There was an expert accountant who was well versed in game theory. He heard that his intelligent niece, who was five years old, always took a 50p piece, when a choice between a 50p piece and a pound coin was offered to her.
He went to see his niece and offered her just such a choice. She took the 50p and said
"Thank you Uncle".
The accountant tried to explain to his niece
"You must understand, a pound coin is twice as valuable as a 50p piece, so you should always choose the pound coin."
The niece replied
"Uncle, but then people will not offer me any money."