genetic factors in aggression

Question 1

genes

Answer 1

• 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

Question 2

how is the link between genes + aggression shown?

Answer 2

• twin studies
• adoption studies
• candidate genes

Question 3

twin studies

Answer 3

• 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

Question 4

adoption studies

Answer 4

• 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

Question 5

candidate genes

Answer 5

• 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

Question 6

neurotransmitter levels + consequential behaviour - candidate genes

Answer 6

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

Question 7

ads of genetic factors

Answer 7

• research support
• selective breeding

Question 8

disads of genetic factors

Answer 8

• XYY
• twin studies validity
• biological determinism

Question 9

research support - ads of genetic factors

Answer 9

• 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

Question 10

selective breeding - ads of genetic factors

Answer 10

• 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

Question 11

XYY - disads of genetic factors

Answer 11

• 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

Question 12

twin studies validity - disads of genetic factors

Answer 12

• 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)

Question 13

biological determinism - disads of genetic factors

Answer 13

• doesn’t take into account free will
• up to hormones