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Thanks so much for the thoughtful engagement Bob. Super interesting paper to read.
Some thoughts and responses:
On Eisemann and your paper: I agree with your point that anecdotes don’t establish prevalence, mechanism, or what “protective” behavior would look like in an insect biomechanics context. I’m also deliberately not treating the passage as “proper evidence” (as described) against sentience or as an argument that insects don’t have aversive experience—I note it may look different and cite work showing wound-tending and motivational trade-offs. I simply use these observations to note that they sit awkwardly with our usual inferences about severe suffering, which is what the section is about. I have kept the Eisemann passage (as an illustration, like I did before) but tempered and clarified some language around it and how it might be interpreted.
The rhetorical problem I’m reacting to is the opposite: advocates often speak as though severe, life-dominating suffering is an almost automatic implication of sentience markers (benthams.substack.com/p…). I cast doubt on such inferences. So granting all that you and Barrett write about Eisemann not being solid evidence against aversive experience (which I agree with), it’s unclear to me what positive evidence might convince us of a serious aversive state and what negative evidence would actually lower such credence. My worry is that severity risks becoming either automatically inferred or empirically unfalsifiable, through which these low credence, high-n beings come to dominate EV math. Would be very interested if you have reading recommendations on the severity of aversive states or pain.
On taxonomic extrapolation and hemiellipsoid bodies: I’m not trying to abandon phylogenetic inference so much as downweight it when there are concrete reasons to suspect divergence. I’m not claiming the hemiellipsoid point (or the pH grooming null) is knockdown evidence against sentience at all (and I hope that’s clear from my writing). I’m using them to resist a stronger rhetorical move I see a lot: “there’s basically no reason to doubt L vannamei is like other decapods, so treat it as probable.” In a data-starved setting, phylogenetic inference is absolutely a tool, but I think the output should be modest credences. And the markedly miniaturized/weakly differentiated integrative regions in penaeids (even granting that morphology ≠ function) is at least a cue to widen uncertainty about whether the specific integrative architecture that may be underwriting the stronger decapod cases is present in the same way here. That doesn’t “defeat” inference from related taxa, but it should widen uncertainty and make straightforward taxonomic borrowing less confident.
On the negative behavioural result: fair. I was surprised to find how few studies have been performed. I don’t consider any of the evidence as strong and certainly don’t think I have presented it that way, but I point out that the very limited evidence we do have doesn’t support making strong inferences that shrimp feel pain.
Your point on “nociception, so nothing”: fair. Pharmacological modulation is something, though it’s not clear it’s pain. It’d really help to see at least one other criterion being fulfilled and ideally efforts are focused there. I’ve edited the article in one spot to emphasize pharmacological modulation as well.
A more general point: I think a lot of what I point out here needs to be read in the context of the broader informational environment on this issue: how the case is often presented by major animal welfare organizations, in the news, and by advocates more generally. I’m not a fan of singling out individuals (I wasn’t sure about citing the RP report either but felt I needed at least one concrete, illustrative example); here are a few illustrative examples:
farmkind.giving/animal-…: “… scientific research has confirmed that shrimp can feel pain”
vox.com/future-perfect/…: “… Jiménez Zorilla … kept reading. And he saw … the evidence that shrimp are sentient: that they are, at the very least, able to feel pain, able to suffer.”
thehumaneleague.org/art…: “Shrimps are fascinating and sentient creatures found in oceans and rivers around the world.”
animal-ethics.org/consi…: “the evidence for shrimps’ ability to feel pain is so compelling that the United Kingdom has legally recognized them as sentient beings”
shrimpwelfareproject.or…: “There is growing behavioral and neurological evidence indicating that shrimps can feel pain — real, subjective pain — not just mechanical, reflexive responses.”
In terms of dramatization on benthams.substack.com/p…: “You personally, at very trivial cost, can spare millions of sentient beings from horrific and excruciating agony.”
I think these examples illustrate not just the rhetoric used around this topic, but also the degree of certainty with which sentience is stated. In response, my article:
Reviews what we actually know, and where there is doubt.
Considers the implications of taking this standard of evidence seriously.
Casts doubt on pain severity inferences based on sentience markers.
It also very much leaves the conversation open, and I don’t think I’ve presented anything as definitive—not that shrimp aren’t sentient, that insects can’t have aversive experiences, or that their experiences can’t possibly be severe.
I think I share your general consideration for precaution and intuitions in terms of preventing gratuitous suffering. But I simultaneously take issue with the broader implications of using this standard of evidence as a strong guide for moral action, and I have concerns about the public perception of animal welfare following from it. All that said, I do figure installing stunners is a solid intervention, but don’t think it should be the main priority.
Again, really appreciate your comments.