Often you don’t need to scrutinize opponents sitting next to you to know when they’re likely to be bluffing. Just turn away and listen. Do you hear them breathing? Harsh or irregular breathing is a sign that an opponent holds a large hand. If you hear nothing, there’s a good chance the opponent is bluffing.
Bluffers try to hide in the shadows for fear of making you suspicious enough to call. One way they do that is to barely breathe — or to not breathe at all! — MC