Genetic Factors in Aggression Flashcards
Gene for aggression
MAOA
Is aggression inherited studies
Twin studies
Adoption studies
Twin studies
A study to specifically study aggressive behaviour using adult twin pairs found that nearly 50% of varience in direct aggressive behaviour could be attributed to genetic factors
If MZ twins are more alike in terms of aggressive behaviour then this should be due to genes rather than environment
Adoption studies
If a +ve correlation is found between adopted child + biological parents = genetics
If found between adopted child + rearing parents = environmental
Study showed a sig number of adopted boys with criminal convictions, had biological parents with criminal convictions = GENETIC
MAOA
Regulates the metabolism of serotonin in the brain + low levels of serotonin are associated with aggression
Dutch famliy = many male members were aggressive: found to have abnormally low levels of MAOA in their bodies + a defect in this gene
2nd study on MAOA
Discovered 1 variant of the gene associated with high MAOA
2nd variant of gene associated with low MAOA
Those with low MAOA = sig more likely to grow up to exhibit antisocial behaviour if maltreated as child
Those with high MAOA maltreated + those with low but not maltreated = no antisocial behaviour
Shows it’s the interaction between genes + environment that determines aggression
What have adoption studies shown?
Highest rates of criminal violence on adopted children occur when both biological + adoptive parents have a history of violent crime = gene-environment interaction
META
Combined results of 51 twin + adoption studies
Concluded that aggressive behaviour was a product of genetic contributions
Another META (Miles + Carey) suggested a strong genetic influence that could account for as much as 50% of variance in aggression
Difficulties in determining the role of genetic factors
More than 1 gene usually contributes to a given behaviour
There are many non-genetic influences on the manifestation of aggressive behaviour
These influences may interact with each other = gene-environment interaction
Methodlogical Issues
Studies fail to distinguish between violent + non-violent crimes = more difficult to untangle role of genetic factors in aggressive violence
All fail to distinguish between habitually violent + one-off criminals
Inconclusive evidence
META: only a low to moderate correlation between heredity + crime
Better designed + more resent provided less support for gene-crime hypothesis
More resent study: ‘The data do not suggest a strong role for heredity in violence’
Animal research
Young et al
Have identified a genetic mutation that causes violent behaviour in mice
The mutation has a range e.g. extremely violent behaviour towards other mice
A counterpart for this gene does exist in humans although its precise function is not known
Real-world Application
If people are predisposed towards aggressive behaviour or violent crime, then q’s about the treatment of such behaviours arise
e.g. chemical castration
Extremely tentitive nature of conclusions that can be reached + far-reaching ethical considerations of labelling an indi as threat to society on basis of genetics, an awareness of limitations of studies is importants
Sampling Problems
Convictions for violent crime are few compared to number of violent attacks by indis that never see a convictions = represents a small minority of those ref involved in aggression
Offenders designated as ‘violent’ on basis of court conviction are no necessarily the most serious, persistent offenders = explain why so many studies found little evidence of heritability
