Biological explanations of Aggression

AQA A-Level Psychology A: Aggression

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Biological explanations of Aggression by Mind Map: Biological explanations of Aggression

1. The role of genetic factors

1.1. Sandberg (1961) - XYY Karyotype

1.1.1. Most people have 46 chromosomes but it is possible for a male to have 47 (extra Y) - about 0.1% of males are XYY - has effects on physical make up of the male (e.g. increased height) - is argued to increase aggressive behaviour.

1.1.2. Court-Brown (1965-1967) - XYY Ps should be hospitalised due to an increased likelihood in aggressive behaviour. Assumption was made prior to the examination of patients This statement was later retracted Too late as many scientists had already incorporated this incorrect view into their thinking

1.1.3. Theilgaard (1984) - compared XYY and XY personalities - thematic apperception testing - XYYs tend to give more aggressive interpretations of images - the issue of XYY aggression is complex: they may seem more aggressive but this does not mean that they would readily violent acts.

1.1.4. Research in this are is conflicting, it is not possible to conclude that XYY alone causes increase in aggression.

1.2. Aggressive tendencies can be passed on through genetics

1.2.1. Nelson (2006) - selective breeding experiments can lead to more aggressive behaviour in animals

1.2.2. Cairns (1983) - mice - he created highly aggressive males and females that would only show their nature at middle age rather than young or old Selective breeding techniques show how important genetic processes are to human behaviour Animal observations - a study of animals cannot give us a true understanding of aggression in humans - not generalisable ? Science is limited by the use of using humans in genetic research but animal studies allow researchers to create more informed models

1.2.3. Difficult to separate the influences of nature and nurture - aggressive environment can also lead to aggressive traits being shown.

2. Hormonal Influences

2.1. Testosterone increases aggressive behaviours

2.1.1. During puberty, aggression increases when androgen levels are higher

2.1.2. Wagner at al (1979) - if a male mouse is castrated, overall levels of aggression tend to reduce - if the castrated mouse receives testosterone, aggression will increase. Correlational - cannot establish cause and effect

2.1.3. Pillay (2006) - using athletes - testosterone levels (measured from saliva samples) differed depending on the sport they played - Ps who played aggressive sports (i.e. wrestling) had the highest levels of testosterone.

2.1.4. Simpson: "testosterone is only one of a myriad of factors that influence aggression and the effects of environmental stimuli have at times been found to correlate more strongly" Ignores potential for individual differences - people may react differently to increase in testosterone i.e. psychologically.

2.1.5. Basal Model of Testosterone An individual's level of testosterone influences their level of dominance, becoming competitive. Huston et al (2007) - men with high levels of testosterone often perform well in competitive tasks but poorly on cooperative tasks. Mazur and Booth (1998) - men with higher levels of testosterone are more likely to divorce, or remain single, be arrested for offences other than traffic violations, to buy and sell stolen property, to incur bad debts and to use weapons in fights.

2.1.6. Reciprocal Model of Testosterone Testosterone levels are influenced by changes in the level of dominance that an individual has.

2.2. Serotonin inhibits aggressive behaviours

2.2.1. Davidson et al (2000) - serotonin may provide an inhibitory function - when comparing violent criminals to non-violent ones, levels of serotonin were higher when Ps were more aggressive.

2.2.2. Animal Studies Mice with ineffective serotonin 1B receptors suffered an increase in aggressive behaviours Reducing serotonin levels in Vervet Monkeys rsulted in an increase in aggressive behaviour, whereas increasing levels of serotonin resulted in a decrease in aggressive occurrences. Studies of domestic pets who have been bred for reduced aggression, show that they seem o have lower levels of serotonin. May not be generalisable to humans as we cannot assume that a person would react or behave in the same way as an animal.

2.2.3. In clinical trials, serotonergic drugs have historically been given to juvenile delinquents and unpredictable institutionalised parents to reduce their aggressive tendencies.

2.2.4. Caution should still be used before simply attributing the cause of aggression to be serotonin levels

3. IDA

3.1. Much scientific research takes place in Western, industrialised societies as this is where scientific facilities are, along with the financial incentives to study it - cultural specific - may not be generalisable to other cultures - cultural bias.

3.2. Reductionist- no scope to appreciate other influences on aggressive behaviour.

3.3. Nature vs nurture - this argument is clearly on the nature side, but there is gravitas to many arguments that nurture has a significant influence and they could be equally important.

3.4. Heavily relies on animal studies - while these reveal some neurological and biochemical influences upon aggression, there are ethical issues - also may not be generalisable.

4. Brain Structure

4.1. Bard (1948) - 'rage' in cats caused by a detachment of the higher and lower brain through lesioning - the hypothalamus initiates aggressive behaviour - cerebral cortex reduces aggressive behaviour.

4.2. Amygdala

4.2.1. 1930s - careful lesioning of the amygdala of aggressive animals was show to have a taming effect.

4.2.2. If an amygdalectomy (surgical removal) is carried out on a human, it reduces violent behaviour - emotion is also lost.

4.2.3. Zadrodzka et al (1998) - damage to the central nucleus of the amygdala ( in cats) significantly contributed to 'predator like attacks'.

4.2.4. Blair et al (2001) - in cases where humans have been hospitalised for psychopathic tendancies, it is often caused by damage to the amygdala.

4.3. Frontal Cortex

4.3.1. Individuals with frontal lobe damage often show impulsive behaviour, irritability, shortness of temper and they are easily provoked. Phineas Gage 1848 - previously a hard working and shrewd character - head impaled by tamping iron, surviving - damage to frontal lobe - he became much more aggressive and negative. This is a case study of just one individual so generalisability is limited Relies on the medical notes of Gage's physician, Hawlow

4.3.2. Closely connected to the functioning of the hypothalamus and amygdala - it is in a good position to influence the other areas that stimulate aggressive responses.