Explain and evaluate the influence of Testosterone on aggression

Testosterone is suggested to be a strong influencer of aggression in males. This is a male sex hormone that is produced within the leydig cells of the testes and the adrenal cortex located within the brain. There are two models which attempt to explain testosterone's influence on aggression. The basal model suggests that more testosterone in individuals leads to them being more dominant and competitive. Individuals then use aggression to achieve the dominance. Therefore, the dominance is a product of the testosterone. The reciprocal model states the opposite: stating that predetermined dominance levels within personality change testosterone levels and this therefore determines aggression. We can support the influence of testosterone with Wagner who did research on mice that had been castrated and found that their aggression reduced. He then later gave them artificial testosterone and their aggression increased again, suggesting that testosterone played a strong role in the aggression. There is additional research by Nelson who found a positive correlation between aggression and testosterone levels in prisoners. However, a major issue with this theory is that no research has been conducted on women and so it is gender biased. This does not allow us to apply this theory to females as there is no strong evidence. Additional criticism comes from Simpson who suggested that testosterone is only 1 factor influencing aggression and environmental factors sometimes even correlate stronger with aggression. This includes factors such as noise and temperature.