14. They simply behave differently than normal
In general, if someone is behaving oddly or out of the ordinary during a conversation, it’s a strong indicator they’ve told a lie. However, it’s up to you to know what is “normal” for that person so that you can identify when they act differently. To do this, you need to establish a baseline, which, according to trained behavioral analysis interviewer/interrogator Roger Strecker, is defined as “the totality of observing nonverbal attributes absent the introduction of stressors and triggers.” In essence, you have to observe how an individual behaves during a (preferably) non-confrontational conversation; where they look, what they do with their hands, etc. From these observations, you can then notice when they deviate from the norm and thus are likely being deceptive. However, Strecker notes it is easier to establish a baseline with people you know more intimately, as you are familiar with their usual behaviors and can play “spot the difference” more quickly.