Neural Mechanisms In Aggression

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serotonin

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Serotonin is a neurotransmitter that has an important role in social decision-making by inhibiting aggressive social responses. Serotonin usually reduces aggression by preventing the stimulation of the amygdala,a structure in the brain's limbic system. Stimulation of the amygdala increases aggressive behaviour but serotonin prevents stimulation, therefore reducing aggression.

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neurotransmitter social decision inhibiting responses reduces aggression preventing amygdala limbic stimulation prevents

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low levels of serotonin

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If there are low levels of serotonin in the brain, there is less inhibition of the amygdala. As a result it becomes more active when stimulated by external events, causing the person to act on their impulses and making aggression more likely. Therefore, low levels of serotonin have been associated with an increased susceptibility to impulsive and aggressive behaviour.

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low serotonin inhibition amygdala active external act impulses associated susceptibility impulsive

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Mann et al

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The relationship between low levels of serotonin and aggression has been supported by a study by Mann et al who manipulated levels of serotonin. They administered the drug dexfenfluramine known to reduce serotonin levels, to 35 healthy adults. They then used a questionnaire to assess hostility and aggression levels, they found that dexfenfluramine treatment in males was associated with an increase in hostility and aggression scores. This supports the fact that serotonin is linked to aggression as when the participants had lower levels of serotonin than usual their aggression level was higher which suggested that the serotonin change was the reason for higher aggression levels and not an extraneous variable. As a consequence this increases the credibility ofthe research into the link between serotonin and aggressive behaviour.

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Relationship manipulated dexfenfluramine depletehostility males associated increase aggression supports linked lower usual higherreason extraneous credibility

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Mann methodology

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Mann’s study used a self-report method ofgaining information from the participants. This reduces the validity of thestudy as participants could have given answers which they thought were sociallydesirable and not truthful ones which means the conclusions Mann drew form thestudy could be based on invalid evidence. It could be argued that manipulatingthe levels of serotonin in humans is unethical as this supposedly leads toincreased levels of aggression. Furthermore, the research conducted by Mann et al (1990) is on a small sampleof 35 adults and is not representative of the wider population, therefore generalizabilitycannot be achieved and consequently reduces the explanatory power serotonin hasas a neural mechanism in aggression.

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Self reduces validity desirable conclusions invalidevidence manipulating unethical sample representative generalisability

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Bond (2005)

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A further strength of the research into the link between serotonin and aggression is that supportive evidence comes from research using antidepressants. Bond(2005) established that low levels of serotonin are associated with aggressive behaviour and drugs that raise serotonin levels (SSRIs) lower aggression. This is a strength because it further establishes a link between lowered levels of serotonin and aggression indicating that this neurotransmitter (or lack of) plays a vital role in displays of aggressive behaviour. As a consequence, the credibility of the research into the link between serotonin and aggression is strengthened.

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Link antidepressants low serotonin associated drugs raise SSRIs lower Establishes neurotransmitter role displays credibility

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IDA; Reductionist

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Oneissue with the research into neural mechanisms of aggression is that it isreductionist as it reduces the complex behaviour of aggression down to simpleneurotransmitter imbalances in the brain. Whilst this allows for aggression tobe studied in great detail, it does not consider other factors that maycontribute to aggressive behaviour in humans. For example the complexity ofhuman social behaviour is ignored. The processes of social learning theory anddeindividuation have been shown to have an impact on aggressive behaviour. Thiscasts doubt on the explanatory power of neural mechanisms in its attempt toexplain aggression. In order to truly understand this complex behaviour, theindividual as a whole must be taken into account.

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Reductionistcomplex neurotransmitter imbalances detail factors complexity SLT impact doubt explanatoryattempt whole

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dopamine

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Thereappears to be a link between the neurotransmitter dopamine and aggression, in thatincreased dopamine levels can produce increased levels of aggressive behavior.For example, the increased rates of aggressive behaviour found in the schizophrenic population are believedto be due to the raised levels of dopamine in the brain.

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Link,increased dopamine increased aggressive schizophrenicraised dopamine brain

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Lavine (1997)

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The role of dopamine in aggression have alsobeen demonstrated in studies which have used amphetamines, which increase levels of dopamine. Lavine (1997) claims thatincreases in dopamine activity via the use of amphetamines have also beenassociated with increases in aggressive behaviour.This demonstrates a clearlink between higher levels of dopamine and aggressive behaviour.

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Role dopamine demonstrated amphetamines increases dopamine via amphetaminesassociated link

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Cherek et al (1986)

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The theory of neural mechanisms as an explanation of aggression argues that there is a link between the neurotransmitter dopamine and aggression. Cherek et al (1986) conducted an experiment where by they administered either amphetamines or caffeine to participants and found that amphetamines raised the frequency of interpersonal hostility whereas caffeine reduced it. This is a strength because it further establishes a link between increased levels of dopamine and aggression indicating that this neurotransmitter plays a vital role in displays of aggressive behaviour. As a consequence, the credibility of the research into the link between dopamine and aggression is strengthened.

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Theoryargues link amphetamines caffeine raised hostility reduced establishes indicatingrole credibility

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correlational evidence

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Aweakness of the neural explanation of aggression is the fact that most researchinto the link between neurotransmitters and aggression relies on correlationalevidence. Therefore, a causal relationship cannot be established as it isdifficult to explain whether low levels of serotonin and high levels ofdopamine influence aggressive behaviour, or if they are a by-product ofaggression.

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Weakness research relies correlational causal establishedexplain low serotonin high dopamine influence by-product