P2.S.1Conformity: majority influence; Asch's line study and variations (group size, unanimity, task difficulty); normative and informational social influence

Conformity is changing your behaviour or opinion to match a group. Solomon Asch (1951, 1955) ran the canonical demonstration.

Asch's line study

Procedure: 123 male US college students were each shown a "standard" line and three comparison lines. They had to say aloud which comparison matched the standard. Easy task; controls scored ~99% correct alone. But each "participant" was placed with 6–8 confederates who, on 12 of 18 trials, deliberately gave the same wrong answer. The participant always answered last but one.

Finding: on the critical trials, 32% of participants conformed to the wrong answer; 75% conformed at least once across the trials.

Variations

Asch ran several variations to identify what affected conformity:

• Group size: conformity rose sharply from one to three confederates, but flattened above three. More than three confederates added little.
• Unanimity: when one confederate broke ranks and gave the right answer, conformity dropped from 32% to ~5%. Even a different wrong answer reduced conformity.
• Task difficulty: making the lines more similar (harder to judge) increased conformity — participants relied on others when uncertain.

Two types of social influence

Deutsch and Gerard (1955) named two motives:

• Normative social influence (NSI): conforming to be liked / accepted — fear of rejection. Leads to compliance (public agreement, private disagreement).
• Informational social influence (ISI): conforming because we believe others know better — uncertainty drives us to look for information. Leads to internalisation (genuine private belief change).

In Asch's easy line task, NSI dominates — participants knew the right answer but conformed publicly to fit in. In the harder variation, ISI plays a bigger role: when in doubt, others must know.

Strengths and limits of Asch

Strengths:

• Clear, replicable lab procedure.
• Variations isolated specific causal factors.
• Demonstrated public conformity even on unambiguous tasks — counter-intuitive and influential.

Limits:

• 1950s American male undergraduates — culturally and demographically narrow.
• Conformity rates have fallen in re-runs (Perrin & Spencer, 1980 — UK engineering students conformed in only 1/396 trials).
• Trivial task; lab setting; demand characteristics.
• Ethical concerns: deception and stress.
• Suggests conformity is culturally specific — collectivist cultures show higher rates than individualist.