Forensic Psychology - 4. Biological Explanations: 2. Genetic Explanations Flashcards
What do genetic explanations propose?
Propose that one or more genes predispose individuals to criminal behaviour
What is the main gene involved in the genetic explanation for crime?
The MAOA gene
What do some people have which means that less MAOA is produced?
Some people have a low level variant of the MAOA gene called MAOA-(L)
What does the MAOA gene produce?
Produces enzymes which breakdown neurotransmitters in the synapse (E.g. serotonin and dopamine)
What can less MAOA production affect?
It can affect neurotransmitter levels (increases neurotransmitter levels as breakdown is reduced) which affects brain activity in important parts of the brain
What parts of the brain can lowered MAOA production (MAOA-(L)) impact?
The amygdala
The prefrontal cortex
What is the amygdala involved in?
Emotions and the fight or flight response
What is the prefrontal cortex involved in?
Decision making
What will happen if the amygdala is affected by differing neurotransmitter levels?
The individual may lack:
-sympathy
-remorse
-empathy
-guilt
-have no conscience
What does a negatively impacted prefrontal cortex do to the person?
Causes them to act differently and maybe carry out crimes for a boost
Result of increased serotonin
Lowered mood
Impulsive decisions
Who did Brunner at al study?
28 males from a large Dutch family who were repeatedly involved in impulsively aggressive violent/sexual behaviour
What did Brunner et al find about the impulsively aggressive men in his study?
Had abnormally low levels of MAOA in their brains
What does Brunner et al’s study support?
Supports the role of MAOA in explaining crime
Who carried out research on genetically engineered mice with low MAOA levels?
Cases et al
What did Cases et al find about the mice with low MAOA levels?
As the mice got older, they demonstrated increased levels of aggression and were aggressive during mating
Negative evaluation of Cases et al’s mice study
Mice and humans are physiologically different and so, although there seems to be a genetic basis for aggression in mice, it doesn’t mean that such findings can be generalised to humans
Animals don’t have a consciousness so therefore can’t exert free will
What did Christiansen study?
A large sample size of over 3500 twin pairs in Denmark
Results of Christiansen’s study
Concordance rate of criminal behaviour for MZ (identical) twins was more than double that of DZ (non-identical) twins amongst males and females in his study
Positive evaluation of Christiansen’s study into twins in Denmark
Results suggest that there is an element of heritability to criminal behaviour
Negative evaluation of Christiansen’s study into twins in Denmark
We would expect the concordance rates to be higher if offending behaviour was purely down to genetics
Who conducted a study into separated identical twins?
Grove
What did Grove study?
The genetic contribution to offending behaviour, using twins who had been separated shortly after birth and grew up in different environments
How many MZ twin pairs did Grove study?
32
What did Grove assess the twins on his his study of separated MZ twins?
Alcohol problems
Drug problems
Symptoms related to antisocial behaviour in childhood and adulthood
Results of Grove’s study of MZ twins
Significant positive correlation between genetic influences and symptoms of childhood antisocial behaviour and adult antisocial behaviour
What do Grove’s results indicate?
Indicate similarity in terms of antisocial behaviour among twins
Positive evaluation of Grove’s study of MZ twins
Highlights that genetic factors have a contribution
Diathesis-stress model
Someone may have biological tendencies towards criminality, but they will need some sort of environment trigger to actually become a criminal
