People so readily generalize that they often ‘know’ in advance what they are going to like and what they are going to dislike. They develop assumptions and expectations, which in part determine their future evaluative responses. Biased assimilation occurs when perceptions of new evidence are interpreted in such a way as to be assimilated into preexisting assumptions and expectations. Because this bias may not be deliberate, people suspect the motives of others who do not share their evaluations, and the bias is difficult to overcome. Biased assimilation most likely occurs, however, because acting as though one’s assumptions and expectations are correct is generally more adaptive than acting as though one’s assumptions and expectations might be wrong. Therefore, overcoming a general tendency toward biased assimilation is not necessarily desirable.