The cognitive load of lies

Deception is thought to involve greater cognitive load than honesty, and in practice has been shown to increase reaction time (RT). However, this has only been measured with closed-questions delivered by a computer. We employed a dual-task methodology, the Detection Response Task (DRT), to assess cognitive load in a live, open-question interview. The DRT requires participants to press a button in response to a stimulus every 3-5 seconds while simultaneously performing a primary task. In this case, 44 first year Psychology students (29 females) aged 18-66 (`M` = 27.1 years, SD = 10.6) watched 26 short films and constructed and delivered narrative lies about their content to an interviewer. Supporting our hypothesis that deception is cognitively harder than telling the truth, participants were significantly slower to respond to the DRT when constructing (`M` = 385, 95%CI[380,391], `p` <.05) and delivering (`M` = 541, 95%CI[531,550], `p` <.001) lies in the first half of the experiment. When lying, they were more likely to fail to respond to the stimulus altogether (by 0.3%) and took longer to start answering (by 33 ms). Further inquiry of the DRT in deception research may improve deception theory and refine lie-detection techniques.