The modern DISC theory first appeared in the 1920s, in William Moulton Marstons book,
The Emotions of Normal People. This was one of the first attempts to apply psychology to ordinary
people, outside a purely clinical setting.
Marston, who is probably best known today for his invention of the polygraph or lie detector,
developed DISC to help demonstrate his ideas of human motivation. Its simple twenty-four-item questionnaire
was intended to help him quickly appraise different behavioural types for analysis and comparison.
From these humble origins, DISC has grown to become one of the most widely-used
assessment systems in the world.