The Keirsey Temperament Sorter (KTS) is a self-assessed personality questionnaire designed to help people better understand themselves and others. It was first introduced in the book Please Understand Me. It is one of the most widely used personality assessments in the world. The KTS is closely associated with the Myers–Briggs Type Indicator (MBTI); however, there are significant practical and theoretical differences between the two personality questionnaires and their associated different descriptions. It has been criticized as pseudoscience. Historical development See also Historical Development of Theories of the Four Temperaments David Keirsey became familiar with the work of Ernst Kretschmer and William Sheldon after WWII in the late 1940s. Keirsey developed the Temperament Sorter after being introduced to the MBTI in 1956. Tracing the idea of temperament back to the ancient Greeks, Keirsey developed a modern temperament theory in his books Please Understand Me (1978), Portraits of Temperament (1988), Presidential Temperament (1992), Please Understand Me II (1998), Brains and Careers (2008), and Personology (2010). The table below shows how Myers' and Keirsey's types correspond to other temperament theories or constructs, dating from ancient times to the present day. Four temperaments Keirsey expanded on the ancient study of temperament by Hippocrates and Plato. In his works, Keirsey used the names suggested by Plato: Artisan (iconic), Guardian (pistic), Idealist (noetic), and Rational (dianoetic). Keirsey divided each of the four temperaments into two categories (roles), each with two types (role variants). The resulting 16 types correlate with the 16 personality types described by Briggs and Myers. Artisan The Artisan temperament is one of four temperaments defined by Keirsey. Correlating with the SP (sensing–perceiving) Myers-Briggs types, the Artisan temperament comprises the following role variants (listed with their correlating Myers-Briggs types): Composer (ISFP), Crafter (ISTP), Performer (ESFP), and Promoter (ESTP). Artisans are concrete and adaptable. Seeking stimulation and virtuosity, they are concerned with making an impact. Their greatest strength is tactics. They excel at troubleshooting, agility, and the manipulation of tools, instruments, and equipment. The two roles are as follows: Operators are the directive (proactive) Artisans. Their most developed intelligence operation is expediting. The attentive Crafters and the expressive Promoters are the two role variants. Entertainers are the informative (reactive) Artisans. Their most developed intelligence operation is improvising. The attentive Composers and the expressive Performers are the two role variants. Guardian The Guardian temperament is one of four temperaments defined by Keirsey. Correlating with the SJ