown by rates of biting attacks) fluctuated according to levels of testosterone before and after castration. Biting peaked before castration and after following treatment with testosterone.
  • Dolan (2001): found a positive correlation between testosterone levels and aggression in 60 max. secruity inmates.
  • The reciprocal model of testosterone suggests that testosterone levels are dependent on the degree to which someone is dominant - testosterone is a consequence rather than a cause.
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Twin / Adoption Studies and Meta-analyses

  • Caccaro (1997): studied adult male twins - MZ concordance rates for physical and verbal aggression were 50% and 28% vs. DZ twins with 19% and 7% in DZ twins.
  • Hutchings and Mednick (1973): significant positvie correlation between violent criminal convictions of biological parents and adopted children, despite being raised apart.
  • Rhee and Waldman (2002): meta analysis of adoption studies found that genetic influences accounted for 41% of the variance in aggression.
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This gene is responsible for the activity of the enzyme monoamine oxidase in the brain. This enzyme is responsible for breaking down neurotransmitters.

  • Brunner (1993): studied 28 males in a Dutch family who had all commited extreme violent acts (e.g. ****, murder). All males appeared to have a defective gene responsible for the production of MAOA. The low activity version of the MAOA resulted in males have abnormally low levels of monoamine oxidase in their brains, meaning their serotonin levels would be heightened since it is not able to be broken down.
  • Diathesis-Stress Model of Aggression: Frazetto (2007): found a link between the low activity MAOA gene and anti-social aggression in males but only those who had experience trauma in the last 15 years. This suggesting that the defective gene interacts with the enviroment.
  • Godar (2014): mice engineered to delete their MAOA gene led to significantly increased serotonin levels and hyper-aggression.
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Ethological Explanation

  • Focuses on innate behaviour of organisms in their natural habitat.
  • Aggression is adaptive and can help to distribute organisms.
  • Innate-releasing mechanism - biological structure that is activated when presented with a stimulus.
  • Fixed-action pattern - sequence of behaviour triggered by the IRM
  • Lea (84): Aggression is always the same, it is not affected by learning, stereotyped, universal, ballistic, single-purposed and in response to a stimulus
  • Hydraulic model - specific stimuli lead to the relaese of built up action specifc energy. So the behaviour cannot be repeated again until the energy is replenished (Lorenz, 1950).
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Ethological Explanations AO3

Tinbergen (1951): male stickleback fish are very territorial when it is mating season and they also develop a red spot on their underbelly. Tinbergen presented them with a series of wooden models with red spots on their undersides. Regardless of the shape of the model, male sticklebacks were aggressive when the red spot was present. The red spot seemed to be a stimulus which activated the stickleback's IRM leading to a FAP. He also found tha these displays of aggression followed an unchanging pattern, supporting Lea (84).

Lehrman (1953): argues that ethological explanations underestimate the role of environmental factors, incl. learning and experience, pointing to subtle variations in members of a species' aggression.

Fox (2000): argues that examples of human aggression, such as warfare, cannot be explained by individual impulses but is instead a 'collective undertaking'. 

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Evolutionary Explanation

  • Aggression is adaptive - a characteristic that has promoted survival / reproduction.
  • Specific traits, like jealousy or bullying, might have conferred an evolutionary advantage.
  • Males are more prone to aggression, due to paternal uncertainty and fear of cuckoldry.
  • Females experience maternal certainty and so they are less susceptible to jealousy-motivated aggression.
  • Males may use mate retention strategies which keep their female mates close to them and away from other males.
  • Direct guarding (males acting possesively), negative inducements (using emotional manipulation / derogatory terms), and sexual coercion are all examples of mate-retention strategies.
  • All of these aggressive acts are rooted in paternal uncertainty. The strategies are used to maximise the chance of males passing on their own genes.
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Evolutionary Explanation AO3

Wilson (1995): women who reported that their partner used mate-retention strategies were twice as likely to suffer from domestic abuse, with 53% saying they had feared for their lives. Supports the link between mate-retention strategies and aggression.

Cultural differences : Humans all have common ancestor traits that were adaptive and so these traits should exist universally but extreme differences in proneness to aggression has been observed. The !Kung San bushman of the Kalihari rarely display acts of aggression as this is discouraged and associated with damage to reputation. In contrast, the Yanomamo of Brazil live in highly structered societies and aggression is used to gain status.

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Frustration-Aggression Hypothesis

Goal --> Goal Blocked --> Frustration --> Aggressive Drive --> Aggression --> Catharsis

Dollard and Miller (1939): frustration is any event or stimulus that prevents an individual from attaining a goal and its accompanying reinforcement quality.

The idea is compatible with the psychodynamic approach as it conceptualises aggression in terms of drives within us. It also slaigns itself with the idea of defense mechanisms, like displacement or sublimation, as often we cannot direct our aggresison at it souce.

If the source is abstract, there is a power division or the source is not present, we are unable to express our aggressive drives and so they are displaced onto another source that is available.

Berkowitz (1969): suggested that frustration doesn't always lead to aggresison but only occurs in the presence of certain cues, such as in the presence of weapons.

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Frustration-Aggression Hypothesis AO3

  • There is evidence to oppose the F-A Hypothesis.
  • Bushman (2002) conducted a study with 2 groups. Both groups were given a poor assessment on an essay to frustrate them and then were either instructed to wait or to punch a punchbag.
  • The F-A Hypothesis would assume that the punchbag group would experience catharsis and feel less angry. But, their anger ratings were higher.
  • Therefore, the study contradicts the anticipated role of catharis, as frustrated participants were still angry after being aggressive.
  • Berkowitz (1989): 2 groups, one with weapon present, one without weapons present. When weapons were present, average shocks given were 6.07 and without weapons 4.67. Therefore, the weapon effect (role of violent cues) has been overlooked by Dollard.
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Social Learning Theory

  • Behaviour is affected by social context
  • People learn through imitation
  • People form associations between a model's behaviour and the consequences that follow. 
  • Mediational process (attention, retention, reproduction, motivation) are cognitive processes that affect the liklihood of a behaviour being reproduced.
  • Behaviours can be internalised and imitated at another time
  • Self-efficacy: the extent to which someone believes that their actions will achieve their goals.
  • People with high self-efficacy of aggression are more likely to imitate aggressive behaviours as they believe their actions will be successful.
  • Reciprocal determinsm: people choose what to observe which effects what behaviour they will internalise and reproduce.
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Social Learning Theory AO3

Poulin and Boivin (2000): studied 9-12 year old boys and found that the more aggressive boys were more likley to befriend other aggressive boys as then they mutually reinforce the aggressive behaviours since acts of aggression will be followed by approval.

Provides a good explanation for proactive aggression but is unable to explain reactive aggression, which can be better explained by negative affect theory.

Cross cultutal relevance: Evidence shows that there are different levels and portrays of aggression in different cultures. E.g. the !Kung San tribe of the Kalihari supports SLT as exposure to models displaying aggression is likely to be culturally relative.

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De-individuation: to lose one's sense of individuality and identity.

  • Le Bon (1896): individuals are more likely to behave in an aggressive manner when part of a large anonymous group as individuals feel less identificable in a group, so normal constraints that prevent aggression may be lost.
  • Diener (1980): deindividuation occurs when self awareness is blocked by environmental events.
    • Stong feelings of group membership
    • Increased levels of arousal
    • Focus on external events
    • Feeling of anonymity
  • Prentice-Dunn and Rogers (1982): 
    • Public self awareness - concern over the impression of yourself when you are wary of being judged.
    • Private self-awareness: your sense of self, consisting of thoughts, feelings, values and internal standards of behaviour
    • Only reductions in private self-awareness can lead to true deindividuation
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De-Indivuation AO3

Zimbardo (1969): Female undergrads - Group 1 wore lab coats with hoods over their faces and group 2 wore large name tags - the p. observed a woman being interviewed and evaluated her performance by giving electric shocks. Group 1 shocked both interviewees equally but group 2 only shocked the obnoxious interviewee more than the pleasant one. So deindividuation increased aggression.

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Dispositional Explanations

The Importation Model (Irwin and Cressey, 1962):

  • Aggression is the product of individual characteristics of inmates and not of the prison environment.
  • So, inmates predisposed to using violence would be likely to do so in any setting.

DeLisi (2011): 813 juvenile delinquents in California institutions bringing several negative dispositional factors into confinement (e.g. high levels of anger, childhood trauma etc.) They commited more acts of physical violence than those who had fewer negative dispositional factors.

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Situational Explanations

The Deprivation Model (Clemmer, 1958):

  • Harsh prison conditions are stressful for inmates, who cope by resorting to aggressive behaviour.
  • E.g. being deprived of material goods, freedom, independence, safety

Steiner (2009): investigated factors that predicted aggression in 512 prisons in the USA. Inmate-on-inmate violence was more common in prisons with more female staff, African American inmates, Hispanic inmates. These are all prison level factors that are independent of the individual characterists of prisoners.

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