2764112
Genetic factors in Aggressive Behaviour
- Twin + adoption studies
- A01
- Genes may not directly cause aggression but
influence elements of our bio that contribute to it
- Twin studies
- MZ twins share 100% of their
genes while DZ only share 50%
- If MZ twins are more alike in terms of their aggressive behaviour
then this should be due to genes rather than environment
- Both types of twins share same environment as each
other but MZ twins are more genetically alike
- Both types of twins share same environment as each
other but MZ twins are more genetically alike
- If MZ twins are more alike in terms of their aggressive behaviour
then this should be due to genes rather than environment
- MZ twins share 100% of their
genes while DZ only share 50%
- Adoption studies
- Help untangle relative contributions of
environment + heredity in aggression
- If +ve correlation between aggressive behaviour in adopted
children + aggression in bio parents is identified, genetic effect is
implied
- If +ve correlation between adoptee's aggressive behaviour +
rearing family is identified, then environmental effect Is implied
- If +ve correlation between adoptee's aggressive behaviour +
rearing family is identified, then environmental effect Is implied
- If +ve correlation between aggressive behaviour in adopted
children + aggression in bio parents is identified, genetic effect is
implied
- Help untangle relative contributions of
environment + heredity in aggression
- Genes may not directly cause aggression but
influence elements of our bio that contribute to it
- A02
- Research support
- Miles + Carey
- Meta-analysis of 24 twin + adoption studies
- Found significant genetic influence on aggressive behaviour
- Found strong influence from both factors BUT that environmental
influence became less + genetic influence became greater as children grew
older
- Found strong influence from both factors BUT that environmental
influence became less + genetic influence became greater as children grew
older
- Found significant genetic influence on aggressive behaviour
- Meta-analysis of 24 twin + adoption studies
- Miles + Carey
- Problems of sampling
- Convictions for violent crime are relatively few compared to vast
no of violent attacks by indivi. that never result in conviction
- Represent small minority of those
regularly involved in aggressive
behaviour
- Offenders designated as 'violent' aren't
necessarily the most serious, persistent offenders
- A convicted murderer would be designated as violent for 1 offence
despite perhaps having otherwise has a lifetime free from crime
- Might explain why so many studies have found
little or no evidence of heritability for violence
- Might explain why so many studies have found
little or no evidence of heritability for violence
- A convicted murderer would be designated as violent for 1 offence
despite perhaps having otherwise has a lifetime free from crime
- Offenders designated as 'violent' aren't
necessarily the most serious, persistent offenders
- Represent small minority of those
regularly involved in aggressive
behaviour
- Convictions for violent crime are relatively few compared to vast
no of violent attacks by indivi. that never result in conviction
- Research support
- A01
- Family history
- A01
- FH studies demonstrate how
genetics can influence aggression
- This is further supported by studies of adopted children
+ the aggression of their bio parents being identified
- This is further supported by studies of adopted children
+ the aggression of their bio parents being identified
- FH studies demonstrate how
genetics can influence aggression
- A02
- Research support
- Hutchings + Mednick
- Found significant correlation between criminal convictions of bio fathers + no.
of criminal convictions of their sons who had been adopted into other families
- Suggests genetic factor not just process of adoption as
correlation between adopted parents + children wasn't significat
- Suggests genetic factor not just process of adoption as
correlation between adopted parents + children wasn't significat
- Found significant correlation between criminal convictions of bio fathers + no.
of criminal convictions of their sons who had been adopted into other families
- Coccaro et al
- Found genes were accountable for around 40% of differences between indivi. but
environment accounted for 50% of IDs in physical + 70% of IDs in verbal aggression
- Genes account for whether or not person became aggressive,
but type of aggression = heavily influenced by environment
- Genes account for whether or not person became aggressive,
but type of aggression = heavily influenced by environment
- Found genes were accountable for around 40% of differences between indivi. but
environment accounted for 50% of IDs in physical + 70% of IDs in verbal aggression
- Hutchings + Mednick
- Research support
- A01
- Role of MAOA
- A01
- No indivi. gene for aggression
has been identified in humans
- Gene producing a protein called monoamine oxidase A
(MAOA) has been associated w/ aggression behaviour
- Regulates metabolism of serotonin in brain, + low levels of
S are associated w/ impulsive + aggressive behaviours
- Regulates metabolism of serotonin in brain, + low levels of
S are associated w/ impulsive + aggressive behaviours
- Gene producing a protein called monoamine oxidase A
(MAOA) has been associated w/ aggression behaviour
- No indivi. gene for aggression
has been identified in humans
- A02
- Research support
- Bruner et al
- Found many M members of Dutch family behaved
in a particularly violent + aggressive way
- Found to have abnormally low levels of MAOA + a defect in this gene was later identified
- Found to have abnormally low levels of MAOA + a defect in this gene was later identified
- Found many M members of Dutch family behaved
in a particularly violent + aggressive way
- Caspi et al
- Found those w/ low levels of MAOA were more
likely to grow up to exhibit antisocial behaviour
- Only if they had been maltreated as a child
- Children w/ high levels who were maltreated + those w/ low levels
who were not maltreated didn't display antisocial behaviour
- Shows it's the interaction between genes +
environments that determine behaviours
- Shows it's the interaction between genes +
environments that determine behaviours
- Children w/ high levels who were maltreated + those w/ low levels
who were not maltreated didn't display antisocial behaviour
- Only if they had been maltreated as a child
- Found those w/ low levels of MAOA were more
likely to grow up to exhibit antisocial behaviour
- Bruner et al
- Research support
- A01
- IDA's
- Value of animal research
- Young et al
- Claim to have identified a genetic mutation
that causes violent behaviour in mice
- Nicknamed 'fierce' it has a range of effects on mice
including extremely violent behaviour towards other mice
- A counterpart of this gene does exist in
humans, although precise function is not
known
- A counterpart of this gene does exist in
humans, although precise function is not
known
- Nicknamed 'fierce' it has a range of effects on mice
including extremely violent behaviour towards other mice
- Claim to have identified a genetic mutation
that causes violent behaviour in mice
- Young et al
- Real-world application
- If people are predisposed towards aggression Qs
will arise about treatment of such behaviours
- Some advocate genetic engineering + others even chemical castration
- But ethical consequences must be taken into account because labelling indivi. as a
threat to society on basis of their genetic inheritance could be more damaging
- But ethical consequences must be taken into account because labelling indivi. as a
threat to society on basis of their genetic inheritance could be more damaging
- Some advocate genetic engineering + others even chemical castration
- If people are predisposed towards aggression Qs
will arise about treatment of such behaviours
- Value of animal research
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