Asch's conformity research (1951, 1952, 1956)

Asch (1951): procedure

Participants: 50 male students from Swarthmore College, USA, told it was a test of visual perception.

Task: say aloud which of three comparison lines (A, B or C) matched a standard line. The right answer was always obvious.

Procedure: each real participant sat second to last among seven confederates. There were 18 trials; on 12 critical trials all the confederates gave the same wrong answer.

Control: a control group judging alone made errors on fewer than 1% of trials.

Results and conclusions

• Average conformity on critical trials: 32% (about one third).
• About 75% conformed at least once; about 25% never conformed.
• About 5% conformed on every critical trial.

In post-experiment interviews most conformers said they knew the answer was wrong but went along to avoid ridicule or standing out: normative social influence leading to compliance. A few said they thought their eyesight must be wrong (informational influence).

The variations (1952, 1956)

Asch changed one feature at a time:

• Group size: 1 confederate, about 3%; 2 confederates, about 13%; 3 confederates, about 32%. Larger groups added little beyond three.
• Unanimity: one confederate giving the right answer cut conformity to about 5%; a dissenter giving a different wrong answer also reduced it sharply. Breaking unanimity matters more than the size of the group.
• Task difficulty: when the lines were more similar, conformity increased (informational influence).
• Privacy: when the real participant wrote answers privately, conformity fell to about 12.5%.

Evaluation

Strengths: high control and a standardised procedure, so it is replicable; the control group shows the task itself was easy, so errors were caused by the group.

Weaknesses: sample of male American students limits generalisability; the task is artificial and trivial (low ecological validity); deception and stress; it measured public answers, so it shows compliance not private change. Perrin and Spencer (1980) found conformity on only 1 of 396 critical trials with British science students, suggesting the 1950s results may reflect their era. Bond and Smith (1996) found conformity was higher in collectivist cultures.

Worked example

In a replication with 12 critical trials, a participant conforms on 4. What percentage of critical trials is that, and how does it compare with Asch's average?

1. 4 / 12 x 100 = 33.3%.
2. Asch's average was 32%, so this participant is close to the average (33.3%).

Answer: 33.3%, close to Asch's average of 32%.

Check yourself

1. Asch's participants conformed on 32% of critical trials on average. Each had 12 critical trials. On average, how many critical trials is that per participant? Give your answer to 2 decimal places.
   Show answer

   3.84 trials. 0.32 x 12 = 3.84 critical trials.

2. Asch used 18 trials, of which 12 were critical. What fraction of trials were critical? Give your answer as a decimal to 2 decimal places.
   Show answer

   0.67. 12 / 18 = 0.67.

3. What happened to conformity when one confederate gave the correct answer?
   • It rose to about 50%
   • It fell to about 5%
   • It stayed at 32%
   • It fell to 0%
   Show answer

   It fell to about 5%. Breaking unanimity gave social support and cut conformity sharply.

4. Which statement about group size matches Asch's findings?
   • Conformity rose steadily with every extra confederate up to fifteen
   • One confederate produced the most conformity
   • Conformity rose up to about three confederates, then levelled off
   • Group size had no effect
   Show answer

   Conformity rose up to about three confederates, then levelled off. 1: about 3%, 2: about 13%, 3: about 32%, then little change.

5. Why did conformity increase when the lines were made more similar?
   • The task became ambiguous, so participants relied on the group for information
   • Participants became bored
   • The confederates gave the correct answer
   • The participants answered in private
   Show answer

   The task became ambiguous, so participants relied on the group for information. Uncertainty increases informational social influence.

6. What was the purpose of Asch's control group?
   • To test the effect of group size
   • To check the confederates' eyesight
   • To show the task was easy, so errors in the main study were caused by group pressure
   • To provide a larger sample of women
   Show answer

   To show the task was easy, so errors in the main study were caused by group pressure. Under 1% errors alone shows the majority caused the errors.

7. Give one reason why Asch's findings may not generalise to conformity today.
   Show answer

   The sample was 1950s American male students; Perrin and Spencer (1980) found almost no conformity with British students, so the results may reflect that era and culture.. Era, culture and sample all limit generalisation.

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Sources

• Pearson Edexcel International Advanced Subsidiary/Advanced Level in Psychology specification (issue January 2026)
• Pearson International A Level Psychology component guide: WPS01
• Simply Psychology: Asch conformity line experiment
• Simply Psychology: What is conformity?
• Summary of Bond and Smith (1996) cross-cultural Asch meta-analysis
• IAL Psychology revision site: Asch's research

Last updated 8 November 2026. Spotted a mistake? Tell us.