Findings from a number of studies (Anderson, 1983; Anderson, Lepper, & Ross, 1980; Carroll, 1978; Gregory, Cialdini, & Carpenter, 1982; Ross, Lepper, Strack, & Steinmetz, 1977; Sherman, Zehner, Johnson, & Hirt, 1983) indicate that when a hypothetical outcome is imagined and/or explained, it becomes subjectively more likely to occur. For example, Gregory et al. (1982) asked subjects to imagine winning a contest or being arrested for a crime. In each case, subjects came to believe more strongly that the event could happen to them. Furthermore, the imagination procedure influenced later compliance behavior as well as probability estimates. Homeowners who imagined watching and enjoying the benefits of a cable television service were subsequently more likely to subscribe to such a service when given the opportunity to do so.

What process underlies these dramatic judgmental and behavioral effects of explaining and imagining hypothetical future events? The work to date indicates an interpretation based on the operation of one of the cognitive heuristics used in judgments under uncertainty, the availability heuristic (Tversky & Kahneman, 1973). According to this heuristic principle, one basis for the judgment of the likelihood of an uncertain outcome is cognitive availability; that is, the ease with which this outcome can be pictured or constructed. The more available an outcome is, the more likely it is perceived to be….

What might one expect, however, if the event in question could be imagined only with great difficulty, or if subjects failed in their attempts to imagine or explain it?