The role of alternative hypotheses in the integration of evidence that disconfirms an acquired belief

Two experiments examined the role of alternative hypotheses in the recognition of belief-incongruent evidence and the consequent attribution of probative value to that evidence. Using a contingency judgement and prediction task, subjects monitored multiple predictor-outcome contingencies. In a subset of three of these contingencies the evidence strongly endorsed a positive contingency in a first phase but strongly endorsed a negative contingency in a second phase. In Experiment 1 the negative evidence was presented, in part, in terms of an alternative contingency involving a new predictor or a new outcome, or in terms of no alternatives. The presence of alternative hypotheses did not influence the recognition of the negative evidence but significantly reduced the subjects' persistence in predicting the outcome in the presence of the predictor. Using the same positive-negative contingencies, Experiment 2 replicated this effect but also demonstrated that error in the feedback during the negative phase strengthened the perseverance in outcome predictions even when subjects acknowledged the negative nature of the evidence. Results from these two experiments indicate that prior beliefs do not bias the recognition of belief-incongruent evidence but the integration of that evidence is determined by the nature of the alternative hypotheses available to the reasoner.