Generating lies produces lower memory predictions and higher memory performance than telling the truth: evidence for a metacognitive illusion

Manipulations that induce disfluency during encoding generally produce lower memory predictions for the disfluent condition than for the fluent condition. Similar to other manipulations of disfluency, generating lies takes longer and requires more mental effort than does telling the truth; hence, a manipulation of lie generation might produce patterns similar to other types of fluency for memory predictions. The current study systematically investigates the effect of a lie-generation manipulation on both actual and predicted memory performance. In a series of experiments, participants told the truth or generated plausible lies to general knowledge questions and made item-by-item predictions about their subsequent memory performance during encoding, followed by a free recall test. Participants consistently predicted their memory performance to be higher for truth than for lies (Experiments 1 through 4), despite their typically superior actual memory performance for lies than for the truth (Experiments 1 through 3), producing double dissociations between memory and metamemory. Moreover, lying led to longer response latencies than did telling the truth, showing that generating lies is in fact objectively more disfluent. An additional experiment compared memory predictions for truth and lie trials via a scenario about the lie-generation manipulation used in the present study, which revealed superior memory predictions of truth than of lies, providing proof for a priori beliefs about the effects of lying on predicted memory (Experiment 5). The effects of the current lie-generation manipulation on metamemory are discussed in light of experience-based and theory-based processes on making judgments of learning. Theoretical and practical implications of this experimental paradigm are also considered.