genetic factors in aggression Flashcards
genes
- consist of DNA strands
- DNA produces instructions for general physical features of an organism (e.g. eye colour, height)
- also specific physical features (e.g. neurotransmitter levels)
= can affect psychological features (e.g. mental health) - genes transmitted from parents to offspring = inherited
- evidence shows that there is a link between genes + aggression
how is the link between genes + aggression shown?
- twin studies
- adoption studies
- candidate genes
twin studies
- studies looked at aggression displayed by MZ + DZ twins
- study found that concordant rate for direct aggression (physical assault) :
MZ - 50%
DZ - 19% - concordant rate for verbal aggression:
MZ - 28%
DZ - 7%
= shows that both verbal + physical aggression are high enough to suggest a genetic component for aggression
adoption studies
- similarities in aggressive behaviour between an adopted child + their biological parents
= suggest that genetic influences are operating - similarities between an adopted child + adoptive parents
= suggest environmental influences are operating - psychs conducted a meta-analysis of adoption studies of direct aggression + anti-social behaviour
= found that genetic influence accounted 41% of these
candidate genes
- specific genes have been identified which have been shown to carry the aggression trait down to individuals
- MAOA L gene:
- ‘warrior gene’
= dysfunction of MAOA gene - too much adrenaline = hypersensitivity in the FoF response
- too much dopamine = aggressive behaviour
- low levels of serotonin = reduction of control over impulsive behaviour
= leads to aggressive behaviour
- psychs found that this gene was possessed by 56% of New Zealand Maori men compared to 34% Caucasians
neurotransmitter levels + consequential behaviour - candidate genes
high dopamine levels = increases likelihood of reward when aggression is carried out
low serotonin levels = lack of inhibition over impulsive behaviours
high noradrenaline levels = overreaction to perceived threats
ads of genetic factors
- research support
- selective breeding
disads of genetic factors
- XYY
- twin studies validity
- biological determinism
research support - ads of genetic factors
- lots of research support for the genetic explanation
- psych found the concordance rate of physical aggression in the form of criminal behaviour for MZ twins was much higher than DZ twins
= suggests that the role of nature plays a strong role in aggression
selective breeding - ads of genetic factors
- scientists have refined selective breeding
- specifically removed the MAOA gene in mice
- mice showed increased aggression + abnormal levels of serotonin
= demonstrates the relationship between genes + neurotransmitters - when the mice were given fluoxetine to raise serotonin levels
= behaviour returned to normal
= study supports the role of genetics, especially the MAOA gene, in aggression
XYY - disads of genetic factors
- not all research supports the role of genetic factors for aggression
- e.g. psych undertook research into men w/ XYY genotype
- found that XYY can cause na increase in height but not an increase in aggression
= shows we can’t make generalisations about aggression
= there is no link between XYY + aggression
twin studies validity - disads of genetic factors
- the use of twin studies may lack validity
- in every pair of twins = share the same environment
- HOWEVER, DZ twins may not share the same environment to the same extent as MZ twins
- e.g. MZ twins treated by parents + significant others the same way as they’re identical
- but DZ won’t, especially if they’re different sex
= MZ twins have identical genes + environment = contribute to their aggression compared to DZ twins
= twin studies research lacks validity
= not only measuring genetic influence on aggression
= but also unintentionally measuring environmental influences
(nature vs nurture)
biological determinism - disads of genetic factors
- doesn’t take into account free will
- up to hormones