Given that people are going around doing things like cutting off octopus limbs in order to understand their distributed neuron processing system, it’s worth asking some questions about how octopuses perceive pain, as well. That’s more complicated than you might think. As Katherine Harmon explains, it’s likely that octopuses have some kind of awareness of when they’re touching something unpleasant. But just how that works, and how similar it might be to the way we vertebrates understand “pain”, is a big mystery.