neural & hormonal mechanisms

• aggression


  -feeling of anger/hostility which often results in violent behaviour
• nature vs nurture stats

  -aggression is a dynamic interplay between nature & nurture

  -7% aggression = just nature

  -17% aggression = mostly nature

  -42% aggression = nature & nurture

  -24% aggression = mostly nurture

  -11% aggression = just nurture
• neural mechanisms

  -abnormalities in the amygdala (part of limbic system)

  -serotonin deficit in the orbitofrontal cortex (less self-control)

  -less grey matter in people with aggression

  -brain deficit in prefrontal cortex in people with antisocial personality disorder (more aggressive, cannot suppress anger)
• hormonal mechanisms

  -increased testosterone

  -decreased progesterone
• limbic system

  -subcortical structures in the brain (hypothalamus & amygdala)

  -involved in regulating emotional behaviour e.g., aggression
• amygdala

  -involved in assessing & responding to threats & challenges

  -links to fight or flight response

  -a more responsive amygdala = more aggression as people are more likely to see something as a threat and react to it
• Mark & Ervin (1970) - neural mechanism

  -a woman received painless electric probe simulation, her amygdala was enraged & she smashed her guitar against a wall

  -shows that a more active amygdala = more aggression

  -AO3: shows causation between the amygdala & aggression. Increases validity
• neural mechanism: serotonin

  -serotonin = inhibitory effect on the brain. Stops excitatory responses from happening (aggression & anxiety)

  -normal levels of serotonin in orbitofrontal cortex = less firing & more self-control.

  -low levels of serotonin in orbitofrontal cortex = more firing, more impulsivity (aggression) & less self-control.

  -Leonard (2008): serotonin is not just linked to aggression but other actions like impulsivity and over-eating.

  -Mann (1990): artificially decreases serotonin levels via drugs, responses to questionnaire = more aggressive (only in males).
• neural mechanisms - AO3

  Strength(s):

  -has use, can inform treatments e.g., drug therapy. Achieves psych aim of helping people.

  
  

  Weakness(es):

  -only considers serotonin & amygdala - could be other neurotransmitters/areas involved. Decreases validity.

  -reductionist as it ignores other factors e.g., environment. Decreases validity.
• hormonal mechanisms: testosterone & progesterone

  Testosterone:

  -male sex hormone responsible for developing masculine features

  -linked to aggression in males - males are statistically more aggressive than females

  -Dolan et al (1991): increased T = more aggression in male prisoners.

  
  

  Progesterone:

  -female hormone involved in the menstrual cycle. Lowest during & just after menstruation

  -thought to be involved in female aggression

  -relaxing hormone for women so when there are deficits in this there is more aggression
• hormonal mechanisms - AO3

  Weakness(es):

  -supporting research = correlational. Can't tell causation, decreases internal val.

  -supporting research = done on animals. Can't generalise to human aggression as humans are more complex.

  -dual hormone hypothesis: increased levels of T only cause aggression when there are lower levels of cortisol. Decreases validity of the hormonal mechanisms (T) as other hormones are involved.

  -Goozen (1997): natural experiment on transgender/sex-change ppts which found that testosterone governs aggression
• The limbic system involves the hypothalamus; hippocampus and the amygdala. The amygdala detects if something is a threat or not and can use past memories stored in the hippocampus to do this, if something is deemed to be a threat the nerve impulse is sent to the hypothalamus which activates the sympathetic nervous system and leads to aggression.