Confirmation bias
Confirmation bias is the tendency to accept evidence confirming what one already feels justified in believing while ignoring, downplaying, or even rejecting evidence that might tend to contradict one's beliefs.
The best scientists consciously strive to overcome this psychological tendency, while advertisers, partisans and many journalists try exploit it.
Ronald Bailey wrote:
- Once a particular notion becomes conventional wisdom, evidence and stories confirming that conventional wisdom are easily accepted and published—and reported in the media. Those that contradict the prevailing views have a much harder time getting a hearing. [1]
The opposite of bias and prejudice is objectivity and even skepticism. Scientists who are open minded avidly seek out data which might potentially contradict their theories - or at least the theories of their colleagues. Ideally, if collected data contradict a prediction made by any theory, then the theory must be reevaluated or even discarded.
Confirmation bias sabotages scientific objectivity by discarding or ignoring data which challenges the prevailing consensus. This often leads to the situation in which an entire generation of scientists must grow old and die before the next generation comes up which is willing to examine newly discovered ideas; see Paradigm shift. It is unfortunate that advocates of global warming and evolution fall prey to confirmation bias, or even willfully allow it to cloud their judgment.