Below is an excerpt:
Asch's Conformity Experiment
Solomon Asch, with experiments originally carried out in the 1950s and well-replicated since, highlighted a phenomenon now known as "conformity". In the classic experiment, a subject sees a puzzle like the one in the nearby diagram: Which of the lines A, B, and C is the same size as the line X? Take a moment to determine your own answer...
The gotcha is that the subject is seated alongside a number of other people looking at the diagram - seemingly other subjects, actually confederates of the experimenter. The other "subjects" in the experiment, one after the other, say that line C seems to be the same size as X. The real subject is seated next-to-last. How many people, placed in this situation, would say "C" - giving an obviously incorrect answer that agrees with the unanimous answer of the other subjects? What do you think the percentage would be?
Three-quarters of the subjects in Asch's experiment gave a "conforming" answer at least once. A third of the subjects conformed more than half the time.
Interviews after the experiment showed that while most subjects claimed to have not really believed their conforming answers, some said they'd really thought that the conforming option was the correct one.
Asch was disturbed by these results:
"That we have found the tendency to conformity in our society so strong... is a matter of concern. It raises questions about our ways of education and about the values that guide our conduct."
Conformity increases strongly up to 3 confederates, but doesn't increase further up to 10-15 confederates. If people are conforming rationally, then the opinion of 15 other subjects should be substantially stronger evidence than the opinion of 3 other subjects.
Adding a single dissenter - just one other person who gives the correct answer, or even an incorrect answer that's different from the group's incorrect answer - reduces conformity very sharply, down to 5-10%. ....
When the single dissenter suddenly switched to conforming to the group, subjects' conformity rates went back up to just as high as in the no-dissenter condition. Being the first dissenter is a valuable (and costly!) social service, but you've got to keep it up.
This reminds me of a quote from Goebbels:
“If you tell a lie big enough and keep repeating it, people will eventually come to believe it. The lie can be maintained only for such time as the State can shield the people from the political, economic and/or military consequences of the lie. It thus becomes vitally important for the State to use all of its powers to repress dissent, for the truth is the mortal enemy of the lie, and thus by extension, the truth is the greatest enemy of the State.”
This is why a dissenting voice, or someone playing Devil's Advocate, is so important.