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Biological explanations of aggression

Neural and hormonal mechanisms and aggression

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Essentially the argument is

• Low levels of serotonin• High levels of dopamine

• High levels of testosterone• Low levels of cortisol

..... are associated with aggression

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Serotonin AO1

• Thought to inhibit aggressive responses to emotional stimuli

• Low levels associated with increased susceptibility to impulsive behaviour, aggression & violent suicide

• Drugs which reduced serotonin increased measures of hostility and aggression in males (but not females)

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Dopamine AO1

• Link less well established than serotonin• Giving amphetamines (which increase

dopamine) increases aggressive behaviour• Giving anti-psychotics (which reduce

dopamine) reduced aggressive behaviour in violent delinquents

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Testosterone AO1

• Thought to act on areas of brain which control aggression from young adulthood onwards

• Thought to be primary biochemical influence on aggression

• Salivary testosterone levels were able to differentiate between violent and non-violent criminals and their crimes

• Aggressive behaviour in drunken males also positively correlated with testosterone levels

• Castrated male mice showed decreased aggression which then increased when given testosterone again

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Cortisol AO1

• Cortisol mediates other hormones such as testosterone

• High levels of cortisol inhibit testosterone and so inhibit aggression

• So low levels of cortisol associated with increased aggression and studies have supported this.

• Low levels of cortisol have been found in habitual violent offenders and also in violent schoolchildren

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AO2 Serotonin

• Findings on serotonin replicated in vervet monkeys (Raleigh et al (1991)) But issue of: – extrapolation

• Meta-analysis (Scerbo 1993) supports low level of serotonin consistently found in aggressive children and adults but found no dopamine abnormalities

• Bond – drugs (anti-depressants) that increase serotonin levels to reduce impulsive aggressive behaviour.

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AO2 Serotonin

• Findings on serotonin also confirmed via studies on anti-depressants

• However Lenard (2008) cautions that serotonin not just linked to aggression: also to impulsive behaviour, depression, over-eating, alcohol abuse; violent suicide

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AO2 Dopamine

• Causal role of dopamine unclear• Perhaps high levels of dopamine are an effect

rather than a cause because dopamine is released by performing aggressive acts, so aggression could be being rewarded in the brain.

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AO2 Testosterone

• Evidence conflicting on role of testosterone• Studies showing positive correlation small

samples and self-report measures• Studies mainly correlational (eg. Wagner) so

not possible to conclude that testosterone causes aggression

• Also testosterone not always associated with negative characteristics: improved sporting and spatial abilities also been found

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AO2 issues and debates

• Gender bias evident as most research done on males (animals and humans) whereas it is known that there are differences between the genders in androgens

• Also cultural bias as most research conducted in western countries

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AO2 debates

• Reductionist to just consider role of biochemistry alone

• Also need to consider genetic factors and brain structure

• Eg. Phineas Gage suffered brain injury and showed heightened levels of aggression

• Also need to consider the contribution of environmental factors such as situational cues, temperature, noise, overcrowding, and the role of learning

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AO2 application

• Clearly a very important & useful area of biopsychological research and theory as aggression associated with many anti-social phenomena in society, eg. numerous forms of crime, violence

• If the role of biochemistry can be understood it can perhaps be treated or managed

• Although there would be ethical issues associated with giving people drugs simply to alleviate aggression (ie. for social control) , or male castration, even if it may be in the interests of multiple parties

• Could perhaps be treated more ethically through diet (tryptophan) and exercise