Negotiators often create barriers to buy time.
There are times when you want to slow the negotiating process. This is when you need to deploy time-buying tactics. Creating barriers is an excellent way to forestall an unacceptable decision.
We live in a society where everyone is supposed to be omnipotent and the best at what they do. Playing dumb to disarm the other person or to buy some time to think over what is being said is a seldom used negotiating tactic. It is very effective.
There is nothing wrong with asking questions or asking for clarification. When the other person is making a major point against you, don't hesitate to interrupt to ask for clarification. It will break their train of thought and give you a chance to think of ways to deflect their argument.
We also live in the real-time world of email and faxes. Just because you receive a proposal by fax or email does not mean you should respond in kind. Feel free to sit on a proposal for a few days before sending a response. This signals several things. That you are too busy to look at the proposal. That you may have other offers. That it is not important to you.
Most important, it "says" you aren't ready to respond for some reason.
Don't be forced into making a hasty decision. Time typically works to your advantage. When you are at the negotiating table and the other person makes a proposal, sit back and ponder, for as long as you want and then some. More times than not the person making the offer will get nervous and improve the offer.
Your silence will signal that you were not satisfied with the terms. Their reaction tells you how much they want to reach an agreement.
As they say, silence is golden.