As per this recent article over on eSide Supply Management on Using ‘Micro Expressions’ to Your Negotiation Advantage, negotiators who can read body language often have an advantage. And if you are emotional, they are sure to pick up on your unfiltered emotional actions and use those against you.
In particular, as per the article, they will be looking for signs of these universal emotions to use to their advantage:
In particular, they will be looking for signs of Fear, since that means they can strong-arm you, Surprise, since that means they can pull a fast one while your mind is otherwise occupied, and Happiness, since that means that they don’t have to sweeten the deal any further to get you to sign.
That’s why, no matter what happens, you should always be cool, calm, and collected against an experienced pro. Don’t take it personally. It’s business, and, more importantly, it’s the organization’s business. No matter what happens, look at it from a neutral, outsider’s perspective. Pretend you’re a third party arbitrator and it’s your job to find a fair resolution to an argument. You might still be out-negotiated, but your counterpart will have less of an advantage.
That’s the reason that good negotiators have a Poker Face.