Compare two or more explanations of human aggression (16 marks)

COMPARE TWO OR MORE EXPLANATIONS OF HUMAN AGGRESSION (16 MARKS)

Neural and hormonal mechanisms in aggression

A01

Neural mechanisms in aggressions

Limbic System

• Subcortical structures in the brain (including the hypothalamus and amygdala) are thought to be directly involved in regulating emotional behaviour.
• Papez (1937) and Maclean (1952) identified the limbic system as including the cingulate gyrus (involved in processing emotions and behaviour regulation), hypothalamus, fornix (acts as a major output tract of the hippocampus) and the amygdala.
• Speed and sensitivity of the limbic system responses to stimuli are important predictors of aggressive behaviour. 
• The amygdala plays a key role in how we assess and respond to environmental threats and challenges. 
• The reactivity in humans has proven to be an important predictor of aggressive behaviour.
• Gospic et al. (2011) carried out brain scans (fMRI) on participants in a lab-based game that provoked aggression. 
• The scans showed aggressive reactions were associated with a fast and heightened response by the amygdala. 
• Benzodiazepine (which reduces the arousal of the autonomic nervous system) taken before the game halved the number of aggressive reactions and also decreased amygdala activity. 

Serotonin

• Serotonin is a neurotransmitter involved in communication of impulses between neurons, it has a widespread inhibitory effect on the brain.
• Normal levels of serotonin in the oribitofrontal cortex are inhibitory and are linked with the reduced firing of neurons, which is associated with a greater degree of behavioural self-control - means no aggressive behaviour.
• Decreased levels of serotonin disturbs this mechanism, reducing self-control and increases impulsive behaviours, including aggression - low levels can lead to aggressive behaviour.
• Vikkunen et al. (1994) compared levels of serotonin metabolite (breakdown by-product, 5-HIAA) in cerebrospinal fluid of violent impulsive and non-impulsive offenders.
• Found that levels were significantly lower in impulsive offenders - disturbance of this pattern implies disruption of serotonin functioning.

Hormonal mechanisms in aggression

Testosterone

• Testosterone is an androgen (what controls the development of male characteristics) produced in male testes and in the adrenal cortex.
• Helps to regulate social behaviour via influence of areas in the brain involved in aggression.
• Dolan at al. (2001) found a positive correlation between testosterone levels and aggressive behaviours in male offenders in UK maximum security hospitals.
• Most suffered from personality disorders and had histories of impulsively violent behaviour.
• Giammanco et al. (2005) animal studies - showed experimental increases in testosterone are related to aggressive behaviour.
• In juxtaposition, testosterone decrease leads to reduction in aggression in castration studies.

Genetic factors in aggression

AO1

Twin studies

• <span>Coccaro et al (1997)</span> studied adult male monozygotic (MZ) and dizygotic (DZ) twins.
• …