A patient goes to a psychiatrist for the first time and is given some tests.
The psychiatrist draws a circle and says, "What does this make you think of?" "Sex."
The psychiatrist draws a tree and repeats his question. "Sex," the patient answers again.
The psychiatrist proceeds to draw simple figures of all sorts... a house, a car, an apple, and so on... each time getting the same response. Sex, sex, and sex.
Finally the psychiatrist says, "You have an obsession with sex." The patient says, "Me? You're the one who's drawing all those dirty pictures!"