Aggression - Biological Explanations Flashcards
Neural and hormonal explanations of aggression?
Brain structure - amygdala and pre frontal cortex
Neurotransmitters - dopamine and serotonin
Hormonal mechanisms - testosterone and cortisol
Biological explanations of aggression?
Neural and hormonal mechanisms
Genetic factors
Neurotransmitters in aggression?
Dopamine and serotonin
Hormonal mechanisms in aggression?
Testosterone and cortisol
How does damage to brain structure influence aggression?
Destroyed pre-frontal cortex = unregulated amygdala = aggression
Research on amygdala?
Narabyashi et al
Narabyashi et al?
43/51 patients with a destroyed amygdala showed reduced aggression
Case study on brain structure?
Phineas gage
Research on pre frontal cortex?
Anderson et al
Anderson et al?
Damage to the pre frontal cortex in infancy = aggression
Role of serotonin in aggression?
Low = aggression
Inhibits responses to emotional stimuli, so low levels are associated with impulsivity, aggression etc.
Research on serotonin?
Mann et al
Mann et al?
Gave 35 subjects dexflenfluaramine (lowers serotonin) and saw increased hostility and aggression scores in males
Role of dopamine in aggression?
High = aggression
Research on dopamine?
Lavine
Lavine?
Amphetamines (increase dopamine) increased aggressive behaviour
Strengths of neurotransmitters?
Supporting research
Effective treatments
Supportive research for neurotransmitters?
Scerbo and Raine
Weaknesses of neurotransmitters?
Is dopamine a cause or effect?
Animal studies
Scerbo and Raine? (Serotonin)
Meta-analysis of 29 studies found low serotonin levels in individuals described as aggressive
Research on cause/effect with dopamine?
Scerbo and Raine
Scerbo and Raine? (Dopamine)
Found no significant rise or fall in dopamine in individuals described as aggressive
Couppis and Kennedy?
Reward pathway in mice that uses dopamine as a positive reinforcer in aggressive events
Example of animal studies on neurotransmitters?
Raleigh et al
Raleigh et al?
Put vervet monkeys on a diet of tryptophan (raises serotonin) and found decreased aggression
Effective treatments due to neurotransmitters?
Bond
Bond?
Antidepressant drugs elevate serotonin levels to reduce irritability and impulsive aggression
Role of testosterone in aggression?
High testosterone = aggression
What is testosterone?
Male sex hormone which acts on brain areas associated with aggression from young adulthood onwards
Research on testosterone?
Dabbs et al
Dabbs et al?
Saliva of 692 male prisoners, high levels of testosterone in violent offenders
Research on testosterone in animals?
Beeman
Beeman?
Castrated male mice and found reduced aggression
Role of cortisol in aggression?
Low cortisol = aggression
What does cortisol do?
Mediates other hormones such as testosterone and increases anxiety and social withdrawal
Research on the challenge hypothesis?
Wingfield et al
Wingfield et al?
Testosterone rises in response to challenges
Strengths of hormonal mechanisms?
Real life applications
Supporting evidence
Weaknesses of hormonal mechanisms?
Gender bias
Aggression or dominance?
Real life applications of hormonal mechanisms?
Klinesmith et al
Klinesmith et al?
Can explain why presence of guns = increased aggression - males interacting with a gun for 15 minutes showed sig greater salivary testosterone and aggression than with a toy
Gender bias in hormonal mechanisms?
Archer et al
Archer et al?
Association between testosterone and aggression is higher for female than male samples
Research on dominance v aggression?
Mazur
Mazur?
Individuals act aggressively when intending to inflict injury, but dominantly when they want to achieve money or status
Support for hormonal mechanisms?
Mcburnett et al
Mcburnett et al?
Boys with consistently low cortisol levels began antisocial acts younger and exhibited 3x number of aggressive symptoms
Genetic factors in aggression?
Twin and adoption studies
Genetics and violent crime
MAOA
Twin study on aggression?
Coccaro et al
Coccaro et al?
50% of variance in direct aggression due to genes
Adoption study on aggression?
Hutchins and mednick
Hutchings and mednick?
Looked at 14000 adoptions and found criminal convictions in those who had biological parents who’d had them
What is MAOA?
The ‘warrior gene’ that produces proteins involved in aggression and regulates the metabolism of serotonin
Influence of MAOA on aggression?
Low MAOA = low serotonin = aggression
Research on MAOA?
Brunner et al
Brunner et al?
Violent and aggressive Dutch family had abnormally low MAOA
View on influence of genetics on violent crime?
There’s no gene, just inherited characteristics that place them at risk
Research on genetics and violent crime?
Brennan and mednick
Brennan and mednick?
Genetic influence is only significant in property crime, not violent
Strengths of genetic factors?
Research support
Weaknesses of genetic factors?
Individual differences
Gene-environment interaction
Inconclusive
Support for genetic influences?
Miles and Carey
Miles and Carey?
Meta-analysis of 24 twin and adoption studies found genetic influence could account for up to 50% of variance in aggressive anti social behaviour
Individual differences in genetic influences?
Rhee and Waldman
Rhee and waldman?
Meta-analysis of 51 twin and adoption studies found several variables moderated influence, eg the older you get the less influence rearing environment has and the more genes have
Gene environment interaction research?
Caspi et al
Caspi et al?
Those with low levels of MAOA were significantly more likely to exhibit anti social behaviour but only if they’d been maltreated as children
Research on genetic factors being inconclusive?
Walters
Walters?
Only found low to moderate correlation between heredity and crime, with better designed and more recent studies providing even less support
