Neural + hormonal factors

• Proactive aggression is a planned method of getting what you want
• Reactive aggression is angry and impulsive, and accompanied by physiological arousal
• reactive aggression is responsible for a greater proportion of social problems
• neural mechanisms are related to neurons such as large neural structures or the actions of neurotransmitters
• The limbic system is a set of neural structures located in the centre of the brain
• The limbic system includes the hypothalamus and amygdala
• amygdala and hypothalamus are key to aggressive responses, and involved in regulating emotional behaviour such as aggression
• Amygdala is linked to the production of aggressive behaviours
• The amygdala has a key role in how organisms asses and respond to environmental threats
• FMRI’s show an increased activity of the amygdala during aggressive responses
• If amygdala malfunctions as a result of a tumour, damage or atypical development, then testosterone levels can be raised, making aggression more likely
• the amygdala plays a vital role in us monitoring and responding to cues in the environment (fight vs flight)
• Hypothalamus has a role in expressing emotional responses and can trigger aggressive behaviour as part of teh fight or flight response
• the amygdala and hypothalamus communicate with the

  orbitofrontal cortex
• Orbitofrontal cortex controls decision making which attempts to control aggression produced by the limbic system
• serotonin is an inhibitory neurotransmitter that is important in controlling aggressive impulses
• Low levels of serotonin in the orbitofrontal cortex have been associated with a reduced sense of self-control, which in turn causes aggression
• testosterone is an androgen (male sex hormone)
• high levels of testosterone is the reason for observed sex differences in aggression, with males showing a much higher level of aggression
• Testosterone levels are highest after the age of 20; men become more aggressive towards other men
• high levels of testosterone in the orbitofrontal cortex lowers its activity, which means it is less able to regulate aggressive impulses coming from the limbic system
• high levels of testosterone increase activity of the amygdala - triggers more aggressive impulses
• Castration studies of animals show that removing the testes reduces aggression in males of many species and giving injections of testosterone to the same animals restores aggressive behaviour
• Dolan et al found positive correlation between testosterone levels and aggressive behaviours in a sample of 60 male offenders - these males had a history of personality disorders + impulsively violent behaviours
• Researchers found a negative correlation between progesterone levels and aggression which suggests lower levels are present in more aggressive women
• cortisol is a key hormone in the body’s long term response to stress
• low levels of cortisol are associated with aggression because high levels of cortisol block the influence of testosterone on the body