Genetic factors in aggression Flashcards
How do twin studies show a genetic influence in aggression
Suggest heritability accounts for 50% of variance in aggression
-E.g Coccaro et al (1997) measured concordance rates:
-Physical= 50% MZ/19% DZ
-Verbal= 28% MZ/7% DZ
How do adoption studies show a genetic influence in aggression
Rhee/Waldman (2002) meta-analysis= genetic influences accounted for 41% of variance in aggression- similar to twin studies
What is the MAOA gene
Controls production of enzyme MAO-A
MAO-A regulates neurotransmitter serotonin
Low activity variant (MAOA-L)= low activity enzyme= + aggressive behaviour
Why is MAOA known as “warrior gene”
Lea/Chambers: 56% New Zealand Maori men had it L variant/34% Caucasians
Maori men known to be warriors
Study of MAOA-L variant in aggression
Brunner et al (1993) studied 28 violent criminal men from large Dutch family= very low levels of MAO-A/had MAOA-L
Gene environment interaction in aggression
Frazzetto et al found association with + aggression and MAOA-L BUT only when had experienced trauma in first 15 years of life
Strength of role of MAOA gene in aggression
Research support
-e.g Mertins et al (2011): Men with low/high variants did money-distributing game
-Men with high= moe co-operative/fewer aggressive moves
Counter-point to Mertins et al study of MAOA-L causing aggression
Also showed non-genetic factors crucial as L variants co-operated when made aware that others were (knowledge of social norms)
-So genes also influenced by environmental factors
Weakness of MAOA-serotonin- aggression link
Precise mechanism unclear as L variant= low activity of MAO-A enzyme which should= + serotonin
-Maybe more accurate to say serotonin levels disrupted not +/- usual
Weakness of genetic explanation
Twin studies may lack validity
-DZs don’t share same environment like MZs as more likely to be treated differently
=equal environments assumption
