ABSTRACT
Scientific studies of persuasive messages consistently demonstrate that voluntarily disclosing harmful information makes the message more convincing. The key is in both the disclosure and an effective rebuttal. Psychologists refer to messages that contain positive arguments but also confront opposing arguments as "two-sided messages" because they address two sides of an argument. Scientists offer a number of reasons for the consistent results of studies that show two-sided messages are more persuasive than one-sided. The "change of meaning" phenomenon has been documented in the trial context in a quite famous study of a criminal trial involving vehicular homicide. As powerful as two-sided messages are, one-sided messages that contain only positive, supporting information are correspondingly weak. Although they can look deceptively persuasive, one-sided messages can actually turn people against the message. Showing flaws in an argument can strengthen it, and putting forward a "perfect" argument can weaken it.
