Katie Lim is the Director of Toy Design for Super Chewer. Here’s her tale from the field as told to Grace Wade. Popular Science’s Play issue is now available to everyone. Read it now, no app or credit card required.

Appealing to a dog’s natural instinct to hunt is a great way to get them to have fun. We test all the contents we send to our BarkBox subscribers by observing pups in play sessions. We look for a lot of factors, like how easily they can grip an object with their feet and teeth—we call that “paw and jaw”—and how well the toy mimics the sound of prey with features like squeakers and crunchy fabrics.

We also pay attention to the scent, since canine noses are 10,000 times as sensitive as ours. This is in part thanks to the vomeronasal organ, which gives our four-legged pals the ability to smell and taste at the same time.

We use those super-sniffer abilities to our advantage. Because dogs are naturally driven to fatty and protein-heavy meals, they love cheese- and peanut-butter-scented chewers. We’ll sometimes mix nontoxic oils into the rubber or infuse them into nylon to imbue our playthings with a whiff of deliciousness.

One time, Moose, a pit bull mix at the office, got so excited about a squealing, bacon-scented ball that he chased it across the room—dragging his owner’s office chair right along behind him. With a reaction like that, we knew we had a winner.