<P> The term type has not been used consistently in psychology and has become the source of some confusion . Furthermore, because personality test scores usually fall on a bell curve rather than in distinct categories, personality type theories have received considerable criticism among psychometric researchers . One study that directly compared a "type" instrument (the MBTI) to a "trait" instrument (the NEO PI) found that the trait measure was a better predictor of personality disorders . Because of these problems, personality type theories have fallen out of favor in psychology . Most researchers now believe that it is impossible to explain the diversity of human personality with a small number of discrete types . They recommend trait models instead, such as the five - factor model . </P> <Ul> <Li> An early form of personality type indicator theory was the Four Temperaments system of Galen, based on the four humours model of Hippocrates; an extended Five Temperaments system based on the classical theory was published in 1958 . </Li> <Li> One example of personality types is Type A and Type B personality theory . According to this theory, impatient, achievement - oriented people are classified as Type A, whereas easy - going, relaxed individuals are designated as Type B . The theory originally suggested that Type A individuals were more at risk for coronary heart disease, but this claim has not been supported by empirical research . </Li> <Li> One study suggests that people with Type A personalities are more likely to develop personality disorders whereas Type B personalities are more likely to become alcoholics . </Li> <Li> Developmental psychologist Jerome Kagan is a prominent advocate of type indicator theory . He suggests that shy, withdrawn children are best viewed as having an inhibited temperament, which is qualitatively different from that of other children . </Li> <Li> As a matter of convenience, trait theorists sometimes use the term type to describe someone who scores exceptionally high or low on a particular personality trait . Hans Eysenck refers to superordinate personality factors as types, and more specific associated traits as traits . </Li> <Li> Several pop psychology theories (e.g., Men Are From Mars, Women Are From Venus, the enneagram) rely on the idea of distinctively different types of people . </Li> </Ul> <Li> An early form of personality type indicator theory was the Four Temperaments system of Galen, based on the four humours model of Hippocrates; an extended Five Temperaments system based on the classical theory was published in 1958 . </Li> <Li> One example of personality types is Type A and Type B personality theory . According to this theory, impatient, achievement - oriented people are classified as Type A, whereas easy - going, relaxed individuals are designated as Type B . The theory originally suggested that Type A individuals were more at risk for coronary heart disease, but this claim has not been supported by empirical research . </Li>

Who describes different types of personality based on glands