neural explanations of aggression a2
DESCRIPTION
TRANSCRIPT
1
Biological explanations of aggression
Neural and hormonal mechanisms and aggression
2
Essentially the argument is
• Low levels of serotonin• High levels of dopamine
• High levels of testosterone• Low levels of cortisol
..... are associated with aggression
3
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)
4
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
5
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
6
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
7
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.
8
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
9
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.
10
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
11
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
12
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
13
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