neural and hormonal mechanisms in aggression Flashcards
what do neural factors in aggression include
structures in the brain and neurotransmitters
what is the main role of the amygdala
regulate emotions such as fear and aggression
what happens when the amygdala is stimulated electrically
animals show aggressive behaviour,
when removed they no longer show aggressive behaviour
non-human animal research evidence for the role of the amygdala
research on hamsters found that stimulation of the amygdala increases aggression and lesioning of this area reduces aggression in hamsters
research has also shown that stimulating the amygdala in cats causes a fearful or anger response to occur
this provides evidence to support the role of the amygdala but this was based on non human animals so it cant be extrapolated to humans because we have a different biological makeup
evidence for role of amygdala in humans
an amygdalectomy is the surgical removal of the amygdala, which reduces aggression in previously violent individuals. However, a side effect of this type of surgery is the loss of emotion.
So it is possible that the amygdala does not directly cause aggression, but is involved in processing associated emotions such as anger.
the frontal lobes may play a role in aggression:
what are the frontal lobes involved in?
decision making, motor functions, and personality
evidence for aggression linked to frontal lobes
Phineas Gage had an accident where iron went through his skull and caused damage to his frontal lobe. This caused a personality change and he became more aggressive, impatient and impulsive.
do low levels or high levels of serotonin lead to aggression, and why
serotonin has a calming influence on people so low levels of serotonin causes people to have less control over their impulsive and aggressive behaviour.
Serotonin also regulates the pre-frontal cortex, therefore lower levels of serotonin affect our response to external stimuli, meaning the person becomes aggressive easily and cant control their responses.
research evidence for the role of serotonin
study on rates.
male adult rats allowed to fight each other at a specific time for ten days. on the eleventh day they were not allowed to fight. Brain chemistry changed - dopamine levels raised by 65% and serotonin levels were reduced by 35%
role of testosterone in aggression
testosterone is the hormone mainly implicated in aggressive behaviour. testosterone is produced in spurts, so testosterone levels can rise suddenly and have an effect within minutes. It varies seasonally within some animals which is why deer become aggressive in the mating period in spring
goetz key study on testosterone method
goetz hypothesised that testosterone might influence the activity of the amygdala =, much like other research has shown serotonin does.
- 16 healthy men tested over 2 days
- all participated in both conditions
- base line testosterone levels were the same before experiment began
- treatment condition - given a dose of testosterone
- control condition received a placebo
- after treatment/placebo they were placed in an fMRI scanner and brain activity was measured while they saw images of faces expressing different emotions
goetz study results and one weakness of study
results showed that the treatment condition the reactivity of the amygdala was higher when participants were shown the angry face.
the study only uses males which is an example of beta bias as they focus on males and do not test females.
support for testosterone in aggression
a researcher castrated mice and aggression levels went down, thus providing support for the theory that testosterone is implicated in aggression
one limitation of the neural and hormonal explanation for aggression
could be considered reductionist because it is reducing aggression down to simple factors such as brain structure and hormones like testosterone and ignoring other factors that could be implicated such as social influences and environmental factors
