Even Worms Feel Pain

Who feels more pain, a person or a cat? A cat or a cockroach? It’s widely assumed animal intelligence and the capacity to feel pain are positively correlated, with brainier animals more likely to feel pain, and vice versa. But what if our intuition is wrong and the opposite is true? Perhaps animals that are less intelligent feel not only as much pain but even more.

Thinking about pain is psychologically challenging. It can be, well, a pain. “To have great pain is to have certainty; to hear about pain is to have doubt,” wrote Elaine Scarry in The Body in Pain. It’s all too easy to dismiss the pain of others while treating our own as unquestioned fact.

This disparity is even more true when it comes to perceiving the pain of animals, where Western society has placed Descartes before the truth. Animals, he famously claimed, are mere automata. They don’t feel pain like we do, and so, carrying the notion of human exceptionalism much too far, Descartes didn’t hesitate to cut animals open while they were alive, without concern for what they were clearly feeling. The same was true of other giants of early science, such as William Harvey, whose discovery of the heart’s role in circulating blood was based in large part on his own heartless vivisection of living dogs.

This argument