Asch's line-judgment studies

What happened

Solomon Asch of Swarthmore College reported a series of line-judgment experiments in a 1956 monograph. The studies ran at three colleges. A group of seven to nine male students judged which of three comparison lines matched a standard line. All but one member had been told to give wrong, unanimous answers on certain trials. The one uninformed person, the critical subject, answered after hearing the others.

The psychological idea

Each session had 18 comparisons, and 12 were critical trials on which the majority was wrong. Judgments were spoken aloud in public. A control group of 37 people wrote their answers privately, so Asch could separate majority-induced errors from ordinary mistakes. Asch framed the study as being about independence as much as yielding.

In practice

No commercial application is documented in this study. Across 123 critical subjects in three experimental groups, the mean error was 36.8 per cent of critical judgments, against 0.7 per cent in the control group. Twenty-nine of the 123 made no errors, so 94 yielded at least once. Individuals differed widely: Asch reported that about a quarter gave majority-determined answers on eight to twelve trials.

Why it mattered

The study is usually called the Asch conformity study, although Asch meant it at least as much to show independence. Friend, Rafferty and Bramel reviewed 99 textbook accounts from 1953 to 1984 and found that many distorted Asch's findings, with a growing stress on conformity. Any consumer reading, such as social proof in advertising, is interpretation and was not tested here.

Evidence behind the claims

• Asch's experiments ran at three colleges with all-male critical subjects aged 17 to 25; groups of seven to nine judged 18 line comparisons aloud, 12 of them critical trials on which an instructed majority gave unanimous wrong answers.

  DocumentedSource: [1]Where: Plan of the investigation (pp. 3-4), The Critical Subjects (p. 5) and Structure of the Task (pp. 6-7)

• In the control group of 37 people who wrote down their judgments of the lines individually, 35 made no errors and the mean error was 0.7 per cent.

  Experimental findingSource: [1]Where: Table 3 (p. 10) and p. 9

• Across the 123 critical subjects the mean error was 36.8 per cent of critical judgments.

  Experimental findingSource: [1]Where: Table 3 (p. 10)

• Twenty-nine of the 123 critical subjects made no errors, which leaves 94 who erred at least once.

  Experimental findingSource: [1]Where: Table 3, 'All experimental groups' column (p. 10); 94 is 123 minus 29

• Asch reported that one-fourth (24 per cent) of the experimental subjects gave errorless estimates and an approximately equal number (27 per cent) gave majority-determined estimates from eight to twelve times.

  Experimental findingSource: [1]Where: Results, p. 11

• Asch argued that independence and resistance to pressure are as much facts about people as conformity, deceived subjects about the majority, and explained the purpose in full in an interview afterward.

  DocumentedSource: [1]Where: Introduction (p. 3) and Postexperimental Interview (p. 9)

• Friend, Rafferty and Bramel reviewed 99 social psychology textbook accounts from 1953 to 1984 and found that many distorted Asch's findings, with accounts increasingly emphasizing conformity and downplaying independence.

  DocumentedSource: [2]Where: Abstract as returned in the Crossref recordChecked at abstract level

People involved

• Solomon Asch. Experimenter, Swarthmore College

In the Psy101 course

• OpenStax Psychology 2e, section 12.4: Conformity, Compliance, and ObedienceChapter 12, Social Psychology. Concept. The section discusses this topic.Opened the page: it describes Asch's line-judgment experiment and says 76 per cent conformed at least once, which matches the count of 94 of 123 in the monograph.

This is course relevance only. It is not evidence for the historical or corporate claims on this page.See the full course map.

Sources and inspection

2 of 2 sources were opened and read at the level shown. A source marked as not verified supports no claim on this page by itself.

1. [1]
   Studies of Independence and Conformity: I. A Minority of One Against a Unanimous MajorityAsch, S. E.. Psychological Monographs: General and Applied, 70(9), Whole No. 416, 1956. Journal article. Primary source.Relevant text checkedReviewer read pages 1 to 11 of the scanned PDF as page images: introduction, plan and procedure, subjects, Tables 1 to 3, Figure 3 and the first quantitative results. The copy sits on a Greek university course site, not the publisher's site. Later chapters of the monograph were not read.
2. [2]
   A puzzling misinterpretation of the Asch 'conformity' studyFriend, R.; Rafferty, Y.; Bramel, D.. European Journal of Social Psychology, 20(1), 29-44, 1990. Journal article. Critique or replication.Abstract or publisher record onlyReviewer read the abstract text returned by the Crossref API record. The article itself was not opened.

Access note: Cross-cultural and replication work (for example Bond and Smith 1996) could not be opened, so it is not used.

Independent source review: Claude review agent, independent of the research agent, 2026-10-21. Verdict: pass-with-edits.

Related records and elsewhere on Psy101

• Milgram's obedience experiment
• Cialdini's Influence and the principles of persuasion
• The MusicLab artificial music market
• The Stanford prison experiment

• Psy101 Timeline: Asch reports line-judgment experiments on conformity and independence
• Psy101 People: Solomon Asch