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Biological Explanation 1: Brain Function - Coggle Diagram
Biological Explanation 1: Brain Function
Phineas Gage
The Phineas Gage study showed that damage to the frontal lobes seemed to cause an increase in aggression; this was an early research findings showed a possible biological basis for aggression.
. This type of research could npt be done under experimental conditions on humans for ethical reasons so typical studies into the biological structures that underlie aggression had to be done using laboratory animals, typically rodents and cats.
Animal Studies
Studies show three different and specific types of aggressive behaviour in these animals.
. Offensive Behaviour - physically attack another animal
. Defensive Behaviour - shown in response to threat of attack
. Predatory Behaviour - attacking another species to gain food
Lesions/ stimulation to different areas of the brain has been shown to activate behaviour associated specifically with one type of aggression. For example, stimulation of:
.
Medial Hypothalamus
- in a cat' brain produces offensive behaviour.
.
Dorsal Hypothalamus
- produces defensive behaviour
.
Lateral Hypothalamus
- results in predatory behaviour (Flynn, Vanegas, Foote & Edwards, 1970s).
SCOUT
Strengths
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Freud
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Research evidence supporting brain function and aggression come from human cases. For example Phineas Gage
. This is further supported by the case studies suggesting that the prefrontal cortex is linked to aggression. In a scientific study by Raine et al (1997) on 41 convicted murderers, they found lower activity in the prefrontal cortex and differences in the functioning of the limbic system in brain scans if impulsive murders
¬ This suggests there is a link between function and aggression.
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The idea that there is a biological basis for aggression is consistent with the genetic explanation because our genetic blueprint builds our brain structures ad therefore people with a genetic blueprint for aggression would have brain structures that predispose them towards aggressive responses.
. This could explain why, on average, males across all cultures tend to be more physically aggressive than females.
Weaknesses
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Research to investigate aggression and the brain has been carried out under laboratory conditions, with the use of specifically bred animals.
. However, there are issues with the use of lab animals in terms of generalisability. This involves selectively damaging brain areas of cats and rodents, although human brains are more complex than those of small mammals.
¬ This has led some researchers to argue that the basics are the same between the species therefore these types of experiments are worthwhile.
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Furthermore, there are ethical considerations in the use of animals in research into human psychology.
. Some would argue that such research is immoral as the animals are harmed by these types of studies
¬ For example through having parts of their brain lesioned.
. Others would argue that using animals for human benefit in this way is no different from using them for meat or keeping them as pets.
¬ Ethical guidelines now ensure that all studies using animals require cost-benefit analysis, which clearly shows that any suffering caused to the animals is outweighed by the potential benefit to humanity.
Individual Differences
The case of Charles Whitman
He had brain damage to the amygdala, which was caused by a tumour and could be linked to aggression.
. Evidence of aggressive behaviour
¬ He witnessed domestic violence, was bullied by his father and has the urge to kill. When he grew up: he beat his wife, abused drugs and was on medication for sleep. He also experienced mood swings, headaches and hypergraphia.
¬ Warning signs he had problems in his amygdala: impulsiveness, irritability, medication and revenge fantasies, which nobody took him seriously with.
¬ Suggested cause of Whitman's aggression and the consequences: mental illness, childhood trauma, misuse of drugs, abuse from his dad and anger towards his mother. The consequences of his actions were 16 killed and 32 wounded.
¬ Other factors which could be the cause of Whitman's aggression: drug abuse, environment, failed career, didn't finish university, angry personality and was a fantasist.
The Limbic System
Hypothalamus
- maintains homeostasis through hormones, including those that regulate sexual function.
. This is linked to aggressive behaviour in males via the production of testosterone.
Midbrain
- coordinates and integrates behavioural responses to perceived internal and external stressors like pain or a threat.
. Lesions to the PAG in rats that have recently given birth show an increase in aggression when the rates are confronted with the potential threat in the form of unfamiliar male rats being introduced to the cage (Lonstein and Stern, 1998).
Complex nerves and networks in the brain, involve several areas near the edge of the cortex concerned with instinct and mood. It controls the basic, emotions (fear, anger, pleasure) and drives (hunger, sex, dominance, care of offspring).
Amygdala
- centre of emotion: integrates internal and external stimuli, which causes us to react to the environment, e.g. being aggressive.
. If we stimulate the amygdala in animals/ people's brains using electrical currents, there is an aggressive response and if removed the animal becomes passive.
Prefrontal Cortex
The prefrontal cortex regulates emotional responses driven by the amygdala.
. The lower the activity in the prefrontal cortex (e.g. as a result of damage or alcohol), the more likely there will be implusivity, immaturity and loss of control.
¬ Researchers assume that the prefrontal cortex is about regulating emotions; therefore aggression itself comes from a lack of regulation (or control) of behaviour.
