negotiation: human behavior
With all these different influences on people it can be extremely difficult to wholly understand the behavior and reactions of those you are negotiating with. Their mental models may differ dramatically from your own, not only because of cultural factors, and it may be difficult to understand them and impossible to empathize with their view of the World. People are not always easy to deal with and not all sets of ideas are equally acceptable.
It's always worth reading Gulliver's Travels, for a view of the follies of others (it's more difficult to see the follies of your own culture).