Windschitl, P. D., & Wells, G. L. (1998). The alternative-outcomes effect. Journal of Personality and Social Psychology, 75, 1411-1423.

Distributions of possible outcomes to scenarios were manipulated without changing the probabilities of focal outcomes (e.g., you hold 3 raffle tickets and each of 7 other people holds 1, versus you hold 3 and another person holds 7). Participants’ probability estimates confirmed that beliefs about the objective likelihood of the focal outcomes were largely unaffected by the manipulations. As expected, however, nonnumeric certainty estimates (Studies 1-3), feelings of concern (Study 4), and choice behaviors (Study 5) revealed that the manipulations did affect subjective certainty. The consistent direction of this "alternative-outcomes effect" and findings from Study 6 suggest that comparisons between the focal outcome and strongest alternative have an important influence on subjective certainty. We describe a potential function for these comparison processes and discuss their similarities with social comparison and social judgment processes.