AGING AND CREDIBILITY JUDGMENT

The purpose of this study was to investigate the effect of aging on credibility judgments and source memory for statements expressing new ''factual'' knowledge. In Experiment 1, we examined the influence of familiarity in young and older adults' credibility judgments by comparing their truth ratings for repeated and nonrepeated statements of unknown credibility. In Experiment 2, we provided information on the actual truth or falsity of some of the repeated statements to determine whether this objective evidence would have less influence in older adults' later credibility judgments than in younger adults' judgments. In both experiments, we examined age-related differences in source memory for the statements. The major findings were as follows: (a) the influence of knowledge familiarity as a subjective basis for credibility judgment did not decline with age; (b) compared to young adults, older adults were just as likely to use objective evidence of statement credibility in their judgments when this evidence confirmed the truth of their knowledge, but were somewhat less likely to do so when this evidence disconfirmed the truth of their knowledge; and (c) older adults' memory for the source of their knowledge was consistently less accurate than that of young adults. These findings suggest that older adults will not be at a disadvantage relative to young adults when their credibility judgments can be based on the subjective evidence of knowledge familiarity, but they will sometimes be at a disadvantage when a more objective basis for judgment is required. In particular, age-related declines in the ability to process evidence that disconfirms the credibility of knowledge may lead to a magnification of the natural tendency to believe rather than disbelieve (cf. Gilbert, 1991).