neural and hormonal mechanisms Flashcards
what is proactive aggression?
- Organised, cold-blooded, and motivated by the anticipation of reward
- Is goal-directed behaviour designed to achieve an objective beyond physical violence
what is reactive aggression?
Impulsive response to a perceived threat or provocation, often associated with high emotional arousal, anxiety, and anger.
What is the limbic system
Subcortical (middle) structures in the brain (hypothalamus, amygdala) involved in regulating emotional behaviour including aggression.
Amygdala
Plays a key role in how mammals assess and respond to environmental threats
The reactivity of the amygdala is an important predictor of aggressive behaviour
- The more responsive the amygdala, the more aggressive the person is.
What was the procedure into Gospic et al research into the role of the amygdala?
- Some participants were subjected to mild provocation.
- When participants reacted aggressively fMRI scans showed a fast and heightened response by the amygdala.
What was the findings into Gospic et al research into the role of the amygdala?
A benzodiazepine drug (which reduces arousal of the autonomic nervous system) taken before the provocation led to two effects:
- It decreased the activity of the amygdala
- Halved the number of rejections (ie. reduced aggression)
What are the neural mechanisms of aggression
Orbitofrontal cortex and Serotonin
What is serotonin and its effects on aggression?
Serotonin is a neurotransmitter that has widespread inhibitory effects in the brain, i.e. it slows down and calms neuronal activity.
- Reduced Serotonin in the orbitofrontal cortex (OFC) has been linked to aggression
What did Denson find about normal levels of serotonin?
Normal levels of serotonin in the orbitofrontal cortex (OFC) are linked with, Reduced firing of neurons which in turn is associated with greater behavioural self-control.
What did Denson find about decreased levels of serotonin?
Decreased serotonin (deficiency) disrupts this mechanism
- Reducing self-control and leading to an increase in impulsive behaviour including aggression
What is the procedure of Berman’s study into neural mechanisms in aggression?
- P’s either a placebo or a dose of Paroxetine (which increases the production of serotonin).
- Ps were asked to take part in a game whereby they could give electric shocks (due to provocation)
What were the findings of Berman’s study into neural mechanisms in aggression?
- They found that those who took paroxetine (and had naturally higher levels
of aggression) gave less shocks than those who took the placebo. - Indicating that higher levels of serotonin result in lower levels of aggression.
What is a limitation of limbic system explanation?
P: One limitation of the limbic explanation is more recent research showing that non-limbic brain structures are also involved in aggression.
EE: Limbic structures (e.g. the amygdala) function together with the orbitofrontal cortex (OFC), which is not part of the limbic system. The OFC is involved in impulse regulation and inhibition of aggressive behaviour. According to Coccaro et al. (2007), OFC activity is reduced in those psychiatric disorders that feature aggression. This reduced activity disrupts the OFC’s impulse-control function, which in turn causes aggressive behaviour.
L: This shows that the neural regulation of aggression is more complex than theories focusing on the amygdala suggest.
What is a strength of serotonin in regards to drugs?
P: One strength of the serotonin explanation is research into the effects of drugs.
EE: Drugs (e.g. paroxetine) that increase serotonin have been found to also reduce levels of aggressive behaviour. Berman et al. (2009) gave participants either a placebo or a dose of paroxetine.
The participants then took part in a lab-based game that involved giving and receiving electric shocks in response to provocation (e.g. insults). The paroxetine group consistently gave fewer and less intense shocks than the placebo group.
L: This study is evidence of a causal link between serotonin function and aggression.
What are the hormonal mechanisms in aggression?
- Progesterone
- Testosterone
What is testosterone?
The male sex hormone testosterone is an androgen responsible for the development of masculine features.
- Testosterone has a role in regulating social behaviour via its influence on certain areas of the brain implicated in aggression.
what did Daly and Wilson find out about testosterone levels in men men?
Men become more aggressive towards other men at a time in development (after age 20 years) when testosterone levels are highest.
what was Glammanco’s Castration study about?
- Castration on animals show that removing the testes (source of testosterone) reduces aggression in the males of many species.
- Giving injections of testosterone to the same animals restores aggressive behaviour
What is Dolan study on Violent offenders.
- Found a positive correlation between testosterone levels and aggressive behaviours in a sample of 60 offenders (men) in UK maximum security hospitals.
- These men mostly had personality disorders and histories of impulsively violent behaviour
what is the role of progesterone in aggression?
- levels vary in menstrual cycle
- low levels linked with increased aggression in women.
- Ziomkiewicz et al. (2012) found a negative correlation between progesterone levels and self-
reported aggression
what is the research supporting animal studies?
P: One strength of hormonal explanations is support from research with non-human animals.
EE: Giammanco et al’s (2005) review of studies confirms the role of testosterone. E.g. , in male rhesus macaque monkeys there is an increase in both testosterone
levels and aggressive behaviour during the mating season.
In rats, castration of males reduces testosterone and also mouse-killing behaviour. Injecting female rats with testosterone increases mouse-killing.
L: These findings show the role of testosterone in a range of animal species.
what is a limitation of testosterone as an hormonal explanation?
P: One limitation is mixed evidence of the link between testosterone and aggression in humans.
EE: Carré and Mehta (2011) developed a dual-hormone hypothesis to explain why. They claim that high levels of testosterone lead to aggressive behaviour but only when levels of cortisol are low. When cortisol is high, testosterone’s influence on aggression is blocked. The hormone cortisol plays a central role in the body’s response to chronic stress. Suggesting this is an incomplete explanation.
L: Therefore the combined activity of testosterone and cortisol may be a better predictor of aggression than either hormone alone.
what is a limitation of the use of animal studies?
P: One limitation may be the use of animal research.
EE: Carré and Mehta (2011) found that aggressive behaviour in humans is more complex than in other mammals. Their findings on the link between testosterone and cortisol can only be applied to human aggression. Also, cognitive factors play a greater role in human aggression, especially in ‘cold- blooded’ proactive aggression as it involves using aggression to achieve some goal, it means planning and thinking about the consequences of aggression.
L: Therefore, animal studies can help us understand hormonal influences on aggression but findings must be treated cautiously because human aggression is more complex.
