genetic explanations of aggression

Question 1

xyy

Answer 1

• one pair of chromosomes decides if we are male (xy) or female (xx)
• believed the cause of aggression could lie in the y chromosome
• focused on people with xyy chromosome, these were referred to as ‘super males’
• crown-brown (1965) found 314 patients with xyy and said they should remain hospitalised due to their likelihood for aggression

Question 2

twin studies

Answer 2

• look into the concordance rates of aggression displayed by mz and dz twins
• they indicate that aggression has a genetic element

Question 3

the MAOA gene

Answer 3

• one variant has been named the ‘warrior gene’
• responsible for the production of the MAOA enzyme (monoamine oxidase) which allows for the metabolising of noradrenaline, serotonin and dopamine
• a dysfunction in this gene can result in these neurotransmitters not being broken down, leading to abnormal levels of them

Question 4

what happens if noradrenaline isn’t metabolised?

Answer 4

leads to high levels of noradrenaline which can cause hypersensitivity and over reactiveness to perceived threats

Question 5

what happens if dopamine isn’t metabolised?

Answer 5

high levels of dopamine increase feelings of reward when aggressive behaviour is carried out

Question 6

what happens if serotonin isn’t metabolised?

Answer 6

low levels of serotonin is linked to a reduction of control over impulsive behaviour

Question 7

give a strength of genetic explanations of aggression

Answer 7

coccaro et al (1997) compared the concordance rates of criminal behaviour in MZ and DZ twins for both twins. they found the MZ twins had a concordance rate of 50%, compared to 19% for DZ twins. this supports the role of genetic in aggression, as the genetically identical twins were more likely to display aggression than the twins who only shared 50% of the same genes

Question 8

give a strength of genetic explanations of aggression

Answer 8

brunner (1993) studied males in a family from the netherlands who were aggressive. 5 of the men had the dysfunctional MAOA gene, the females were not affected by the genetic dysfunction. the MAOA gene is carried on the x chromosome, and since women have 2 of these, even if they have the dysfunctional MAOA gene, their other functional x chromosome will likely be dominant. this study supports the role of the dysfunctional MAOA gene in aggression

Question 9

give a strength of genetic explanations of aggression

Answer 9

stuart et al (2014) studied 97 men who had been involved in domestic abuse against their partners. they found that the most aggressive men had the dysfunctional MAOA gene, these men engaged in the most physical and psychological aggression, inflicting the most harm. this study demonstrates a clear link between the MAOA gene and aggression

COUNTER = results are only correlational

Question 10

give a limitation of genetic explanations of aggression

Answer 10

theilgaard (1984) researched men with the XYY genotype and found that although it can cause an increase in height, it cannot cause an increase in aggression. this refutes the role of genetics, suggesting there is no link between the XYY genotype and high levels of aggression