Most people are not good at detecting a lie, as they focus their attention on behavioral cues. For example, to tell if someone is lying, we tend to look out for signs of nervousness. However, such cues may not exist, or may not be observable.
Researchers Stel and Van Dijk proceeded to test whether it is easier to detect a lie by observing facial expressions than looking at behavioral cues. Dutch authors also found that liars find it harder to fake a negative emotion than a positive one, although it is difficult for people to distinguish between genuine and fake emotions.
Nonetheless, Stel and Van Dijk conducted studies to test their hypotheses. In their first study, they found that it was easier for participants to correctly identify negative emotions in the actors than positive ones. In the second study, participants could not identify a lie, but could accurately tell if the actor felt bad or not. One reason for the increased accuracy in judging negative emotions could be due to the fact that we make better cognitive judgements when in a bad mood. This bad mood can be the result of observing someone who is experiencing a negative emotion.
This study shows that rather than trying to question if the person is telling a lie or not, we should ask ourselves if we can identify the emotion experienced by the person. We can then try to match the emotion we identified to the words they speak and see if they are coherent.
Source material from Psychology Today