The PTI was developed and first published in 1997. The initial design was based on an understanding of Jungian typology and a range of type indicators.
The PTI has its foundations in the theory of Carl Jung as a measure of personality type, but goes further by differentiating between personality type, as described by Jung, and behavior, as described by Kurt Lewin's "Field Theory." Lewin postulated that behavior is best understood by understanding the influence of a person's environment on their innate and stable personality.
The unique design of the PTI scoring system provides the key to seeing personality type in the context of how personality can be influenced by environment. Conditions that fall outside our natural preference boundaries will be less preferred and, consequently, are more likely to be avoided. For example, an individual with a naturally strong preference for introversion may find that he or she can cope with one-to-one interpersonal contact, but expresses anxiety about group social settings. This is clearly highlighted by how the PTI displays and individual's results.