EXPRESS: Effects of initial experiences on risky choice.

When people make risky choices based on prior experience, biases in learning and memory can affect their preferences. One such bias is the primacy effect, whereby outcomes experienced during initial learning disproportionately affect later memory and choice. Here we investigated potential primacy effects with two features of risky options: outcome probability and relative value. In the first two experiments (total N = 382), the order of experiencing different outcome probabilities was varied across three groups, and neither experiment revealed any primacy effects. In the last experiment (total N = 390), the relative value of outcomes was manipulated by including an extra wildcard option. This wildcard option sometimes had more extreme outcomes than the rest of the choice set and sometimes had more moderate outcomes. The order of experiencing the more-extreme wildcard option was manipulated to evaluate potential primacy effects. During initial learning, including the more-extreme wildcard option affected choice as compared to a group with a wildcard that yielded moderate outcomes; adding that same more-extreme wildcard later in the session, however, had no effect on choice. Together, these results suggest that risk preferences based on relative value show a lasting primacy effect, but that learning about outcome probabilities is more continuously updated.