The experiment is related closely to the Stanford Prison and Milgram Experiments, in that it tries to show how perfectly normal human beings can be pressured into unusual behavior by authority figures, or by the consensus of opinion around them.
For the experiment, eight subjects were seated around a table, with the seating plan carefully constructed to prevent any suspicion.
Only one participant was actually a genuine subject for the experiment, the rest being confederates, carefully tutored to give certain pre-selected responses. Careful experimental construction placed a varying amount of peer pressure on the individual test subject.
The experiment was simple in its construction; each participant, in turn, was asked to answer a series of questions, such as which line was longest or which matched the reference line. (Fig 1)
The participants gave a variety of answers, at first correct, to avoid arousing suspicion in the subject, but then with some incorrect responses added.
This would allow Asch to determine how the answers of the subject would change with the added influence of peer pressure.
The Asch Experiment results were interesting and showed that peer pressure could have a measurable influence on the answers given.
The control group, those not exposed to peer pressure where everybody gave correct answers, threw up only one incorrect response out of 35; this could probably be explained by experimental error.
The results for the other groups were interesting; when surrounded by people giving an incorrect answer, over one third of the subjects also voiced an incorrect opinion.
At least 75% of the subjects gave the wrong answer to at least one question, although experimental error may have had some influence on this figure. There was no doubt, however, that peer pressure can cause conformity.
It was debated whether this is because people disbelieve the evidence of their own eyes or if it was just compliance, that people hide their opinions.
Follow ups to the Asch Experiment showed that the number of dissenting voices made a difference to the results, as did the forcefulness of the confederates.
One incorrect confederate made little difference to the answers, but the influence steadily increased if two or three people disagreed.
The figures did not change much after this point; more confederates made little difference. The number of people in the group also made a difference; the influence of dissenting voices leveled off for groups of more than six or seven people.
The experiments also showed that, even if only one other participant disagreed with the confederates, the subject was more likely to resist peer pressure; it appears to be more difficult to resist the majority if isolated.
The Asch Experiment showed that one voice can make a difference amongst many.
There have been a number of criticisms of Asch's experiments; the subjects were all young males, and they tend to be much more impressionable than older men. More mature people have had enough experience of life, and more mental strength; they are more likely to hold true to their convictions.
Another criticism, that the experiment lacks ecological credibility and does not relate to real-life situations, is one that can be leveled at many psychological experiments, including the Milgram Experiment and the Stanford Prison Experiment.
Other follow up experiments, where the subjects were allowed to write down responses anonymously, showed far fewer incorrect answers. The comfort of anonymity made sure that looking foolish became much less of a pressure.