3.1.6 - the role of hormones to explain aggression Flashcards
what are hormones?
chemical messages which transmit information around the body and can alter the structure and functioning of organs
what are key features of hormones?
they are carried in the blood
they take longer to work than neurotransmitters, but their effects are longer-lasting
what is the endocrine system?
the system of glands which produce and secrete hormones
what is an organising effect?
the effect a hormone has in influencing the structure of an organ
what is an activating effect?
the effect a hormone has in influencing the function of an organ
what is an example of a hormone, where and why is it produced and what is its effect on behaviour?
cortisol
secreted from the adrenal cortex
secreted as part of circadian rhythms and in response to stress
can activate fight or flight response, inhibit aggressive behaviour through fear responses and cause irritability and depression
what is testosterone?
an androgen hormone (develops or maintains male characteristics) found in males and females, but at a higher level in males
what is the organising effect of testosterone?
exposure during development may alter the structure of parts of the amygdala, hippocampus and hypothalamus (however there are no clear differences in brain structure between men and women)
during puberty for males it increases muscle mass and makes jaw more square
what is the activating effect of testosterone?
it acts like a neurotransmitter in the brain, binding to receptors in the amygdala and enhancing its activity
what is the effect of testosterone immediately after birth and what evidence is there for this?
it sensitises certain neural circuits eg. stimulating cell growth in the amygdala and hypothalamus, which later sets up the action of testosterone to affect aggression in adults
Motelica-Heino, Edward and Roffi (1993) - in castrated (testicles removed) rodents, testosterone injections have a limited effect on aggression when they are newborn, but if they are over 10 days old, the replacement testosterone brings aggression levels back to normal for uncastrated rats
why is the effect of testosterone on neurotransmission complex?
because serotonin for example produces a modulating effect on aggression - increases in serotonin inhibit aggression, while low levels increase aggression (Goldman, Lappalainen and Ozaki, 1996)
what did Carre et al. (2011) suggest the effect of testosterone on the brain was?
it weakens the link between the orbitofrontal cortex and amygdala so less impulse control)
it makes the amygdala more reactive
therefore, increased testosterone increases the probability of an aggressive response
supporting evidence - Dabbs et al. (1995)?
measured prisoners’ salivary testosterone levels (sample=692 male prisoners), found those with high testosterone levels were more likely to have been convicted of violent offences and have more prison rule violations on record
Dabbs et al. (1995) - evaluation?
criminal sample - less generalisable
large sample size - generalisable to criminals
little chance of demand characteristics - increased validity
all male sample - not generalisable to females
measurement of testosterone levels is objective but interpretation of how violent crimes were is subjective
correlation study
supporting evidence - human studies?
D’Andrade (1966) - boys have higher exposure to testosterone pre- and post- natally and are on average more aggressive than girls
Mazur (1983) - there is a strong positive correlation between testosterone levels increasing in early teens and aggressive behaviour/inter-male fighting
contradictory evidence - Tricker et al. (1996)?
experimental study where 43 male participants were given 600mg of testosterone a week for 10 weeks, or a placebo
double blind trial
participants tested with anger questionnaires and those around them were asked to report on their mood and aggressive behaviour
no significant difference found between aggression levels in the two groups
Tricker et al. (1996) - evaluation?
relied on self-report and peer-report data - may have led to social desirability bias
small sample size - not generalisable
sample of ordinary men - generalisable to normal population
double blind - reduces chance of demand characteristics and researcher bias
men not kept under same conditions - likely to be extraneous variables
experimental study - more valid than correlational
what does the reciprocal model of testosterone suggest?
testosterone is an effect of aggressive dominance, not a cause
what does the basal model of testosterone suggest?
testosterone causes changes in aggressive dominance
evaluation - direction of causality?
we don’t know know whether increases in testosterone causes aggression (basal model), or vice versa (reciprocal model)
Mazur and Booth (1998) found support for both models - testosterone levels varied based on environmental status (marriage decreased levels, divorce increased them), but men with higher levels of testosterone were more likely to use weapons in fights
evaluation - generalisability?
lots of research which suggests testosterone is linked to aggression is done on rodents eg. Albert et al. (1966) (found testosterone affects aggressive behaviour in rats) and primates - this reduces generalisability of findings because the brain areas said to be affected by testosterone have different functions across species (cingulate gyrus - fear-induced aggression in monkeys, irritability in dogs and cats)
evaluation - ethics?
can’t ethically carry out research into theory on humans
limited studies on convicted sex offenders have found that castrating them decreases aggression eg. Hawke (1951), but findings aren’t generalisable to normal population and studies lack control groups and fully objective measures of aggression
what are distal influences?
factors which influence the structure and function of the nervous system, and consequently influence cognition, emotion and behaviour
what are examples of distal influences?
physical environment, psychosocial influences (relationships with other people), biological influences (hormones, genes)
