Completely normal
"Would you mind telling me, Doctor," Bob asked, "how you detect a mental deficiency in somebody who appears completely normal?" "Nothing is easier," he replied, "You ask him a simple question which everyone should answer with no trouble. If he hesitates, that puts you on the track." "Well, what sort of question?" "Well, you might ask him, 'Captain Cook made three trips around the world and died during one of them. Which one?' " Bob thought for a moment, and then said with a nervous laugh, "You wouldn't happen to have another example would you? I must confess I don't know much about history."
“醫生，你能不能告訴我，”鮑勃問，“對于一個看上去很正常的'人，你是怎樣判斷出他有智力缺陷的呢?”“再沒有比這容易的了，”醫生回答，“問他一個簡單的問題，簡單到所有人都知道答案，如果他回答得不干脆，那你就知道是怎么回事了。”“那要問什么樣的問題呢?”“嗯，你可以這樣問，‘庫克船長環球旅行了三次，但是在其中一次的途中他去世了，是哪一次呢?’”鮑勃想了一會兒，緊張的回答道，“你就不能問另外一個問題嗎?坦率地說，我對歷史了解的不是很多。”