After a leg injury, pain makes a person avoid putting too much weight on the affected leg. Shielding the injury gives it time to heal. An injured insect shows no such shielding response. Some have...

After a leg injury, pain makes a person avoid putting too much weight on the affected leg. Shielding the injury gives it time to heal. An injured insect shows no such shielding response. Some have cited the lack of such a response as evidence that insects do not feel pain. But insects do produce substances similar to our natural painkillers. Is the presence of these compounds in insects sufficient evidence to conclude that they feel pain?