Neural and Hormonal mechanisms in aggression Flashcards
What is the Brain’s limbic system?
Co-ordinates basic motivational/emotional states such as fear and aggression.
It contains two struggles that have been associated with aggression, the amygdala and the hippocampus.
What are the two structures in the brains limbic system associated with aggression?
Amygdala
Hippocampus
What is the Amygdala?
Amygdala evaluated the emotional importance of stimuli and produces an appropriate response.
What is the hippocampus?
Stores long-term memories of previous experiences with stimuli.
Therefore, animals may respond to other animals with aggression or fear depending on what they experienced in previous encounters.
What can damage to hippocampus cause?
May cause the amygdala to respond inappropriate to stimuli - thus, aggression may be displayed at inappropriate stimuli e.g. someone who is not a threat.
What evidence supports amygdala being associated with aggression?
Kluver ‘37
Pardini ‘14
What was the study conducted by Kluver ‘37 that supports the amygdala being associated with aggression?
Kluver found that removal of a dominant monkey’s amygdala caused it to lose its place at the top of the group hierarchy, and electrical stimulation of the amygdala will cause animals to automatically exhibit aggressive responses e.g. cat hissing.
What was the study conducted by Pardini ‘14 that supports the amygdala being associated with aggression?
A longitudinal study was carried out on males from childhood to adulthood. Aged 26, MRI scans revealed a negative correlation between aggression and amygdala size.
This was true even when other potential confounding variables were taken into account. This implies that the amygdala does play an important role in a accurately evaluating emotional stimuli and that lower amygdala volume may make inappropriate aggressive responses more likely.
What is Serotonin?
A neurotransmitter thought to inhibit behaviours. Therefore, if a person is provoked it will play a role in preventing the expression of an aggressive response.
Low levels of serotonin are linked to impulsive behaviours including aggression and violent suicide.
What do low levels of serotonin cause?
Low levels of serotonin are linked to impulsive behaviours including aggression and violent suicide.
What evidence supports that low levels of serotonin are linked to more impulsive behaviours?
Mann ‘90’ gave 35 volunteers dexfenfluramine a substance that reduces serotonin. The subjects self-reported increases in hostility and aggression, supporting the idea that aggression is at least partially biologically determined.
Raleigh (91) fed Vervet monkeys a diet either high or low in tryptophan to increase or decrease serotonin levels. High tryptophan diets decreased aggressive tendencies, whilst low tryptophan diets increased aggression.
What was the study that showed low levels of serotonin are associated with a failure to regulate emotions?
Lindberg 85’ compared the serotonin levels of 16 males convicted of violent crimes, 22 males who had attempted suicide and 39 healthy males.
Serotonin levels were measured from cerebrospinal fluid. Lowest levels of serotonin were found in those who had killed a partner or attempted suicide.
Suggesting that low levels of serotonin are associated with a failure to regulate emotions, resulting in negative emotions and impulsive behaviours.
What sex hormone is thought to influence aggression from young adulthood onwards due to its action on brain areas controlling aggression?
Testosterone
What evidence is there supporting the hormone Testosterone is related to aggression?
Wenger 79 noticed that after mice were castrated aggression, operationalised through counting biting attacks, decreased.
Klinesmith 06 had male students provide a saliva sample to measure testosterone, then either interact with a gun or a child’s toy for 15mins and then provide another saliva sample. Males who interacted with the gun showed significantly greater increases in testosterone than the control group.
What was the study by Dabbs 87 that suggested that testosterone levels are directly linked to aggression?
Dabbs measured the salivary tester one of violent and non-violent criminals and found that those with the highest testosterone levels had a history of primarily violent crimes and those with the lowest levels mainly non-violent crimes.
This suggests that testosterone levels are directly linked to aggression.
