Degree of relatedness among personality types affects vocational preference.
(2) Differentiation. Some persons and/or environments can essentially represent one personality type rather than a mixture of types; these are clearly differentiated people or environments. Mixtures of many types are said to be undifferentiated or loosely defined.
(3) Identity. To the extent that a person or an environment has clarity with respect to goals, tasks, interest,s talents, rewards, etc., the person or environment may be said to have a stable identity.
(4) Congruence. To the extent that a person's personality type and the environmental type are the same, there is congruence between the individual's needs and the rewards supplied by the environment.
(5) Calculus. A single geographic model can be used to explain all relationships within and between personality types or environments.
From the foregoing assumptions and sub-assumptions, Holland derives a set of several conceptual principles. These can be delineated as follows: (a) Vocational interests and choices arise from personality type; (b) An assessment of a person's occupational interests is also an assessment of his or her personality type; (c) There are valid vocational stereotypes, e.g. the stereotype that actors are self-centered, that scientists have social difficulties, etc.; (d) Those who choose a particular vocation are similar in personality and in develo