A mother and father took their 6 year old son to a nude beach. As the boy walked along the beach, he noticed the some of the ladies had boobs bigger than his mother's and asked her why. The mother told her son, "The bigger they are, the dumber that person is."
Satisfied with the answer, the boy left to play in the ocean, but returned to tell his mother that many of the men have larger pee-pees than his dad. His mother explained, "The bigger they are, the dumber that person is."
Again, satisfied with answer, the boy returned to the ocean to play. Shortly after, the boy returned again, promptly informing his mother, "Daddy is talking to the dumbest girl on the beach and the longer he talks, the dumber he gets."