irritated easily. I often feel blue. I am relaxed most of the time. (Reversed) I seldom feel blue. (Reversed) History Finding the five factors In 1884, British scientist Sir Francis Galton became the first person known to consider deriving a comprehensive taxonomy of human personality traits by sampling language. The idea that this may be possible is known as the lexical hypothesis. In 1936, American psychologists Gordon Allport of Harvard University and Henry Odbert of Dartmouth College implemented Galton's hypothesis. They organised for three anonymous people to categorise adjectives from Webster's New International Dictionary and a list of common slang words. The result was a list of 4504 adjectives they believed were descriptive of observable and relatively permanent traits. In 1943, the British-American Raymond Cattell of Harvard University took Allport and Odbert's list and reduced this to a list of "160 odd" terms by eliminating words with very similar meanings. To these, he added terms from 22 other psychological categories, and additional "interest" and "abilities" terms. This resulted in a list of 171 traits. From this he used factor analysis to derive 60 "personality clusters or syndromes", plus an additional 7 minor clusters. Cattell then narrowed this down to 35 terms, and later added a 36th factor in the form of an IQ measure. Through factor analysis in 1945, 1947 and 1948 he created 11 or 12 factor solutions. The 1947 study surveyed university students, which Cattell deemed to have a broad range of personalities due to the cohort including many recently returned war veterans. Also in 1947, German-British psychologist Hans Eysenck of University College London published his book Dimensions of Personality. He posited that the two most important personality dimensions were "Extraversion" and "Neuroticism" (a term he himself coined). In July 1949, American Donald Fiske of the University of Chicago used 22 terms either taken or adapted from Cattell's 1947 study, and through surveys of male university students and statistics derived five factors: "Social Adaptability", "Emotional Control", "Conformity", "Inquiring Intellect", and "Confident Self-expression." Also in 1949, Cattell found 4 additional factors, which he believed consisted of information that could only be provided through self-rating. With this understanding, he created the sixteen factor 16PF Questionnaire. In 1953, American John W French of Educational Testing Service published an extensive meta-analysis of personality trait factor studies. In 1957, American Ernest Tupes of the United States Air Force undertook a personality trait study