No one likes to be deceived, but spotting a liar can be incredibly difficult. Are there reliable ways to tell when someone is lying to you?
To answer this question, researchers across the world have studied video clips from court cases and interrogations, and listened to hours of interviews and testimony. Although there are, as yet, no foolproof guidelines, here are some of the most well-established findings.
Bella dePaulo and Wendy Morris at the University of California pooled results from a number of studies on deception. They found that, when lying, individuals are more likely to have increased pupil size and to speak in a higher pitched voice, features associated with higher levels of tension and concentration.
Liars tend to repeat words and phrases more frequently than truth-tellers, and they are often seen to press their lips together. Contrary to popular belief, however, they noted that liars don't blink more often than truth-tellers, nor do they necessarily appear more tense or fidgety.
Edward Geiselman at UCLA noted that liars engage in more self-grooming behaviours while lying - for example, playing with their hair or fingernails - and that they often repeat a question before answering, presumably to buy time to compose a convincing lie. They also insist on justifying their answers more often than do truth-tellers.
Rada Mihalcea and colleagues at the University of Michigan studied video clips of high profile court cases. They discovered that, contrary to expectations, liars made more direct eye contact with their interrogators than did truth-tellers. They also tended to scowl or grimace significantly more often, and they used hand gestures more frequently than those who told the truth. When answering questions, liars punctuated their speech more often with vocal fillers such as "um" and "ah".
James Pennebaker at the University of Texas was interested in spotting the difference between truth-telling and lies in written material. He found that liars use more negative emotional words - for example, "hate" and "sad". They also use fewer exclusionary words such as "but", "except" and "nor", words that mark the distinction between what the author did and did not do.
Pennebaker also found that liars have a tendency to distance themselves from what they're saying by avoiding the use of the word "I". Instead, they describe situations using the third person - "he" or "she".
Of course, liars - as well as those who are looking out for them - have access to this information, so those who intend to deceive can teach themselves to behave as if they're telling the truth. Nevertheless, it's difficult to hold on to a plausible lie at the same time as remembering how to appear and how to present evidence convincingly.
Therefore, the key is to look for multiple cues, both in body language as well as in the content and structure of the explanations given.
Linda Blair is a clinical psychologist, author of The Key To Calm.