When false recognition meets metacognition: The distinctiveness heuristic

We investigated the contribution of a distinctiveness heuristic to rejecting false memories. Individuals studied words, pictures, or both types of items and then completed a recogntion test on which the studied items appeared once, whereas the new words appeared twice. Participants who had studied pictures were less likely to falsely recognize repeated new words than were participants who had studied words. We argue that studying pictures provides a basis for using a distinctiveness heuristic during the recogntion test: participants infer from the absence of memory for expected picture information that a test item is "new." These experiments also investigated the influence of two variables-diagnosticity and metacognitive control-on the use of the distinctiveness heuristic. We examined the role of diagnostic information in eliciting the heuristic by varying the proportion of studied items that appeared as pictures. Compared to a word encoding condition, participants successfully rejected repeated new words after studying 50, 25, and 33% of the items as pictures in Experiments 1, 2, and 3, respectively. Thus, the distinctive information need not be completely diagnostic (i.e,. perfectly predictive of an item's oldness) for participants to used the heuristic. We also show that the distinctiveness heuristic is under metacognitive control such that it can be turned on or off depending on participants' expectations about its usefulness for reducing memory errors. (C) 2002 Elsevier Science (USA).