An explanation of conservatism in the bookbag-and-pokerchips situation

An experiment is described in which subjective probability revisions were obtained in a standard probability estimation task, the ‘bookbag-and-pokerchips’situation. Three aspects of probability revision were examined: conservatism, sequential effects, and coherence. Under two experimental conditions, the conservatism effect obtained was closely related to subjects' use of a simple strategy. A recency effect was also obtained. Coherence of the probability estimates was excellent. Conditions under which the observed strategy leads to conservatism are explored and previously published results are reconsidered in the light of this strategy. Conservatism in the bookbag- and-pokerchips situation is explained as an artefact of subjects' strategies