Aggression Flashcards
The Limbic System
Helps to coordinate behaviours which satisfy emotional urges.
Contains the :
Amygdala
Hippocampus
Hypothalamus
The Amygdala
Quickly evaluates importance of sensory info and prompts appropriate response.
If certain areas are electrically stimulated, animal responds aggressively.
If these areas are removed the animal no longer displays aggression to the same stimuli.
Kluver and Bucy found when they destroyed monkeys’ amygdalas they became less dominant.
The hippocampus
Involved with forming LTMs.
Allows animal to compare the current threat to a past experience.
If hippocampus is damaged, the nervous system won’t be able to put the event in context.
This may cause the amygdala to respond innapropriately and prompt an aggressive ressponse.
Boccardi found that prisoners often had damaged hippocampus’.
Serotonin
Neurotransmitter that inhibits neuronal firing in the brain (inhibits firing of the amygdala).
Low serotonin levels remove the inhibitory effect, so individuals are less able to control aggressive behaviour.
Therefore when the amygdala is stimulated, a person is more likely to act on their impulses.
Testosterone
Hormone which produces male characteristics, also involved in aggressive and dominant behaviours.
Sapolsky- Removing source of testosterone reduce aggressive behavior in animals, giving same animals testosterone increased aggression levels again.
Evidence for role of hippocampus
Raine et al.
Studied violent offenders.
The offenders were put in two groups, those who had faced conviction, and those who had avoided conviction.
The second group were thought to be more cold and calculated, whereas the first group were thought to be more impulsive.
The unsuccesful, impulsive criminals were found to have an unsymmetrical hippocampus, damaging its ability to work with the amygdala.
Evidence for role of amygdala
Pardini et al .
Reduced amygdala volume can predict severe and persistant aggression developing.
Longitidional study of males from childhood to adulthood. Out of all ppts, 56 of them with a violent history had a brain MRI at 26.
Ppts with lower amygdala volume showed higher aggression and violence.
Shows that the amygdala has an important role in evaliating the emotiomal importance of sensory information.
Twin studies
Mz (Identical) - Share all genes
Dz (Non-identical) - Share 50% of genes
If mz twins are alike in terms of aggression then this is likely because of genes
Adoption studies
Used to differentiate between environment and heredity in aggression.
If there is a correlation with aggression with biological parents- genetic
If there is a correlation with adoption parents- environment
Research on Genetic factors in aggression
Miles and Carey - meta analysis of 24 twin and adoption studies.
Results- Strong genetic influence could could for 50% of aggression
In youth, both genetic and family environment affected development of aggression
In adults, the influence of environment decreased and the influence of genes increased.
Role of MAOA gene
Responsible for producing an enzyme called MAOA
MAOA regulated the metabolism of serotonin in the brain. Low levels of serotonin are associated with aggressive behaviour.
Dutch family were particularly aggressive- found to have abnormally low levels of MAOA.
MAOA-H and MAOA-L
Gene associated with High levels of MAOA - MAOA-H
Gene associated with Low levels of MAOA - MAOA-L
ONLY Those who were mistreated and had MAOA-L showed aggression.
Those who had MAOA-H and those who had MAOA-L but were not mistreated showed no signs of aggression
Warrior Gene
MAOA-L gene more common in populations with history of warfare. (2/3 of pop.)
vs 1/3 of pop. of other populations
Problems of assessing aggression
Many studies on aggression have relied on self report or parental report techniques of aggressive behaviour. (rather than observational techniques)
Miles and Carey found that genetic factors explained a large proportion of the variance in aggressive behaviour that had used parental/ self reports. BUT, when observational techniques were used, they found environmental factors played a greater role.
This makes it harder to accurately assess genetic/ environmental causes.
Fixed Action Pattern
Innate behaviours which all members of a species carry out without ever having to learn then.
