A University student delivers a pizza to an old man’s house.

“I suppose you want a tip?” says the old man.

“That would be great,” says the student, “but the other guy who does deliveries told me not to expect too much – he said if I got 50 cents, I’d be lucky.”

The old man looks hurt. “Well, to prove him wrong, here’s 5 dollars. What are you studying?”

“Applied Psychology,” replies the student.