Aggression Flashcards
Analyse Raine et al (1997) - Summary (Aim)
To investigate whether there is a difference in the brain activity of people who have committed murder and those who have not.
Raine wanted to determine if there was a biological reason for some people acting more aggressively than others.
Analyse Raine et al (1997) - Summary (Method)
Used 41 offenders who pled Not Guilty by Reason of Insanity and 41 non-offenders.
Participants were brought to the university of California and were injected with a glucose tracer to allow fora PET scan to find out which parts of the brain were active.
Participants were asked to complete a continuous performance task which was designed to force participants to use parts of the brain that researchers were interested in. such as the Amygdala and prefrontal cortex. They did this task 32 minutes before the PET scan.
The study used a matched participant design as participants were matched on age and gender and the schizophrenics were matched with schizophrenics from the other group.
Analyse Raine et al (1997) - Summary (Results)
It was found that in the NGRI group there was increased activity in the amygdala compared to control group and decreased activity in the prefrontal cortex.
There were no differences in some areas that were associated with mental illness but not violence.
There were abnormal asymmetries as there was reduced activity on the left and increased activity on the right which applies to some areas that have been identified to be linked with violence.
Analyse Raine et al (1997) - Evaluation (Strengths)
The participants participated under protocols and consent forms approved by the Human Subjects Committee of University of California which meant participants were protected from harm and gave informed consent.
Raine ensured there was methodological control by making sure participants were not taking any other medications that may have changed the PET scan results. The participants were also given time to familiarise themselves with the performance task before the study started which improves the reliability of the results.
Analyse Raine et al (1997) - Evaluation (Weaknesses)
The sample of aggressive people only contained murders who pled NGRI which means it doesn’t represent all types of violence so the results cannot be applied to all aggression.
The PET images were unclear and hard to read which reduces the reliability of the results.
It could be potentially be dangerous to apply the findings of the study to wider society. If it is suggested that brain structure leads to violent behaviour, it may lead to defense lawyers using this idea to defend their clients.
Analyse Raine et al (1997) - Link
The prefrontal cortex is responsible for decision-making and impulse control. Its main job is to control our emotional responses to stress. Damage to this part of the brain would reduced the inhibition of the amygdala resulting in higher levels of aggression.
Evidence of this is that neuropsychological tests have found impairment in the prefrontal cortex in juvenile offenders.
The amygdala is a brain structure located in the limbic system that controls our emotional responses. Because of this, the amygdala is strongly linked to feelings of anger or fear that can result in aggressive behaviours.
Analyse Raine et al (1997) - Comparison
Barroni et al did neuropsychological tests that found impairment in the prefrontal cortex in juvenile offenders which agrees with Raine’s findings that murderers who pled NGRI had reduced prefrontal cortex activity.
Summer (2007) found that the aggression levels of a girl who was showing extreme aggressive behaviour went back to normal once she had a tumour removed that was pressing on her amygdala which agrees with the results of Raine which found that murderers who pled NGRI had increased activity in the amygdala.
Gospic et al did FMRIs which found that increased activity in the amygdala was present in participants showing aggressive behaviour which agrees with Raine’s results.
King (1961) demonstrated that when the amygdala was electrically stimulated,
participants became threatening and verbally abusive which also agrees with Raine’s results.
Grafman et al found that vietnam veterans with prefrontal brain injuries demonstrate higher levels of aggression than that which they had shown before the injury which supports Raine’s results.
Bufkin did MRI and PET studies which have shown reduced volume and metabolism of the prefrontal
cortex in aggressive people which agrees with Raine’s findings that murderers who pled NGRI had reduced prefrontal cortex activity compared to the control group.
Analyse Raine et al (1997) - Implications
This could mean that both defense and prosecution lawyers could use brain scans on the accused in order to see whether their brain activity lines up with the brain activity present in violent people. However this could lead to negative consequences as if their brain activity is similar then it may make them seem like a more likely culprit however that isn’t necessarily the case as not as aggressive people are criminals.
Biological Influences - Neural (Limbic system)
The limbic system can affect aggression as it is the part of the brain which controls aggression which controls emotion, learning and memory.
It also regulates our primitive urges such as sleep, appetite, fear and sex drive.
The amygdala is a brain structure located in the limbic system which controls our emotion responses. Because of this it is strongly linked to feelings of anger or fear that can result in aggressive behaviours.
Evidence of this is Summer (2007) which conducted a case study on a 14-year-old girl showing extreme aggressive behaviour as well as epileptic fits. MRI scans revealed a tumour pressing on her amygdala. After it was removed her aggression levels became normal.
Biological Influences - Neural (Prefrontal Cortex)
The prefrontal cortex is responsible for decision-making and impulse control. Its main job is to control our emotional responses to stress. Damage to the prefrontal cortex would reduce the inhibition of the amygdala resulting in higher levels of aggression.
Evidence of this is Barroni et al (2022) which did neuropsychological tests that found impairment in the prefrontal cortex in juvenile offenders.
Biological Influences - Hormones (Serotonin)
Serotonin helps maintain our mood and impulse control. A decrease or lack of serotonin disrupts this mechanism and can lead to an increase in impulsiveness and aggression.
Evidence of this is Virkkunen et al (1994) which found that violent, impulsive offenders have lower levels of serotonin than non-violent offenders.
Biological Influences - Hormonal (Testosterone)
Testosterone is the primary sex hormone in males. It is strongly associated with competition and aggression.
The challenge hypothesis suggests that testosterone promotes aggression when it would be beneficial for reproduction, such as mate guarding or fighting off challengers.
Evidence of this is Edwards (1968) which gave testosterone to female mice and found that they began to act with much more aggression than normal.
Biological Influences - Neural/Hormonal (strengths)
Research studies have found evidence to support the idea that high levels of testosterone can lead to aggression. For example, Van Goozen (1997) conducted a natural observation on people who were transitioning to the opposite sex. It was found that males who were given testosterone suppressants were less aggressive whereas females given testosterone boosters were more aggressive.
Most violent behaviours are carried out by men (who have more testosterone) which supports this idea.
Biological Influences - Neural and Hormonal (weaknesses)
It is unclear whether hormone imbalances cause aggression or aggressive behaviour causes hormone imbalance.
This explanation is reductionist. All aggression cannot be explained purely by biology.
Not all men are violent and if testosterone was the only reason, this would not be the case.
This explanation is deterministic and assumes humans have no free will or control of their aggressive behaviours. We know this is not true and not everyone with hormone/neurotransmitter imbalances will act on their aggressive thoughts.
Biological Influences- Genetic
One specific gene that has been identified to carry the aggression trait is Monoamine Oxidase A (MAOA) which is known as the “warrior gene” due to many research studies identifying a relationship between the gene and increased levels of violence.
MAO is a protein that helps nerve cells transfer serotonin, norepinephrine and dopamine.
MAOA leads to there not being enough MAO which means that there is too much serotonin, norepinephrine and dopamine in the body. This leads to too much adrenaline which causes the hypersensitivity of the fight or flight response.
Evidence of this is McDermott (2009) which found that those with the MAOA gene were much more likely to administer higher levels of hot sauce (causing them more harm and therefore showing more aggression) than those without the MAOA gene.
