A noted psychiatrist was a guest speaker at a large gathering, and his blonde hostess broached a subject of which the doctor was most at ease.

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

"Nothing is easier," he replied. "You ask a simple question, one which anyone should be able to answer without any problem. If he or she hesitates, that puts you on the track."

"What sort of question?" asked the hostess.

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

The blonde thought for a moment, then said, "You wouldn't happen to have another example, would you? I've never known very much about history!"