The cognitive effort of lying

Abstract

Being able to directly measure if an individual is lying or not can have many advantages. The current study set out to determine if there were differences in cognitive effort when lying and telling the truth. Participants (N=20) were asked to create or recall 8 events from the Life Events Inventory list. In half of the trials participants told a story, in the other half they told a story and performed an irrelevant simple reaction time task. Disfluency in the participant’s narratives and reaction time in the reaction time task were measured to assess how well participants performed each task. For the reaction time task, there were significant differences between the task type conditions, but not between the story type conditions. For the disfluency measures, there were significant main effects of story type (truth versus lie) for all measures, but no main effects of task type (dual versus single). There was an interaction for filled pauses which indicated more filled pauses for the single, lie condition than any other condition. Overall, reaction times suggested no difference in cognitive effort when lying or telling the truth, whereas disfluency suggested there were some cognitive differences.