Aggression Flashcards
Define Aggression ?
An intentional action aimed at doing harm or causing pain, this action can be psychical or verbal.
Describe the role of the Hypothalamus and how its related to aggression ?
The role of the Hypothalamus is to maintain homeostasis, it keeps the body in balance by regulating physical experiences like hunger and temperature as well as behavioural responses such as pain and threats. One of these behavioural responses includes controlling the hormone testosterone which is related to aggression.
Describe the role of the Amygdala and how its related to aggression.
The amygdala is a small almond like structure deep in the limbic system. It enables our instinctive reactions to the environment with emotions such as happiness, anxiety and anger. When we are exposed to threatening stimuli the amygdala is activated and results in an increased emotional arousal, as a result we either take flight (run away) or prepare to fight and become aggressive towards the threat. This is known as the fight or flight response. The amygdala itself doesn’t actually produce aggression it is linked to other brain structure that do, but it is necessary to initiate aggressive responses. without it we wouldn’t experience the immediate emotional reaction associated with aggression.
What evidence supports the role of the limbic system in aggression.
Case studies of brain damaged patients support the idea that the limbic system is linked to aggressive behaviour for example. Charles Whitman was a student at the University of Texas and an ex-marine. In the early morning of August 1st 1966 he first killed his Wife and mother in their homes before going on a shooting rampage on the university campus and killing 14 people and injuring 32 others. After being shot down by the police, it was found in is autopsy to have a cancerous tumour in the hypothalamus and near the amygdala.
Describe the role of the prefrontal cortex and how its related to aggression ?
The prefrontal cortex sits in the frontal lobe of the brain and is thought to be one of the latest evolutionary developments within the human brain. It has various executive functions, including planning, problem solving, social judgement, decision making and the regulation of emotional responses. The prefrontal cortex appears to allow us to control reactive impulses that stem from the amygdala. When exposed to a threatening stimuli the amgdala is activated, this activation increases the chances of us producing an aggressive response. If left uncontrolled, the amygdala activation would cause a highly aggressive response. However the prefrontal cortex also becomes activated when a threatening stimuli is presented and this mechanism inhibits us from automatically reacting to threats and allows us to to think about the appropriate course of action.
What evidence supports the role of the prefrontal cortex in aggression ?
Can studies of brain damaged patient such as Phineas gage support this theory. Phineas get was a railway worker who suffered accidental damage to his prefrontal cortex when a bold went through is left cheek and up through his left eye into his brain. Following this injury he covered well physically, but psychologically the became a different person. He went from being a sober, quiet family man to an aggressive, irritable drunk. This was one of the earliest cases (19 century) that suggest the prefrontal cortex id involved in moderation of our aggressive behaviour.
Describe the role of the neurotransmitter serotonin and how its related to aggression ?
Research has shown that the serotonin pathways of the brain are involved in the regulation of a vast range of psychological and biological functions including mood, anger, sleep and appetite. Of particular relevance is that low levels of the neurotransmitter serotonin has been found to be associated with increase tendency towards impulsive and reactive aggressive behaviour. The serotonin pathways in the brain are extensive and pass through the prefrontal cortex. Biological models suggest that low levels of serotonin in the prefrontal cortex results in this region no longer inhibiting the flight or fight response of the amygdala and thus increasing the linktlyhood of reactive, impulsive aggression. Under normal circumstances serotonin works in the brain to inhibit the firing of the amygdala, so if there are low levels of serotonin in the brain, the amygdala will be more active when stimulated by external events causing a person to act on instincts and be more aggressive.
What evidence supports the role of the neurotransmitter serotonin in aggression ?
1) Evidence for the role of serotonin comes form the use of drugs that raise levels of serotonin in the brain, such as antidepressants. in clinical studies, antidepressants which increase serotonin also tend to reduce irritability and impulsive aggression. This suggests increased serotonin levels do leas to reduced aggression.
2) Ferrari et al studied the link between neurotransmitters and aggression in rats. They allowed rats to fight everyday for 10 days at approximately the same time, by introducing an intruder rate into the test rats cage. On the 11th day no intruder rat was introduced, the researchers measured the rates serotonin levels and found in the tests rat Brian the serotonin levels decreased because they were anticipating a fight.
What is the title of the classic study for biological psychology and who developed it ?
Raine et al developed the classic study for biological psychology titled, Brain abnormalities in murderers indicated by positron emission tomography.
What is meant by NGRI plea ?
NGRI stands by not guilty by reason of insanity, when the defence admits to committing the crime but when doing so they were not responsible for their behaviour, either due to mental illness or biological aspects impacting their behaviour like brain abnormalities.
What was the aim of Raine et al classic study ?
Raine et al wanted to find out which brain areas were dysfunctional in violent offenders, using PET scans. They hypothesised that participants pleading NGRI would show brain dysfunctions in areas of the brain associated with violence for example the ore-frontal, amygdala and the hypothalamus.
What was the sample used in Raine et al classic study ?
There were two groups used in this study with 41 participants (39 males and 2 females in each group. The experimental group consisted of 41 criminals with convictions for murder or manslaughter who were being tested to gain evidence to support their NGRI claim. Of these 42 murders they had various mental health issues such as schizophrenia, paranoid personality disorder whilst others suffered from brain damage. Participants in this group were called ‘seriously violent individuals’ by the researchers. The control group was matched to the experimental group on a number of variables such as age, gender and psychiatric illnesses. The control group was further screened for their mental and physical health. They underwent a physical examination, the researchers had access to their medical history and went through a psychiatric interview.
What was the research method used in Raine et al classic study ?
The method is a laboratory experiment using matched pairs design. The main independent variable is whether the participant had commuted murder/manslaughter or not. The dependent variables were the results of the PET scans. This design is referred to a quasi or natural experiment because the researchers didn’t have control over the independent variable, the experimental group was pre-existing so participants couldn’t be placed into random conditions.
What was the procedure of Raine et al classic study ?
participants were required to perform a continuous performance task involving them starring at screen while various blurred symbols appeared, participants were to press a button when a particular shape appeared, requiring constant attention on the scree. They did this for 10 minutes was a practice trail. Then a radioactive glucose tracer, flurodeoxgyglucose was injected into the participant. After a further 32 minutes of the task, the subjects brains were PET scanned in order to determine the glucose metabolic rate throughout the brain to determine the level go activity in various regions of the brain.
What were the results from Raine et al classic study ?
Support was found for the hypothesis, the NGRI group has brain dysfunction in areas that had previously be implicated in violent behaviour.
1) Lower levels of brain activity in both hemispheres compared to the control group in the prefrontal cortex, the parietal cortex and the corpus callosum.
2) There were abnormal asymmetrical levels of activity in the limbic system compared to the control group:
● In the thalamus right hemisphere was higher than controls
●In the amygdala the right hemisphere was higher than the controls and the left was lower than controls.
●In the Temporal lobe the right side was higher than the controls and the left hemisphere was lower than the controls.
3) There was no overall difference in level of activity in the amygdala, thalamus and temporal lobe between the murders and the control group.
