It would be unfair for teachers to give the students they like easier exams than those they dislike, for federal regulators to require that foreign products pass sticker safety tests than domestic products, or for judges to insist that the defense attorney make better arguments than the prosecutor.
And yet, this is just the sort of uneven treatment most of us give to facts that confirm and disconfirm our favored conclusions.
For example, volunteers in one study were told that they had performed very well or very poorly on a social-sensitivity test and were then asked to assess two scientific reports—one that suggested the test was valid and one that suggested it was not. Volunteers who had performed well on the test believed that the studies in the validating report used sounder scientific methods than did the studies in the invalidating report, but volunteers who performed poorly on the test believed precisely the opposite.
To ensure that our views are credible, our brain accepts what our eye sees. To ensure that our views are positive, our eye looks for what our brain wants.
Daniel Gilbert, Stumbling on Happiness