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.”
Well what we feel as pain is ultimately chemical reactions. Now I can’t go into the entire set of chemical reactions that another being would qualify as “pain”, much less hypothesize as to what word another being would qualify anything. I’ll leave the spectrum of chemical reactions and non-human pain thresholds to others.