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.

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages) This article may be confusing or unclear to readers. (December 2012) This article may lack focus or may be about more than one topic. (December 2012) This article's lead section may be too short to adequately summarize the key points. (May 2013) Some of this article's listed sources may not be reliable. (December 2012)

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.^[1] 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.^[2]

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.

This theory would also be extended to humans.

Alfred Adler (1879–1937) measured "activity" (connected with "energy") against "social interest", yielding the four "styles of life":^[3]

• Ruling or Dominant type: high activity, low social interest
• Getting or Leaning type: low activity, high social interest
• Avoiding type: low activity, low social interest
• Socially Useful type: high activity, high social interest

These he compared to the choleric, phlegmatic, melancholic and sanguine respectively.^[4]

Erich Fromm's (1900–1980) factors were acquiring and assimilating things ("assimilation"), and reacting to people ("socialization"). These two factors form four types of character, which he calls Receptive, Exploitative, Hoarding and Marketing.

Also deserving mention is a single scale invented in the 1940s by Karen Horney (1885–1952). This one dimension measured "movement" towards, against and away from people. This would result in the coping strategies, in which these three "neurotic" patterns would be paired with a fourth, "healthy" one called "movement with people". These would describe behaviors associated with both extroversion and reacting to people, in which people attempt to avoid getting hurt, by either distancing themselves from others or maintaining self-sufficiency and independence on one hand; or approaching others, attempting to control or exploit them, and otherwise gain power and recognition; or "give in" to them to gain acceptance and approval, on the other.

Other factors devised along the way measured other aspects of personality, mostly cognitive aspects. This would form a second strain of temperament theory, one which enjoys the most popularity today.

Immanuel Kant (1724–1804) defined his typology by a duality of the beautiful and sublime, and concluded it was possible to represent the four temperaments with a square of opposition using the presence or absence of the two attributes. He determined that the phlegmatic type has no interest in either the beautiful or the sublime, so there was an absence of both (sb). The melancholic had a feeling for both (SB), and the sanguine had a predominating feeling for the beautiful (sB), while the choleric, he determined after comparing with the melancholic, lacked a sense of beauty and had only a sense of the sublime (Sb).^[9]

Hans Eysenck (1916–1997) was one of the first psychologists to analyze personality differences using a psycho-statistical method (factor analysis), and his research led him to believe that temperament is biologically based. In his book Dimensions of Personality (1947) he paired Extraversion (E), which was "the tendency to enjoy positive events", especially social ones, with Neuroticism (N), which was the tendency to experience negative emotions. By pairing the two dimensions, Eysenck noted how the results were similar to the four ancient temperaments.

• High N, High E = Choleric
• High N, Low E = Melancholy (also called "Melancholic")
• Low N, High E = Sanguine
• Low N, Low E = Phlegmatic

He later added a third dimension, psychoticism, resulting in his "P-E-N" three factor model of personality. This has been correlated with two separate factors developed by the Big Five personality traits (Five Factor Model), called "agreeableness" and "conscientiousness"; the former being similar to the people/task orientation scale elaborated above. Neuroticism in Eysenck's case acted like the people/task-orientation scale (except for being inverted as to which temperaments were "high" or "low"), but was later separated as a distinct factor in the Big Five.

Carl Jung, in the early 20th century, introduced the four factors that would become a part of the later MBTI, and these included extroversion/introversion, sensing and intuition, and thinking/feeling, which would be correlated to Agreeableness, with Judging-Perceiving roughly as Conscientiousness.

Ernst Kretschmer (1888–1964) divided personality into two "constitutional groups": Schizothymic, which contain a "Psychaesthetic proportion" between sensitive and cold poles, and Cyclothymic which contain a "Diathetic" proportion between gay and sad. The Schizoids consist of the Hyperesthetic (sensitive) and Anesthetic (Cold) characters, and the Cycloids consist of the Depressive (or "melancholic") and Hypomanic characters.

David W. Keirsey would make the connection of the two groups with Myers' Sensors and iNtuitors, providing the two factors for his four temperaments.^[10] He would rename Sensing to "Observant" or "Concrete", and Intuiting to "Introspection" or "Abstract", and pair it with "Cooperative" versus "Pragmatic" (or "Utilitarian") which would be the "Conscientiousness" scale; to form:

• SP Artisan (Concrete, Pragmatic)
• SJ Guardian (Concrete, Cooperative)
• NT Rational (Abstract, Pragmatic)
• NF Idealist (Abstract, Cooperative)

Keirsey also divided his temperaments by "Role-Informative"/"Role Directive" to form eight "intelligence types"; and finally by E/I, to yield the 16 types of the MBTI. It was when his former student, Berens, paired the latter two factors separately that she yielded here Interaction Styles, discussed above. Keirsey also divided the intelligence types by I/E into "roles of interaction".^[11]

The Enneagram of Personality would map its nine types to a matrix, whose scales are "Surface Direction" and "Deep Direction". These are similar to Extroversion and people/task-orientation, but instead of the types being plotted on a scale of 0–9, Horney's original three grades of "towards", "away", and "against" were retained, and now used in both dimensions (graded respectively, as "+", "0" and "-"). This changes the criteria, as the "moderate" (0) grade is considered "away", but this does not necessarily correspond to the moderate extroversion or agreeableness scores of the other instruments.

• California Psychological Inventory