Do worms feel pain and are ants happy? Why the science on invertebrate feelings is evolving

In fact, new research has shown that many responses in the larger invertebrates were complex, long-lasting, and pretty consistent with criteria for pain that had been produced initially for vertebrates such as rats. Octopuses, for example, can perform amazing feats of learning to avoid painful environments and choose painkilling environments. All this establishes and quantifies “feelings” in beings that are very different from us.

Yet, however far the science gets us, we could use the precautionary principle: we could assume it is possible that invertebrates have feelings, however differently they may be crafted by the millions of years of evolution they went through before we arrived.