Aggression Flashcards
What is the limbic system and who first linked it to aggression?
The limbic system is subcortical structures in the brain ( like the amygdala and hypothalamus) thought to be closely involved in regulating emotional behaviour including aggression. It was first linked by James Papez and revised by Paul Maclean.
What did Gospic find when investigating the limbic systems relationship to aggression?
She used a lab study and used the ultimatum game. This uses two players, the proposer and the responder , the responder is offered to split money with the proper. If the responder accepts , the money is split as proposed but if the responder rejects the offer then none receive money. Using fMRIS the researchers found that when responders rejected unfair offers scans revealed a fast and heightened response by the amygdala. They also found that when pps were on benzodiazepine it halved the number of rejections and decreased the activity of the amygdala as the drug slows the autonomic nervous system.
What does serotonin do?
It is a neurotransmitter involved in the communication of impulses between neurons, it has inhibitory effects on the brain and slows down, dampening neuronal activity.
How are different levels of serotonin linked to aggression?
Normal levels of serotonin in the orbitofrontal cortex are linked to reducing firing of neurons and this is associated with a greater degree of behavioural self - control. Lower levels of of serotonin may disturb this mechanism , reducing self control and lead to an increase in impulsive behaviour including aggression.
What did Virkkunen find about serotonin?
He compared levels of a serotonin breakdown product in the cerebrospinal fluid of violent impulsive and violent non-impulsive offenders. Levels were significantly lower in the impulsive offenders and they also suffered from more sleep irregularities. This is significant as serotonin regulates sleep patterns and disturbance of this pattern strongly implies that there is some disruption of serotonin functioning, further supporting the role of serotonin in reactive aggression.
Evaluation of neural mechanisms in aggression ( limbic system and serotonin)?
In recent studies it has been found that the amygdala does not operate in isolation. It appears to operate in tandem with the orbitofrontal cortex which is not part of the limbic system. Coracco found that in patients with psychiatric disorders that featured aggression, activity in the OFC is reduced, disrupting its impulse-control function and leading to increased aggression. Therefore, there are multiple structures involved in levels of aggression.
Supporting drug evidence: Berman conducted a study which found that when pps took part in a lab study where they had to give and receive shocks while on a placebo or paroxetine , a drug which enhances serotonin activity . Those on paroxetine gave fewer and less intense shocks than those in the placebo group.
What did animal studies find about aggression levels due to testosterone?
Animal studies have demonstrated that experimental increases in testosterone are related to greater aggressive behaviour in several species.
What did Dolan find about testosterone?
They found that there was a positive correlation between testosterone levels and aggressive behaviours in a sample of 60 male offenders in the UK maximum security hospitals. These men suffered from personality disorders and had histories of impulsively violent behaviour.
Evaluation on hormonal mechanisms in aggression (testosterone)?
High validity - Mazur developed the biosocial model of status which argued that testosterone levels change in response to social interactions related to status , e. g in competitions if you lose or win. Mehta and Josephs reinforce this theory with their study which found that when pps took part in a competitive game and lost, those whose testosterone levels dropped, only 22% rechallenged. Whereas of the losers whose testosterone levels rose after they lost, 77% of those pps rechallenged.
Other hormones may be involved in aggression, Carre and Mehta found that high levels of testosterone lead to aggressive behaviour only when cortisol levels are low. When cortisol levels are high testosterones influence on aggression is blocked. Therefore, just considering testosterone may not be an entirely comprehensive outlook.
What did Coccaro find about twin studies and the genetic factors on aggression?
concordance rates of 50% in MZ twins and 19% for DZ. This is because DZs share only 50% of there genes while MZs share 100% on average.
What did Rhee and Waldman find about adoption studies?
They carried out a meta analysis of adoption studies pf direct aggression and antisocial behaviour , a prominent feature of which is aggressive behaviour. They found genetic influences accounted for 41% of the variance in aggression , more or less in line with findings from twin studies.
What role does the MAOA gene take?
It is the gene responsible for activity of the enzyme monamine oxidase in the brain. It breaks down the neurotransmitters (usually serotonin) into its contituent chemicals to be recycled or excreted. The production of this enzyme is is determined by the MAOA gene. A dysfunction in the operation of this gene would lead to abnormal activity of the MAOA enzyme and therefore create affects of the levels of serotonin.
Which studies investigates the MAOA gene and what did they find?
Brunner studies a large Dutch family (28 male members) which had aggressive pasts of rape and attempted murder and were found to have abnormally low levels of MAOA in their brains and had the low-activity version of MAOA.
Stuart then studied 97 men who had been involved in inflicting violence and found that men with the low activity MAOA gene were found to be the most violent perpetrators of this violence and would inflict the worse injuries onto their partners.
What type of MAOA gene activity causes more aggressive behaviours?
Low activity
What did Frazzetto find for genetic factors in aggression?
They found that men who had not experienced trauma during the first 15 years of life did not have particularly high levels of aggression as adults even if they possessed the low activity MAOA gene.
Evaluation of genetic factors in aggression (MAOA gene)?
You cant easily separate environmental factors and genetic factors. An individual may possess a gene associated with aggression but that behaviour is only expressed if the environmental conditions are favourable - when they are provoked.
There are multiple genetic influences, in Stuarts study it was found that not only was the MAOA gene involved but so was a serotonin transporter gene, meaning that the combination is what was linked to the increased aggression.
In Rhee and Waldman’s meta analysis genetic factors had a greater influence on aggression when self reports were used in comparison to when parent and teacher reports were used - low validity.
What is the ethological explanation of aggression?
An explanation that seeks to understand the innate behaviour of animals by studying them in their natural environments. Main function of aggression is to be adaptive.
What is ritualistic aggression?
Lorenz found that fights between animals of the same species made little actual damage to the animal that they were fighting with. He found that intra-species aggression end with ritual appeasement displays that indicate defeat ( like a wolf exposing its neck at the end of a fight). This is adaptive as if every aggressive encounter ended with the death of one of the combatants this could threaten the existence of the species.
What is an innate releasing mechanism?
It is a built in physiological process like a network of neurons in the brain. An environmental stimuli will trigger the IRM which then releases a specific sequence of behaviours. This sequence is named a fixed action pattern.
