Abstract

Base-rate neglect refers to the tendency for people to underweight base-rate probabilities in favor of diagnostic information. It is commonly held that base-rate neglect occurs because effortful reasoning is required to process base-rate information, whereas diagnostic information is accessible to fast, intuitive processing. To test this account, we instructed participants to respond to base-rate problems on the basis of “beliefs” or “statistics,” both in free time and under a time limit. Participants were given problems with salient stereotypes that either conflicted or coincided with base-rate probabilities. If utilizing base-rates requires Type 2 processing, they should not interfere with the processing of the presumably faster belief-based judgments, whereas belief-based judgments should always interfere with statistics judgments. However, base-rates interfered with belief judgments to the same extent as the stereotypes interfered with statistical judgments, as indexed by increased response time and decreased confidence for conflict problems relative to nonconflict. These data suggest that base-rates, while typically underweighted or neglected, do not require Type 2 processing and may, in fact, be accessible to Type 1 processing