Three experiments are reported which were intended to replicate a group-induced shift toward greater pessimism in probability estimation and evaluate the extent to which it might be produced by procedural artifacts. In only one experiment was a statistically reliable shift toward pessimism obtained. In this experiment, item-by-item variation was eliminated as a significant factor in the shift. Results of the other two experiments were inconclusive, leaving doubt regarding the reliability and generality of the presumed shift toward pessimism.
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