Neural and Hormonal Mechanisms in Aggression

Question 1

What parts of the brain make up the limbic system?

Answer 1

• Hypothalamus
• Amygdala
• & parts of the hippocampus

the part of the brain involved in our emotional & behavioural responses especially when it comes to behaviours we need for feeding, reproduction, caring for our young & fight or flight

Question 2

Define the limbic system.

Answer 2

• A group of interconnected brain structures that help regulate your emotions and behavior

Question 3

What research was conducted into the amygdala and aggression?

Answer 3

• Potegal et al (1996)
• Found that stimulation of the amygdala increases aggression and leisioning of this area reduces aggression in hamsters
• Groves & Schlesinger (1982)
• Found that surgical removal of the amygdala reduced human aggression in previously violent individuals. However a side affect of this type of surgery is the loss of emotion, initiative & enthusiasm

Question 4

What research was conducted into the hypothalamus and aggression?

Answer 4

• Flyn (2006)
• Stimulating the lateral area of the hypothalamus in cats led to predatory aggression
• Whereas rage type aggression was elicted by stimulation of the medial (middle) hypothalamus

This suggests that different types of aggression are controlled by different brain areas

Question 5

What actually are neural mechanisms?

Answer 5

• Mechanisms related to the nervous system (both central & peripheral)

Question 6

What is serotonin & its role?

Answer 6

• A neurotransmitter that has widespread inhibitory effects on the brain
• It slows down & calms neuronal activity

Question 7

How do the different levels of serotonin work?

Answer 7

• 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
• Decreased serotonin (deficiency) disrupts this mechanism, reducing self control and leading to an increase in impulsive behaviour including aggression

Question 8

What research has been conducted to support the idea of low levels of serotonin and aggression

Answer 8

• Davidson et al (2000)
• Suggested that a reduction of serotonin increases the incidence of showing aggressive behaviour as the levels of serotonin in violent criminals were markedly lower than in the non-violent criminals
• Linnolia et al
• Reported that low levels of serotonin are linked to impulsivity and explosive acts of institutionalised patients to reduce their aggressive tendencies

Question 9

What is testosterone?

Answer 9

• A male sex hormone which is an androgen & is responsible for the development of masculine features

Question 10

What research studies were conducted on testosterone within aggression?

Answer 10

• Daly & Wilson - Males become more aggressive towards other males at a time in development (after age 20yrs) when testosterone levels are at its highest
• Giammanco- Castration studies of animals show that removing the testes reduces aggression in the males of many species - giving injections of testosterone to the same animals restores aggressive behaviour

Question 11

What research evidence is there where progesterone looks into levels of aggression?

Answer 11

• Researchers found a negative correlation between progesterone levels and self reported aggression
• This suggests that low levels of progesterone are linked to increased aggression in women

Question 12

Give one limitation of the limbic explanation.

Answer 12

• More recent research showing that non-limbic brain structures are also involved in aggression
• Limbic strucutres e.g. the amygdala function together with the orbitofrontal cortex which is not part of the limbic system
• The OFC is involved in impulse regulation & inhibition of aggressive behaviour
• This shows that the neural regulation of aggression is more complex than theories focusing on the amygdala suggest

Question 13

Give one strength of the serotonin explanation.

Answer 13

• OS is the research into the effects of drugs.
• Drugs that increase serotonin have been found to also reduce levels of aggressive behaviour.
• Drugs e.g. (paroxetine) that increase serotonin have been found to also reduce levels of aggressive behaviour.
• Mitchell Berman et al gave participants either a placebo or a dose of paroxetine- the ppts then took part in a lab based game that involved giving \7 recieving electric shocks in response to provocation (insults).
• The paroxetine group consistently gave fewer & less intense shocks than the placebo group
• This study is evidence of a casual link between serotonin function & aggression.

Question 14

Give one strength of hormonal research support.

Answer 14

• OS is support from research with non-human animals
• Mark Gimmancos review of studies confirms the role of testosterone
• e.g. in male macaque monkeys there is an increase in both testosterone levels & aggressive behaviour during the mating season
• In rats castration of males reducing testosterone increases mouse-killing.
• These findings show the role of testosterone in a range of animal species

Question 15

Give one limitation of the hormonal hypothesis.

Answer 15

• OL: Is mixed evidence of the link between testosterone & aggression in humans
• Researchers developed a dual-hormone hypothesis to explain why.
• They claim high levels of testosterone lead to aggressive behaviour but only when levels of cortisol are low.
• When cortisol is high testosterone’s influence on the aggression is blocked.
• The hormone cortisol plays a central role in the bodys response to chronic stress
• Therefore combined activity of testosterone & cortisol may be a better predictor of aggression than either hormone alone.