(Laboratory experiment) Sherif used the autokinetic effect. This is where a dot of light is projected onto a screen in a dark room. The light appears to move even though it's not moving. The dot appearing to move is a visual illusion.
Participants were led to believe that someone was moving the light. They were asked to guess how far the light moved.
They were tested in three phases.
Phase 1 - Participants made guesses individually.
Phase 2 - Participants made guesses in groups of three.
Phase 3 - Participants made guesses individually.