One of the controversies that has persisted throughout the history of psychology has to do with the extent to which personality is learned or inborn. Although there is considerable evidence supporting the impact of early childhood relationships on adult personality, there is also solid evidence that many personality traits—such as shyness, extraversion, sensation-seeking, and even impulse control—are genetically determined. In the early 1990s, Robert Cloninger proposed that personality reflected the combination of both temperament and character. He defined temperament as inborn, genetically transmitted traits that influence the way we process information. He proposed three specific traits of temperament: harm avoidance, novelty seeking, and reward dependence. He later added persistence, which refers to the tendency to persevere toward a goal despite setbacks.

Both harm avoidance, which involves the tendency to avoid risk, and novelty seeking, which involves the tendency to seek out stimulation even if it involves risk, have received considerable support in the literature and do seem to have a genetic component. Harm avoidance may be mediated by the neurotransmitter serotonin, while novelty seeking has been associated with both dopamine and norepinephrine.