Lesson 1 - Neural mechanisms in aggression Flashcards
What are neural mechanisms?
Neural mechanisms are structures such as neurons, neural circuits and regions of the brain. They are also substances such as neurotransmitters and hormones. Neural mechanisms regulate aggression.
What is proactive aggression?
This is essentially planned or pre-meditated aggression.
What is reactive aggression?
This is an impulsive and angry reaction, usually accompanied by physiological arousal.
What three structures do the limbic system consist of?
Amygdala, hypothalamus and hippocampus
What does the limbic system do?
The limbic system plays a key role in how an organism responds to environmental threats. It decides whether an organism responds aggressively or not.
What does the hypothalamus do?
The hypothalamus is responsible for the regulation of the automatic nervous system, and this regulates responses to emotional circumstances. Therefore, damage to this area can result in an inappropriate and aggressive response to a perceived threat.
What does the amygdala do?
The amygdala is responsible for attaching emotional significance to sensory information.
What does the prefrontal cortex do?
The prefrontal cortex regulates social behaviour and aggressive responses. Damage to the prefrontal cortex would reduce the inhibition of the amygdala, resulting in higher levels of aggression.
What is serotonin?
Serotonin is a neurotransmitter that has widespread inhibitory effects in the brain, it slows down and calms neuronal activity. Consequently, serotonin has a calming influence, and low levels of serotonin means that people cannot control their impulsive and aggressive behaviour.
Evaluation of neural mechanisms in aggression - Animal Studies (Rhesus Monkeys)
Kluver and Bucy were researchers who used Rhesus monkeys. They removed the main areas of the limbic system. Amygdala, hippocampus and surrounding cortical areas.
These monkeys with these areas removed displayed an absence of emotional, motor and vocal reactions connected with fear or anger. Lesioned monkeys also did not understand the social understanding of group hierarchies and tried to fight larger and more dominant members of the group.
Evaluation of neural mechanisms - MRI scans
Wong et al undertook MRI scans of 19 violent male criminals and compared the size of their amygdala with 20 ‘normal’ control subjects. Wong found that the volume of the amygdala was significantly smaller in the violent criminals.
Evaluation of neural mechanisms - Animal studies (Rats)
Ferrari et al, allowed male rats to fight with another rat at a specific time for ten days. On the eleventh day, the rats were not allowed to fight. However it was found that the rat’s dopamine levels had raised by 65% and his serotonin levels were reduced by 35%. Even though the rat was not fighting, the rat’s brain chemistry changed to get ready for the combat.
Evaluation of neural mechanisms - Issues with animal studies
Using animals to provide evidence for aggression in humans is flawed. There are differences between human and animal physiology, even between humans and monkeys despite them possessing similar neural structures. We cannot be sure that the processes involved in mediating aggression in humans are the same as those in animals.
Evaluation of neural mechanisms - Issues with Wong
Wong’s research lacked population validity. The sample was relatively small, and this creates issues with generalising it to the wider population. The research can also be accused of gender bias, as this research was only done among males. This is beta bias as it was generalised to everyone.
Evaluation of neural mechanisms - Beta Bias
Wong’s study shows beta bias.
Mann administered the drug dexfenfluramine to 35 healthy adults. This drug is meant to deplete serotonin. The researchers then used a questionnaire to assess hostility and aggression levels. These rose among males but not among females. This shows that there is a clear difference between males and females when it comes to physiological factors, but this is not stated clearly enough.
