Perceived susceptibility, one's belief about the likelihood of personal harm, is a key concept in many theories of health behavior (Cummings, Becker, & Maile, 1980; Weinstein, 1993). Such beliefs often turn out to be unrealistically optimistic: People show a consistent tendency to claim that they are less likely than their peers to suffer harm. This optimistic bias in relative risk has been demonstrated with several methods, various age groups, and a wide range of hazards (Weinstein, 1987). In some situations, of course, such optimism may be beneficial (Taylor & Brown, 1988). Positive illusions about the effectiveness of precautions, for example, can sustain attempts to change behavior, and underestimations of risk can protect people from anxiety when there is little they can do to reduce their vulnerability (e.g., Taylor et al., 1992). However, when health problems have not yet appeared and are controllable, a tendency to downplay one's own risk may interfere with appropriate self-protective action.

A few studies have demonstrated that informing people about their susceptibility can increase preventive action (e.g., Blalock, DeVellis, & Afifi, 1990; Wurtele, 1988), but others have been unable to alter risk perceptions (Griffeth & Rogers, 1976; Sutton & Eiser, 1990) or have produced changes too small to result in significant changes in action (Schoenbach, 1987; Siero, Kok, & Pruyn, 1984; Weinstein, Sandman, & Roberts, 1991; Wurtele & Maddux, 1987).

The studies reported here varied the way in which risk-factor information was presented in an attempt to reduce optimistic biases.