Can people detect liars better if they just rely on their unconscious? What is the evidence for using gut feelings? There is little to no evidence that the unconscious can help us detect lies.
In our review (Street & Vadillo, 2016), we argue that research on unconscious lie detection does not exclude the possibility that conscious processes are being used to detect deception, and that methods thought to engage unconscious lie detection do not give accuracy rates any better than using methods that allow for conscious judgments. Much of the research on unconscious lie detection uses the indirect lie detection method, described below. We show that this method does not allow us to claim anything about the unconscious – instead, it seems that indirect lie detection tells us about conscious judgments.
The “indirect lie detection” method is the largest body of research suggesting there are benefits to relying on the unconscious. To supposedly access unconscious thinking, participants are asked to judge only a single behaviour related to lying – is this person thinking hard or not? Liars generally end up in the thinking-hard category and truth-tellers in the not-thinking-hard category. In fact, this method better separates liars and truth-tellers than asking people to explicitly decide who is lying and who is not.
The boost in accuracy has nothing to do with an unconscious store of additional knowledge. Instead, the benefit comes from using a single, reliable clue to deception – thinking hard – ignoring all the other behaviours present. But when people make lie and truth judgments, they also incorporate other behaviours, some of which the liar use to make themselves appear honest – e.g., telling a plausible tale. This creates a conflict: one behaviour suggests deception but the other suggests honesty. This gives rise to an ambiguity and increases the room for error in making the judgment. Reducing the conflict between cues by focusing attention to only a single reliable cue is what is thought to increase accuracy, which we call the focal account (Street & Richardson, 2015)
To spot a liar, we should not trust our intuitions. Instead, we should make reasoned, conscious judgments. Look for highly reliable clues like Pinocchio’s nose, and ignore those that have low reliability because they will increase the possibility of error.
Street, C. N. H., & Richardson, D. C. (2015). The focal account: Indirect lie detection need not access unconscious, implicit knowledge. Journal of Experimental Psychology: Applied, 24(1), 342-355. doi: 10.1037/xap0000058 [pdf] [press]
Street, C. N. H., & Vadillo, M. A. (2016). Can the unconscious boost lie detection accuracy? Current Directions in Psychological Science. [pdf]