Just to add to this. Pain is further associated with the fear-terror-excitement response axis, which can be thought of as the ability to anticipate and remember

Just to add to this. Pain is further associated with the fear-terror-excitement response axis, which can be thought of as the ability to anticipate and remember pain/loss and ramp metabolism in response. Fight-or-flight basically. This is more developed in mammals and birds, warm-blooded animals can turn their metabolism up and down at will as part of their survival strategy. All vertebrates have it to some extent, but e.g. quadrupeds can run faster, most birds can only choose to fly or not at all. My take-away is that we should be more concerned about how we treat animals that are very clearly capable of a wide range of emotions, and which humanity currently treats extremely poorly - pigs and cattle especially.