For a person dealing with conflict and training people in principled WIN-WIN negotiation, it is always very frustrating to meet with dirty tricks in negotiation. Those inherently adversarial unethical (and/or not broadly accepted as ethical) negotiation ploys misuse some of the cognitive biases in favour of the active party to the detriment of the opposing party.
The most common commonly known dirty trick would be walkouts but there are some more sophisticated ones as calling higher authority and bad cop-good cop approach. Those tools may poison the mediation procedure that supposes to be problem-solving oriented and amicable in nature and even abort dispute settlement procedure due to loss of trust. For those instruments are incompatible with mediation, every mediator needs to know the way how to tackle them efficiently and smoothly: He or she has to know how to support the party against which the trick is used and how to educate the parties which are employing it in a way that would neither embarrass them, nor discourage them to mediate on.
