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.”
I don’t think tending to damage is enough to prove pain.
Microbes detect and move away from danger. Plants detect danger and react to defend themselves. They also redirect resources to heal. Pain isn’t necessary for this.
Pain is for learning, so you avoid what caused the pain. Beings that don’t learn shouldn’t feel pain, it would just be a waste of energy. That’d only happen in evolutionary quirks (ie loss of capacity to learn after gaining pain). Nature is cruel (grasshoppers get their heads eaten during mating) but not just for the sake of it.
And of course, there’s humans that have a condition that makes them not feel pain. They still learn self preservation, and they have some reflexes too.
The article makes the comparison with a hurt dog. Dogs remember for life what hurt them. It’s very obvious they learn from pain.