A Psychological Test
Five balls; four white, one black. The balls are placed in a bag and shaken up.
Each participant takes a random ball whilst the performer looks away. Only the participants know the colour of their own ball.
The performer then asks random questions to the participants, to which they have the freedom to tell the truth or lie.
One by one, the performer will supposedly analyse the participant's honesty and then accurately deduce the ball's colour based on the final question: 'Are you holding the black ball?'
(The performer knows who has the black ball from the beginning)
This effect is perfect for pseudo psycho analysis. Leading the audience to believe the performer is a master of reading people/their minds.