Aggression: Neural

Aggression: Neural

1. Serotonin

   • • Serotonin reduces aggression. » Calming inhibitory effect on neural firing. » Can cause reduction in aggression behaviour. » Inhibits responses to emotional stimuli. • Low levels of serotonin remove inhibitory effect. » Less able to control impulsive behaviours. • Mann et al (1990) – gave 35 ppts dexfenfluramine (depletes serotonin). » Used questionnaire to assess hostility and aggression. » Aggression levels on the questionnaire increased after taking the drug – although only in males.
     • AO2: Supported by Raleigh et al (1991). • Studied vervet monkeys fed diet containing tryptophan (increases serotonin). » Diet high in tryptophan = decreased levels of aggression. » Diet low in tryptophan = exhibited increased aggressive behaviours. •Suggests the difference in aggression can be attributed to levels of serotonin.
       • AO3: • An issue with using vervet monekeys is the Lack of external validity (population validity) as it is animal research trying to explain human behaviours. • Humans have different, more complex cognitions. » Cannot be generalised to aggression in humans.
     • AO2: Also supported by Bond (2005). • Clinical studies of anti-depressants (elevate serotonin levels). • Reduced irritability and impulsive aggressive behaviours. • Suggests low levels of serotonin are associated with low impulse control and aggressive behaviours. » Drugs that clinically raise serotonin levels produce a concurrent lowering in aggression.
       • AO3: • Theory is deterministic. • Implies that anti-depressants cause a reduction in aggressive behaviours. • Anti-depressants are prescribed to treat depression not aggression. • Fails to consider free will - choose to be less violent and aggressive when irritable.
     • AO2: Supported by Badawy (2006). • Alcohol consumption disturbs metabolism of serotonin. » Heavy alcohol intake depletes serotonin in normal individuals. » Depletion may induce aggressive behaviours in susceptible individuals. • Explains why some people are aggressive after consuming large amounts of alcohol – low levels of serotonin.
       • AO3: • Ethical issues. • Unethical to make people consume large amounts of alcohol to see the effect on aggressive behaviours. • Ppts have no protection from harm – it is unhealthy and may become unpredictable.

2. Dopamine

   • • Dopamine increases aggressive behaviours. • Lavine (1997) – increased dopamine levels as result of taking amphetamines is associated with increased aggressive behaviour. • Dopamine is associated with pleasurable stimuli. » Release of dopamine during aggression reinforces aggressive behaviours. » Seek out encounters for rewarding sensation. • Buitelaar (2003) – inhibition of dopamine by anti-psychotic drugs decreased aggressive behaviours in violent delinquents.
     • AO2: Supported by Ferrari et al. • Allowed rat to fight at same time every day for 10 days. • 11th day rat did not fight but measured dopamine levels in brain. » Increased in anticipation of fight. • Experience changed animal’s brain chemistry by altering levels of dopamine consistent with aggressive behaviour.
       • AO3: • Theory is reductionist. • Only focuses on biological approach suggesting that neurotransmitter levels are the cause of aggression. • Fails to consider social learning theory. » Aggression learnt vicariously through models and repeated due to positive reinforcements e.g. attention from others.