In this column, we discuss a version of the utility maximization hypothesis that can be tested—and we find that it is false. We review empirical challenges to utility maximization, which return to the old question of whether preferences optimize the experience of outcomes. Much of this work has focused on a necessary condition for utility-maximizing choices: an ability of economic agents to make accurate, or at least unbiased, forecasts of the hedonic outcomes of potential choices. The research we review shows that this condition is not satisfied: people do not always know what they will like; they often make systematic errors in predicting their future experience of outcomes and, as a result, fail to maximize their experienced utility. We discuss four areas in which errors of hedonic forecasting and choice have been documented: 1) where the emotional or motivational state of the agent is very different at t0 and at t1; 2) where the nature of the decision focuses attention on aspects of the outcome that will not be salient when it is actually experienced; 3) when choices are made on the basis of flawed evaluations of past experiences; and 4) when people forecast their future adjustment to new life circumstances.