Stereotypes are inaccurate generalizations about groups. Symbols are neutral descriptions of phenomena. We follow communication rules even when we are not consciously aware of them. Symbols are ambiguous. It is therefore highly unlikely that two people completely understand how each other thinks and feels.
All communication is aimed at reducing as much as possible the vagueness of symbols.
Regulative rules are those conventions by which we assign meaning to communication based on the communication's actual content. Lunching with Nguyen, Ted hears but does not really listen to much of what she says. However, when Alice mentions the Celtics, Ted listens attentively. This is an example of preoccupation. Noise is external interference with our communication.