Aggression is defined as intended injurious or negative behaviour (Bandura, 1978). It has many forms of aggression: physical, verbal, mental and emotional. The causes of aggression have been continuing debate either people innately aggressive or they learned to be aggressive. The argument for innately people aggressive is related to gender and possible biological reasons like chemical or hormonal. The arguments for aggression by learning are related to how they learned: observing, imitating and reinforcement from the surrounding.
The kind of aggression suffered and the amount of harm received by individual may influenced violence behaviour besides of gender factor (Storch, Masia-Warner, Crisp, & Klein, 2005). United Kingdom’s, Australia’s, and New Zealand’s psychologists found that female adolescents are less likely to be involved in violent behaviour than male adolescents (Carter, McGee, Taylor, & Williams, 2007; Owens, Daly, & Slee, 2005; Sutherland & Shepherd, 2002).
Terrie Moffitt et al (1998) analysed blood serotonin level of 21-year-old people. They found that aggressive men's mean serotonin level was 0.48 standard deviations higher the males standard as a group. Besides, mean serotonin level of aggressive men’s exceeds 0.56 SD the mean of men who are not aggressive. The result of the experiment was focus on violence. High levels of blood serotonin but low brain levels of serotonin related to behaviour disorders. The reason for that is because of different in serotonin origin and role in blood and brain.
People argued when there is no relationship between serotonin levels and aggression among female. Therefore, they seem to think that may be due to testosterone (male sex hormone) level. Adult men have twice as much testosterone as women do. Normally males involved in crime during the early teens to mid-teens as the testosterone levels rise at that particular time. Research on the relation between testosterone level and...