the role of hormones (e.g., testosterone) to explain human behaviour such as aggression

Question 1

define innate

Answer 1

• things you’re born with (genes/hormones)

Question 2

define a hormone

Answer 2

• chemical messengers produced by the body that sends messages to organs of the body via the bloodstream
• hypothalamus and pituitary gland control how much testosterone the testes produce and secrete
• hypothalamus sends a signal to pituitary gland to release gonadotrophic substances

Question 3

why are males more aggressive than females?

Answer 3

• could be due to gender norms
• girls: Barbie dolls, boys: pirates, construction (toys)
• males genetically stronger
• men have protection over females
• females more stereotypically verbal

Question 4

what do hormones affect?

Answer 4

• behaviour and physical changes in body
• eg oxytocin is hormone released by pituitary gland, which has been shown to increase trust between people

Question 5

what is a testosterone?

Answer 5

• androgen
  
  • chemical that develops and maintains male characteristics
• we all have testosterones in our body but its present more in the average male

Question 6

how does testosterone lead to aggression?

Answer 6

• antenatal (before birth) exposure to testosterone has an organising effect on the developing brain
• leads to increased spatial ability and competitive aggression
• also a critical period immediately following birth when testosterone sensitises certain neural circuits
• eg stimulates cell growth in areas of hypothalamus and amygdala (Naftoli, Garcia-Segura and Keefe) which later sets up the action of testosterone as an adult to effect aggression

Question 7

supporting: animal studies

Answer 7

• castrated male rodents (which stop producing testosterone) show little or no aggressive behaviour compared to control rodents
• when testosterone is injected into these castrated rodents, they display typical aggressive behaviour
• age of the rodent at the time of castration affects how they respond to testosterone:
  
  • newborn rodents show limited aggression after testosterone injections
  • rodents over 10 days old quickly return to normal aggression levels after testosterone replacement (Motelica-Heinz, Edwards, and Roffi)
• neonatal female rodents injected with testosterone act more aggressively as adults compared to control females (Edwards)
• this supports the idea that testosterone is involved in aggression and that the neural circuitry is sensitised after birth, making it more responsive to testosterone later on

Question 8

supporting study: neurotransmitters

Answer 8

• testosterone influences aggressive behaviour by affecting changes in neurotransmitters but the relationship is complex
• one important neurotransmitter involved is serotonin which is linked to mood regulation
• increased activity of serotonergic synapses inhibits aggression
• low levels of serotonin increase aggression
• this shows that serotonin modulates the effects of testosterone on aggression (goldman, lappalainen, and ozaki)

Question 9

supporting study: human studies + CA

Answer 9

• human studies generally support the link between testosterone and aggression
• boys are, on average, more aggressive than girls and have higher exposure to testosterone both pre- and post-natally (d’andrade)
• testosterone levels increase during the early teens and there’s a strong positive correlation with **aggressive behaviour and inter-male fighting (mazur)*(
• CA: however, correlation doesn’t indicate causality and other variables such as socialisation might affect these factors
• convicted sex offenders who were castrated showed removal of aggression and loss of sex drive (hawke)
• these studies support the idea that testosterone is influential in aggression but CA: lack scientific rigour such as control groups and objective measures of aggression
• current ethical standards would prevent such studies from taking place

Question 10

supporting evidence: dabbs

Answer 10

• found that levels of testosterone were higher in those who had been involved in violent crimes
• those with higher levels of testosterone were rated by their peers as being tough

Question 11

supporting: Mann

Answer 11

• found that people given a drug that lowers levels of serotonin were found to be more aggressive
• aggression was measured by questionnaire

Question 12

other things: direction of causality in testosterone and aggression

Answer 12

• direction of causality is an issue when linking testosterone and aggression
• it could be that raised levels of testosterone occur as an effect of being aggressive or achieving dominance
• reciprocal model of testosterone suggests that testosterone is an effect of dominance and not the cause of it

Question 13

supporting study: mazur and booth (1998) on testosterone and aggression

Answer 13

• found that individual testosterone levels varied across the lifespan based on environmental status
• eg being married decreased testosterone levels, while divorce increased them
• same study found support for the basal model, suggesting testosterone causes changes in aggressive dominance
• men with higher levels of testosterone were more likely to get arrested and use weapons in fights

Question 14

other things: limitations of testosterone and aggression research

Answer 14

• most research on testosterone and aggression is on small mammals, limiting generalisability
• brain areas affected by testosterone serve different functions across species (eg cingulate gyrus causes fear-induced aggression in monkeys, irritability in dogs/cats)

Question 15

other things: ethical limitations of testosterone and aggression research

Answer 15

• experimental research on humans can’t ethically be done
• limited case studies of convicted sex offenders being castrated support animal research, but they aren’t representative of the general population because perpetrators of such crimes are atypical

Question 16

strengths of hormones (testosterone) as a cause of aggression

Answer 16

• animal studies have large number of controls eg castrated/non castrated mice in same environment) which means studies have been replicated. aggressive behaviours can be observed in a controlled way which improves reliability
• castrating mice ensures lower levels testosterone which means studies have internal validity
• studies on humans show a very strong correlation between testosterone and aggression. these studies are supported by animal studies and so have good predictive validity

Question 17

weaknesses of hormones (testosterone) as a cause of aggression

Answer 17

• human studies only show correlation between testosterone levels and aggression, they don’t show a ’cause and effect’ eg we can’t say that high levels of testosterone lead to aggression, another explanation could be that being aggressive leads to an increase in testosterone
• it’s difficult to generalise from animal studies as mice brain structures and function is different to humans. this reduces the validity of using animal studies to explain human behaviour
• investigating testosterone as a cause of aggression is reductionist as other hormones and neurotransmitters are also known to affect aggression. eg the stress hormone cortisol can also lead to increased aggression (Barzman) found that boys rated as aggressive had higher levels of testosterone and higher levels of cortisol (in the morning)