"Breast Obsession" joke

A man was obsessed with women's breasts, so he went to a psychologist and told him his problem.
"Let's play a little word association game," the doctor said. "I'll say a word and you say the first thing that comes to your mind."
"Plums," said the doctor.
"Breasts," the patient said.
"Oranges."
"Breasts," the patient replied.
"Watermelons."
"Breasts," said the patient.
"Wipers."
"Breasts," the patient said.
"Wait a minute!" the doctor said. "I can understand the connection between plums, oranges, watermelons and breasts. But, automobile wipers? Where's the connection?"
"Easy, doc," the patient explained, "one on the left and one on the right!"