Lesson 3- genetic factors in aggression

Question 1

genetics and aggression

Answer 1

-early psychologists investigating aggression believed genetic cause of aggression could lie in Y chromosome, especially XYY chromosome, ‘super males’
-Court-Brown 1965 discovered 314 patients that had xyy chromosome, put forward view that patients should remain hospitalised given their increased likelihood of aggressive behaviour
-more recent research focused on selective breeding in animals and found aggression is a trait that can be transmitted from parent to offspring

Question 2

twin studies and aggression

Answer 2

-looks at aggression displayed by mz and dz twins
-Coccaro et al 1997 studied pairs of male adult twins who were either mz or dz, found concordance rate for aggression defined as direct physical assault for mz twins was about 50% and dz twins was 19%, concordance rate for verbal aggression was 28% for mz twins and 7% for dz twins

Question 3

adoption studies and aggression

Answer 3

-similarities in aggressive behaviour between adopted child and biological parents suggest genetic influences are operating
-similarities between adopted child and adoptive parents suggest environmental influences are operating
-Rhee and Waldman 2002, meta analysis of adoption studies of direct aggression and antisocial behaviour, found genetic influences accounted for 41%

Question 4

candidate genes

Answer 4

-MAOA gene responsible for production of protein monoamine oxidase, allows metabolising of noradrenaline, serotonin, dopamine
-dysfunction in gene can result in these neurotransmitters not being broken down in the body, if adrenaline isnt metabolised then too much adrenaline, causes hypersensitivity in fight or flight, individuals may overreact to external stimulus, perceive a threat when does not exist
-dopamine not broken down, increased/excessive levels of dopamine also linked to aggressive behaviour
-serotonin has calming influence, low levels implicated in reduction of control over impulsive behaviour
-low activity variant of MAOA gene, MAOA-L ‘warrior gene’, likely to be aggressive
-Lea and Chambers 2007 found gene was possessed by 56% of New Zealand Maori men compared to 34% caucasians, historic reputation for being ferocious behaviours

Question 5

genetic factors strengths

Answer 5

-Coccaro et al 1997, concordance rate of physical aggression in form of criminal behaviour for mz twins was much higher than dz twins suggesting role of nature/genetics
-Godar et al 2014, refined selective breeding by specifically removing certain genes in mice, maoa knock out mice showed increased aggresssion and abnormal levels of serotonin, mice given fluoxetine to raise serotonin levels behaviour returned to normal
-Brunner 1993 studied 28 men from large dutch family who were repeatedly involved in impulsively aggressive violent criminal behaviour such as rape, attempted murder and physical assault, men possessed maoa-L gene
-Stuart et al 2014 studied 97 men involved in severe domestic abuse to partners, found most violent men had faulty maoa gene, engaged in highest level of physical and psychological aggression and inflicted worst injuries on partners

Question 6

genetic factors weaknesses

Answer 6

-Theilgaard 1984 undertook research into men with xyy genotype and found can cause increase in height in individuals but not increase in aggression, cannot make generalisations about aggression
-twin studies may lack validity, twins often share same environment but mz and dz may have different environmental influences