Personal biases are subliminal obstacles that can undermine impartial decision making. They commonly introduce unwarranted opinions and feelings into contemplation of an issue, making it hard to come to an objective and neutral decision. Common biases include confirmation bias, the halo effect, overconfidence bias and groupthink.
Confirmation bias is the tendency for individuals to seek out evidence that confirms their own beliefs, while simultaneously discounting refuting evidence. For example, an individual who believes in holistic medicine seeks out success stories while ignoring or criticizing evidence that downplays its efficacy. The halo effect is the application of a person's positive characteristics to diverse traits and scenarios. For example, there is a tendency for attractive people to be automatically deemed friendly, generous and intelligent, even though these traits may not necessarily apply.
Overconfidence bias is a strong overestimation in the credibility and knowledge of an individual or source. For example, many individuals might automatically believe a claim simply because it was furthered by a doctor or an expert. Finally, groupthink is the idea that a group of decision makers will tend to make decisions that confirms the uniformity or harmony of the group, resulting in faulty or irrational decisions. Groupthink becomes evident when groups overestimate their power and righteousness, hold closed-minded attitudes, and are pressured to maintain unanimity within the group.