The Relevance of Irrelevant Alternatives

An experimental investigation of risky choices

Abstract

Experimental economists have discovered various violations of expected utility theory and offered alternative models that can explain laboratory results. This study discovers a new violation in risky choices that cannot be explained by theories like Prospect Theory, Disappoint- ment or Regret Theory. In an experimental setting using a between- subject design, the influence of a dominated alternative on certainty equivalents is shown. One group of subjects was offered a series of choices between a lottery ticket with a 50-50 chance of winning and a sure payoff. A second group was offered the same choice plus a third alternative, that as it turned out was not chosen by any participant. As a result, the average chosen sure payoff in the second group was higher than in the first group. That means, by adding a dominated alternative to a choice set, the certainty equivalent of a lottery is in- creased.