Negativity bias describes a cognitive bias in which more attention and importance are placed on negative experiences and information. A bias is a tendency to perceive things in a distorted manner that alters our way of thinking.
This particular bias makes negative information have a larger impact on behavior and perception than positive information. If a person with many positive traits displays one bad trait to another person the bad trait will be recalled more easily than any of the good qualities present.
Studies have looked at this bias in detail and when presented with friendly, neutral, and threatening faces subjects were able to recall the threatening faces more easily and with greater detail than the friendly or neutral ones. There is a possible evolutionary adaptation to the negativity bias. By responding to negative or threatening stimuli quickly humans could avoid possibly dangerous situations.