Two people insisting a blue slide was green swayed a six-person group

In a 1969 experiment, two confederates in a six-person group consistently called clearly blue slides 'green.' Participants judging alone almost never made that error, but with a persistent minority in the room, real participants echoed the wrong answer on a measurable share of trials. An inconsistent minority barely moved anyone at all — consistency, not numbers, was what mattered.

— Serge Moscovici, Elisabeth Lage & Martine Naffrechoux, Influence of a Consistent Minority on the Responses of a Majority in a Color Perception Task — Sociometry, Vol. 32, No. 4 (1969)