Base rates: Both neglected and intuitive

Gordon Pennycook*, Dries Trippas, Simon J. Handley, Valerie A. Thompson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

98 Citations (Scopus)


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 (Type 2) reasoning is required to process base-rate information, whereas diagnostic information is accessible to fast, intuitive (Type 1) processing (e.g., Kahneman & Frederick, 2002). To test this account, we instructed participants to respond to base-rate problems on the basis of "beliefs" or "statistics," both in free time (Experiments 1 and 3) and under a time limit (Experiment 2). Participants were given problems with salient stereotypes (e.g., "Jake lives in a beautiful home in a posh suburb") that either conflicted or coincided with base-rate probabilities (e.g., "Jake was randomly selected from a sample of 5 doctors and 995 nurses for conflict; 995 doctors and 5 nurses for nonconflict"). 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 baserates, while typically underweighted or neglected, do not require Type 2 processing and may, in fact, be accessible to Type 1 processing.

Original languageEnglish
Pages (from-to)544-554
Number of pages11
JournalJournal of Experimental Psychology: Learning, Memory, and Cognition
Issue number2
Publication statusPublished - Mar 2014
Externally publishedYes


  • Base-rate neglect
  • Conflict detection
  • Dual-process theories
  • Intuition


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