Two-factor models of personality

The two-factor model of personality is a widely used psychological factor analysis measurement of personality, behavior and temperament. It most often consists of a matrix measuring the factor of introversion and extroversion with some form of people versus task orientation. The Roman physician Galen mapped the four temperaments (sanguine, phlegmatic, choleric and melancholic) to a matrix of hot/cold and dry/wet, taken from the four classical elements. Two of these temperaments, sanguine and choleric, shared a common trait: quickness of response (corresponding to "heat"), while the melancholic and phlegmatic shared the opposite, a longer response (coldness). The melancholic and choleric, however, shared a sustained response (dryness), and the sanguine and phlegmatic shared a short-lived response (wetness). This meant that the choleric and melancholic both would tend to hang on to emotions like anger, and thus appear more serious and critical than the fun-loving sanguine, and the peaceful phlegmatic. However, the choleric would be characterized by quick expressions of anger (like the sanguine, with the difference being that the sanguine cools off); while the melancholic would build up anger slowly, silently, before exploding. Also, the melancholic and sanguine would be sort of "opposites", as the choleric and phlegmatic, since they have opposite traits. These are the basis of the two factors that would define temperament in the modern theory. In the last few centuries, various psychologists would begin expressing the four temperaments in terms of pairs of behaviors that were held in common by two temperaments each. Ivan Pavlov (1849–1936), from his work with dogs, came up with the factors of "passivity" (active or passive) and "extremeness" (extreme response or moderate response). His view of the temperaments in dogs was: The Melancholic type (Weak inhibitory): categorized as "weak" dogs; Choleric type (Strong excitatory): strong, unbalanced, easily aroused (excitable); Sanguine type (Lively): strong, balanced, mobile; Phlegmatic type (Calm imperturbable): strong, balanced, sluggish.