Brain dysfuntion (e.g. Raine's work on the cortex and other work)

Genes and serotonin (e.g Brunner 1991)

Gender (e.g. Daly & wilson 1988)

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  • Created on: 05-04-10 13:02

Brain Dysfunction (e.g. Raine's work on the cortex

Adrian Raine of the university of southern California has conducted reasearch using PET scanning and found abnormalities in some parts of the brain in violent criminals. He found that low physiological arousal, birth conplications, fearless and increased size are early markers for later aggressive behaviour.

Aim: To see if murders who have pleaded not guilty by reason of insanity(NGRI) show evidence of brain abnormalities using PET scans.

Sample: Total of 82 people were used for this study. This consisted of 2 groups: Experimental Group: 41 'normal' people as matched comparisons
Control Group: 41 'normal' people as matched comparisons.

Experimental Group: 'The Murders'
There were 39 men, 2 woman, 14 were black, 27 were white. Mean age:34.3 years.
These people had all been referred to the university of california Brain Imaging Centre to obtain eveidence relating to an NGRI defence. (Not guilty by reason of insanity) or to show that they were not fit to stand trial.

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Brain Dysfunction (e.g. Raine's work on the cortex

Control Group:
These people were matched to the experimental group on age, gender and schizophenia. They were not talking any medication and had no history of psychiatric or significant physical ilness. None had any history of seizure disorder, head trauma or substance abuse. Obviously, none of these people had any history of, or convictions for violent behaviour.

-Unrine tests done on all murders to ensure free of medication
-All of the participants were injected with a gluecose tracer, required to work at a continuous performance task that was based around target recognition for 32 minutes, and then given a PET scan. This has shown to increase glucose metabolic rates in frontal lobes, parietal & temporal lobes.
-The NGRI'S were compared with the controls on the level of activity (glucose metabolism) in the right and left hemispheres of the brain in 14 selected areas.
-Data is analysed using a statistical test called a MANOVA test. (Multivariate analysis of variance)

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Brain Dysfunction (e.g. Raine's work on the cortex

- In this study, compared to the controls, the NGRI'S were found to have less activity in their frontal lobes & parietal areas, more activity in their occipital areas, and no difference in their temporal areas.

Raine's Conclusion:
-There were some diffrences in the brain functioning of the murderers and the control group, and that this study provides preliminary evidence that murders have diffrent brain functioning.
-It gives initial suggestions for which specific neural processes may predisposes NGRIs to violent behaviour.
-However, Raine states that the study does not provide a complete account of the neurophysiology of violence. Also, the brain is very complex and structures network togther to produce effects.
-Raine says that future replications, refinements and extensions are needed to help understand the realationship between the brain and murder.

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Genes and serotonin (e.g. Brunner 1991)

Inside every living thing are sets of instructions called GENES. Genes are the building blocks of DNA andthey tell bodies how to grow and develop.

Male Chromosome=
Female Chromosome=
Males with a extra y chromosome were predisposed to be violent criminals. This genetic abnormality became known as the supermale chromosome individuals who had it, were above average height and below average intelligence. The XYY theory offerd the prospect of genetic explanatiom "XXY syndrome" is an abnormal number of the sex chromosome, It might be the latter characteristic (Low intelligence) that accounts for their over representation in prison populations.

This theory suggest that certain genetic combinations predispose people to criminality.
(Predisposition IS natural built-in tendency creatures have to behave or develop a certain way.)

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Genetic Theory

This suggestions is that criminality runs in families and the the reason for this is that a sequnce of 'criminal' genes from one or both of the parents is passed onto the child. the child is then more likley to display criminal behaviour. Therefore we would expect children of criminal parents to be more likley to display criminality than children from parents who do have history of criminality. The predition of the genetic theory is the more genes you share with someone who has been convicted of crime the more likley you are to become a criminal. A good way of testing the genetic theory is to look at identical and non-identical twins. Identical twins share 100% of their genes whereas non-identical twins.share 50% of their genes. if criminal behaviour is gentic then we would expect identical twins to be more likley to both be criminals that non-identical twins.

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Chrisianses looked at 3586 twin pairs in Denmark a 52% concordance rate for criminality was found for monozygotic (identical) twins, compared to just 22% for dizygotic (non-identical) twins.

Evaluation of twin studies One problem with twin studies is that the sample size in these studies is usually quite small due to the relatively few cases of identical twins who both are criminals. Therefore we cannot genralise the findings to the general population because these cases of identical twins may be expectional in other ways e.g. having unusual upbringings. Another problem is that there may be an enviromental explanation for the findings. Identical twins look the same and are therefore likley to be treated the same by teachers etc. Therefore if one twin is a criminal the teachers may also treat the other twin as though they are criminals leading to a self fuffiling prophecy. A further problem is that the concordance rate for identical twins is not high which we would expect if criminality were sole due to genes. Therefore, there must be an enviromental element to criminality.

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Brunner et al: A study of violence in a family wit

Aim: They wanted to explain the behaviour of a large family in the netherlands where the males are affected by a syndrome of borderline mental retardation and abnormal violent behaviour. The violent behaviours were: Impulsive agression, arrson, attempted **** and exhibitionism. Participants 5 affected males from the family Methodology Data collected from analysis of urine samples over a 24- hour period. Results: -Tests showed: Disturbed monoamine metabolism associated with a deficit of the enzyme monoamine oxidase a (MAOA) -In each of the 5 males a point mutation was identified in the x chromosome of the gene responsible for production of MAOA. Conclusion: MAOA is involved in serotonin metabolism. Serotonin is a neurotransmitter which is chemical used in the communication of brain cells. Serotonin has been linked to a variety of behaviours including emotion. it plays an important role in the regulation of anger and aggression; lower levels than normal levels role in regulation of anger and agression; lower levels that normal levels can lead to . Impaired metabolism of serotonin could also be linked to behaviour.

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Daly & Wilson 2001- Investigation of gender- relat

Daly & Wilson noticed that young male offenders had a 'short term horizon' this means that these individuals want instant gratification. They have a short lifespan expectation due to the risky behaviour that they engage in. Evolutionary theories suggest that the male role of hunter and protector predisposes them to more risky behaviour than females. Aim: -To find out if homoicide rates would vary as a function of local life expectancy in Chicago. Procedure:

Procedure: - This was a correlation study using survey data from police records, school records and local demographic records. - Local area average life expectancies, ranging from 54.3-77.4 were compared to homocide rates in those areas. Findings: -The homicide rates varied from 1.3 to 156 homicides per 100,000 persons per annum in the local area. -The correlation between life expectancy and homicide rate were strong (-0.88), This means that lower life expectancy were correlated with higher homicide rates. -School absenteeism was also negatively correlated with life expectancy.

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Daly & Wilson 2001- Investigation of gender- relat

Conclusion: - Daily & Wilson concluded that young men from disadvantaged neighbourhoods expected to live shorter lives and were therefore more likely to engage in risky behaviour. -However, these findings could be explained by social factors such as poverty and inequality rather than life expectancy. Biological theories of crime: Conclusions Biological theories of crimes are reductionist and determinist. These theories can only really explain certain types of crime, mainly violent ones. There is a danger of labelling individuals before a crime has actually been commited. However, they are attractive, abd persuasive because they offer the possibilites of screening for criminality, intervention programmes and treatment. In reality, It is the interction between upbringing, enviroment, cognitive provesses, biology and individual diffrences between people that influence whether or not they turn to crime. It must be remembered that everyone has free will; we choose whether or not to break the law.

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