I first read about the concept of the rider and the elephant in Switch by Chip and Dan Heath. From that book I traced the source back to a guy called Jonathan Haidt, the author of The Happiness Hypothesis. He has been teaching psychology using this concept for more than a decade now.
Suppose you have 2 urns in front of you, Urn A and Urn B . Both urns contain red marbles and black marbles. Urn A has 50 of each colour, making it to a total of 100 marbles, but Urn B’s mixture is unknown. What we know however is that it also contains 100 marbles.
If I offer you a bet, say RM100 per correct guess, which colour will you bet on: