Essays on Decision Making under Uncertainty

This dissertation consists of three chapters about decision making under uncertainty.Chapter 1: “Testing between Models of Smoking Risk Perceptions”Research in social and health psychology reports that smokers systematically underestimate the personal smoking risk. I build a model that captures potential determinants of smoking risk perceptions to investigate how smoking may cause an underestimation of the risk. The model is based on the premise that smokers have an incentive to be optimistic: because quitting may be hard, they find it reassuring to think that smoking is not so risky. Drawing upon the theoretical framework, I suggest two empirical tests of the model—one using survey data and another based on a laboratory experiment. Chapter 2: “Does Uncertainty Cause Inertia in Decision Making? An Experimental Study of the Role of Regret Aversion and Indecisiveness”Previous research has shown that in many situations there is clear inertia in individual decision making—that is, a tendency for decision makers to choose a status quo option. The status quo option may be the result of a previous choice, or may simply be the option designated as the “default.” While inertia may simply reflect the fact that individuals view the status quo option as optimal, there are other factors that may explain this observed behavior. I conduct a laboratory experiment to thoroughly investigate two potential determinants of inertia in uncertain environments: (i) regret aversion and (ii) indecisiveness. A decision maker may experience regret when the outcome of a choice compares unfavorably to the outcome that would have occurred had she made a different choice. Alternatively, a decision maker may be indecisive among the options if she does not know the probability distributions over the relevant outcomes. I use a between-subjects design, with varying conditions, to identify the effects of regret aversion and indecisiveness on choice behavior. In each condition, participants choose between two simple real gambles, one of which is assigned to be the status quo. I find that inertia is quite large and that both mechanisms are equally important.Chapter 3: “Risk, Ambiguity, and Diversification”Attitudes toward risk influence the decision to diversify among uncertain options. Yet, because in most situations the probability distributions over outcomes are unknown, attitudes toward ambiguity may also play an important role. In a simple laboratory experiment, I investigate the effect of ambiguity on the decision to diversify. Participants have the opportunity to diversify between gambles; in one condition, all gambles are risky, whereas in the other all gambles are ambiguous. I find that diversification is more prevalent and more persistent under ambiguity than under risk. Moreover, excess diversification under ambiguity is driven by participants who stick with a status quo gamble when diversification is not feasible. This behavioral pattern cannot be accommodated by major theories of choice under ambiguity