#3 It takes them longer than usual to respond

When someone is lying, they are juggling two stories at once: the truth and the one they are telling themselves. This requires a lot of mental effort, which can lead to extended pauses and rambling answers to relatively straightforward questions. A liar might rephrase your question, add information that you did not request, pause, stumble, or use more “um,” “uh,” and “ah” filler words.

Those who are telling the truth generally sound more invested, direct, and assured, whereas those who are lying tend to use language that can be interpreted in a number of different ways.

So, a person who is very unsure about the story that they are telling you has a higher chance of being a liar.