Genetic factors in aggression Flashcards
(7 cards)
What did Emil Coccaro’s (1997) Twin studies on Aggression find with concordance rates on a) physical aggression and b) verbal aggression for MZ and DZ twins?
a)in physical aggression the concordance rates for MZ = 50% and DZ =19%
-For verbal aggression they were 28% and 7%
How much did Rhee and Waldman (2002) meta-analysis on adoption studies suggest genetic influences accounted for variance in aggression?
-carried out a meta-analysis of adoption studies (studying adopted child and biological parents) of direct aggression and anti-social behaviour
- found that genetic influences accounted for 41% of the variance in aggression.
What is the MAOA gene
-MAOA gene produces the enzyme MAO-A which regulates the neurotransmitter serotonin- serotonin involved with impulsive aggression
-MAOA gene has been nicknamed “warrior gene” because of Rod lee and Geoff Chambers (2007) which found that MAOA-L gene is in 56% of Maori New Zealand men and only 34% in caucasians.
What is the MAOA-L variant and what is it linked with?
-MAOA-L is low activity of the MAOA enzyme
-MAOA-L variant has been linked with high levels of aggression.
What earned the MAOA gene the name “warrior gene”?
-Rod lee and Geoff Chambers (2007) found that MAOA-L gene is 56% of Maori New Zealand men and only 34% in caucasians.
Strengths of genetic explanations for aggression
Research support: Venessa Martins et al. (2011) found that high levels of MAOA gene result in fewer aggressive moves than the low levels of MAOA in a money-distributing game.
HOWEVER: Martins also emphasised that environmental factors also play a part. Low activity MAOA gene also behaved cooperatively when they learnt others were.
Animal studies :Godar (2014) used the gene deletion technique and found that knocking out the MAOA gene in mice led to increased serotonin and hyper aggression.In addition, when serotonin was blocked by fluoxetine, the mice reverted back to their non-aggressive behaviour. Therefore, this adds validity to the genetic role that MAOA gene plays in aggression.
Limitations of genetic explanations for aggression.
-Methodology issues: For example, many studies use self-reports, parent/teacher reports and direct observations which may affect whether aggression is accurately measured. This is shown in Rhee and Wladman’s (2002) meta-analysis which found that when studies used self-report rather than teacher/parent reports, there was a greater influence of genetic factors found. Therefore, this questions the validity of conclusions drawn about the role of genetic factors if they depend on how aggression was measured.
-Issues with twin studies: General environment assumptions may be wrong. DZ and MZ twins may have different environments. MZ twins are treated exactly the same by parents - all wear the same clothes but DZ twins aren’t always treated the same. Therefore, concordance rates may be skewed in Coccaro’s studies.
