The four temperament theory is a proto-psychological theory which suggests that there are four fundamental personality types: sanguine, choleric, melancholic, and phlegmatic. Most formulations include the possibility of mixtures among the types where an individual's personality types overlap and they share two or more temperaments.

Sanguine:Optimistic, cheerful, sociable, outgoing, enthusiastic, talkative, and enjoys being around people.

Choleric:Dominant, decisive, opinionated, goal-oriented, ambitious, and can be assertive or even bossy.

Melancholic:Analytical, detail-oriented, thoughtful, sensitive, perfectionistic, and often prefers solitude.

Phlegmatic:Calm, easygoing, peaceful, diplomatic, patient, and adaptable.