neural explanations Flashcards
what is the biological explanation for aggression?
aggression is due to the structure and/or function of our body, our genes, brain anatomy, hormonal or neuronal activity
what is the limbic system?
A network of structures deep in the brain
Papez and Maclean (1952) identified the limbic system as comprising of the hypothalamus, amygdala, parts of hippocampus and thalamus etc. For aggression, amygdala is most important
what is the amygdala’s role?
It’s key role in human and non-human animals is how they assess and respond to environmental threats and challenges. The reactivity of the amygdala in humans has been seen to be an important predictor of aggressive behaviour
what did Gospic find in 2011?
Gospic used a well know lab method of assessing aggressive behaviour known as the ultimatum game which features two players and money being offered to being split in certain ways.
PPs played as responders whilst having an fMRI (objective measure)
researchers found that when responders rejected unfair offers (aggressive reaction to social provocation), scans revealed a fast and heightened response by the amygdala.
what was found by Gospic when participants took BZs before the game?
BZs are drugs to decrease amygdala activity, and when these were taken before the game, there were two effects found on responses to unfair offers. It halved the number of rejections (ie reduced aggression) and decreased activity in the amygdala.
Strong evidence of an association of reactive aggression and amygdala activity.
what was found when the amygdala was stimulated in cats
a fearful or anger responses was created
what did Bushman find with rats?
rat lesion studies suggest different types of aggression may be controlled by different subsets of brain structures
-limbic subcortical sites involved are amygdala, hypothalamus amongst others
what did Raine find with PET scans?
Raine 1997 used PET scans to look at 41 murderers brains and 41 controls. They found abnormalities in the functioning of the limbic system implicated in aggression.
Raine 2000 also found that the prefrontal cortex which inhibits aggressive behaviour was 14% less active than normal in non-abused murderers & 15% smaller in anti-social males
correlational - suggests brain anomaly could be a factor involved in explanations of aggression but doesn’t necessarily cause it, could be the other way round
what is the case study of Charles Whitman?
Texan marine who murdered his family and shot a dozen strangers in a killing spree before taking his own life. He left a note begging for his brain to be studied and his autopsy revealed he had a tumour pressing on his amygdala
Sumer case study
case study of 14 year old girl who was epileptic and violent - diagnosed with tumour in limbic system following MRI and after drug therapy became less aggressive with more normal levels of behaviour suggesting high levels of aggression could have been prompted by the tumour in the limbic system.
Phineas gage
rod damaged pre-frontal cortex
this region is implicated in personality changed and aggression/violence
within months his personality changed dramatically
- he became extravagant and anti-social, a foul mouth liar with bad manners and frequently got into fights and assaults
- could no longer hold a job or a plan
how does alcohol affect aggression?
individuals prone to aggression are more likely to drink & become aggressive while drunk - alcohol affects brain
alcohol reduces self-awareness & disinhibits (deindividuates), it also switches off the pre-frontal areas, leaving the aggressive limbic areas without cognitive control
what is the evaluation of the limbic system as an explanation of aggression?
the role of the limbic system is not clear cut, the system is made up of many components and the extent to which each different structure is involved isn’t fully understood, equally it could be an interaction of the various components
research supporting the link between aggression and brain abnormalities is only correlational. In addition, not all people with limbic system abnormalities display aggressive behaviour. We cannot therefore ascertain c+e
what neurotransmitters are linked to aggression
high levels of dopamine and low levels of serotonin
what is serotonin
a neurotransmitter that has a widespread inhibitory effect on the brain
it slows down and dampens neuronal activity
normal levels of serotonin are linked with reduced firing of neurons, and this is associated with a greater degree of self-control
decreased serotonin may well disturb this mechanism, reducing self-control and leading to an increase in impulsive behaviour e.g. aggression (Denson 2012)
what research can be used as AO3 for serotonin as an explanation?
lower levels of serotonin are found in children and adults prone to violence - Bond (2005)
lowering serotonin levels in the lab increases their response to aversive events and willingness to deliver supposed electric shocks Bond 2005
Mann (1990) - when levels of serotonin were artificially reduced by a drug, participants responses to a hostility and aggression questionnaire were increased (not in females though!) - suggests low serotonin has influence but not fully as females don’t have the same response
Berman gave pps either a placebo or paroxetine (which enhances serotonin activity)
pps then took part in a lab based game where electric shocks of varying intensity were given or received in response to provocation
group with paroxetine gave fewer and less intense electric shocks compared to placebo group however this was only true of those who had no history of aggressive behaviour
what does research into monkeys by Raleigh show?
vervet monkeys studied
monkeys fed on diets high in tryptophan (which increase serotonin levels in brain) exhibited lower levels of aggression. Those fed on diets low in tryptophan exhibited increased levels of aggression.
what does research into rats by Ferrari show 2003?
Ferrari conducted an experiment that forced rats to fight at exactly the same time every day for 10 days and on the 11th day they were not allowed to fight and the level of serotonin and dopamine was measured in their brain
it was found that rat’s serotonin levels has decreased and their levels of dopamine had increased
this demonstrates that consistent aggressive behaviour can alter brain chemistry
what is dopamine
dopamine is the chemical that mediates pleasure in the brain
it’s released during pleasurable situations and stimulates one to seek out the pleasurable activity
food sex and drugs are the main stimulants of dopamine in the brain particularly in areas such as the prefrontal cortex
what research is there into dopamine affecting aggression?
Lavine (1997)
increase of dopamine activity via use of amphetamines (stimulant drugs) has been associated increases in aggressive behaviour
Buitlaar (2003)
antipsychotics, which have been shown to reduce dopamine activity in the brain have been shown to reduce aggressive behaviour in violent delinquents
what is AO3 of research into effects of dopamine and serotonin?
reductionist - oversimplifying complex human behaviour
unethical - research onto animals is unethical and limited in application to humans
legal system implications - criminals could blame crimes on biological reasons which has further impact on society
what is testosterone?
an androgen produced in the testes which is responsible for the development of masculine features, found in lower levels in females and can be associated with aggression
it doesn’t always manifest into aggressive behaviour, it can sometimes just mean an athletic prowess or competitiveness
some women with low testosterone also behave with great aggression
what are the naturally occurring examples?
teens with higher levels of testosterone were more prone to delinquency, hard drug use & provocations Dabbs 1987
what is found with people undergoing a sex change?
Vangoozen found that;
- women changing to men who received testosterone injections and became more aggressive
- men changing to women received testosterone suppressants and became less aggressive
animal research on testosterone
bertold (1849) - castrated cockerels and marked changes in aggression, reversed when testes were replaced
Simpson - various species castrated which lead to a marked decrease in aggression, hormone therapy in castrated animals increases and restores aggression levels
