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Have you ever caught someone in a lie? If so, it's likely that what really gave them away was not the cold hard facts or their verbal statements—it was probably their body language. Even if neither of you realized it, human psychology tells us that there's a complex exchange of physical signals during tense interactions. Some people may glance around the room furtively, others may stare at the floor. Blinking rapidly, fidgeting, and crossing arms or legs can all be warning signs as well. You may not catch these signs immediately, but if you know where to look, you can spot a liar in seconds.
On the flipside, understanding these “tells” can enable you to use them to your advantage, and use your body language to bluff when you're at a disadvantage. This can throw off anyone who might be looking to take advantage of your weakness, whether that's in a game of cards or a very real and dangerous negotiation.
The following infographic from Visual.ly shows some facts about body language, as well as how to identify liars and bluff convincingly. Again, these techniques are shown in the context of a poker game, but they could easily be applied to almost any real-life circumstance—a business negotiation, convincing a criminal you don't pose a threat, or bartering for goods in a survival scenario.