3.3.1 classic study Flashcards
What was the classic study
Raine et al 1997 brain abnormalities in murderers
What was the aim
To find out if there is a difference in the structure of brain activity between people who are committed murder and non-murderers. In particular rain wanted to see if the findings of studies linking brain structure to aggression in animals could be generalised to humans
What was the procedure
independent variable: where are the participant is an offender pleading not guilty by reason of insanity to murder or a non-murderer in the control group.
dependent variable: the relative glucose levels in a different parts of the brain e.g. prefrontal cortex, amygdala as revealed by a pet scan
type of experiment: natural experiment and independent groups design
sample: 41 offenders pleading not guilty for reasons of insanity to the crime of murder and 41 controls
The not guilty for reason of insanity opportunity samples with 39 men and two women. 23 had a history of brain damage, three with a history of drug abuse, six with schizophrenia, two with epilepsy and seven with other emotional learning disorders. The controls were people of the same age and gender with no history of crime or mental illnesses except six controls who had schizophrenia
The participants were tested at the University of California, each was injected with the glucose tracer and then performed the continuous performance task for 32 minutes. Then the pet scan was carried out. He also used are the experimental controls e.g. the participants were allowed to practice the CPT 10 minutes before the glucose trace it was injected to make sure they were all equally familiar with it and he made sure none of the participants will medication for two weeks prior to the pet scan
What were the results
The pet scan was broken down into digital slices in boxes, enabling raine To measure the relative amount of trace a present in the brains for cortical and sub cortical regions and as expected the murderers showed less activity in the frontal lobe, especially the prefrontal cortex which is associated with rational thinking, self restraint and memory
there was also less activity in the parietal lobe which is associated with abstract thinking like morality and justice
in the sub cortical region the murderers had less activity in the corpus callosum associated with long-term planning
There was also an imbalance of activity between the left and right hemispheres in limbic system and there was less activity on the left I’m on the right and amygdala and hippocampus and these are areas of the brain associated with aggression in animals
What was the conclusion
raine suggested how the brain abnormalities in the murderers might translate into violence or antisocial behaviour
prefrontal deficits might make someone more impulsive and emotional, deficits in the limbic system might make someone aggressive and deficits in the corpus callosum make it harder for the brain to hemispheres to communicate, making it difficult to think through long-term consequences and make decisions. Also areas like the amygdala and hippocampus have a part to play in recognition. deficits here might make it harder for someone to judge social situations, leading them to overreact
He concluded that findings from animal studies into aggression can be generalised to humans and that there is a link between brain structure and aggression and he believed that these brain deficits can be prevented if they are identified early enough
Evaluate the study
Generalisability: use the largest sample at the time for the source study which included a control group of good matching pairs design however the fact there was 39 men and two women therefore lacks generalisability. Also the murderer is unusual offenders, there are people who have killed someone but I don’t remember doing it or to confuse to stand trial and therefore these people are not representative of typical murderers and or not guilty for reasons of insanity killed the victims violently or aggressively
reliability: pet scans are a reliable brain imaging technique that has been used since the 1970s it produces objective and replicable results also the CPT insured that all participants were concentrating on the same thing and was a standardised procedure. However he admitted that there was still problems with the reliability of pet scanning in the 90s and sometimes the results were unclear and had to be interpreted and is therefore would introduce subjectivity and low reliability
Application: he suggested that if the damage that causes the bees brain deficits can be prevented, people might be prevented from becoming murderers. This involves early intervention with at risk children, programs to stay young people away from drugs and monitoring people have received brain injury.
Validity: low ecological validity the CPT use by rain could be criticised for being artificial and unconnected to violence and the participants or doing an unusual task and in an unusual state of mind when the pet scan was carried out. As a natural experiment, this study cannot short show cause and effect e.g. the murderer is might have developed their brain deficit after the kitchen because of the stress of the event etc. Also is a very reductions view of human behaviour as it only looks at brain activity from one hour perspective
Ethics: each participant did give prior consent and did agree to have the pet test because it would help their court case. Pet imaging is an invasive procedure because the participants have to be injected with a radioactive tracer although is not serious or a danger procedure it is an unnecessary medical procedure.
