Anyone who has spent any prolonged amount of time around young children might notice a stage around four or five years old when they fall deeply in love with the mail carrier. It’s not always the mail carrier. Bus drivers are also very popular, and I’ve heard of a few baristas who are visited daily by an adoring toddler. Among my favorite genre of cute YouTube videos — somewhere between “birds playing with cups” and “cat is best friends with . . . ” — is “kid loves sanitation workers.”

At the risk of ruining the preciousness, there is a developmental explanation for this apparent sweetness. Around that age, kids become aggregators, as opposed to atomizers. Their weird little brains are observing the people and places consistent to their routines — it’s how they learn to identify systems, networks, processes, and even social collaboration.

This is the appeal of the Busytown books by children’s author and illustrator Richard Scarry. The series features little bustling scenes of anthropomorphic cats, rabbits, hippos, lions, and other animals, all hard at work, keeping Busytown productive and strong. White-collar jobs like doctor, nurse, teacher, reporter, and engineer are featured alongside housepainters, carpenters, farmers, coal miners, and lumberjacks, and even children doing household chores.