Supplement: Smullyan

Puzzles from Smullyan

4.

A man was looking at a portrait. Someone asked him "Whose picture are you looking at?" He replied: "Brothers and sisters have I none, but this man's father is my father's son." ("This man's father" means, of course, the father of the man in the picture.)

Whose picture was the man looking at?

... A remarkably large number of people arrive at the wrong answer that the man is looking at his own picture. They put themselves in the place of the man looking at the picture, and reason as follows: "Since I have no brothers or sisters, then my father's son must be me. Therefore I am looking at a picture of myself."

Comment

Logically, "my father's son" must be the viewer himself, since he is his father's son and has no brothers or sisters. Therefore, substituting "me" for "my father's son" gives "this man's father is me," i.e., this man is my son.

Cognitively, the puzzle activates a scenario (or narrative schema) containing two question-answering scripts. The first script involves a question to the portrait-viewer, the second to the reader. The reader, it seems, is encouraged to adopt the perspective of the portrait-viewer, which causes the difficulty. This may be a variety of the "point of view" effect (Pichert & Anderson).

213.

[Von Neumann] was consulted by a group who was building a rocket ship to send into outer space. When he saw the incomplete structure, he asked, "Where did you get the plans for this ship?" He was told, "We have our own staff of engineers." He disdainfully replied: "Engineers! Why I have completely sewn up the whole mathematical theory of rocketry. See my paper of 1952." Well, the group consulted the 1952 paper, completely scrapped their 10 million dollar structure, and rebuilt the rocket exactly according to Von Neumann's plans. The minute they launched it, the entire structure blew up. They angrily called Von Neumann back and said: "We followed your instructions to the letter. Yet when we started it, it blew up! Why?" Von Neumann replied, "Ah yes; that is technically known as the blow-up problem - I treated that in my paper of 1954."

227.

Professor and Mrs. Hilbert were giving a party. After one guest arrived, Mrs. Hilbert took David aside and said, "David, go up and change your tie." Hilbert went up; an hour passed and he didn't come down. Mrs. Hilbert was worried, went up to the bedroom, and found Hilbert in bed asleep. When awakened, he recalled that when he took off his tie, he automatically went through the motions of taking off the rest of his clothes, putting on his pajamas, and getting into bed.

Further materials

Return to Concepts