As people develop relationships, they form unspoken, nonrational, and often unconscious expectations of each other. Individuals within the relationship have a strong sense and expectation of “how things should be.” For the most part, individuals in these relationships perform as expected; they may become worried or upset when others act in ways that are unexpected or feel inappropriate. Such expectations develop in part because of the history that the people in the relationship share; but individual expectations sometimes, develop because of a person’s past experiences in other relationships. This sense of how things should be can be described as a “psychological contract”: Psychological, because it originates and is evaluated (even if unconsciously) in the minds of the participants, and contract, because there is an agreement (even if unspoken) that things will happen in a certain way.
Beginning Ministry Together, Roy M. Oswald, James M. Heath, Ann W. Heath, page 123