Mixed in a World of Truth and Lies: List Composition Moderates the Effects of a Lie Fabrication Manipulation on Memory and Metamemory

Research has shown that list composition moderates the effects of encoding manipulations on memory performance; differential memory performance is observed at distinct levels of the independent variable in mixed lists, but not in pure lists. The current study aims to investigate the effect of list composition on predicted and actual memory performance using a semantic lie fabrication manipulation. In Experiment 1, participants either told the truth or fabricated a lie in response to a set of general knowledge questions in a mixed-list design, made memory predictions for each response, and received a free recall test. Experiments 2A and 2B compared the effect of list composition by employing mixed and pure lists, respectively. The results showed that the lie fabrication led to a metacognitive illusion in mixed lists by inducing a crossed double dissociation between memory and metamemory. Participants produced higher memory performance and lower memory predictions for lies than the truth. In contrast, predicted and actual memory performance were similar for truth and lies in pure lists. These findings contribute to the existing body of knowledge on list composition and have implications for situations where individuals need to maintain and remember their fabricated lies.