Based on the two-step flow hypothesis, the term "personal influence" came to illustrate the process intervening between the media's direct message and the audience's reaction to that message. Opinion leaders tend to be similar to those they influence—based on personality, interests, demographics, or socio-economic factors. These leaders tend to influence others to change their attitudes and behaviors. The two-step theory refined the ability to predict how media messages influence audience behavior and explains why certain media campaigns do not alter audiences' attitudes. This hypothesis provided a basis for the two-step flow theory of mass communication.