Quantitative prediction of belief and opinion change: A further test of a subjective probability model

Tested implications of the hypothesis that relations among beliefs, if defined in terms of subjective probabilities, are predictable by applying the laws of objective probability. Of particular interest was the extent to which change in 1 belief would predictably affect other beliefs which were related to it. 9 hypothetical situations were constructed, each of which pertained to an event (A) and its relation to a 2nd event (B). Descriptions of each situation were presented to 49 undergraduates in 2 parts: the 1st to produce a low estimate of the likelihood of occurrence of A, and the 2nd to increase this estimate. Ss estimated various probabilities associated with occurrence of A and B after reading each part of the communication. Estimates of the probability of B and the change in these estimates after reading the 2nd part of the communication were both predicted accurately by applying the laws of objective probability. These predictions were more accurate than those generated by the 1960 model proposed by W. J. McGuire. Obtained and predicted estimates of the conjunctive and disjunctive probabilities of A and B were also compared. In general, the hypothesis appeared to be of substantial value in generating accurate quantitative descriptions of the relations among beliefs. (PsycINFO Database Record (c) 2006 APA, all rights reserved).