Aggression A03 - Year 13 Jan Mock - 1st 2 bullet points on spec Flashcards
Support for the role of the amygdala in aggression (link to the limbic system)
Sumer et al. They conducted by looking at a 14-year-old girl with excessive aggression. An MRI scan revealed that she had a tumour pressing onto her amygdala. The tumour was causing more nerve impulses being sent to the hypothalamus and therefore increased the activity of the amygdala. Therefore thus supporting the suggestion that the limbic system is implicated in aggressive behaviour, particularly the amygdala plays an important role in aggressive behaviour
Support for the role of the hippocampus in aggression (link to the limbic system)
Raine et al (2004) cinducted MRI scans on convicted violent offenders and found asymmetries - size of it in either hemisphere differed in size, an imbalance presumed to have arisen early in brain development. This suggests that the asymmetry of the hippocampus impaired the ability of the hippocampus and the amygdala to work together and communicate with each other. Therefore, emotional information cannot be processed correctly which could therefore lead to inappropriate verbal and physical aggression responses. This supporting research evidence indicates that the limbic system, particularly the hippocampus and the amygdala play an important role in aggressive behaviour.
Support for the role of the amygdala in aggression (link to the limbic system) - 2
Pardini et al (2014) longitudinal study, Male patients from childhood to adulthood. Some pts (56) with a history of aggression/violence. He found the participants with lower amygdala volume displayed more aggressive and violent behaviour. Therefore this suggests that this reduction in the amygdala volume can predict aggression. As the amygdala plays an important role in evaluating the emotional importance of sensory information this reduced volume of the amygdala can lead to inappropriate and hence more aggressive behaviour than someone with a regular volume of the amygdala. This also then suggests that the limbic system and especially the role of the amygdala is important when it comes to aggression.
Limitation of the limbic system (Animal research)
A limitation of the research that has been carried out on animals that indicates the limbic system plays a role in aggression is that we need to be cautious when suggesting that the exact biological neural mechanisms cause the same aggressive behaviour in humans. For example, stimulating the amygdala or destroying the hypothalamus may not have the same consequences in cats on aggressive behaviour as it would in humans. The brain consists of many neural networks which connect different brain areas together; stimulation or lesion of these brain areas would undoubtedly affect other neural mechanisms as well as other behaviours. For example, the hypothalamus Is also implicated in eating, behaviour, behaviour, thirst and temperature. Furthermore, human behaviour Is driven by many cognitive processes, such as high order thinking’s and emotion, which some psychologists would argue are absent on animals. Therefore it Is questionable as to whether the findings on neural mechanisms and aggression are linked to human aggression and consequently this limits the support for the role of the limbic system in aggressive behaviour.
Limitation of the limbic system (oversimplistic)
To assume that It is solely the limbic system that is involved in aggressive behaviour. For example, the orbitofrontal cortex which is responsible for self-control and impulse regulation could also play a part. Other neural mechanisms in aggressive behaviour are far more complex than previously thought and potentially involves many neural mechanisms working together. Research indicated could be a genetic vulnerability (XYY chromosomal abnormality and MAOA mutation) to aggressive behaviour. Consequently, a holistic approach Is necessary to fully understand aggressive behaviour and its causes.
Support for the role of serotonin - Valzelli and Higley
There is research to support the role of serotonin in aggressive behaviour. Valzelli (1973) showed that, in a laboratory experiment with mice, males with lower serotonin levels were more likely to fight when put together. Furthermore, later research by Higley et at (1996) he studied very source monkeys in their natural environment found that males with the lowest serotonin levels were most likely to fight, had the most scars and wounds, and were more likely to be dead by age 6 when compared with male monkeys who had higher levels of serotonin. Aggressive monkeys were more likely to pick fights with meals they could not possibly be and showed higher risk-taking behaviour. This suggests that the lower the levels of serotonin the higher the levels of aggression are and the higher levels of serotonin the lower the levels of aggression are. Therefore, this supports the role of the limbic system and serotonin in aggressive behaviour indicating both plays a vital role.
Support for the role of serotonin - Passamonti
Passamonti et al. (2012) altered serotonin levels in healthy participants by manipulating their diet to contain, on consecutive days, either no or normal levels of tryptophan. Participants were also given a questionnaire to assess their tendencies towards behaving aggressively. FMRI scans we are performed to measure brain activity when participants were shown pictures of angry, sad and neutral expressions. It was found that on low serotonin (no tryptophan), communication between the pre-frontal cortex and the limbic system was weaker compared to normal serotonin days. This communication appeared particularly weak in those assessed by the questionnaire to have an existing tendency to behave aggressively. This suggests that when serotonin levels are low, it is more difficult for the pre-frontal cortex to control emotions generated by the limbic system. Individuals predisposed to aggression or particularly sensitive to reductions in serotonin, and therefore more susceptible to allowing aggressive impulses to become aggressive behaviour. This supports the role of the limbic system and serotonin in aggressive behaviour indicating both plays a vital role.
Limitation of the role of serotonin - Animal Research
A limitation of the research that has been carried out on animals that indicate serotonin plays a role in aggression is that we need to be cautious when suggesting that the exact same biological neural mechanism causes the same aggressive behaviour in humans. For example, manipulating levels of serotonin may not have the same consequences on aggressive behaviour as it would in animals. Furthermore, serotonin is implicated in many other behaviours, such as eating and sleep; thus altering levels of serotonin to examine the impact on aggression would undoubtedly impact on other behaviours. Despite similar neural systems to humans, animals are not the same; human behaviour is driven by cognitive processes, such as higher-order thinking and emotion, which some psychologist would argue are absent in animals. Therefore it is questionable as to whether the findings on serotonin and aggression or generalisable to human aggression and consequently this limits the support for the role of this neurotransmitter in aggressive behaviour.
Limitation of the role of serotonin - IDA reductionist
This explanation is flawed since it reduces a complex behaviour like aggression down to a simple basic component of a single trance neurotransmitter (i.e. low levels of serotonin.) This is, therefore, biological reductionism, and as a result, it then ignores firstly other biological components in aggressive behaviour; these include dysfunction in neurotransmitter levels (e.g. high levels of testosterone), neural structures (OFC( as well as genetic factors )
(XYY/MAOA gene). Secondly. it also ignores psychological explanations of aggression which are not considered, such as SLT.
Supports the role of testosterone - Kouri
There is research evidence to support the role of testosterone in aggressive behaviour. Curie at owl 1995 administrated increasing doses of testosterone over three week period two participants. Before and after the testosterone injections participants were given a pressed button task by which they could either accumulate points exchangeable for money or subtract from what they thought was an opponent. Another group of participants control had exactly the same experience except that their injections were placebos. Aggression was measured by how participants responded to having points deducted by a fictitious opponent. It was found that the experimental group who received his fostering injections were more likely to respond themselves by deducting points which was interpreted as an act of aggression. This suggests that an imbalance in total testosterone lead to the participants being more aggressive. Therefore high levels of testosterone are linked to higher levels of aggression.
Supports the role of testosterone - Animal Study
There is research evidence from animal studies to support the role of testosterone in aggressive behaviour. Wagner et al (1979) found that if a male mouse was castrated, overall levels of aggression reduced. If the castrated Mouse receives testosterone, aggression levels increased. This suggests there is a correlation between testosterone and aggression levels. Therefore I levels of testosterone lead to the male mouses’ aggression levels increase.
Limitation for the role of testosterone - Gender Bias
A limitation of explaining aggression as a result of increased levels of the hormone testosterone is that it may be gender-biased. As males produce far more testosterone than females eight times more, most research about this relationship is based on the studies of males, e.g. androcentric research by Mehta and Joseph (2006) - as testosterone is easier to measure and its effect our clearer than in females. Consequently, there is very little research on testosterone - aggression links and females. Although some research has suggested that high testosterone women are more likely to be aggressive archer et al (2005), other studies have found a relationship. With so many conflicting results, the relationship between testosterone and aggression in females is far less established than it is for males, plus you must be cautious when generalising the findings on testosterone and aggression to females. This means that the hormonal explanation of aggression could be considered to be alpha biased - exaggerating the differences in aggression levels between men and women, thus reinforcing gender stereotypes.
Limitation for the role of testosterone - Oversimplistic
It could be argued that testosterone alone cannot be the sole hormonal mechanism that causes aggression. The entire Endo crying system is a complicated structure involving numerous hormones, none of which work independently of others. For example, Carre and Mehta (2011) put forward that to Home and hypotheses which suggest increased levels of testosterone only results in aggressive behaviour when cortisol levels (a hormone involved in the stress response) are low. Consequently, although testosterone may play a role in aggression, although hormonal, neural and biological factors are also implicated. Furthermore, hormones cannot directly cause behavioural outcomes such as aggression and the simple presence of testosterone does not inevitably cause aggression; (e.g. there is a significant majority of high testosterone then who are not aggressive.) Thus research in one woman in isolation is not sufficient to fully understand aggressive behaviour.
Support for genetics in aggression (Twin studies)
There is research from twin studies to support the role of genetic factors in aggression. Coccaro et al (1997) support for the role of genetics in aggression. For example, he found that the concordance rates fir male twins for direct physical assaults was 50% for MZ and 19% for DZ twins, for verbal aggression 28% for MZ twins whereas only 7% for DZ twins. This suggests that genes play a key role in aggression since the more genetic material shared, the greater the chance that both individuals have high levels of aggression. Therefore genetic explanation for aggression is valid.
Support for genetics in aggression (Adoption studies)
There is research from adoption studies to support the role of genetic factors in aggression. Hutching and Medrick (1975). 1400 adoptions in Denmark found that a significant number of adopted males with criminal convictions had a biological parent (particularly the father) with convictions of violence (positive correlation ). This suggests that despite growing up in a different environment from their parents, their genetic inheritance made them vulnerable to aggression. Therefore genetic explanation for aggression is valid.
