Do you mean in the sense that you need to assume that the other person will react to and integrate information in the same way you would, if you were in their place? That is important for communication, to be able to guess accurately how the target will interpret the information.
However, on a more simple level you can also communicate by simply observing cause and effect; ie "if I say this sort of thing, they act that way" without actually trying to understand how or why they react that way at all. A lot of people actually communicate this way. Like, they understand that if they compliment somebody they will like them more and be nicer to them and have a better mood, but they won't even think about WHY that is the case.
