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Mind Map by James Farley, updated more than 1 year ago
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Created by James Farley
over 8 years ago
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The role of
genetic factors on
aggression
- Twin Studies
- McGuffin and
Gottesman
(1985)
- Research provides support for the role of genes in aggression as they found a concordance rate of
87% for aggressive and antisocial behaviour for MZ twins, compared to 72% for DZ twins. Therefore
evidence suggests that due to fact antisocial behaviour is more prevalent in MZ twins compared to
DZ, the assumption can be made that genes do influence aggression due to MZ twins having 100% of
their genes in common compared to 50% for that of DZ twins. However the ability to give a genetic
explanation for the evidence to provided by twin studies depends on the "equal environment
assumption."
- Research provides support for the role of genes in aggression as they found a concordance rate of
87% for aggressive and antisocial behaviour for MZ twins, compared to 72% for DZ twins. Therefore
evidence suggests that due to fact antisocial behaviour is more prevalent in MZ twins compared to
DZ, the assumption can be made that genes do influence aggression due to MZ twins having 100% of
their genes in common compared to 50% for that of DZ twins. However the ability to give a genetic
explanation for the evidence to provided by twin studies depends on the "equal environment
assumption."
- Twin studies are praised for providing valuable insight into the role of genetic factors
on aggressive behaviour. If there is a genetic contribution to aggression, studies
should revel a relationship between the number of shared genes (100% MZ 50% DZ)
and the concordance rate of aggression; the closer the genetic relationship, the higher
the concordance rate. It can be assumed that if the environments are similar for both
types of twins, then a higher rate of concordance for MZ twins can be interpreted as
support for genetic factors on the likelihood of displaying aggressive behaviour.
- Rhee and Waldman (2002)
- Findings regarding the role of genes in aggression
should be used with caution due to methodological
issues. Rhee and Waldman suggest that the
variability of the finding s may be partly due to the
methods used to assess aggressive behaviour. Their
meta-analysis of 51 twin and adoption studies
indicated significant differences in the size of
genetic and environmental effects depending on
how aggression was measured.
- Findings regarding the role of genes in aggression
should be used with caution due to methodological
issues. Rhee and Waldman suggest that the
variability of the finding s may be partly due to the
methods used to assess aggressive behaviour. Their
meta-analysis of 51 twin and adoption studies
indicated significant differences in the size of
genetic and environmental effects depending on
how aggression was measured.
- Miles and
Carey (1997)
- Variability in the findings from twin studies, ranging from
0.14-0.72 for MZ twins, reduces the reliability of the findings
obtained from twin studies into the effects of genes on
aggressive behaviour.
- Variability in the findings from twin studies, ranging from
0.14-0.72 for MZ twins, reduces the reliability of the findings
obtained from twin studies into the effects of genes on
aggressive behaviour.
- McGuffin and
Gottesman
(1985)
- IDA
- Nature/Nurture
- The central debate is not about whether heredity or the environment is responsible
for aggressive behaviour. Genetic factors do not work in isolation but alongside
environmental factors, as shown by Caspi's research conducted into the MAOA gene.
Hence the debate is about the extent to which these factors influence human
development and more importantly the way that these factors interact with each
other. Genes predispose an individual to displaying aggression, however these
aggressive characteristics are only portrayed when exposed to certain environmental
factors, such as domestic violence. Therefore findings regarding the infunece of genes
on aggression should be used in conjunction with that of environmental factors to
gain a more comprehensive explanation of aggression.
- The central debate is not about whether heredity or the environment is responsible
for aggressive behaviour. Genetic factors do not work in isolation but alongside
environmental factors, as shown by Caspi's research conducted into the MAOA gene.
Hence the debate is about the extent to which these factors influence human
development and more importantly the way that these factors interact with each
other. Genes predispose an individual to displaying aggression, however these
aggressive characteristics are only portrayed when exposed to certain environmental
factors, such as domestic violence. Therefore findings regarding the infunece of genes
on aggression should be used in conjunction with that of environmental factors to
gain a more comprehensive explanation of aggression.
- Reductionism
- This Biological explanation of
aggression may be considered
reductionist as it is not possible to
identify one single gene (/hormone/
neurotransmitter) responsible for
aggressive behaviour. Genetic
deficiencies may exert some influence
on an individual's behaviour, however
they are not the sole cause of
aggressive behaviour.
- This Biological explanation of
aggression may be considered
reductionist as it is not possible to
identify one single gene (/hormone/
neurotransmitter) responsible for
aggressive behaviour. Genetic
deficiencies may exert some influence
on an individual's behaviour, however
they are not the sole cause of
aggressive behaviour.
- Determinsim
- Genes do not determine behaviour, and only poorly
predict the likelihood that an individual will display
higher levels of aggression. Although the role of genetic
influence is more straightforward in animal research,
demonstrated in studies of selective breeding; the
absolute genetic explanation ignores the role of
environmental factors and their influence upon how
genes are displayed (phenotype) Moreover the genetic
explanation ignores free will and individual choices and
suggests that we are not responsible for aggressive
acts. This is considered controversial as it opposes the
view of the judicial system in that humans have free
will and are able to show restraint and not display
anger through aggression. Therefore the absolute
genetic explanation of aggression should be used with
caution as it only partial insight into the factors
affecting aggressive behaviour.
- Genes do not determine behaviour, and only poorly
predict the likelihood that an individual will display
higher levels of aggression. Although the role of genetic
influence is more straightforward in animal research,
demonstrated in studies of selective breeding; the
absolute genetic explanation ignores the role of
environmental factors and their influence upon how
genes are displayed (phenotype) Moreover the genetic
explanation ignores free will and individual choices and
suggests that we are not responsible for aggressive
acts. This is considered controversial as it opposes the
view of the judicial system in that humans have free
will and are able to show restraint and not display
anger through aggression. Therefore the absolute
genetic explanation of aggression should be used with
caution as it only partial insight into the factors
affecting aggressive behaviour.
- Nature/Nurture
- Adoption Studies
- Hutchings and Mendnick (1973)
- Research conduced by Hutchingson
and Mednick provides support for the
effect of genes on aggressive
behaviour. They found a significant
positive correlation in over 1,300
adoptions between the number of
violent convictions for criminal violence
among the biological parents and the
incidence of criminal violence among
their adopted sons. This suggests that
despite being separated from their
biological parents, their inherited genes
predisposed their sons to displaying
aggression, depicting that genes have a
major influence in aggression.
- Research conduced by Hutchingson
and Mednick provides support for the
effect of genes on aggressive
behaviour. They found a significant
positive correlation in over 1,300
adoptions between the number of
violent convictions for criminal violence
among the biological parents and the
incidence of criminal violence among
their adopted sons. This suggests that
despite being separated from their
biological parents, their inherited genes
predisposed their sons to displaying
aggression, depicting that genes have a
major influence in aggression.
- Tremblay (2003)
- Research found that parents giving
up their children for adoption
displayed a higher level of aggression
than adoptive parents. These findings
however may be explained by
social/psychological factors, such as
anti-social behaviour and feelings of
abandonment of the child. Therefore it
is difficult to draw conclusions into
the effect of genes on aggression.
- Research found that parents giving
up their children for adoption
displayed a higher level of aggression
than adoptive parents. These findings
however may be explained by
social/psychological factors, such as
anti-social behaviour and feelings of
abandonment of the child. Therefore it
is difficult to draw conclusions into
the effect of genes on aggression.
- Hutchings and Mendnick (1973)
- MAOA Gene
- Brunner et al
(1993)
- A study of Dutch family
supported the role of
genetic factors on
aggressive behaviour as it
was found that
predominantly male
members of the family
behaved in a particularly
aggessive/violent manner
and a large proportion has
been involvee in crimes
such as rape/arson. Upon
further investigation it
was revealed that these
men had abnormally low
levels of MAOA in their
bodies and a defect in this
gene was later identified.
Their reduced ability to
breakdown dopamine and
serotonin was responsible
for their aggressive
tendencies and was due
to a genetic defect,
depicting genetic factors
do influence aggression.
- A study of Dutch family
supported the role of
genetic factors on
aggressive behaviour as it
was found that
predominantly male
members of the family
behaved in a particularly
aggessive/violent manner
and a large proportion has
been involvee in crimes
such as rape/arson. Upon
further investigation it
was revealed that these
men had abnormally low
levels of MAOA in their
bodies and a defect in this
gene was later identified.
Their reduced ability to
breakdown dopamine and
serotonin was responsible
for their aggressive
tendencies and was due
to a genetic defect,
depicting genetic factors
do influence aggression.
- Caspi et al (2002)
- Research found that
men with low levels of
MAOA were
significantly more likely
to grow up to exhibit
antisocial behaviour,
but ONLY if they had
been mistreated as
children. On it's own
the MAOA gene variant
had no effect. Men with
high levels fo
MAOA/those not
mistreated did not
display antisocial
behaviour. Therefore it
can be concluded that
inherited genes
predisposed children to
aggressive behaviour
when maltreated
themselves, highlighting
the importance of the
interaction between
genetic and
environmental factors.
- Research found that
men with low levels of
MAOA were
significantly more likely
to grow up to exhibit
antisocial behaviour,
but ONLY if they had
been mistreated as
children. On it's own
the MAOA gene variant
had no effect. Men with
high levels fo
MAOA/those not
mistreated did not
display antisocial
behaviour. Therefore it
can be concluded that
inherited genes
predisposed children to
aggressive behaviour
when maltreated
themselves, highlighting
the importance of the
interaction between
genetic and
environmental factors.
- Brunner et al
(1993)
- Animal studies
- Cairns (1983)
- Research found that through selective
breeding of mice, highly aggressive
male and female mice were created
who displayed aggression at abnormal
parts during development (e.g. during
middle age not youth.) This suggests
that genes do play a role in an
individuals likelihood to display
aggression. Animal studies are praised
for showing how aggressive behaviour
can be produced through isolation and
manipulation of aggressive genes.
- Research conducted by Cairns can be criticised for
anthropomorphism as it is considered inappropriate to
compare the genetic make up of mice to that of humans.
Humans are far more physiologically and cognitively
advanced than mice, so therefore findings obtained from
animal studies should be used with caution when
explaining the effect of genetic factors on human
aggession.
- However research by Cairns can be
praised for providing a valuable insight into
the effects of genetic factors on
aggression. Evolutionary psychologists
would argue that since the same basic
principles can be applied across species,
findings obtained from animal studies can
be used to explain the role of genes on
human aggression
- Research conducted by Cairns can be criticised for
anthropomorphism as it is considered inappropriate to
compare the genetic make up of mice to that of humans.
Humans are far more physiologically and cognitively
advanced than mice, so therefore findings obtained from
animal studies should be used with caution when
explaining the effect of genetic factors on human
aggession.
- Research found that through selective
breeding of mice, highly aggressive
male and female mice were created
who displayed aggression at abnormal
parts during development (e.g. during
middle age not youth.) This suggests
that genes do play a role in an
individuals likelihood to display
aggression. Animal studies are praised
for showing how aggressive behaviour
can be produced through isolation and
manipulation of aggressive genes.
- Cairns (1983)
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