Known as the Four Temperaments from Hippocrates, and The Four Humors from Galen, these great medical minds believed that a balance of four bodily fluids was necessary to maintain health.

What were previously external elements became bodily fluids (or humors), which affected our behaviors, but this time from internal influences. Phlegm/Phlegmatic was associated with the element water, representing calmness. Blood/Sanguine was associated with the element air, representing cheerfulness. Yellow Bile/choleric was associated with the element fire, representing enthusiasm. Black bile/Melancholic was associated with the element earth, representing being somber. One’s dominant humor was believed to have determined his or her personality type.

Phlegmatic (phlegm/calm), Sanguine (blood/cheerful), Choleric (yellow bile/enthusiastic), and Melancholic (black bile/somber)

From ancient elements and humor, we move forward in time to Carl Gustav Jung and the development of the Myers Briggs Type Indicator (MBTI). Still attributing personality to internal influences, Jung determined that our behavior is based on the way we think and process. He contributed much to the understanding of “type” behaviors, believing that individuals had a “Psychological Type” and that people vary by how they perceive things and make decisions. In 1921, Jung published the book, Psychological Types, identifying four ways in which we experience the world: Sensation, Intuition, Feeling and Thinking.

William Moulton Marston graduated from doctoral studies at Harvard in the newly developing field of psychology. In his landmark book, Emotions of Normal People, published in 1928, Marston set out to examine observable “normal” behavior in a particular environment. He believed our personality styles are both natural, internal and innate, but also largely impacted by our particular environment at any given time. This combines the idea that we are impacted both internally and externally, which affects our behaviors.

Marston showcased his extensive research and theory behind the DISC model in his book. He found that behavioral characteristics could be grouped together in four main divisions, called personality styles. People with similar styles tend to exhibit specific, observable behavioral characteristics common to that style. Marston named these four personality styles and created a means to identify the relative propensity of individuals to behave accordingly.