There's an interesting story today in the Washington Post by a former FBI agent and author discussing body language and relationships. Joe Novarro spent 25 years spotting spies for the government; it has led him to make pick out meaning in every day movement, whether he wants to or not.
Some of the information in the story is on the obvious side, such as his note that a woman playing with her hair indicates her romantic/sexual interest. There is one standout tidbit, though:
I noticed that my friend's wife made a fist under her chin as she grasped her necklace. This behavior stood out to me as powerfully as if someone had shouted, "Danger!"
I watched the words and gestures of the other couples at the table, and everyone seemed ecstatic -- everyone but one, that is. She continued to smile, but her smile was tense.
Her husband has treated me as a brother for more than 15 years, and I consider him the dearest of friends. At that moment I knew that things between him and his wife were turning for the worse.
Sure enough, six months later, the couple divorced. Turns out she was a cheatin' spouse.
Make sure to check out the rest of the piece, plus the accompanying slideshow, which is animated and rather informative.