Many everyday tasks involve repeated choices in which past outcomes are used to estimate payoffs but in which present payoffs may differ from past ones. Two experiments with 10 decision problems employing the decisions-from-feedback paradigm examined the choice between two risky options, wherein the payoff probabilities for one option could change over a sequence of trials. Participants either saw the outcomes associated with each option, or additionally were given a "history" summarizing the outcomes of previous trials. Participants adapted quickly to new problems, but adapted slowly to payoff changes. Providing a history improved initial choices, but had a null or negative impact on later ones - although, appropriately, the summary received less weight in later trials. An associative choice model captured changes in preference, but not initial patterns of choice. The findings emphasize the adaptive value of forgetting in unstable decision environments, but illustrate how providing additional relevant information may hinder this.