aggression😡 (genetic factors) Flashcards
what did coccaro find in twin studies of aggression?
concordance rates for physical aggression-
MZ (identical)- 50%
DZ (non identical)- 19%
verbal aggression
MZ- 28%
DZ- 7%
What did Rhee and Waldman carry out?
what did they find?
meta-analysis of adoption studies of direct aggression and antisocial behaviour.
found that genetic influences accounted for 41% of variance in aggression, more or less in line w findings of twin studies
what is the MAOA gene?
an enzyme, which acts to mop up neurotransmitters in the brain after a nerve impulse has been transmitted from one neutron to another
how does the MAOA gene mop up neurotransmitters?
what is the production of this enzyme determined by?
breaks down neurotransmitter- esp serotonin- into constituent chemicals to be recycled or excreted.
MAOA gene
what may happen if there’s a dysfunction in operation of MAOA gene?
may lead to abnormal activity of MAOA enzyme, which then affects serotonin lvls in brain
what does the variant ‘warrior gene’ of MAOA do?
leads to low MAOA activity in areas of brain, and has been associated w various forms of aggressive behaviour.
ehwhat did Brunner et al study?
what did he find?
28 male members of large dutch family, who were receptively involved in impulsively aggressive violent criminal behaviours ie, rape, attempted murder n psychical assault.
that men had abnormal low lvls of MAOA in brains and low activity version of MAOA gene
what did Stuart et al study?
what did he find?
97 men involved in inflicting intimate partner violence, were part of batterer treatment programme.
men with low activity MAOA gene were most violent perpetrators or IPV. they engaged in highest lvls of physical and psychological aggression + inflicted worst injuries on their partners
how do the genes work?
what is the case w low-MAOA gene activity?
what did frazzetto find?
they don’t function alone and they r vital.
only related to adult aggression when combined w early traumatic life events.
aggression only the case if they had experienced trauma (physical/sexual abuse) during first 15yrs of life. those who didn’t have trauma like this didn’t have particularly high lvls of aggression as adults even if they possessed the low-activity MAOA gene
AO3✅
strength?
mertins et al studied ppts with low activity and high activity variants of MAOA gene in money distributing game. ppts had to make decisions whether or not to contribute the money for the good of the group. the researchers found that males w high activity variant were more cooperative and made fewer aggressive moves than low activity ppts.
AO3❌
2 weaknesses?
challenging to establish how influential genes r in aggressive behaviour. a reason for this is the difficulty researchers have in separating genetic and environmental factors. a individual may possess a gene associated w aggression but that behaviour is only expressed when environmental conditions are favourable. eg, mcdermott et al showed that ppts w low MAOA gene behaved aggressively in lab based money allocation game, but only when they were provoked. otherwise they were no more or less aggressive than other ppts.
the hypothesis that MAOA gene may play a role in human aggression originated with a mice study. genetic deletion techniques allows researchers to knock out single genes, an experimental manipulation that lets them observe subsequent effects on aggression. eg Godar et al showed that MAOA knockout mice have significantly increased brain serotonin lvls and r hyper aggressive. furthermore when serotonin was blocked by fluoxetine drug, the mice reverted to their non aggressive behaviour. also animal studies cannot be generalised to humans
