Alone in the dark, strangers converge on the same made-up answer

Muzafer Sherif put people alone in a dark room and asked how far a stationary pinpoint of light seemed to drift — an illusion with no real answer. Individual estimates varied wildly, but tested in groups they converged on a shared figure that stuck even when people were retested alone later. Sherif took it as evidence that groups spontaneously manufacture norms, then internalise them as fact.

— Muzafer Sherif, The Psychology of Social Norms — Harper & Row, 1936
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