Aggression

Papez and Maclean limbic system
More responsive amygdala = more aggression
Gospic 2011
Denson 2012
Virkkunen 1994

Linked to emotion
Hypothalamus
Amygdala
Hippocampus

Gave benzodiazepine (lowers ANS arousal)
Reduced amygdala acitivity
Reduced aggression

Lowered serotonin
Reduced self control
More impulsive
More aggression

Metabolite 5-HIAA breaks down serotonin
Violent impulsive offenders had low 5-HIAA compared to non violent

+ Evidence for serotonin
(- Only if there's pre-existing aggression)
- Amygdala = reductionist

Berman
A = placebo
B = paroxetine (increases serotonin)
Pps gave shocks in response to provocation
B = fewer shocks
- Only if pp had pré existing aggression

Coccaro
Psychopath-aggression link
Psychopaths = low activity in orbital frontal cortex
Not just amygdala

Aggression more likely in males than females
Daly and Wilson
Dolan 2001
Giammenco 2005
Low progesterone = more aggression in women

Males most aggressive when at testosterone peak
20y+

+ive correlation between testosterone and aggression
Looked at male offenders with violent impulsive behaviour

Non human animals
Castration reduced aggression
Testosterone injections increased aggression

- Testosterone = too simple
- Ignores nurture

Carre and Mehta
Dual hormone hypothesis
Increased testosterone and low cortisol = aggression
High cortisol tops testosterone aggression link

High amygdala activity/high testosterone doesn't determine aggression
Suggests behaviour cannot be controlled
SLT and frustration-aggression

XYY
Twin studies - Coccaro 1997
Adoption - Rhee and Waldmen
MAOA gene

Believed extra Y = increased aggression
Court-Brown believed XYY should remain hospitalised

Twin studies
Examined concordence of criminal behaviour
Physical aggression:
MZ = 50%
DZ = 19%
Verbal aggression:
MZ = 28%
DZ = 7%

Meta analysis of adoption
Genes account for 41% variation in aggression

Regulates serotonin
Reduced activity of MAOA enzyme = more aggressive
MAOA - L (low) = warrior gene
MAOA enzyme breaks down serotonin

Lea and Chambers 2007
56% New Zealand Maori males had MAOA gene (Maori warriors were fierce)
34% caucasians

+ MAOA support
( - Nature or nurture)
- XYY counter evidence
- Twin study support
- MAOA-L and serotonin link unclear

Brunner
28 men of a Dutch family
Repeatedly involved in aggression - rape, attempted murder, assault
Had MAOA-L and low MAO-A activity (the enzyme)
- Nature or nurture?

Theilgaard
XYY = taller but not aggressive

Nature or nurture
Not 100% for MZ

Low serotonin = increased aggression
MAOA-L = reduced break down of serotonin so more serotonin and reduced aggression
MAOA-L disrupts serotonin (not increase or decrease)

Desensitisation
Disinhibition
Cognitive priming

Continual exposure to a violent stimulus decreases the emotional and physiological response

Wiez and Earls 1995
Pps watched Straw Dogs
Increased acceptance of rape myths and reduced sympathy for victim and less likely to find rape defendent guilty
Males only showed this

Normal restraints loosened after exposure to media violence
Aggression and revenge normalised and seen an acceptable response

Aggression is rewarded
Games reward violence
Strengthens social norms

Aggressive media provides scripts for aggression, stored as memories
Automatic and direct our behaviour without awareness
Triggered when we encounter cues

+ Desensitisation support
+ Disinhibition support
- Low eco validity
- Reduces aggression?

Krahe
Violent vs non-violent films
Habitual violence watchers = low arousal and louder bursts of white noise to confed in unprovoked aggression test

Berkowitz and Alioto
Pps watched vengeance film
Gave more electric shocks to confed
Aggression is justifiable

Labs
Aggression measured using questionnaires/noise tasks
Aggression in public less likely due to fear of repurcussions

Watching violent media may satisfy aggressive drive
Catharsis
So in theory, should reduce aggression

TV
Computer games

Robertson 2013
Bandura 1963
Paik and Comstock 1994

Hours watching TV associated with adult convictions for aggressive/violent crimes
Watching TV = reduced social interaction and less education

Film of Bobo doll beaten by aggressive model
Children imitate

Meta analysis of 200 studies
+ice correlation between watching TV violence and antisocial behaviour
BUT TV only accounted for 10% variance of aggression

Bartholow and Anderson 2002
Delisi 2013

10 mins Mortal Kombat vs golf game
MK = high vol in white noise blast task

+ive correlation between time spent playing violent video games and aggressiom
Link is so significant, should be deemed a public health issue

+ SLT is a convincing theoretical framework
+ Support
- Methodologically weak
- Can't compare studies

Children likely to imitate aggressive behaviour
Especially when they identify with on-screen characters

Anderson
Meta analysis of 136 studies
Violent video games = increased aggression in men and women
Higher quality studies = more significant effect

Studies in meta analyses = poor quality and confounds
Correlation doesn't mean causation
Aggressive ppl may be drawn to violent games
Artificial tasks

Different measures of aggression
Delisi = violent behaviour
Bartholow and Anderson = White noise vol
Robertson = criminal convictions