The genetic explanation Flashcards
(13 cards)
What does the genetic explanation suggest?
Aggression is innate.
It is inherited through genetic transmission.
If aggression is genetic we would expect individuals that are more genetically similar to show similar levels.
Example - Twins
What is the importance of twin studies in aggression?
Twin studies compared MZ and DZ twins.
MZ = Identical - Share 100% of DNA.
DZ= Non-identical - Share 50% of DNA
Expected for MZ to have higher concordance rate in traits.
What is the concordance rate?
Degree of similarity
What did Coccaro find in his twin studies?
Concordance rates for MZ twins higher than DZ in both physical/verbal aggression.
MZ - Physical = 50%
MZ- Verbal = 28%
DZ- Physical = 19%
DZ- Verbal = 7%
These findings suggest a genetic influence on aggression.
MZ twins show higher concordance rates than DZ.
Study was controlled as both groups shared same environment so good control of extraneous/confounding variables.
What do adoption studies show?
Compare the aggression levels of adopted children with adopted parent and biological parent.
Demonstrates whether aggression is due to genetic influences or biological influences.
Similarities between adopted child and biological parent = Genetic influence.
Similarities between adopted child and adopted parent = Environmental influence.
What are findings for adoption studies?
Rhee/Waldman - Meta-analysis on multiple adoption studies.
Found that genetics play a clear role but environment also has a part to play.
41% in variance in aggression suggest genetic factors.
What is the MAOA gene?
MAOA is an enzyme that breaks down serotonin
What is the MAOA-L variant?
Lower activity (reduced enzyme production)
Leading to higher levels of aggression.
This is because there is a low production of the MAOA enzyme leading to higher levels of serotonin in the brain.
What is the MAOA-L variant also known as?
The warrior gene.
This is because it is associated with higher levels of aggression.
Research support - Lea/Chambers (2007)
They found that 57% of Maori men carried this gene compared to 34% of caucasian males.
Maori people have a reputation for being more aggressive.
This suggests that certain genes are associated with the display of aggressive behaviour.
Research support - Brunner (1993) - Family study
Brunner syndrome
Family study - Extended family in the netherlands.
28 male members of the family.
History of impulsive aggressive behaviour/criminal
Had the MAOA-L variant.
Show that genes can influence aggression.
For evaluation can use general evaluation that used for Neural/hormone mechanisms.
Biologically
Deterministic
Reductionist
Social sensitive research
Bad evaluation - Gene/environment interaction
Genes do not interact on their own.
They interact with the environment to produce behaviours.
So for adult aggression to occur with people with the MAOA-L gene they also need to of have early traumatic life experiences.
MAOA-L activity + Early traumatic life experience = Adult aggression.
