Understanding the effects of lying by fabrication on memory for the truth

Accurate memory matters nowhere more than in criminal cases, but research shows that people’s memory reports can be contaminated by misinformation spread by others. An increasing body of evidence shows that people can also contaminate their own memories when they lie. However, a theory of how lying can affect memory has been slow to develop. The experiments within this thesis therefore aimed to further our understanding of how fabrication can affect later memory for the truth and test some of the hypotheses generated by two existing relevant theories: von Hippel and Trivers’ theory of self-deception and the memory and deception (MAD) framework. Experiments 1-3 test von Hippel and Trivers’ proposal that repeating lies can promote forgetting of the truth via retrieval-induced forgetting. No evidence was found for this claim: Memory for information that participants repeatedly lied about did not differ from baseline. The thesis then turns to the relationship between the cognitive effort of fabrication and subsequent memory errors, as both theories are centered on the concept of cognitive load in deception. Some challenges are presented to the MAD framework’s hypotheses concerning the relationship between the cognitive effort of fabrication and subsequent memory errors. The findings of Experiments 4-5 highlight the need to reconsider the nature of this relationship: Different methods of increasing liars’ cognitive load moderated the effect of fabrication on memory. Finally, Experiment 6 tested the possibility that fabricating in a previous interview might decrease the accuracy of the Concealed Information Test (CIT)—a physiological deception detection test that relies on strong memory for the truth. Prior fabrication did not decrease the CIT’s accuracy. Together, these findings help to refine models of lying and memory. Additionally, the findings raise concerns about contamination of revised testimonies after fabrication and highlight potential issues for increasing cognitive load for lie detection