Stop looking for anxiety and start looking for "cognitive load"
Lying well is hard — but not in the way you might think.
We usually look for nervousness as one of the signs of lying. Like the person is worried about getting caught. But that's actually a weak predictor.
Some people are so confident they don't fear getting caught. Others are great at hiding it.
Some get nervous when questioned so you get false positives. And others are lying to themselves — so they show no signs of deliberate deception.
So lying isn't necessarily hard in terms of stress. But it is hard in terms of "cognitive load." What's that mean?
Lying is hard because it makes you think. You need to think up the lies. That's extra work.
Looking for nervousness can be a wild goose chase. Looking for signs of thinking hard can be a great strategy.
Lying can be cognitively demanding. You must suppress the truth and construct a falsehood that is plausible on its face and does not contradict anything known by the listener, nor likely to be known. You must tell it in a convincing way and you must remember the story. This usually takes time and concentration, both of which may give off secondary cues and reduce performance on simultaneous tasks. [The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life]This also means that many of the signs of lying we often look for aren't accurate. And things we're not looking for can be good indicators.
For the rest of the story: http://theweek.com/article/index/258917/heres-how-to-really-detect-lies