6.1.1 Biological explanations, including brain injury, amygdala and aggression, XYY
syndrome and personality.
Biological explanations for crime and anti-social behaviour:
Brain injury
➔ There are two types of brain injuries: acquired brain injury (ABI) which is caused by
internal force like tumour or low oxygen, and traumatic brain injury (TBI) which is
caused by external force which can be directly like car crash or indirectly through
drug/alcohol abuse (interferes with absorption of vitamin B1).
➔ Injuries to immature brains can interrupt the development of young people’s ability to
resist their impulses and poor decision making. This makes them more likely to
offend.
➔ Injuries to immature brains may also destabilise mood and concentration making the
individual more likely to offend.
➔ Williams et al. (2010) studied prisoners from a UK prison and found that 60% of them
had suffered traumatic brain injury. These prisoners were relatively young when they
went to prison. The brain injuries may have led to an inability to control impulses, as
the brain had not fully developed. Issues with impulse control and planning are more
common in individuals with brain injuries, potentially leading to their involvement in
criminal activities.
Strengths of brain injury explaining criminal behaviour:
➢ Pincus (2001) found correlation between drug abuse, brain damage, and aggression.
In particular, alcohol damages frontal lobes.
Weaknesses of brain injury explaining criminal behaviour:
➢ Many offenders may have a history of substance misuse, pre-existing personality
disorders or been exposed to violence as a child. These are known to increase
criminality. So it is difficult to know what the actual cause of crime is as there are so
many factors.
➢ Kreutzer et al. (1991) found 20% of 74 TBI patients had a criminal history before the
injury and 10% after. While they couldn't prove a cause-and-effect relationship, they
suggested that post-injury changes might lead to criminal behaviour. Further
research led them to conclude that having a substance abuse history and TBI is not a
risk factor for criminal behaviour.
Amygdala
➔ The amygdala is responsible for controlling human emotions. Damage to this area of
the brain can lead to a person becoming emotionless or reacting excessively to their
emotions.
➔ Evidence using brain-scanning techniques shows that the brain of a psychopath
works differently than the brain of a non-psychopath. People with psychopathic
personalities have a smaller amygdala. These behaviours were evident since
childhood. It was found that individuals with a smaller amygdala were three times
more likely than those with a larger amygdala to show aggression, violence, and
psychotic features. Therefore suggesting amygdala size can predict future violence.
, ➔ Raine et al. (1997) studied 41 murderers who pleaded NGRI. They all had a range of
mental illnesses. PET scans were used to show brain activity in different areas of
their brain. They found differences in the amygdala and the hippocampus. This
abnormal functioning could explain why all the participants in the experimental group
had all committed murder.
Strengths of amygdala explaining criminal behaviour:
➔ It is possible that having a smaller amygdala may not always lead to psychopathic
personalities. James Falloon looked at brains using MRI scans and showed an ability
to identify psychopathic individuals just by looking at their brains. However, he had
infamously identified one brain as being psychopathic, but was in fact incorrect. This
brain was his own.
Weaknesses of amygdala explaining criminal behaviour:
➔ Robert Hare argues that psychopaths are not just found among a criminal population.
Traits of a psychopath, like lack of empathy, arguably make individuals suitable for
high-level management positions. Also a lack of fear often encourages psychopaths
to take part in extreme sports like skydiving.
XYY syndrome
➔ XYY syndrome is a rare genetic condition where a male has an extra Y chromosome,
resulting in 47 chromosomes. Most individuals with XYY syndrome have normal
development, but some may grow faster and be taller than others. They may also
show slightly lower intelligence than their siblings, behavioural problems, and be
easily distracted. They are also believed to be more aggressive and lack empathy.
Strengths of XYY syndrome explaining criminal behaviour:
➢ There is support from twin studies suggesting that criminal behaviour is likely due to
genes rather than environment. Slutske et al. (1997) found there is a higher
incidence rate for conduct disorder in twins compared to singletons.
Weaknesses of XYY syndrome explaining criminal behaviour:
➢ Determining the rate of XXY in a criminal population requires skilled staff and is
resource intensive.It is therefore not practical to look at the genetics of all male
offenders to see if they are XYY. This also means the true extent of the prevalence of
XYY is unknown.
➢ Women also engage in criminal behaviour, including violent crimes. As women do
not have Y chromosomes, XYY fails to account for criminal behaviour among
women. It is androcentric.
Personality
➔ Hans Eysenck's personality theory reduces individual differences in personality to 5
dimensions: Extraversion (E), Introversion (I), Neuroticism (N), Stability (S), and
Psychoticism (P). He suggests that the combination of Psychoticism, Extraversion,
and Neuroticism (PEN) can influence an individual's criminal behaviour, due to its
biological link.
➔ Eysenck's arousal theory suggests that extraversion is linked to cortical arousal in
the brain. Introverts have higher levels of activity, leading to increased cortical
syndrome and personality.
Biological explanations for crime and anti-social behaviour:
Brain injury
➔ There are two types of brain injuries: acquired brain injury (ABI) which is caused by
internal force like tumour or low oxygen, and traumatic brain injury (TBI) which is
caused by external force which can be directly like car crash or indirectly through
drug/alcohol abuse (interferes with absorption of vitamin B1).
➔ Injuries to immature brains can interrupt the development of young people’s ability to
resist their impulses and poor decision making. This makes them more likely to
offend.
➔ Injuries to immature brains may also destabilise mood and concentration making the
individual more likely to offend.
➔ Williams et al. (2010) studied prisoners from a UK prison and found that 60% of them
had suffered traumatic brain injury. These prisoners were relatively young when they
went to prison. The brain injuries may have led to an inability to control impulses, as
the brain had not fully developed. Issues with impulse control and planning are more
common in individuals with brain injuries, potentially leading to their involvement in
criminal activities.
Strengths of brain injury explaining criminal behaviour:
➢ Pincus (2001) found correlation between drug abuse, brain damage, and aggression.
In particular, alcohol damages frontal lobes.
Weaknesses of brain injury explaining criminal behaviour:
➢ Many offenders may have a history of substance misuse, pre-existing personality
disorders or been exposed to violence as a child. These are known to increase
criminality. So it is difficult to know what the actual cause of crime is as there are so
many factors.
➢ Kreutzer et al. (1991) found 20% of 74 TBI patients had a criminal history before the
injury and 10% after. While they couldn't prove a cause-and-effect relationship, they
suggested that post-injury changes might lead to criminal behaviour. Further
research led them to conclude that having a substance abuse history and TBI is not a
risk factor for criminal behaviour.
Amygdala
➔ The amygdala is responsible for controlling human emotions. Damage to this area of
the brain can lead to a person becoming emotionless or reacting excessively to their
emotions.
➔ Evidence using brain-scanning techniques shows that the brain of a psychopath
works differently than the brain of a non-psychopath. People with psychopathic
personalities have a smaller amygdala. These behaviours were evident since
childhood. It was found that individuals with a smaller amygdala were three times
more likely than those with a larger amygdala to show aggression, violence, and
psychotic features. Therefore suggesting amygdala size can predict future violence.
, ➔ Raine et al. (1997) studied 41 murderers who pleaded NGRI. They all had a range of
mental illnesses. PET scans were used to show brain activity in different areas of
their brain. They found differences in the amygdala and the hippocampus. This
abnormal functioning could explain why all the participants in the experimental group
had all committed murder.
Strengths of amygdala explaining criminal behaviour:
➔ It is possible that having a smaller amygdala may not always lead to psychopathic
personalities. James Falloon looked at brains using MRI scans and showed an ability
to identify psychopathic individuals just by looking at their brains. However, he had
infamously identified one brain as being psychopathic, but was in fact incorrect. This
brain was his own.
Weaknesses of amygdala explaining criminal behaviour:
➔ Robert Hare argues that psychopaths are not just found among a criminal population.
Traits of a psychopath, like lack of empathy, arguably make individuals suitable for
high-level management positions. Also a lack of fear often encourages psychopaths
to take part in extreme sports like skydiving.
XYY syndrome
➔ XYY syndrome is a rare genetic condition where a male has an extra Y chromosome,
resulting in 47 chromosomes. Most individuals with XYY syndrome have normal
development, but some may grow faster and be taller than others. They may also
show slightly lower intelligence than their siblings, behavioural problems, and be
easily distracted. They are also believed to be more aggressive and lack empathy.
Strengths of XYY syndrome explaining criminal behaviour:
➢ There is support from twin studies suggesting that criminal behaviour is likely due to
genes rather than environment. Slutske et al. (1997) found there is a higher
incidence rate for conduct disorder in twins compared to singletons.
Weaknesses of XYY syndrome explaining criminal behaviour:
➢ Determining the rate of XXY in a criminal population requires skilled staff and is
resource intensive.It is therefore not practical to look at the genetics of all male
offenders to see if they are XYY. This also means the true extent of the prevalence of
XYY is unknown.
➢ Women also engage in criminal behaviour, including violent crimes. As women do
not have Y chromosomes, XYY fails to account for criminal behaviour among
women. It is androcentric.
Personality
➔ Hans Eysenck's personality theory reduces individual differences in personality to 5
dimensions: Extraversion (E), Introversion (I), Neuroticism (N), Stability (S), and
Psychoticism (P). He suggests that the combination of Psychoticism, Extraversion,
and Neuroticism (PEN) can influence an individual's criminal behaviour, due to its
biological link.
➔ Eysenck's arousal theory suggests that extraversion is linked to cortical arousal in
the brain. Introverts have higher levels of activity, leading to increased cortical
