The theory behind the SDS was an outgrowth of John Holland's practical experience in the fields of job classification and career choices. As a classification interviewer with the army, Dr. Holland realized that many people seemed to be examples of common personality types. This led to his first formulation of the six basic categories in a person-environment typology.
Over the next 25 years, the typology was revised several times and was the basis for numerous research studies that documented its predictive power. The SDS was designed to help people make career and educational choices that match their own interests and abilities.
In 1995, Dr. Holland received the prestigious American Psychological Association Award for Distinguished Contributions to Knowledge for his theory of careers that "provided an intellectual tool for integrating our knowledge of vocational intentions, vocational interests, personalities, and work histories."