Dr Gordon was a guest at a chic gathering, and his hostess naturally broached the subject in which he was most at ease.

"Would you mind telling me, Doctor," she asked, "how you detect a mental deficiency in somebody who appears completely normal?"

"Nothing is easier," Dr Gordon replied. "You ask him a simple question which everyone should answer with no trouble. If he hesitates, that puts you on the right track."

"What sort of question?" asked the hostess.

"Well, you might ask him, ´Captain Cook made three trips around the world and died during one of them. Which one?´"

The hostess thought a moment, 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."