Professor Key’s arguments comes down to a number of key points:
Only humans can report feeling pain. In contrast, pain in animals is typically inferred on the basis of nonverbal behaviour
There is compelling evidence that pain in humans is generated by neural activity in the cerebral cortex, in particular a “dynamic core” consisting of somatosensory areas I and II, prefrontal cortex, anterior cingulate cortex and the insular cortex.
According to bioengineering principles, the function of brain regions is determined by their structure, and the specific structure and integration of the cortical regions in the “dynamic core” are necessary for the function of feeling pain
Fish lack the above mentioned neural architecture for feeling pain
Therefore fish do not feel pain
It all seems fairly logical…
But, in order to accept his conclusion, one must accept the veracity of Professor Key’s premises, and this is where the plot thickens. Because, the journal of Animal Sentience uses the fantastic structure of inviting and publishing expert commentaries on Key’s target paper, along with replies from the original author on the commentaries (all of it fully open access to boot). What ensues is a rigorous academic back and forth that is as much about profound questions of human pain and consciousness, as it is about whether a salmon can feel a pulled hypaxial muscle.
At the heart of Professor Key’s argument is a proposition about how humans experience pain, and his paper provides an easily digestible summary of his position regarding the brain structure and function that is responsible for the conscious experience of pain. However it is this key proposition that is most targeted for debate in the commentaries. Amongst the commentators are some real luminaries in the domains of neuroscience, cognitive neuroscience and philosophy of mind, here’s just a sampling:
Riccardo Manzotti – No evidence that pain is painful neural process
“I counterargue that no conclusive evidence supports the sufficiency of any mammalian neural structure to produce pain. We cannot move from contingent necessity in mammals to necessity in every organism.”
Antonio Damasio – Pain and other feelings in animal
“Evidence from neuroanatomy, neurophysiology, and neuropsychology suggests that the experience of feelings in humans does not depend exclusively on structures of the cerebral cortex. It does not seem warranted to deny the possibility of feeling in animals on the grounds that their cerebral cortices are not comparable to those of humans.”
Marshall Devor – Where is pain in the brain?
“Imaging indeed shows that pain-relevant signals reach the cortex, but not that they underlie the subjective experience of pain. Lesions and stimulation data are more to the point, but Key paints an idiosyncratic and misleading picture of their effects. S1 and S2 ablation does not eliminate evoked or spontaneous pain, although there may be up- or down-modulation…Overall, the case for the cerebral cortex being an essential substrate for pain experience in humans is too equivocal a starting point for ruling out the possibility of pain experience in fish.”
Anil Seth – Why fish pain cannot and should not be ruled out
“[Key’s] strategy fails in three ways. First, non-mammalian consciousness — if it exists — may depend on different mechanisms. Second, accumulating neurophysiological and behavioural evidence, evolutionary considerations, and emerging Bayesian brain theories suggest that if fish can feel at all, they can feel pain. Finally, the qualitative nature of pain and suffering obliges us, via the precautionary principle, to accommodate the possibility of its existence where doubt remains.”
“I was a bit chagrined that Key spent so much time denying that any form of consciousness can exist below the cortex. Obviously it can…”
Of the 34 commentaries published, only three support Professor Key’s position. But, as Key points out in one of his replies, “science does not prevail by popular opinion. History is plagued with numerous (and often widely accepted) examples of biological phenomena being explained by mysterious forces.” However, Key’s rejoinder in this case seems a little disingenuous, and at risk of sneaking in a straw man. None of the commentaries resort to an appeal to mysterious forces, rather, they focus on Key’s narrow necessity and sufficiency conditions for consciousness experiences of pain, that is – the mammalian cortex. Devor, Damasio and Panksepp all challenge this idea and do so without resorting to “opinion” – they each provide supporting evidence, while also questioning Key’s use and interpretation of empirical evidence offered to support his claims.
For me, the really juicy stuff comes in the commentaries from Anil Seth and Riccardo Manzotti. Seth, cognitive and computational neuroscientist and Editor-in-chief of the just-launched, open access journal Neuroscience of Consciousness, points out that “the biophysical substrates of conscious states (including pain and suffering) in any species, including humans, cannot yet be confidently identified“. More simply put, Seth is arguing that, despite Key’s confidence that conscious experience arises in/from the cortex, we really don’t understand (some would argue we don’t even have the beginning of an idea) how the human brain, or any brains, gives rise to conscious experience. Seth has suggested that the question of how the brain generates conscious experience (begging an obvious question…) is the “most interesting problem in science”. Along with interesting, it may also be one of the most intractable problems in science, and it highlights that despite much progress in understanding pain, we still have no idea how all the carry on in certain nerve fibres and the brain might give rise to ‘hurt’.
Manzotti, professor of psychology at IULM University (Milan) and a proponent of a more radical position on consciousness, points out that “there is no definitive proof that neural activity is sufficient to generate pain. In all known cases, neural structures are involved, but so are bodies, the environment, stimuli, tissue damage, past and future behavior, and social interactions. We have no reason to discard all of that in favor of the neural underpinnings alone.” Manzotti rejects not only Key’s idea that the cortex gives rise to the conscious experience of pain, but rejects the notion that even the entire brain can produce consciousness. Although this idea can sound a bit out-there, Manzotti is certainly not alone in this view, with philosophers of mind such as Alva Noë, Kevin O’Regan, and Evan Thompson (to name just a few that have made past appearances here on NOIjam), and others in the Embodied Cognition and Extended Mind camps arguing, in various flavours, that consciousness experience can not, and does not arise solely from the brain.
If you’ve stuck it out thus far, I hope you can see that the question of whether Nemo feels any pain is, in many ways, really just a subset of the much bigger, and deeper question of how it is that humans experience pain – or consciously experience anything at all. This makes the entire series of Key’s target paper and subsequent commentaries a rich (open access) trove of profound questions and ideas about brains, human pain and conscious experience. I think you’ll enjoy reading many of the papers – and what a great time of year to get comfortable, grab something nice to drink and enjoy some thought provoking, erudite and weighty philosophy of mind reading – that is, if you’re into this kind of thing.
Thoughts, comments and questions, as always, welcome below.