In part, the work grows out of a frustration with other methods. Liars do not avert their eyes in an interview on average any more than people telling the truth do, researchers report; they do not fidget, sweat or slump in a chair any more often. They may produce distinct, fleeting changes in expression, experts say, but it is not clear yet how useful it is to analyze those.

Nor have technological advances proved very helpful. No brain-imaging machine can reliably distinguish a doctored story from the truthful one, for instance; ditto for polygraphs, which track changes in physiology as an indirect measure of lying.

Wish I had had this training while I was teaching.

Some people think everything that comes out of their mouth is the truth just because they said it.