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Key Study: Asch’s Lines Experiment

Solomon Asch (1951)

Updated: 12/01/13

BACKGROUND & AIMS: To determine whether a majority can influence a minority even when the situation is unambiguous. Asch questioned the results of Muzafer Sherif (1935) and other researchers exploring what would become termed informational influence - see Conformity - Majority Influence - reasoning that the participants probably conformed because the stimulus was ambiguous. Asch aimed to find out if the effects of majority influence that had previously been found in such situations are so great that they are still present when it is apparently obvious that the majority have responded incorrectly.

PROCEDURE (METHOD): Asch set up a situation in which 7 male student volunteers all sat looking at a display. In turn, they had to say out loud which one of the three lines A, B, or C was the same length as a given stimulus line X [see below]. All but one of the participants were confederates of the experimenter, and on some ‘critical’ trials the confederates were instructed unanimously to give the same wrong answer - 12 of the 18 trials. The students always gave their answers in the same order and the one genuine participant was the last (or the last but one) to offer his/her opinion on each trial. The performance of participants exposed to such group pressure was

compared to performance in a control condition in which there were no confederates. In all 123 genuine participants were tested.

FINDINGS (RESULTS): On the 12 critical trials where the confederates gave the same wrong answer, the genuine participants also gave the wrong answer on 36.8% of these trials. This should be compared against an error rate of only 0.7% in the control condition - in other words, control group participants answered correctly over 99% of the time when there was no social pressure. 25% of the participants never gave a wrong answer on any of the trials.

Many of the participants who had given wrong responses admitted they had yielded to majority influence because they didn’t want to stand out.

Individuals who gave only correct answers said either that they were confident in the accuracy of their own judgement or focused on doing the task as directed (ie: being accurate and correct).

CONCLUSIONS: A majority can influence a minority even in an unambiguous situation in which the correct answer is obvious (as was shown by the almost perfect performance in the control condition). Asch showed convincingly that group pressures to conform in terms of majority influence are much stronger than had been thought previously. However, on about 2/3 of the crucial trials, the genuine participant gave the correct answer, so many people managed to resist majority influence.
The participants were perceived to be responding to what would be termed
normative influence.


Graphic copyright © 2001 Psychology Press Ltd

Excerpt from a TV documentary replication of Asch’s experiment