When it comes to dating and relationships a highly referenced problem is that of 'understanding'; or rather the lack of it. Speaking as a man (I'm not qualified to speak as a woman), one way this problem manifests itself is in 'unrealistic expectations'. To my mind, unrealistic expectations refers to the problem where person A has a particular expectation in their mind of what person B will do or say if they are interested in pursuing a relationship, and if person B does not then fulfill the requirements of the expectation, then person A will assume they are not interested.
A perfect example is where women expect men to approach them if they are interested, and that a lack of approach indicates a lack of interest. This is a general example. A specific example can be taken from a friend of mine who told me that if a man does not speak to her, she assigns that man the label of 'not interested'. So in her mind she has the expectation that if man X is interested in her, then man X will speak to her. Lack of conversation means man X fails in the expectation and my friend then loses any interest she may have had to begin with. Her body language becomes closed, and the man is unlikely to approach even if he was originally considering it.
By setting up entirely internal expectations in our heads, measuring people against them, then using these expectations to make clear-cut, unambiguous decisions about that person, means that a lot of confusion arises. In any given situation it is impossible to say "if that person were interested in me they would do " because there is no universal mode of behaviour.