Suppressing the truth as a mechanism of deception: Delta plots reveal the role of response inhibition in lying

• We tested the hypothesis that lying requires inhibition using delta plots.
• Delta plots display RT effects as a function of RT and are usually positive-going.
• The involvement of response inhibition can counteract the positive slope.
• Inhibitory skills modulated the delta-plot pattern.
• Our findings support the role of response inhibition in lying.

Lying takes more time than telling the truth. Because lying involves withholding the truth, this “lie effect” has been related to response inhibition. We investigated the response inhibition hypothesis of lying using the delta-plot method: A leveling-off of the standard increase of the lie effect with slower reaction times would be indicative of successful response inhibition. Participants performed a reaction-time task that required them to alternate between lying and truth telling in response to autobiographical questions. In two experiments, we found that the delta plot of the lie effect leveled off with longer response latencies, but only in a group of participants who had better inhibitory skills as indexed by relatively small lie effects. This finding supports the role of response inhibition in lying. We elaborate on repercussions for cognitive models of deception and the data analysis of reaction-time based lie tests.