Visiting his parents’ retirement village in Florida, my middle-aged friend, Tim, went for a swim in the community pool while his elderly father took a walk.

Tim struck up a conversation with the only other person in the pool, a five-year-old boy. After a while, Tim’s father returned from his walk and called out, "I’m ready to leave."

Tim then turned to his new friend and announced that he had to leave because his father was calling. Astonished, the wide-eyed little boy cried, "You’re a kid?"