Experiments led by Solomon Asch asked groups of students to participate in a "vision test." In reality, all but one of the participants were confederates of the experimenter, and the study was really about how the remaining student would react to the confederates' behavior.
In the basic Asch paradigm, the participants — the real subject and the confederates — were all seated in a classroom. They were asked a variety of question about the lines (which line was longer than the other, which lines were the same length, etc.) The group was told to announce their answers to each question out loud and the confederates always provided their answers before the study participant. The confederates always gave the same answer. They answered a few questions correctly but eventually began providing incorrect responses.
It is important to note that the questions asked in this study were very easy. In a control group, with no pressure to conform to an erroneous view, only 1 subject out of 35 ever gave an incorrect answer. However, when surrounded by individuals all voicing an incorrect answer, participants provided incorrect responses on a high proportion of the questions (37%). 75% of the participants gave an incorrect answer to at least one question.
Variations of the basic paradigm tested how many confederates were necessary to induce conformity, examining the influence of just 1 confederate and as many as 15 confederates. Results indicate that 1 confederate has virtually no influence and 2 confederates have only a small influence. When 3 or more confederates are present, the tendency to conform is relatively stable.
The unanimity of the confederates has also been varied. When the confederates are not unanimous in their judgment, even if only 1 confederate voices a different opinion, participants are much more likely to resist the urge to conform than when the confederates all agree. This finding illuminates the power that even a small dissenting minority can have. Interestingly, this finding holds whether or not the dissenting confederate gives the correct answer. As long as the dissenting confederate gives an answer that is different from the majority, participants are more likely to give the correct answer.
One difference between the Asch conformity experiments and the Milgram experiment as carried out by Stanley Milgram (also famous in social psychology) is that the subjects of these studies attributed their performance to their own misjudgment and "poor eyesight", while those in the Milgram experiment blamed the experimenter in explaining their behavior. Conformity may be much less salient than authority pressure.
The Asch experiments may provide some vivid empirical evidence relevant to some of the ideas raised in George Orwell's Nineteen Eighty-Four (see two plus two makes five). This also helps illustrate the concept of "point at a deer and call it a horse" (Traditional Chinese: 指鹿為馬, Simplified Chinese: 指鹿为马) that was made infamous by Zhao Gao.
Asch's experiment only tested behavioral acquiescence and not attitude change.
A 2005 study (described in ) using Functional magnetic resonance imaging showed that social conformity engages regions of the brain devoted to spatial awareness.