jUnit 7 - Applications of psychology
Biological Approaches to explain criminal behaviour:
XYY chromosome hypothesis - on powerpoint & in green book
Case study on Theilgaard
A psychological study of the personalities of XYY and XXY men (1984), the validity of the
extra Y chromosome explanation, aims and findings.
1) Describe the above study and explain the result from the study
2) What does the above study reveal, with regard to XYY syndrome
Alice Theilgaard carried out this study to see if criminals had a particular gene that could be
responsible for their criminal behaviours.
To carry out the study, blood samples of over 30,000 men born in the 1940’s had their blood
samples taken. From this, two chromosome abnormalities were found, the XXY and the
XYY.
From the results, 16 of the people had XXY and 12 had XYY.
These men were then interviewed by a social worker, to provide insight on their
background/criminal history and to complete an intelligence test.
To further this, they carried out personality tests, to see if they displayed higher levels of
aggression than the XY males.
The study reveals that people with XYY had slightly lower intelligence and tended to be more
aggressive. This could explain the sign of criminality from the presence of an extra
chromosome.
There were far more similarities than differences between the XXY and XYY chromosomes.
However, no solid evidence of a criminal gene was found.
Warrior Gene:
1) Warrior gene - MAOA breaks down serotonin, possibly making someone more
impulsive without this neurotransmitter.
2) Monoamine oxidase A (MAOA)
3) The warrior gene completely knocks out the functioning of MAOA, so it doesn’t work
properly, to inform us on how to behave. When it's deficient, we can struggle to
control urges and become more impulsive.
4) It is a molecule in the brain which breaks down serotonin. Neurotransmitters send the
signal between cells in the brain
, 5) A Woman in the Netherlands enters a hospital, reporting her male family members
committing violent crimes. Testing was made showing genetic change.
6) Dutch Study was carried out
7) New Zealand study
8) Finland study - 2 ⁄ 3 of prisoners in one institution, had committed 1 violent crime.
10-15% had committed 10+ violent crimes.
9) 6 in 10 people have low activity MAOA
10) It cannot be proven that genetics causes this, but i had been used as defence in
court from convictions
11) 2 cases in Italian court, and many in American court, lawyers use low existing MAOA
to argue against death penalty or life sentences for their client
12) Different versions of MAOA
The Warrior Gene is commonly recognised by impulsive or violent behaviours. The warrior
gene completely knocks out the functioning of MAOA, so it doesn’t work properly, to inform
us on how to behave. When it's deficient, we can struggle to control urges and become more
impulsive. It is a molecule in the brain which breaks down serotonin. Neurotransmitters send
the signal between cells in the brain. The warrior gene completely knocks out the functioning
of MAOA, so it doesn’t work properly, to inform us on how to behave. When it's deficient, we
can struggle to control urges and become more impulsive.
It is a molecule in the brain which breaks down serotonin. Neurotransmitters send the signal
between cells in the brain As a result, it causes someone to act more impulsively, due to the
deficiency of this neurotransmitter. Each person has two copies of this gene, and there are
many versions of it. The Warrior gene was first noticed in the Netherlands, when a woman
entered a hospital. She reported that all the males in her family, going back generations, had
committed violent crimes and was there any cause of this. When this was brought to their
attention, the men were tested on. Results showed that all of these men had a genetic
change.
Studies in New Zealand were carried out, this study was aimed around the Māori people of
New Zealand, to better understand if they carry the warrior gene, hence their strong willed
nature.
Furthermore, studies were carried out in Finland within a prison. Eight hundred of the
inmates were genetically tested to identify possible MAOA gene presence. Two of the three
inmates had committed at least one violent crime and 10 - 15 % had committed at least ten
or more.
Following these studies, on average 6 in 10 people have low activity MAOA. Whilst it can’t
be proven that genetics causes an influx in criminal behaviour, it can suggest a lack of
control or thrill seeking behaviour. The presence of the MAOA gene has been used in court
by lawyers to argue against the death penalty or life sentences for their clients.
, Twin studies:
What is the difference between identical and non identical twins?
Monozygotic twins (Identical twins)
These twins are a result from the fertilisation of one egg and one sperm. The
fertilised egg then splits into. They will share the same placenta and develop
together.
Monozygotic twins share the same chromosomes and are genetically near identical.
They are always the same sex, providing they haven't experienced a mutation during
their development
Dizygotic twins (non identical)
These twins are a result from the fertilisation of two separate eggs and two separate
sperms. The two embryos grow on their own, and have individual placentas.
On average 1 in 250 pregnancies result in identical twins.
Twin studies compare the rate of criminal behaviour of identical twins to the rate of
criminal behaviour of non identical twins.
This assesses the role of genetics and environmental influence.
It has been identified that the similarity between monozygotic twins is greater than
dizygotic twins, and so genetics may influence this.
To date, 10 Twin studies have been carried out across the world. They have been
tested for a genetic effect in crime.
The studies on twins can help support the theory that genetics may have an impact
on someone's criminal behaviour.
