Confirmation bias

Confirmation bias is the tendency to accept reports which confirm what you already "know", i.e., what you already feel justified in believing - while rejecting reports which contradict your beliefs.

The best scientists work extra hard to overcome this psychological tendency, while advertisers, partisans and many journalists 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 being objective and even skeptical. Scientists who are open minded avidly seek data which contradict their theories - or at least the theories of their colleagues. The predominant idea in science is that if collected data contradict a prediction made by any theory, then the theory must be reevaluated or even discarded.