Neural And Hormonal Influences Flashcards
What do these influences refer to?
The effect of neurotransmitters and the nervous system. It is said that some people are more pre-disposed to aggression through their biological characteristics.
What is the limbic system?
The area of the brain that helps to co-ordinate behaviour, and especially emotion and motivation. Two of the key emotions involved are aggression and fear. Speed and sensitivity of limbic system responses to stimuli are important predictors of aggressive behaviour in humans.
What is the amygdala?
This is the part of the brain which gives us anger. If you artificially stimulate an animals amygdala, they will respond with aimless aggression. Conversely, if you remove an animal’s amygdala they will no longer experience rage in response to the same stimuli. The amygdala is the brain’s quick response to stimuli and is a very primitive part of the brain.
What is the hippocampus?
This is part of the brain primitively responsible for memory. This helps us to respond to stimuli which we remember should be linked to aggression. Damage to the hippocampi can affect our normal responses to aggressive stimuli.
Examples of activation of the amygdala.
- Turning around and seeing a tiger running towards you.
2. Stubbing your toe on the coffee table.
Examples of the activation of the hippocampus.
- Seeing the person who stole your car.
2. Watching a weather report which says that there will be no sunshine for two weeks.
What is serotonin?
This is a neurotransmitter which is linked to the inhibition of emotional reactions to stimuli by inhibiting the amygdala. Normal levels of serotonin in the orbitofrontal cortex are inhibitory and linked with reduced firing of neurones and associated with greater behavioural self control. If your serotonin is too low you are more likely to react in an emotional way because you have a reduced level of self control, it increases impulse behaviours including aggression.
A study supporting serotonin as a way of reducing emotional responses.
Mann gave healthy participants a drug known as dexfenfluramine which is known to reduce serotonin. Mann then gave participants a questionnaire to assess their hostility and aggression levels. They found that this drug actually increased their hostility and aggression although this was only found in male participants, but not female participants.
Strength of neural influences-research support
Lower levels of serotonin can lead to increased levels of aggression. Raleigh et al found that vervet monkeys who were fed on diets high in tryptophan (increases serotonin) became less aggressive than monkeys who were fed on diets low in tryptophan (therefore had lower levels of serotonin). This clearly shows that serotonin is linked to the inhibition of aggressive behaviours. But this research was conducted on non-human participants. Vervet monkeys have different social behaviours to humans and therefore we cannot necessarily extrapolate from their neural influences to ours.
Strength of neural influences-further human research evidence.
Mann found that human participants who were given dexfenfluramine to reduce their serotonin levels also showed higher levels of aggression, thus suggesting that serotonin inhibits aggression even in human participants (reinforces Raleigh et al’s research).
What is testosterone?
A hormone significantly more plentiful in men than in women. Testosterone levels peak in young men from adolescence onwards, before declining through adulthood. It is responsible for the development of masculine features and helps regulate social behaviour via influence on areas of the brain involved in aggression.
What can the claim that testosterone increase aggression levels explain?
- Why men are more aggressive than women.
- Why males become more aggressive when they hit puberty, peaking between 21 and 35.
- Why prison inmates who were convicted of violent crimes had significantly higher testosterone levels than those with non-violent crimes.
- Why testosterone levels fluctuate due to events and social changes, and is linked to changes in aggression through the activation of the amygdala. For instance, in response to angry facial expressions.
Strength of hormonal influences: research support
Daly and Wilson found that males become more aggressive when they hit puberty, peaking between the ages of 21-35.
Weakness-evidence for testosterone doesnt always suggest a link with aggressive behaviour.
Testosterone leads to status-seeking behaviour, not just aggression. Aggression has an evolutionary benefit: to increase an individual’s chances of mating by being aggressive to same-sex individuals and to increase the chance of survival by being protective of food or territory etc.
Eisenegger et al found that testosterone can actually make women nicer, which could be a useful way of acquiring status.
Limitation of limbic system: it excluded other possibilities.
The amygdala functions in tandem with the orbitofrontal cortex (OFC) to maintain self control and inhibit aggression. Coccaro et al showed OFC activity is reduced in patients with psychiatric disorders that feature aggression. This shows the regulation of aggression cannot be explained by the limbic system alone - it is highly complex.
