Do animals feel pain? Science author Ed Yong says that’s the wrong question.

Every school year at the small Maine college I attended began with a lobster bake. More than a thousand bright red crustaceans, served with butter, or, for the vegetarians and the squeamish, chicken, steak, or portobello mushrooms. I ate the lobster, but suspected the squeamish had it right. It’s hard to look into the eyes of your food and not wonder what it might be like to end in a pot of boiling water.

As I ate, it turns out, biologists in the United Kingdom were answering that question. Two decades of experiments have shown lobsters, hermit crabs, and their cousins experiencing something that looks a lot like pain. Laws have been written based on those findings. Now, if you want to eat a lobster in Switzerland, you can’t boil it alive. The crustacean can only be legally cooked if it’s stunned with electricity—or knifed in the head.

But what does pain even mean to a lobster? As science journalist Ed Yong writes in his newest book, that’s a much harder question. Animals sense physical reality differently than humans, through smells, through electric fields, through currents of water, and those senses shape the very world they inhabit in ways that are fundamentally unknowable. To imagine the world of an insect crawling on a leaf “is like setting foot upon an alien planet,”  he writes.

An Immense World, the Pulitzer Prize winner’s second book, is a travelogue across those planets, and a tribute to the power of human empathy. Since reading it, I found myself returning to the portraits of animal pain. Early in our conversation, I suggested to Yong that of all the animal senses, pain was the one that most people had spent time pondering. He disagreed. Often, he says, the question is boiled down to: “Do they feel it or not? In some ways, that is a very boring question to ask. The more sensible question is: what kinds of pain do they feel?”

In that way, An Immense World is not just about the minds of animals—but also the radical empathy of experts who are trying to see through their eyes.

“Scientists are people. Everyone I talked to has absolutely thought about ‘what is the world like to the creature that I study,’” Yong says. “Whenever I ask, ‘what is it like to be an electric fish, or a bat,’ they have answers, and they have interesting answers. That kind of informs the book—their speculation and feats of imagination are both vital and very much part of the story.”

“That kind of subjective, imaginative stuff is not in [scientific] papers, because it runs counter to how a lot of scientists are trained to think about their work. It’s a bit woolier and emotional and speculative. And important! But it doesn’t appear in the scientific literature very much.”

[Related: Temperature tells honey bees what time it is]

Yong delights in the ingenuity of the experiments that researchers have concocted to step into another sensory universe. Star-nosed moles filmed running their exquisitely sensitive face-tentacles over pieces of rubber; audio engineers remixing birdsong for finches and canaries; elephants freezing in response to rumbles played through buried speakers.

But much like neuroscientists have come to understand the human brain by studying what happens when a stroke kills neurons, some of the earliest insights into the sheer variety of animal senses involved mutilating them. In what Yong describes as “a series of cruel experiments,” an 18th-century Italian priest blinded bats, then tested whether they could fly. If he further deafened or gagged them, he found, they would “blunder into objects.”

Those grim experiments laid the groundwork for the studies in the mid-1900s that discovered echolocation, which opened the door for research into other senses that humans can only imagine: worlds shaped by electric fields, magnetism, or the vibrations of a leaf.

“It’s difficult when at least part of the body of knowledge that you are referring to comes through work that is hard to contemplate,” Yong says. “There are some experiments that honestly I wish had never been done. But l benefit from the knowledge gained through that. And I think probably one of the most important questions for sensory biologists right now is to sort of weigh that out. How much is it worth it?”

The human experience of pain comes down to two elements. The physical part is driven by nociceptors, which are nerves located all over the body that light up when cut, or crushed, or heated, or exposed to chemicals. Then there’s the conscious experience of that “nociception.” As Yong puts it, nociception is “an ancient sense” that shows up in shockingly similar ways in everything from sea slugs to people. But just because an animal registers pain signals in its brain doesn’t necessarily mean it suffers.

“A leech will writhe when pinched, but are those movements analogous to human suffering, or to an arm unconsciously pulling away from a hot pan?” Yong writes in the book. Sometimes, the answer seems to be yes. In one study from 2003, trout injected with bee venom rocked from side to side, rubbed their lips on gravel, and ignored new objects for hours, suggesting that they experienced something beyond a simple reflex to a chemical.

But because pain carries such moral weight for humans, it can be hard to imagine what it would mean to bear it differently. So Yong turns to an analogy in color vision, which is both a physical and conscious experience and works much like pain. As Yong points out, we can see the color spectrum because our neural hardware is set up to do quick arithmetic with wavelengths of light. (Not to mention how our language shapes our ability to notice fine variations in color.) A mantis shrimp, meanwhile, has four times as many types of wavelength-sensing receptors—but appears to experience the world in only 12 colors, “like a child’s coloring book,” Yong writes. 

Even when animals experience pain, it might not present in familiar ways. Squid appear to experience the shock of an injury across their entire body and become hyper-sensitive to touch. Naked mole rats, on the other hand, don’t seem to register certain painful stimuli. In experiments, they didn’t react to carbon dioxide levels that would cause human eyes to sting, or when researchers injected them with acid, or when their skin made contact with capsaicin. They did, however, flinch when pinched or burned. 

And so the same researchers who try to place themselves in the minds of animals find themselves inflicting pain. “A lot of the people I talked to who study how animals sense painful stimuli want to do that work to help those creatures, to inform their welfare, and how we might want to make moral ethical decisions about them,” Yong says. “But to do that, you also need to inflict pain on creatures.”

“How do you weigh up the need to get a statistically robust number of experimental subjects versus the imperative to inflict as little pain upon as few creatures as possible?” he asks.

[Related: How science came to rely on the humble lab rat]

The book’s final chapters is a close look at how the human world is encroaching on animals’ sensory lives. The focus isn’t pain, so much as the way that light from LEDs and the constant rumble of highways reshapes the worlds of species who see and hear and feel differently from us. “When we ask if animals can feel pain, we’re asking less about the animals themselves, and more about what we can do to them,” Yong writes in an earlier chapter. In other words, by focusing on pain to the exclusion of other senses, we’re left with a deeply anthropocentric view of what it means to protect nature.

To imagine the world of an animal is a remarkable act of empathy and a deep source of joy. But in the face of ever-louder roads and ever-brighter nights, is that enough? Even when we recognize the pain we cause to other living creatures, it’s not enough to change our behavior. The researcher behind the trout-bee venom study told Yong that now, when she asks fishing groups if they think their catch feels pain, the answer is almost universally yes. And still, they keep casting their lines.

As Yong writes, animals feel pain in a diversity of ways to survive the perils particular to their species. Humans can prevent some of that pain, at least, the kinds they’re responsible for—but it’s not enough. If we’re going to help species survive the Anthropocene, we need to understand the worlds they live in.

Buy An Immense World by Ed Yong here.