If you've ever cooked lobster for dinner, you might have boiled it alive thanks to the idea that it can feel pain. But how would you even know if lobster pain is like human pain? It's not like you can ask the lobster, "Hey is the water too hot for ya?" 

Luckily, their anatomy and behavior can give us some clues about how they're feeling. Anatomy-wise, lobsters don't have the same pain-relaying fibers that we have, but they do have pain receptors. We just don't know if those receptors sense pain in the same way we do. 

We can, however, see how they behave. For example if crustaceans have an irritated antenna, they'll rub it and protect it from further injury. And they don't do this if scientists numb their antenna.  These behaviors and receptors suggest they might process pain, but maybe through a different mechanism than humans. 

So some chefs quickly cut into their heads before boiling, just in case.