There is a universal premise in all negotiations that both sides want to be heard and understood.
Listening is the cheapest yet most effective concession we can make while in the throes of negotiating. While listening intensely, a negotiator shows empathy and demonstrates they have a real concern about what the other side is experiencing.
The use of non-verbal communication (such as leaning in, nodding the head and giving ample eye contact) will send the message that you care and want to understand where your counterpart is coming from.
Psychotherapy research shows that when we feel listened to, we begin to listen to ourselves better and to the internal messages that drive our points of view.
Lastly, when people feel listened to and understood, they become less defensive and oppositional. This is huge when trying to work through a negotiation with someone because it helps them become more open to other points of view and ultimately leads them to a more calm and rational state of mind.