My first publication was in the journal Science (which allows me to joke that my publication history has been downhill from there); oddly, for someone in my position, the article didn’t involve social influence or social psychology or even human behavior. It concerned ethology, and it emerged from an observation I’d made in an undergraduate laboratory class in which we were recording the conditioned responding of earthworms to electric shock. Things weren’t proceeding well with the earthworm I was trying to condition; so I secured a second worm, putting it into the same small box where the first had been repeatedly buzzed and had secreted a creamy precipitate from its skin. Soon, I became the shocked party, as I witnessed my new subject begin trying frantically to escape up the walls. After getting the same reaction from a third and fourth worm, I called over the lab instructor to watch. Wide-eyed, he said, “I think we’ve found an alarm pheromone (a chemical signal certain animals send out to alert conspecifics to danger) that hasn’t been recorded before.” With a pair of his graduate students, we explored the reliability and functionality of the phenomenon, after which we successfully submitted a report to Science.

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?