Number of words: 168

You know, of course, that water holds up a fish that is placed in it. Well, here is a problem. Suppose we have a bucket which is partly full of water. We place the bucket on the scales and find that with the water in it, it weighs exactly 45 pounds. Then we put a 5-pound fish into the bucket of water. Now, what will the whole thing weigh?

Most adults answered that 45 pounds plus 5 pounds is 50 pounds. The person giving the test was then supposed to ask “How can this be correct, since the water itself holds up the fish?” Wrote Terman, “If the subject keeps changing his answer or says that he thinks the weight would be 50 pounds, but is not certain, the score is failure.” Only if the subject logically defended  his correct answer  to two successive challenges from the test-giver was the answer marked correct.

Excerpted from page numbers 87-88 of ‘How Would You Move Mount Fuji?’ by William Poundstone.