Aggression: Bio 3 Flashcards
Where are the Hypothalamus and Amygdala found in the brain?
The limbic system
Describe the role of the hypothalamus in aggression
The Hypothalamus regulates our behavioral responses to things like pain, threats and sexual satisfaction by controlling hormone levels in the body.
This includes testosterone, which has been linked to aggressive behaviour.
Define the term homeostasis
The process that maintains the stability of the human body in response to changes in external conditions eg. Temperature
Describe the role of the amygdala in aggression
- *When we are exposed to threatening stimuli,** our amygdala is activated and results in increased emotional arousal. As a result we either take flight or fight and become aggressive.
- *The amygdala itself doesn’t actually produce aggression**; it is connected to other parts of the brain that produce aggression. BUT, it is necessary to initiate the aggression. Without it, we wouldn’t experience the immediate emotional reaction associated with aggression.
What is meant by the term ‘reactive aggression’
- *Aggression in direct response to a**
- *provocative stimulus with little planning** is referred to as impulsive or reactive aggression.
What evidence is the to show the role of the limbic system in aggression?
- Case Studies of Brain Damaged Patients
- fMRI scanning
Provide evidence of a case study that shows evidence for the role of the Limbic System in aggression
Charles Whilman was a student at the University of Texas and an ex-Marine. He first killed his wife and mother and then went on a shooting rampage on and around the university’s campus in 1966. After his death he was found to have a cancerous tumour in the hypothalamus & near the amygdala.
Provide evidence of brain scanning using fMRI that shows evidence for the role of the Limbic System in aggression
Coccaro et al. (2006) showed patients with Intermittent Explosive Disorder (IED) a threatening stimuli (e.g. an angry face) and measured brain activity using fMRI scans.
Compared to a control group the patients with IED had a greater amount of activity in their amygdala and less activity in a region in their prefrontal cortex - which may have meant it was less able to inhibit the amygdala.
It is not clear from this research why the lED patients had increased activity in the amygdala and decreased activity in the prefrontal cortex as fMRI scanners do not tell us this.
How does the fMRI detect BOLD contrast?
A magnetic field causes molecules within the body to move in a slightly different way and release radio waves which the scanner can then detect.
The fMRI scanner can detect the difference between radio waves
emitted from oxyhemoglobin and from deoxyhaemoglobin, thus enabling the BOLD contrast to be detected.
Give two advantages of fMRI scans
•Provides exact locations of increased
neural activity during tasks as sensitivity to blood flow changes is very precise, therefore increasing validity and reliability.
•Non-invasive as it does not involve
exposure to radiation like PET and CAT scans, so therefore more ethical
Give two disadvantages of fMRI scans
•Unable to detect activity of individual
neurones so gives limited information on functioning.
•Scanning participants that have metal implants can be troublesome due to the strong magnetic fields. And participants need to remain extremely still during the scan.
Describe the role of the prefrontal
cortex in aggressive behaviour
The prefrontal cortex regulates aggressive behaviour. It allows us to control reactive aggressive impulses that stem from the amygdala.
This mechanism inhibits us from automatically reacting to threats and allows us to think about an appropriate course of action.
What is pro-active aggression?
Aggression that has a great amount of control
Explain how the case of Phineas Gage supports the role of the pre-frontal cortex in aggressive behaviour.
Phineas Gage suffered accidental damage to his pre-frontal lobe and
following this injury, he went from being a sober, quiet person to an aggressive, irritable drunk.
This suggests that the pre-frontal cortex is involved in the moderation of our aggressive behaviour.
Describe one piece of evidence
that supports the role of the pre-frontal cortex in aggression using brain scanning
Grafman et al. (1996) showed using CAT scans that veterans from the Vietnam War with structural damage to their Prefrontal Cortex were more aggressive than veterans with structural damage to other areas of their brain.
Give two advantages of CAT scans
•Provides detailed structural images of the brain which is useful for detecting structural abnormalities.
•Less sensitive to movement of the
participant compared to fMRI.
Give two disadvantages of CAT scans
•Not sensitive enough to detect precise details of soft tissue in the brain.
•Participants are exposed to radiation
(although only a small amount)
Give three disadvantages of PET scans
•The resolution of the image is lower
compared to fMRI, therefore it is less
precise and valid
•Interpretations of the images could be
biased.
•Participants are exposed to radiation
Give one advantage of PET Scans
Shown to be a reliable and valid technique for measuring the activity of the brain as it detects blood flow, oxygen use and metabolism in the brain.
Describe the link between serotonin and aggression.
Low levels of the neurotransmitter
serotonin are associated with an
increased tendency towards impulsive and reactive aggressive behaviour.
Low levels of serotonin in the prefrontal cortex means it no longer inhibits the fight/flight response of the amygdala increasing the likelihood of
reactive, impulsive aggression.
Describe evidence from clinics drug studies that support the role of serotonin in aggression
In clinical studies, antidepressant drugs which increase serotonin levels also tend to reduce irritability and impulsive aggression.
This suggests that increased serotonin levels do lead to reduced aggression.
Describe evidence from lab experiments with animals that support the role of serotonin in aggression
Ferrari et al. (2003) studied the link between neurotransmitters and aggression in rats.
By introduced an “intruder rat” allowing the rats to fight every day for 10 days at the same time, on the 11th day, no intruder rat was introduced.
The conclusion was that serotonin levels in the rats decreased, because they were anticipating a fight.
This study also illustrates brain plasticity, since the rats brain chemistry appeared to change to adapt to what it experienced.
What is your Classic study for biological psychology?
Raine et al. (1997)
Brain abnormalities in murderers indicated by positron emission tomography.
Give a brief background to the classic study
At the time of Raine et al’s study it was thought that such individuals had brain impairments, but there had been little brain imaging research on this important population to support or refute this notion.
What was the aim of Raine et al study?
To discover using PET scans whether there are brain abnormalities in murders who pleaded not guilt by reason of insanity.
Describe the sample and participants in Raine’s study
- Two groups each with 41 people (39 Ms and 2 Fs)
- The experimental group were 41 criminal with convictions for murder, being tested to support a claim of NGRI
- The control group was matched to the experimental group on variables such as: age, gender and psychiatric illnesses. (Matched pairs)
The main purpose of using a matched pairs design in psychology experiments is to control for participant variables.
Explain how this is a benefit of the matched pairs design used in Raine’s study
P: A benefit of controlling for participant variables in Raine’s study is that this allows for any confounding variables which may have influenced
violent behaviour to be eliminated.
E: For example, those murderers who had a psychiatric illness such as
schizophrenia were matched with a person who also had a psychiatric
disorder.
What was the research method in Raine’s study? Are there any reasons against it being this research method?
The method is a laboratory experiment using matched pairs design.
The main IV is whether the participant had committed murder/ manslaughter or not. The DVs were the results of the PET scans.
This design is sometimes referred to as a quasi or natural experiment because the researchers do not have total control over the IV.
Describe the procedure of Raine’s study
Participants performed a Continuous Performance Task (CPT) involving the participant staring at a screen while various blurred symbols appear. The participant had to press a button when a particular symbol appeared, thus requiring constant attention to the screen.
They did this task for 10 minutes as a practice trial.
A radioactive glucose tracer was then injected into the participant.
After a further 32 minutes of the task, the subject’s brains were PET scanned in order to determine the glucose metabolic rate throughout the brain to determine the level of activity in various regions of the brain.
What were the Results from Raine’s study?
Cortical areas of the brain
•The NGRIs had Lower levels of brain activity in both hemispheres compared to the control group in the prefrontal cortex
Subcortical areas of the brain
•The NGRI group also showed there were abnormal asymmetrical levels of limbic system activity in the amygdala compared to the controls (right hem higher left hem lower)
What are the conclusions from Raine et al’s classic study?
Reduced activity in certain areas of the brain such as the prefrontal cortex, together with abnormal asymmetries of activity in structures of the limbic system such as the amygdala and hippocampus could predispose a person towards violent behaviour.
Raine et al. suggest that:
1. The lack of functioning in the prefrontal cortex results in the reduced ability to regulate the activity of the limbic system and thus it is less able to control impulsiveness and aggressive
responses to threatening stimuli.
2. The abnormal functioning of the amygdala, which is responsible for emotional processing, results in the murderers being fearless. This fearlessness could result in the increase chance of acting violently.
What does Raine warn about the conclusion for his study?
Raine says that these conclusions cannot be used in isolation and is cautious of the implications of his findings. The findings cannot be taken as evidence that violence is determined by biology alone. Or that PET scans can be used to identify potential murderers.
Give one strength of reliability when evaluating Raine et al’s study (PEEC)
- P= Reliability of the study is high on the whole
- E= This is because standardised procedures and equipment were used on every participant therefore increasing replicability.
- E= For example, All participants were given the same continuous performance task to complete for 32 minutes and were then PET scanned with the same scanner to measure their brain activity.
- C= Furthermore, PET scans produce quantitative data which increases replicability
Give one strength of validity when evaluating Raine et al’s study (PEEC)
•P= Some variables in this study were well controlled.
•E= This is a strength because it increases the validity (accuracy) by reducing the confounding variables that could effect the outcome i.e. differences in brain activity
•E= For example: Participants did not take any medication for two weeks leading up to the scan. This was done to be sure that medication had not influenced brain activity.
AND/OR
The control group was matched to the experimental group on several factors such as age, gender and psychiatric illnesses.
This was needed to control the effect of participant variables. It increases validity because we can be fairly sure that any differences in brain activity between the 41 murderers and the control group was probably not due to individual differences
C= However, Raine et al did not have control of all the confounding variables as he had no control over the upbringing of his sample or the situation in which the murder occurred. Therefore, any finding that shows differences in brain activity between the two groups does not mean that brain dysfunction caused the murders.
Give one weakness of ethics in Raine et al’s study (PEEC)
- P= The participants were not always protected fully from harm
- E= this means that although ethical guidelines were followed there were still costs for the participants
- E= For example All participants were taken off their medication for 2 weeks. And they were all subject to the invasive procedure of the injection of a radioactive tracer.
- However, these problems might be outweighed for the participants because of their hope to have a plea of NGRI accepted (meaning, for some of them, escaping the death penalty!)
Give one weakness of generalisability in Raine et al’s study
- P=One weakness of this study is the sample consisted of mainly men
- E= therefore it is less likely to be representative of female violent offenders
- E= For example, this can be seen in the sample of the study which consisted of 41 violent murders only two of whom were women
- C= However, most extremely violent offender are male so the results may give us some valid information on brain dysfunction in this relatively small group of people.
Give one weakness of validity in Raine et al’s study
P= The study is reductionist and this means that its validity is reduced.
E= This is because it is limited in its explanation of the causes of violent aggression.
E= For example Reductionism can be seen in this research because it focused on dysfunction in brain
activity in certain structures of the brain like the PFC and the amygdala to explain the violent behaviour of the sample. This does not take into account the factors such as the upbringing of the participants or the situation at the time of the murder so does not give a completely accurate account of their behaviour.
C= However, reductionism is a valuable characteristic in science and in this research it allows Raine
et al to focus on the biological variable of greatest importance in these 41 murderers.
What are the applications for Raine et al’s study?
• P= The study is useful for society as it suggests that pre-dispositions for
committing violent criminal acts could be identified using PET scans.
• E= This would be useful as violent offending could be predicted and early
interventions could be used to prevent violent criminal offences
• E= For example, . E.G. The PET scans showed that the murderers had abnormal brain activity in structures like the PFC and the amygdala compared to the controls. This could show who may become violent offenders.
• C= However, Raine himself suggests that caution is needed. He emphasises that having certain kinds of brain activity does not mean that somebodv will be a violent offender. i.e. PET scans cannot and should not be used as a diagnostic tool to predict violent offending
Give 2 strengths for using brain structure and function as an explanation for aggression
•Scientific credibility is high:
Theories on the link between brain structure and dysfunction are falsifiable (testable): Brian scanning techniques such as PET scans, fMRIs and CAT scans now allow researchers to directly observe the structure and functioning of the brain allowing anomalies to be detected and
measured in an objective manner.
For example: Grafman et al. (1996) studied veterans of the Vietnam war. Using CAT scans, the researchers showed that veterans with structural damage to their PFC were more aggressive than veterans with structural damage to other areas of their brain.
•Supporting evidence is extensive and wide-ranging: Many different research methods have been used including very well controlled lab based experiments with animals. Furthermore, research tends to be easily replicable and similar results have been recorded repeatedly. This gives high reliability to the findings of these studies.
For example; the use of animals in lab based experiments on aggression allows both individual differences and situational variables to be under the strict control of the researchers to a level that would not be possible with humans due to ethical constrains
Furthermore, animals make excellent participants as demand characteristics are not an issue!
Explain the weakness of determinism when using brain structure and function as an explanation for aggression
•Determinism: Could suggest those with smaller amygdala and lower activity in the PFC are destined to be aggressive and they have not free will as to how they behave. This could provide excuses for some people to engage in violence and limit their willingness to engage in treatments such as anger management programs as they might believe them to be futile in the face of biological factors.
Describe the link between testosterone and aggression
High levels of testosterone are linked to high levels of aggressive behaviour. Testosterone may influence serotonin levels in areas of the brain that are involved in aggressive reactions, such as the amygdala and the pre-frontal cortex.
Describe the research evidence showing gender difference in aggression
Maccoby and Jacklin (1974) after undertaking dozens of laboratory experiments and field studies amongst different social classes in various cultures, concluded that boys are consistently more aggressive than girs. It is also the case that men are far more frequently charged with violent
offences than women, whereas women are usually charged with offences against property.
How does testosterone explain findings that males are more aggressive than females on average.
Males produce more testosterone than females (although female ovaries do produce testosterone) and boys have more exposure to testosterone both in the womb and post-natally.
The male sex hormone testosterone is thought to increase levels of aggression from young
adulthood onwards - there is a great deal of inter-male fighting in the teenage years - but testosterone levels drop off in older men.
What are the key issues of gender when using testosterone to explain gender differences in aggression.
Males do have more testosterone than females and do commit more violent
crimes but three things must be taken into consideration.
1.Aggression is a complex behaviour and is not just seen in violence - social aggression such as spiteful comments and ignoring people to cause psychological pain can also be seen as aggression
2. All males are not violent and women are capable of violence
3. Reductionism is a problem here as testosterone is not the only biological variable at play in aggressive behaviour
Describe a piece of correlational research that shows a link between testosterone and aggression
Dabbs et al (1987) measured testosterone levels in the saliva of 89 male prisoners.
They found that the more Violent prisoners tended to have higher levels of testosterone whereas the non- violent prisoners tended to have lower levels of testosterone.
In addition, those with high levels of testosterone were rated by their peers as ‘tough’