neural and hormonal mechanisms

Question 1

what are the neural mechanisms in aggression?

Answer 1

• the limbic system
• NT serotonin

Question 2

what is the limbic system?

Answer 2

• the limbic system plays a key role in how an organism responds to environmental threats
• involved in reactive aggression
• it is a key factor to whether we respond aggressively or not to an external stimulus

Question 3

what are the components of the limbic system?

Answer 3

• the hypothalamus
• the hippocampus
• the amygdala
• the cingulate gyrus

Question 4

what is the role of the hypothalamus in aggression?

Answer 4

• regulates the autonomic nervous system, which regulates responses to emotional circumstances
• damage to this area can result in inappropriate aggressive responses to perceived threats

Question 5

what is the role of the amygdala in aggression?

Answer 5

• responsible for attaching emotional significance to sensory info
• in animals, if this is electrically stimulated, they respond aggressively (snarling)
• if the same areas are surgically removed, the animal no longer responds aggressively

Question 6

what is the role of the pre-frontal cortex in aggression?

Answer 6

• the prefrontal cortex is crucial for regulating social behaviour and aggressive responses.
• damage to the prefrontal cortex would reduce the inhibition of the amygdala resulting in higher levels of aggression.

Question 7

what is the most important structure of the limbic system?

Answer 7

the amygdala

Question 8

what 2 researchers conducted research on the amygdala on aggression?

Answer 8

• Egger + Flynn
• Wong

Question 9

outline Egger + Flynn’s research into the amygdala

Answer 9

• introduced a rat to a cat’s cage and found that the 2 animals would ignore each other
• when the amygdala was electrically stimulated, the cat immediately attacked and killed the rat (reactive aggression)
• they found that stimulation of different parts of the amygdala caused the cat to ignore the rat and attack the experimenter

Question 10

what does Egger and Flynn’s research demonstrate?

Answer 10

the importance of the limbic system in regulating aggressive responses

Question 11

outline Wong’s research into the amygdala

Answer 11

• conducted MRI scans on 19 male violent criminals in Broadmoor hospital
• compared the size of the amygdala with 20 ‘normal’ control subjects
• he found that the volume of the amygdala was significantly smaller in the 19 violent criminals
• supporting the role of the amygdala and limbic system in aggression

Question 12

what is serotonin?

Answer 12

a NT that enables impulses in the brain, to be sent from one area of the brain to another

Question 13

what is serotonin’s role in aggression?

Answer 13

• has an inhibitory effect on impulsive behaviour
• normal levels = calming and inhibits response to emotion
• low levels = unable to control impulsive behaviour (aggression, suicide)

Question 14

how have drugs shown the role of serotonin in aggression?

Answer 14

drugs that alter serotonin levels are shown to increase aggressive behaviour e.g. dexfenfluramine

Question 15

who researched serotonin in aggression?

Answer 15

Berman

Question 16

outline Berman’s research into serotonin

Answer 16

• ppt’s were placed in a scenario where they had to administer electric shocks to other ppt’s
  1. experimental condition (paroxetine SSRI)
  2. control condition (placebo)
• experimental condition gave fewer and less intense shocks
• the study provides useful evidence of a link between serotonin function and aggression

Question 17

what is the main hormone associated with aggression?

Answer 17

testosterone - male sex hormone

Question 18

what is testosterone’s role in aggression?

Answer 18

• thought to influence aggression from young adulthood
• has a role in regulating social behaviour via its influence on certain areas of the brain related to aggression
• male testosterone rises in response to social challenges, such as threat to status, this then leads to an aggressive response to deal with the challenge

Question 19

how is testosterone linked to aggression in criminals?

Answer 19

criminals with a history of violent crimes have been found to have the highest levels of testosterone

Question 20

who researched testosterone in aggression?

Answer 20

Dabbs et al.

Question 21

outline Dabbs’ research into testosterone in aggression

Answer 21

• measured salivary testosterone in violent and non-violent criminals
• those with highest levels had a history of primarily violent crimes
• those with lowest levels had committed only non-violent crimes

Question 22

who researched testosterone in castrated animals?

Answer 22

Wagner

Question 23

outline Wagner’s findings

Answer 23

Wagner castrated mice and aggression levels went down, providing support to the theory that testosterone is implicated in aggression

Question 24

evaluation neural mechanisms: research support

Answer 24

ID: there is evidence supporting the negative correlation between increasing serotonin levels and decreasing levels of aggression.
Q: Berman et al. conducted research that supports this role
EV: ppt’s were placed in a scenario where they had to administer electric shocks to other ppt’s
1. experimental condition (paroxetine SSRI)
2. control condition (placebo)
he found that the experimental condition gave fewer and less intense shocks
AN: this suggests that increased levels of serotonin leads to lower levels of aggression, providing useful evidence of a link between serotonin function and aggression and improving the credibility of serotonin as an explanation

Question 25

evaluation neural mechanisms: correlation vs. causation

Answer 25

ID: issues of correlation vs causation
Q: although there are correlations between aggressive behaviour and limbic system abnormalities, this does not necessarily prove that limbic system abnormalities cause aggressive behaviour.
EV: for example, there are people with limbic system abnormalities who are not overly aggressive, and there are aggressive people with normal limbic systems.
AN: therefore, it is impossible to establish cause and effect, meaning the limbic system cannot conclusively be said to cause aggression. this reduces the internal validity of the claim

Question 26

evaluation hormonal mechanisms: alternative explanations of testosterone role

Answer 26

ID: there is conflicting research about the role of testosterone in aggression
Q: Carre and Mehta suggest that, through their dual-hormone hypothesis, testosterone does not work alone in determining aggression
EV: for example, they explain that testosterone has an antagonistic relationship with the stress hormone cortisol, where increased levels of aggression are associated with increased testosterone levels but only when cortisol is low.
AN: therefore, this implies that different hormones have different predictive values for aggression and are part of a system when developing aggressive behaviour.

Question 27

evaluation hormonal mechanisms: research support + ELAB

Answer 27

ID: there are supporting studies to suggest a positive correlation between testosterone and aggression.
Q: such as Dabbs’ research into criminal aggression
EV: for example, he measured salivary testosterone in violent criminals and found that those with the highest levels of testosterone had a history of primarily violent crimes. however, those with lowest levels of testosterone had committed only non-violent crimes.
AN: this increases the validity of testosterone as an explanation for aggression
ELAB: however, prison studies can be criticised for lacking population validity as we cannot generalise studies on prisoners to the general population.