3. They will force a smile, but won't smile with their eyes

Fiction writers will often describe a person’s smile as “not meeting their eyes,” and this is actually a good way to spot a lie. Smiles are a universal expression, recognized all over the globe as a sign of happiness. When a smile is genuine, the skin beneath the eyes bunches up, and you see wrinkles beside the eyes as well due to contractions of the muscles located there. These movements cannot be faked or forced, so their absence during a conversation indicates a lack of positive emotion in the individual and thus a lie, or at the very least a half-truth. This is why elderly people who have smiled and laughed often throughout their lives tend to have a greater number of wrinkles (known as “crow’s feet”) around their eyes. Although it may sound simple enough to tell the difference between a real and a fake smile, scientists have shown it’s actually more difficult than expected; according to psychologist Richard Wiseman, the public can correctly spot the difference only about 60% of the time.