Earlier this month, under the cover of night, an octopus named Inky hauled his basketball-sized body out of the tank he shared with a companion at the National Aquarium of New Zealand, heaved himself across the floor, and squeezed his gelatinous mantle into a narrow drain leading to the Pacific Ocean. It was an escape story fit for a Pixar film, and the Internet responded with corresponding glee. One Twitter user hailed Inky as “the world’s greatest hero,” while another warned that “we're about to be slaves to our new great leader, #Inky.” Comparisons to El Chapo and “The Shawshank Redemption” were made. At Vice’s Motherboard, one writer even created a work of Inky fan fiction, imagining the cephalopod free but heartbroken at being separated from his tank mate, Blotchy. “He felt the joy of a mollusc reborn,” the story goes, imagining the moment when Blotchy escapes to meet Inky in the ocean. “They would live out their days in briny bliss, free from the tank that bound them!”

Part of the fun of the Inky story, like that of the Pizza Rat and the escaping llama duo before him, is indulging in a bit of knowing anthropomorphizing: animals, they’re just like us! In the case of octopuses, this pleasure is especially pronounced, because the creatures’ great intelligence comes packaged in bodies so vastly different from our own. How is it that an eight-tentacled sea alien can open jars and recognize faces? Octopuses have been observed moving around the ocean floor carrying cracked coconut shells, which they close around themselves as portable armor. They exhibit sophisticated play behavior, blowing objects around in the water and even fiddling with Legos.

Attributing human-like behaviors to animals is often thought of as unscientific, but in a new book on animal behavior, “Are We Smart Enough to Know How Smart Animals Are?,” the Dutch primatologist Frans de Waal argues that it is not, in fact, anthropomorphizing but its opposite—an unwillingness to recognize the human-like traits of animals, or what he terms “anthropodenial”—that has too often characterized our attitudes toward other species. Analyzing decades of animal-cognition research, he shows that, with the exception of full-fledged language, animals have been shown to exhibit many of the key behaviors that were thought to distinguish humans from animals: the ability to consider the past and the future, to demonstrate empathy and self-awareness, and to anticipate the motives of others. Crows can recognize human faces and even hold grudges against the biologists who capture and tag them; orcas use highly coördinated synchronized swimming to push seals off ice floes and into the water; a sea lion at a Santa Cruz lab learned, like a fledgling math student, to associate symbols, figuring out that if A goes with B and B goes with C, then A and C belong together as well. Animals, in other words, are far smarter than we’ve been giving them credit for.

Anthropodenial, in de Waal’s view, is a relatively modern phenomenon. In medieval and early modern Europe, the animal mind was considered sophisticated enough that errant dogs, pigs, and other domesticated animals could be put on trial for crimes. In one famous case, in fifteenth-century France, a sow and several piglets were charged with killing a child; the piglets were acquitted, but their mother was sentenced to death and hanged. As recently as the nineteenth century, many naturalists sought out the connections between human and animal intelligence. “The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind,” one Victorian-era naturalist wrote. And this was no pig-prosecuting crackpot; it was Charles Darwin.

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