Every decision a person makes is typically influenced by an interest of the person.   Getting to these interests are very important in solving conflict.  Understanding the differences behind an interest vs a position (something we say we want) is extremely important; and also very easy.

You goal is to find out the interest behind why someone wants to do something.    So in casual conversation with your test subject try to get the individual to make a decision; what to eat, what show to watch, etc.   Then using the why and why not sequence, see if you can differentiate between responses that are positional and the statement that unlocks the interest of the individual.