The behavioural cue of ‘flexible self-protection’ is a way to establish whether an animal feels pain, scientists say
Crickets that received the hot probe “overwhelmingly” directed their attention to the affected antenna – they groomed it more frequently, and tended to it over a longer period of time, he says. “They weren’t just agitated and flustered. They were directing their attention to the actual antennae that was hit with this hot probe.”
Some people don’t even believe in evolution, do there it is.
And besides that, some people want to believe their food don’t have feelings.
It makes sense all organisms feel some sort of pain because it’s related to self preservation, but not all of them have an ability to communicate about the pain. And even less number of them communicate pain in a way we could understand, and even less that we actually care to listen.