A mother and father took their six-year-old son to a nude beach. As the boy
walked along the beach, he noticed that some of the ladies had boobs bigger
than his mother's, and asked her why.
She told her son, "The bigger they are the dumber the person is."
Pleased with the answer, the boy goes to play in the ocean but returns to tell his mother that many of the men have larger "parts" than his dad.
His mother replied, "The bigger they are the dumber the person is."
Satisfied with this answer, the boy returned to the ocean to play.
Shortly after, the boy returned again. He promptly told his mother, "Daddy is talking to the dumbest girl on the beach and the longer he talks, the dumber he gets."