The basic assumption of these theories is the need of the individual for consistency. There must be consistency between attitudes, between behaviors, and among attitudes and behaviors. A lack of consistency causes discomfort so that an individual attempts to ease the tension by adjusting attitudes or behaviors in order to once again achieve balance or consistency. One of the earliest consistency theories was balance theory (Himmelfarb & Eagly, 1974; Kiesler, Collins & Miller, 1969; O'Keefe, 1990).