When my son was a little less than two years old, I used to play a game he liked, bouncing him up and down on my knee while chanting a nursery rhyme:
Half a pound of tuppeny rice
Half a pound of treacle
Mix them up and make them nice
Pop goes the weasel
On “Pop goes the weasel”, I would sharply drop my knee all the way down and let him bump to the floor. He always chortled. He liked the game so much that one day he asked me to repeat it over and over again, laughing at each bump except the final one, when he turned to me in surprise and asked, “Why it’s not funny any more?” From outside himself, he understood something within himself. He had discovered that something repeated over and over again becomes progressively less funny until it’s not funny at all.
Source: Emanuel Derman, ‘Models.behaving.badly’, Chapter 3 (‘The Absolute’)