Psychology Revision – Aggression
Neuronal mechanisms in aggression STR – effects of drugs on serotonin
- The Limbic system → System beneath the cortex that → Berman et al – gave ppts either a placebo or a drug
is responsible for emotional behavior. It consists of the which increases levels of serotonin → the ppts then
amygdala, hypothalamus and hippocampus. played a game where they had to give different
amounts of shocks – ones with drug gave less intense
Amygdala: shocks – shows decrease in serotonin = decrease in
→ evaluates emotional importance of sensory stimuli aggression
and provides an appropriate response
→ Increased levels of activity in the amygdala leads to STR – influence of serotonin on animals
an increase in aggression. → Raleigh et al – monkeys were on experimental diet
→ Gospic et al – ppts brains scanned using fMRIs while consisting of high tryptophan (increases serotonin) and
they played a game showed decrease in aggressive behaviour compared to
Findings: when ppts rejected unfair offers in the game control grp.
(aggressive behaviour) they showed heightened CA – can’t generalise to humans
activity in the amygdala
→ Gospic then gave ppts benzodiazepine drug LIM – Role of other brain structures
(reduces arousal of autonomic system, so the → Coccaro et al – patients with psychiatric disorders
amygdala) the number of aggressive behaviour halved who show increased aggression are seen to have low
and so did the activity in the amygdala activity in the orbitofrontal cortex → this is against
Gospic et al and suggests that the amygdala might not
Serotonin: be the only structure in the limbic system that regulate
→ a neurotransmitter that has inhibitory and calming aggression
effects
→ Reduced levels of serotonin in the orbitofrontal
cortex leads to more aggressive behaviour
→ Mann et al – 35 healthy ppts given dexfenfluramine
drug which reduces serotonin levels
Findings: Males had higher aggressive scores in a
questionnaire
Hormonal mechanisms in aggression STR – Research support
→ Dolan et al
Testosterone → Dabbs et al
→ a hormone mainly produced by males associated CA – both studies are correlational and hard to
with developing sexual characteristics in men, establish one single source and filter out extraneous
including aggression variables
→ Increased levels of aggression lead to increase in
aggressive behaviours LIM – Dual-hormones hypothesis
→ Dolan et al – found positive correlation between → high levels of testosterone only increase aggressive
testosterone levels and aggressive behaviours in 60 behaviour when levels of cortisol are low – high
offenders in the UK – these offenders had a history of cortisol blocks effects of testosterone
violent behaviours → Pompa et al – studied teenage boys and found that
→ Dabbs et al – measured saliva testosterone of testosterone and cortisol are antagonistically working
violent and non-violent offenders on the influence of aggression
Findings: criminals that showed high testosterone
levels were the ones that committed violent crimes
Genetic Factor factors in aggression STR – Research Support
→ Brunner et al
MAOA gene → Mertins et al – found people with the high activity
variant gene of MAOA had low levels of aggression –
, → The MAO-A enzyme regulates the metabolism of in money distributing game the ppts with MAOA-H
serotonin in the brain and this enzyne id coded by the were more co-operative than the ones with MAOA-L.
MAOA gene CA – however found that even ppts with MAOA-L gene
→ MAOA gene controls activity of the enzyme behaved co-operatively when they acknowledged that
→ MAOA gene has a variant, MAOA-L, which is other ppts were acting calmly → shows effects of
associated with low levels of activity of the enzyme environment
and therefore serotonin
→High levels of MAOA-L leads to increased aggression LIM – Diathesis-stress model
→ Brunner et al – studied males in a Dutch family who → individual may have a gene for a behaviour but that
had a history of violent behaviours behaviour is only expressed when it is reinforced by
Findings: abnormally low levels of MAOA and high suitable Enviromental factors
levels of MAOA-L → Caspi et al – studied 500 male childrens and found:
- Ppts with MAOA-L were more likely to grow
Twin Studies up to be anti-social, only if they were
→ MZ twins share 100% of genetic material and DZ maltreated as kids
only 50% - Ppts with MAOA-H who were maltreated and
→ Coccaro et al – found concordance rates of 50% for those with MAOA-L who weren't maltreated
MZ and 19% for DZ twins for physical aggressive did not show anti-social behaviour
behaviour → 28% and 7% for verbal → Findings shows gene-environment interaction and
that genetic factors cannot be isolate
Adoption Studies
→ Hutchings and Medrick – significant amount of LIM – Measuring aggression
adopted boys in Denmark that had a criminal record → Studies usually use self-reporting methods such as
had biological parents with criminal records observations and questionnaires – subjective
→Rhee and Waldman – meta-analysis of adoption
studies and found:
- Genetic factors had greater effect on
aggression when self-reports were used
→ findings are invalid as they change based on the
technique used
LIM – Twin studies lack validity
→ all twin studies make the assumption that both
twins share the same environment
→ DZ twins share less similar environments and are
treated less equally meaning concordance rates are
inflated
Neuronal mechanisms in aggression STR – effects of drugs on serotonin
- The Limbic system → System beneath the cortex that → Berman et al – gave ppts either a placebo or a drug
is responsible for emotional behavior. It consists of the which increases levels of serotonin → the ppts then
amygdala, hypothalamus and hippocampus. played a game where they had to give different
amounts of shocks – ones with drug gave less intense
Amygdala: shocks – shows decrease in serotonin = decrease in
→ evaluates emotional importance of sensory stimuli aggression
and provides an appropriate response
→ Increased levels of activity in the amygdala leads to STR – influence of serotonin on animals
an increase in aggression. → Raleigh et al – monkeys were on experimental diet
→ Gospic et al – ppts brains scanned using fMRIs while consisting of high tryptophan (increases serotonin) and
they played a game showed decrease in aggressive behaviour compared to
Findings: when ppts rejected unfair offers in the game control grp.
(aggressive behaviour) they showed heightened CA – can’t generalise to humans
activity in the amygdala
→ Gospic then gave ppts benzodiazepine drug LIM – Role of other brain structures
(reduces arousal of autonomic system, so the → Coccaro et al – patients with psychiatric disorders
amygdala) the number of aggressive behaviour halved who show increased aggression are seen to have low
and so did the activity in the amygdala activity in the orbitofrontal cortex → this is against
Gospic et al and suggests that the amygdala might not
Serotonin: be the only structure in the limbic system that regulate
→ a neurotransmitter that has inhibitory and calming aggression
effects
→ Reduced levels of serotonin in the orbitofrontal
cortex leads to more aggressive behaviour
→ Mann et al – 35 healthy ppts given dexfenfluramine
drug which reduces serotonin levels
Findings: Males had higher aggressive scores in a
questionnaire
Hormonal mechanisms in aggression STR – Research support
→ Dolan et al
Testosterone → Dabbs et al
→ a hormone mainly produced by males associated CA – both studies are correlational and hard to
with developing sexual characteristics in men, establish one single source and filter out extraneous
including aggression variables
→ Increased levels of aggression lead to increase in
aggressive behaviours LIM – Dual-hormones hypothesis
→ Dolan et al – found positive correlation between → high levels of testosterone only increase aggressive
testosterone levels and aggressive behaviours in 60 behaviour when levels of cortisol are low – high
offenders in the UK – these offenders had a history of cortisol blocks effects of testosterone
violent behaviours → Pompa et al – studied teenage boys and found that
→ Dabbs et al – measured saliva testosterone of testosterone and cortisol are antagonistically working
violent and non-violent offenders on the influence of aggression
Findings: criminals that showed high testosterone
levels were the ones that committed violent crimes
Genetic Factor factors in aggression STR – Research Support
→ Brunner et al
MAOA gene → Mertins et al – found people with the high activity
variant gene of MAOA had low levels of aggression –
, → The MAO-A enzyme regulates the metabolism of in money distributing game the ppts with MAOA-H
serotonin in the brain and this enzyne id coded by the were more co-operative than the ones with MAOA-L.
MAOA gene CA – however found that even ppts with MAOA-L gene
→ MAOA gene controls activity of the enzyme behaved co-operatively when they acknowledged that
→ MAOA gene has a variant, MAOA-L, which is other ppts were acting calmly → shows effects of
associated with low levels of activity of the enzyme environment
and therefore serotonin
→High levels of MAOA-L leads to increased aggression LIM – Diathesis-stress model
→ Brunner et al – studied males in a Dutch family who → individual may have a gene for a behaviour but that
had a history of violent behaviours behaviour is only expressed when it is reinforced by
Findings: abnormally low levels of MAOA and high suitable Enviromental factors
levels of MAOA-L → Caspi et al – studied 500 male childrens and found:
- Ppts with MAOA-L were more likely to grow
Twin Studies up to be anti-social, only if they were
→ MZ twins share 100% of genetic material and DZ maltreated as kids
only 50% - Ppts with MAOA-H who were maltreated and
→ Coccaro et al – found concordance rates of 50% for those with MAOA-L who weren't maltreated
MZ and 19% for DZ twins for physical aggressive did not show anti-social behaviour
behaviour → 28% and 7% for verbal → Findings shows gene-environment interaction and
that genetic factors cannot be isolate
Adoption Studies
→ Hutchings and Medrick – significant amount of LIM – Measuring aggression
adopted boys in Denmark that had a criminal record → Studies usually use self-reporting methods such as
had biological parents with criminal records observations and questionnaires – subjective
→Rhee and Waldman – meta-analysis of adoption
studies and found:
- Genetic factors had greater effect on
aggression when self-reports were used
→ findings are invalid as they change based on the
technique used
LIM – Twin studies lack validity
→ all twin studies make the assumption that both
twins share the same environment
→ DZ twins share less similar environments and are
treated less equally meaning concordance rates are
inflated
