title: Waiting for the bus: when base-rates refuse to be neglected.
abstract: The paper reports the results from 16 versions of a simple probability estimation task, where probability estimates derived from base-rate information have to be modified by case knowledge. In the bus problem [adapted from Falk, R., Lipson, A., & Konold, C. (1994). The ups and downs of the hope function in a fruitless search. In G. Wright & P. Ayton (Eds.), Subjective probability (pp. 353-377). Chichester, UK: Wiley], a passenger waits for a bus that departs before schedule in 10% of the cases, and is more than 10 min delayed in another 10%. What are Fred's chances of catching the bus on a day when he arrives on time and waits for 10 min? Most respondents think his probability is 10%, or 90%, instead of 50%, which is the correct answer. The experiments demonstrate the difficulties people have in replacing the original three-category 1/8/1 partitioning with a normalized, binary partitioning, where the middle category is discarded. In contrast with typical studies of "base-rate neglect", or under-weighing of base-rates, this task demonstrates a reversed base-rate fallacy, where frequentistic information is overextended and case information ignored. Possible explanations for this robust phenomenon are briefly discussed.
authors.affiliation: Department of Psychology, University of Oslo, Blindern, Oslo, Norway. k.h.teigen@psykologi.uio.no
authors.forename: Karl Halvor
authors.initials: KH
authors.lastname: Teigen
authors.forename: Gideon
authors.initials: G
authors.lastname: Keren
mesh_terms: D006801:Humans; D013998:Time Perception; D014186:Transportation