Aggression Flashcards
Which structures are involved in the limbic system?
Hypothalamus
Thalamus
Amygdala
Hippocampus
What is the main function of the limbic system?
To control a range of emotional behaviours including aggression
It also connects the brain stem to the cortex
Outline the role of the amygdala
It is responsible for quickly evaluating the emotional importance of sensory information and prompting an appropriate response (milliseconds)
Outline research into the role of the amygdala in aggression
Cat - responds aggressively when areas of the amygdala are electrically stimulated e.g snarling and adopting an aggressive posture
MARK AND ERVIN - Julia; exhibited facial grimacing, became very angry and flung herself at the wall.
Outline the role of the orbitofrontal cortex
It regulates the emotional responses driven by the amygdala.
Damage to this results in impulsivity and loss of control.
Outline study into orbitofrontal cortex
RAINE ET AL investigated brain activity in 41 murderers using PET scans and found reduced glucose metabolism in the orbitofrontal cortex, suggesting this brain area is less active than in normal controls
suggests the regulation of aggression is complex involving the amygdala, the OFC and the connection between them
Further evidence is frontal lobotomies- had a calming effect on patients
Outline the role of serotonin
Neurotransmitter involved in the communication of impulses between neurons.
Widespread inhibitory effect on the brain
Serotonin typically inhibits the firing of the amygdala
Normal levels of serotonin- calming, inhibitory effect on neuronal firing in the brain
Low levels - in the prefrontal cortex remove this inhibitory effect (individuals are then less able to control impulsive and aggressive responses
Outline research into serotonins effect on aggression
RALEIGH gave different diets to vervet monkeys. Tryptophan increases serotonin levels in the brain. Monkeys with high levels of tryptophan in diets showed decreased levels of aggression. Vice versa.
PASSAMONTI manipulated tryptophan levels in healthy participants diets. Given a questionnaire to assess their aggressive tendencies and fMRI scans to measure their reaction to pictures of angry, sad and neutral expressions. On low serotonin days communication between the prefrontal cortex and the limbic system was weaker(especially in those with existing aggressive attributes)
What are the practical applications of research into serotonin
Diets to raise serotonin levels such as tryptophan could be given to juvenile delinquents and unpredictable institutionalised patients
Outline hormonal mechanisms in aggression-the role of testosterone
Testosterone is an androgen secreted by the testes in males and to a lesser degree, the ovaries in female.
Males about 8 times more testosterone than females.
WAGNER castrated male mice and found that aggression was reduced. He injected the mice with testosterone which re-established their aggression. Castration has long been used as a method for making domestic and farm animals more manageable
Males of species are typically more aggressive than females.
DABBS measured testosterone in the saliva of 692 adult male prisoners and found higher levels in rapists and violent offenders than in burglars and thieves.
HOWEVER, not all research has supported this link. CARRE put forward the dual-hormone hypothesis to explain this. They claim that high levels of testosterone led to aggressive behaviour only when levels of cortisol are low. When cortisol is high, testosterone’s influence on aggression is blocked.
Outline genetic factors in aggression, including the MAOA gene
Suggests there is no free will
Through genetic transmission, aggression can be passed from one generation to the next. Social psychological explanations are played down as influences of aggression.
In reality, genes do not directly cause aggression but influence elements of our biology that contribute to it.
Structural effects - the genes contribute elements necessary for aggression, such as muscle and bone development.
Functional effects - they influence neurochemical and hormonal systems.
Outline Lagerspetz
Carried out an influential laboratory based selective breeding study. She isolated a group of mice after weaning in order to identify mice that were more prone to aggression.
She then interbred the aggressive mice so that after 19 generations, rates of aggression were 10 times higher than in controls. The aggressive mice also had heavier testes and forebrains and altered levels of serotonin and noradrenaline, supporting the notion that genes influence both the structural and functional aspects of an animals biology.
Does not claim genes are the only cause of aggression as it was possible to condition these mice to behave less aggressively, something that is not surprising considering that wild animals can be tamed to an extent through conditioning.
Evaluate the use of animal research into genetic factors of aggression
Offers useful comparisons for understanding human behaviour as there is sufficient similarity in physiology to justify these comparisons.
However, understanding the influence of genes on human aggression is a much more difficult task than it is with lower animals.
Not only are humans much more complex organisms because of our highly revolved brains, but we live in complex environments which influence behaviour in many and often unpredictable ways. This difficulty with generalisability is one of the problems with using animal research in psychology. Further problem is the ethical issues of such research. Researchers argue that animal experimenters are guilty of ‘speciesism’ i.e. Putting human benefit before animal.
Outline twin studies into genetic factors of aggression
COCCARO used a questionnaire to measure hostility in male participants (182 MZ and 118 DZ twin pairs)
They found concordance rates of 50% for MZ twins and 19% for DZ twins. -suggesting genetic factors do play a part in aggressive behaviour, but that the environment is important too.
Outline adoption studies into genetic factors of aggression
RHEE AND WALDMAN carried out a meta-analysis of adoption studies. They found genetic influences account for 41% of the variance in aggression. Therefore, genetic factors are important in aggression, but not as important as environmental factors
