The biological explanation for aggression states that aggression is innate behavior in people and the environment around them does not cause it. Neurotransmitters in the brain, chemicals that allow impulses to be transmitted from one area to another, can be used to explain why some people are aggressive. There is evidence to suggest that the neurotransmitters serotonin and dopamine are linked to aggression, low levels of serotonin and high levels of dopamine. Serotonin is a hormone that makes you happy; it helps to reduce aggression and inhibits responses to emotional stimuli that could potentially lead to aggression. Low levels of aggression are associated with increased susceptibility to impulsive behavior, aggression and violent suicide. Some drugs can alter the serotonin levels in our bodies and cause increased aggression levels. Dopamine is another hormone in the body that is associated with aggression, however the link between dopamine and aggression is not as well established as the link between serotonin and aggression. Increased levels of dopamine via amphetamines can be linked to increased aggression levels. Anti-psychotic drugs that are used to reduce levels of dopamine in the brain reduce aggressive behavior in people.
These explanations for aggression can be evaluated using studies, one study by Mann et al looked at what effects depleting levels of serotonin by taking dexfenfluramine does to individuals. Using a questionnaire the study found that reduced levels of serotonin due to dexfenfluramine increased aggression and hostility in males but not in females. This shows us that serotonin does have some effects on levels of aggression but because it only affected males there must be another factor that that is only apparent in males that enhancing the effects of the serotonin. However one issue with this study is that the levels of aggression were assessed using questionnaires, these