Psychology seems like it should be a good place to start trying to figure out how to sift the truth from the lies. If you don’t have access to a polygraph, there may be some behavioral clues that can tip you off.
With this background, here are the 9 basic rating scales from the PBCAT that will allow you to detect when you’re being told a lie:
Leaves out sensory details. A liar skips many of the little flourishes that embellish stories told by honest people.
Admits frequently to faulty memory. People telling the truth don’t have that much trouble remembering a true event, situation, or occurrence. They lived it, so it comes pretty easily to them. Liars, however, will give themselves the “excuse” of having a poor memory when, in reality, it’s only the lies they’re having trouble recalling.
Makes spontaneous corrections. Because liars have to backtrack so much, they will edit heavily their stories: “Her name was Lily, no it was Lisa, wait, maybe it was Linda.”
Keeps it short and vague. The longer, more complete, and spelled out a story is, the more likely it is to be true.
Doesn’t make sense and is full of contradictions. By now, if you’re catching on, it should be clear that a true story will hang together better than a string of lies.
Seems to be thinking hard. If your speaker seems to be unsure or, worse, to be putting a great deal of effort into coming up with a plausible account of events, this is a cue that the his or her cognitive load is mounting.
Is nervous, tense, and fidgety. It takes a great liar to be able to pull off a string of falsehoods without looking at least a little anxious. (In fact, that’s one of the cues to suggest that someone might be a psychopath.)
Makes few complaints or negative comments. This seems counterintuitive, but it makes sense that someone trying to create a good impression would want to be positive.
Talks unusually slowly. The speech of a truth-teller is reasonably normal, but people who are lying tend to take quite a bit longer as they self-edit, try to be consistent, and leave out negative commentaries.