What scientific idea can lead to a certain personality types A, B, C, D?  

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mrsbundy eNotes educator| Certified Educator

The Goldsmith Theory of personality types was first published in the 1950s.  That study divided personality into a binary of high-strung A-types and easy-going B-types.  The study's initial purpose was to find a correlation between personality type (behavior and attitude) and coronary disease.  The type D personality was defined by Johan Denollet in the late 1990s and attempts to further refine Goldsmith's theory.  He finds that over 20% of the population has what he calls a Type D personality, characterized by social inhibition, worry and anxiety.  Around 50% of Denollet's cardiac patients fall into this type D category, linking stress with heart disease.