As watch-and-wait hunters, cats have big, round eyes planted right in the center of their heads, giving them excellent depth perception when they leap for a kill. They have little snub noses, since they lurk in hiding places instead of snuffling after prey for miles like dogs. And they have rounded faces and chubby “cheeks,” the byproduct of short, powerful jaws designed to deliver a killing bite.

These facial features, a terrifying distillation of feline lethality, happen to also be what humans consider cute. They remind us of own faces, and especially of our babies, since humans, too, have big eyes planted in the center of our heads, which we use in large part to read the facial expressions of others. Through this uncanny but accidental interspecies resemblance, cat faces prime us to communicate, whether by post, tweet or pin.

In nature cats themselves aren’t big communicators. Most interact with other members of their own species only when they fight or mate. Unlike group-living dogs, which have a large, expressive repertoire, cats have faces that are empty canvases, as the animal behaviorist John Bradshaw suggests — strikingly human but also perpetually deadpan.

This is why cat photos seem to cry out for captioning: We feel moved to fill in their blanks.