Initial credibility, use and non-use of evidence, and language intensity manipulate belief formation and change. Evidence supports the hypothesis that if a group of subject is exposed to a communicator who carries impressive credentials, uses specific data, and phrases a message in intense, fear-producing terms, the subjects will respond with positive belief. However, when these factors are less present, belief is correspondingly reduced. The research methodology used is a first step toward the development of a more complete persuasion testing paradigm. (CH)