Remembering words not presented in lists: The role of testing in producing a memory illusion
McDermott, Kathleen Blyth
Roediger, Henry L., III
Doctor of Philosophy
The experiments reported here illuminate current understanding of the factors influencing false recall. These experiments employ a procedure reported by Roediger and McDermott (1995), who demonstrated that reliable, predictable intrusions can be elicited in single trial free recall by presenting subjects with short lists of words (e.g., bed, rest, awake, tired, dream, etc.), all of which are associates of a critical nonpresented word (e.g., sleep); the critical nonpresented word is recalled and recognized as having occurred in the list. In Experiment 1, high levels of false recall were obtained, replicating Roediger and McDermott's (1995) results; in addition, although introduction of a short (30 s) filled delay resulted in forgetting of studied items, false recall was maintained over the delay. On a final free recall test occurring 2 days later, the probability of false recall was increased when an initial test had been taken on the first day, relative to a condition in which no initial test had occurred. In addition, the probability of false recall exceeded the probability of veridical recall on the final test. In Experiment 2, when multiple successive tests were taken, the probability that subjects would later claim to remember the critical nonpresented item (i.e., to recollect something specific about its presentation) was enhanced relative to a single test condition. Experiment 3 examined the persistence of this memory illusion by giving subjects multiple opportunities to hear the list (in a multitrial free recall procedure). Although the probability of free recall diminished across successive trials, robust levels of false recall were still obtained after 5 study-test trials. When subjects returned 1 day later, the probability of free recall was enhanced (relative to the last trial of Day 1), whereas the probability of veridical recall diminished across the delay. Overall, results demonstrate that illusory memories can be extremely robust, persisting across time and repeated retrieval attempts. In some cases, the probability of false recall exceeds the probability of veridical recall. Results converge upon the conclusion that the act of retrieval can play a critical role in determining false recall.
Experimental psychology; Cognitive psychology