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Biological Approaches
in Aggression
Penny Baker…read more

Slide 2

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Genetic Factors MAOA Gene
Biological Approaches in Aggression Selective
Hormonal Mechanisms Testosterone
The Limbic
Neural Mechanisms
The Frontal
Serotonin…read more

Slide 3

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Genetic factors in Aggressive Behaviour:
Chromosomal Abnormalities
A01 A02
47 XYY karyotype (male with extra Y COURT-BROWN: Sample of 314
chromosome) hospital patients. Males with XYY were
more aggressive than others. Suggests
Suggestion that men with this correlation between genetics and
karyotype were more aggressive aggression.
Prior to study, Court-Brown believed
this chromosome arrangement led to
increased aggression. Affecting
interpretation of results and validity
of conclusions.
THEILGAARD: Only characteristic
associated with XYY was increased
height. No clear link between
abnormalities in sex chromosomes and
levels of aggression.…read more

Slide 4

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Genetic factors in Aggressive Behaviour:
Evidence that mice with
A 0 2
MANUCK ET AL: Study of 110 men
abnormalities in MAOA gene more found abnormality in MAOA gene
likely to be aggressive. linked with aggression, also linked
with high levels of noradrenaline
Gene produces enzyme which
which has also been linked to
regulates metabolism of serotonin.
Low levels of serotonin are
CASPI ET AL: Studied 1037 children
associated with aggression.
(477 boys) in New Zealand, for 25
BRUNNER ET AL: Male members of years, from birth to adulthood.
extremely aggressive Dutch family Found high levels of aggression in
carried rare MAOA gene mutation. those with deficient MAOA gene,
but only if they had been abused as
children.…read more

Slide 5

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Genetic factors in Aggressive Behaviour:
Selective Breeding
A01 A02
Choosing animals with aggressive LAGERSPERTZ: Classified mice as
characteristics and mating them to aggressive/non-aggressive.
enhance this trait. Selectively interbred for 19
generations. Aggressive `biting
Indicates genetic cause to
behaviour' observed in 52% of
aggressive behaviour.
aggressive compared to 5% of non-
aggressive. Shows genes have
strong influence on aggressive
behaviour. However Lagerspertz
suggests genetic factors and
environmental factors are
important. Both strains of mice can
be conditioned to make them less
aggressive.…read more

Slide 6

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Genetic factors in Aggressive
Behaviour: IDA
Animal Studies: Many differences between animals and humans which makes
generalisation difficult. Humans have more complex brains and live in more
complex environments, both having effect on aggression. The work on MAOA
shows similar mechanisms in operation in animals and humans, suggesting it's
possible to link genetic causes of aggression in humans and animals.
Free Will and Determinism: If genetic makeup predisposes people to violent
criminal behaviour, it's not clear whether they can be held responsible for
their actions. Legal experts now question whether a violent offender can
exercise free will if they possess a genetic predisposition to violent crime.
Suggesting we might have to revise our notions of moral and legal
responsibility. However, future research may enable us to identify potential
offenders sooner and intervene at early stage.…read more

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