People are susceptible to boredom and seek an optimal level of arousal. Psychopathic individuals appear to be low on arousal, and they try to elevate this by seeking novelty and taking risks. Ways to achieve the optimal level by sensation-seeking include transgressions such as violence, arson and theft. These can have sexual associations and are sometimes accompanied by masturbation. Dopamine activation is at the basis of elevations in arousal. Serial lust killers commonly have a history of committing non-sexual crimes and arson. The internal organs of the body are under the control of the autonomic nervous system, high arousal being associated with dominance of the sympathetic branch and low arousal with the parasympathetic branch. Arousal is largely non-specific, and it takes a positive or negative value according to context. Switches can be made from negative to positive, which appears to lie at the basis of some lust killing.