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History of traits
The concept of traits was originated by Gordon Allport. Raymond Cattell pioneered the use of factor analysis to analyse the structure of personality traits. He used this procedure to organise the large number of traits described by Allport into a smaller number of broader factors. These were the 16 Personality Factors  assessed by the  16PF Questionnaire.

Psychobiological models
A number of trait theories have been developed based on psychobiological theories that attempt to explain the underlying causes of personality traits. These include Eysenck's three factor model, Marvin Zuckerman's Alternative five model of personality and Cloninger's seven factor model assessed by the Temperament and Character Inventory.