Neural and hormonal mechanisms Flashcards
What are two neural influences in aggression?
What is one hormonal influence on aggression?
- The limbic system
- Serotonin
- Testosterone
What is the limbic system?
A system of subcortical structures in the brain associated with regulating emotional behaviour.
Which key structures make up the limbic system?
· Amygdala
· Hippocampus
· Hypothalamus
What is the amygdala?
Primary role is allowing organisms to assess and respond to environmental stimuli. Evaluates emotional importance of sensory information in the environment and prompts an appropriate response.
How is the amygdala implicated in aggression?
Increased reactivity/sensitivity of amygdala has been linked to increased aggression.
What is serotonin?
A neurotransmitter that has inhibitory, calming effects on the brain and aids in the regulation of bodily systems.
Explain how serotonin can influence aggression.
Reduced levels of serotonin remove the inhibitory, dampening effect and can lead to an increased firing of neurones which leads to more impulsive and aggressive behaviour.
What is testosterone?
A hormone produced mainly by the testes in males, associated with development of male primary and secondary sexual characteristics, but also implicated in aggression.
State and describe a study which shows support for the role of the amygdala in aggression
Gospic et al. (2011)
Gave participants a range of scenarios in an ultimatum game and their brains fMRI scanned. It was found that when participants rejected unfair offers, scans showed a heightened response by the amygdala.
When participants were given benzodiazepine which reduces the arousal of the limbic system activity in the amygdala decreased, as did the number of rejections (aggressive responses) by half.
Outline a study which shows the influence of serotonin on aggression. However…
Mann et al (1990) found that after taking an appetite suppressant to reduce serotonin levels, there was increased hostility and aggression scores on a questionnaire.
However, these findings are only correlational. We cannot conclude that the reduction in serotonin caused the increase in aggression
2 Strengths for neural mechanisms as an explanation for aggression ( 1 COUNTER)
Effect of drugs which increase serotonin activity. Berman et al (2009) gave 80 participants either a placebo or an SSRI to enhance serotonergic activity. Aggression was assessed during a reaction time game whereby provocation was manipulated through varying intensity electric shocks. Found drugged participants less aggressive versus placebo participants.
Animal evidence:
Raleigh et al (1991) fed monkeys a diet high in tryptophan which increases serotonin levels in the brain. This diet change resulted in decreased aggression and dominance in comparison to the monkeys not on this diet.
However, this lacks generalisability as humans are a more complex species.
1 Limitation of neural mechanisms as an explanation for aggression
Role of other brain structures:
It has been found that the amygdala does not operate in isolation in determining aggression. It functions in tandem with the orbitofrontal cortex which is a non-limbic brain structure. The OFC has been found to be implicated in impulse regulation and inhibition of aggressive behaviours.
Coccaro et al (2007) found that patients with psychiatric disorders which feature aggressive behaviours had reduced OFC activity. This reduction disrupts the OFCs impulse control function, leading to increased aggression.
Suggests the regulation of aggression involves more than just the activity of a singular structure.
Outline 2 studies that show support for the role of testosterone in aggression
Dolan et al (2001)
Found a positive correlation between testosterone levels and aggressive behaviour in 60 UK offenders with a history of violence.
Dabs et al (1987) measured salivary testosterone in criminals. Those with higher testosterone levels had a history of primarily violent crimes whereas those with the lowest levels committed only non-violent crimes.
1 Strength and 1 limitation for hormonal mechanisms as explanations for aggression
- Dolan et al 2001, Dabbs et al 1987
- Other hormones involved:
Mehta and Josephs (2010) proposed the dual-hormone hypothesis whereby testosterone is positively associated with status seeking tendencies including aggression especially in individuals with low levels of cortisol. Cortisol regulates stress reponse.
Pampa et al (2007) found found basal testosterone correlated positively with aggression and violence among low cortisol but not high cortisol delinquent adolescents. Combined activity of testosterone and low cortisol a better predictor than either hormone alone.
