The "first impressions" of a person are actually the sensory data (along with the corresponding judgments) we use to form an initial judgment of someone. Is this sensory data chosen or merely received? I think in many cases we choose the data, especially when we are trying to evaluate someone's character. We look for signs of certain personal qualities, or the lack of these qualities. Sometimes this selectivity can be exclusive to the point that we miss other signs, or we judge prematurely. Hence the need for other moral virtues to aid us in making good judgments about character.