In any negotiation, says Roger Fisher, the Samuel Williston Professor Emeritus of Law and the director of the Harvard Negotiation Project, “there are a handful of things you can easily do, and you’d be dumb not to do them.” Expressing appreciation for one’s interlocutor is one of them.

And appreciation is one of the five “core concerns” that Fisher and his co-author Daniel Shapiro, associate director of the Harvard Negotiation Project, have identified as essential to address whenever parties get together to work out a deal, whether it’s the handoff of children by one half of a divorced couple to the other or a labor contract or a peace treaty.

Anyone in a negotiation wants to feel appreciated, Fisher and Shapiro maintain. They also want to feel “affiliated,” want to feel some personal connection to others. Negotiators also want to preserve, and preferably expand, their autonomy. They want their status acknowledged: Perhaps this is a function of their rank within an organization, or of their specialized knowledge or institutional memory. And they want to choose and play a fulfilling role within the negotiation.

When either side in a negotiation feels these core concerns are not being addressed, the result is negative emotions, such as anger, fear, and guilt, which trigger competitive action – including old-style “I want mine” kind of bargaining. When those core concerns are addressed, positive emotions, leading to cooperative action, are fostered, and the result is much likelier to be a “win-win” agreement.