genetic factors Flashcards
how many genes do MZ twins share
100%
what do twin studies suggest
heritability accounts for 50% of aggressive behaviour
how many genes do DZ twins share
50%
what did researchers find in concordance rates
50% MZ twins
19% DZ twins
in adoption studies what suggests that genetic influences are operating
when there are similarities in aggr beh between adopted child and their bio parents
in adoption studies what suggests that environmental influences are operating
similarities between adopted child and their adoptive parents
what did Rhee and Waldman do
meta analysis of adoption studies of aggressive anti social behaviour
what did Rhee and Waldman find
genetic influences accounted for 41% of the variance in aggression, so in line with twin studies
what does the MAOA gene control
the production of enzyme MAO-A which regulates serotonin (serotonin thought to play important role in impulsive aggression)
what does a low activity variant MAOA gene cause
low activity of MAO-A enzyme which is linked to high levels of aggressive behaviour
MAOA gene, when is it triggered
gene is inherited, but activated by an environmental experience
nature v nurture
both
nature- evidence shows genes act as a direct cause of aggression
nurture- environmental factors also play a role eg childhood trauma
Caspi et al (nature v nurture)
MAOA gene had not effect on its own, only in circumstances of abuse
strength of genetic factors
research support shows that the low activity variant of the MAOA-L gene is associated w greater aggression
research support study
Martins et al
Martins et al findings
men w high activity variant of MAOA gene were more cooperative and made fewer aggressive moves than the low activity ppt.
this supports relationship between MAOA gene activity and aggression
limitation of Martins study
showed non-genetic factors were also crucial, knowledge of social norm partly determined their aggression
= genes influenced by environmental factors
limitation of genetic factors
problems w twin studies
problems with twin studies
they may lack validity
DZ twins may not share their environment to the same extent MZ twins share theirs, MZ twins are treated more similarly
suggests concordance rates are inflated, perhaps genetic influences may not be as great as twin studies suggest
