"There is nothing more deceptive than an obvious fact."

— Sherlock Holmes, in "The Boscombe Valley Mystery" by Arthur Conan Doyle

1. Introduction

You just won the lottery, and your first purchase will fulfill a childhood dream: buying a Ferrari. You visit a luxury car website, find a gorgeous Ferrari sports car, and click "Find Similar." The results? Four Ferraris (great!), one Lamborghini (cool!), and a Ferrari SUV (wait, what?). You love the Ferrari and Lamborghini recommendations. But the Ferrari SUV? That's way off from what you had in mind.

Why did the Lamborghini appear? Because it shares the visual characteristics that attracted you to the Ferrari: similar low profile, smooth curves, and sporty design. And the Ferrari SUV? Perhaps the retrieval system gave a large weight to characteristics associated with the Ferrari brand, despite its very different shape.…