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.
This is right if the confederates are modeled as honest, rational people giving answers based solely on what they see. But if they are rational, it seems that they would be updating appropiately on the previous answers. After 3 of them, the answer would be locked in, and they would conform even if they would have disagreed if asked independantly, so further conforming answers are not much evidence. An honest, rational dissenter, on the other hand would imply considerable confidence to overcome the evidence in favor of conforming, and this confidence is itself evidence that would support the test subject in dissenting.
Why would the answer be locked in after three responders? They should also be partially discounting on the likelihood that the two people after the first altered their answers to conform. Each successive response in agreement is weaker evidence than the one before it, but I can't see any reason why three responders would constitute a magic point beyond which additional responders account for negligible evidence.
With common knowledge of sufficiently low variance in the confidence people have in their own direct observations, two answers would be enough for lock in. With greater variance it took more. Not knowing the actual variance, I said 3 because it fit the data.
Today's post, Asch's Conformity Experiment was originally published on 26 December 2007. A summary (taken from the LW wiki):
The unanimous agreement of surrounding others can make subjects disbelieve (or at least, fail to report) what's right before their eyes. The addition of just one dissenter is enough to dramatically reduce the rates of improper conformity.
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