In a famous experiment, two juries were assembled and presented with evidence. In the first trial, jurors were given the evidence, and after deliberating, only 18% of the jurors voted for conviction. However, in a second, separate trial, the jurors were given the same evidence, but with the additional statement that an eyewitness had identified the defendant as the perpetrator of the crime. Not surprisingly, a whopping 72% of the jurors voted for conviction.
Then, after having voted for conviction, emergency evidence was rushed to the jury: it turns out that the eyewitness was legally blind. Despite the obvious fact that the blind witness could not have seen the crime, most of the jurors maintained their conviction, and 68% voted that the defendant was guilty.Fortunately, the trial itself was only an experiment, but it provided a frightening demonstration of the confirmation trap - that is, the tendency to see what we already believe and discard evidence to the contrary. The confirmation bias has a powerful effect upon our ability to learn.
The confirmation trap arises from the fact that as human beings we pay attention to information that confirms our existing beliefs and ignore information that contradicts what we believe. That is why the jurors in the mock trial wouldn’t change their opinion after they learned that the eye witness was blind. Not surprisingly, it also the reason why entrepreneurs have trouble changing directions when information that contradicts their ideas is received. Focusing on information that confirms your perspective while ignoring contrary evidence makes it difficult to develop an accurate view of the market.
(See Nail It Then Scale It, pgs. 45-46)