Biological explanations of aggression Neural and hormonal mechanisms and aggression 1

Essentially the argument is Low levels of serotonin High levels of dopamine High levels of testosterone Low levels of cortisol..... are associated with aggression 2

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) 3

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 4

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 5

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 6

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. 7

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 8

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. 9

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 10

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 11

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 12

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 13