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Biological explanations ofaggression

Neural and hormonal mechanisms andaggression

Essentially the argument is

•Low levels of serotonin

•High levels of dopamine

•High levels of testosterone

•Low levels of cortisol

..... are associated with aggression

Serotonin AO1

•Thought to inhibit aggressive responses toemotional stimuli

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

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

Dopamine AO1

•Link less well established than serotonin

•Giving amphetamines (which increasedopamine) increases aggressive behaviour

•Giving anti-psychotics (which reducedopamine) reduced aggressive behaviour inviolent delinquents

Testosterone AO1

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

•Thought to be primary biochemical influence onaggression

•Salivary testosterone levels were able todifferentiate between violent and non-violentcriminals and their crimes

•Aggressive behaviour in drunken males alsopositively correlated with testosterone levels

•Castrated male mice showed decreasedaggression which then increased when giventestosterone again

Cortisol AO1

•Cortisol mediates other hormones such astestosterone

•High levels of cortisol inhibit testosterone and soinhibit aggression

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

•Low levels of cortisol have been found inhabitual violent offenders and also in violentschoolchildren

AO2 Serotonin

•Findings on serotonin replicated in vervetmonkeys (Raleigh et al (1991)) But issue of:

–extrapolation

•Meta-analysis (Scerbo 1993) supports low level ofserotonin consistently found in aggressivechildren and adults but found no dopamineabnormalities

•Bond – drugs (anti-depressants) that increaseserotonin levels to reduce impulsive aggressivebehaviour.

AO2 Serotonin

•Findings on serotonin also confirmed viastudies on anti-depressants

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

AO2 Dopamine

•Causal role of dopamine unclear

•Perhaps high levels of dopamine are an effectrather than a cause because dopamine isreleased by performing aggressive acts, soaggression could be being rewarded in thebrain.

AO2 Testosterone

•Evidence conflicting on role of testosterone

•Studies showing positive correlation smallsamples and self-report measures

•Studies mainly correlational (eg. Wagner) sonot possible to conclude that testosteronecauses aggression

•Also testosterone not always associated withnegative characteristics: improved sportingand spatial abilities also been found

AO2 issues and debates

•Gender bias evident as most research done onmales (animals and humans) whereas it isknown that there are differences between thegenders in androgens

•Also cultural bias as most research conductedin western countries

AO2 debates

•Reductionist to just consider role ofbiochemistry alone

•Also need to consider genetic factors andbrain structure

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

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

AO2 application

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

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

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

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