Research and ethical questions in arthropod experience of "pain"

@teellbee @bobby23 what we really call pain is an emotion-coloured event, for now we don’t see worms having emotions, what they have is pure physiological raction. And if you want take insects for an example, you can stab them and if it doesn’t affect their movements they won’t try to do anything with the object in them and just continue live their live, without any sign of distraction. Worms always moving when they’re out of ground where they belong, they do some crazy moves just from one touch of yours, do they feel pain at the moment? No.

For me it’s quite simple, if you don’t know if something can feel pain, assume that it does. Studies are proving again and again that all kinds of organisms are much more complex than we previously thought. There is so much we don’t know about even the consciousness of our own species, let alone creatures as alien to us as invertebrates. I don’t think we can comfortably assume much about how they perceive the world yet, and so as a precaution, I’d rather overestimate their capabilities than underestimate them and perhaps be guilty of torturing a living being that might be in excruciating pain.


yes, I think these comments kind of summarise it…

even if we assume they have a “consciousness something is physically wrong with its body” as @teellbee said , how do we measure how impacting that is, from a simple touch to being stabbed?

I would be curious to know how these things have been measured already in arthropods. That said, even the idea of measuring how much you are inflicting conscious discomfort on another being sounds horrific to me! (imagining aliens coming to Earth and doing similar consciousness tests on us in order to decide whether they farm us or whether they take over our habitat doesn’t sound like much fun)

…but I think its a bit of a different ball game again if we can see a visible lack of reaction, as @davidenrique mentioned re:orthoptera …or as I’ve heard accounts of with cockroaches eating their own abdomens… or spiders eating their partner whilst mating perhaps. Then it becomes so alien to me, that I’m no longer sure where the boundaries of conservative assumption and clear conscious discomfort lie. I think there’s a valid argument there in conservatively assuming this is a fundamentally different experience to them than for example, smelling a noxious smell and recoiling.

Even if we are being conservative …if we can’t see discomfort, do we still assume it?
Do we overestimate as @stanvrem says?
If so, then how do we grapple with the moral considerations of plant life or slime moulds and how will that in turn play out in robotics?
We will need to delineate somehow, whether people like it or not.

To extrapolate singular examples of arthropod experience to all arthropod species seems weak to me though anyhow. I very much doubt one could argue these sorts of examples indicate a lack of discomfort for all the million different species of arthropods, in all situations…

If cockroaches lack nerve endings, or visible recoil under some circumstances which might lead us to believe they don’t experience discomfort ,like the hypothetical p-zombie @coniontises mentioned, then the ethics do seem to become more complex. e.g. How do we grapple with the example of the cockroach hacking kit that is on sale in the US in order to remote control cockroaches by inserting electrodes into their brain …

Many are (rightly I think!) fairly disturbed by this. But in the tutorial video where they insert the electrodes, there isn’t actually much in the way of visible recoil. Though one could argue there are limits to how much a cockroach can visibly recoil (they don’t have the flexibility of the worm).

But say we want to argue against this happening, what lines of attack are available if you take sentient pain or conscious discomfort out of the equation?
Even if I agree that for me the measure of pain or sentience seems like a fallacy as @bobby23 says, or agree to overestimate not underestimate as @stanvrem says, it doesn’t stop the need to be able to argue the ethical case.


Very well said.


Fascinating “can of worms” you all have opened up. Unfortunately, since humans have probably been thinking about these subjects for thousands of years, anyone hoping for a clear answer to this question is likely to be disappointed.

I like a lot what @bobby23 says above, and I think it should point us toward humility and a deeper consideration of what ethics are. My belief is that an ethical principle of “do not cause pain, or less pain is better than more pain” is not just technically unworkable (how do you define pain, who experiences it, how do you measure its intensity?), it’s also woefully incomplete.

For biologists, who have a natural tendency to classify and sort organisms, the impulse to sort organisms into “feels pain” and “does not feel pain” is a natural one, but in doing so we actually avoid the harder question of what is ethical. Whether something is conscious, aware, feels pain, has memory, these are all important things to consider but they do not necessarily give you an answer to what is ethical. (as an aside, mindfulness, cognitive behavioral therapy, and various religious practices can actually help us separate our feelings of pain, fear, desire etc, from judgement. In other words, we can experience pain without necessarily experiencing it as bad. This is very helpful therapy for people with chronic pain [see:]. If this is true it raises larger questions as well about what pain is and how it relates to positive/negative judgments of value–but I digress).

Beyond the question of ethics there is a separate and fascinating issue of consciousness and “qualia” of pain to discuss. Here too, we have to be humble. We are simple biological beings whose lifespan and experience is only a tiny slice of reality. We really don’t know a lot . Many of assume that consciousness is something in the brain of vertebrates–or at least in the brain of things with brains! But this assumption is really not as logical as it seems. You might think: 1) our brains are made of neurons that are made of molecules, and these obey the laws of physics, and 2) consciousness is created only in the brains of animals. Explore those two assumptions with more skepticism. If the matter in brains creates experiences of pain and awareness, then what is it exactly that does this in the brain? Does it happen in a single neuron? Does it take more than one neuron? If it takes more than one neuron than how many? One hundred, one billion? It seems ridiculous to think that there is a “magic number” out there of brain complexity or or neurological function that delineates these things!

A far simpler assumption is that all matter has a subjective experience (I know crazy!). In this case the brain is an organ, like any other that helps us do things but it doesn’t “create” or define our consciousness any more than the kidney does. If this is true, maybe consciousness extends beyond Planarians to plants, and even pants!

At this point, I’m exhausting even myself! But there are some fascinating discussions going on between philosophers, cognitive scientists and even physicists surrounding these ideas. Maybe it’s B.S. but I think it’s a wonderful thing for us lowly humans to think about more:

see also:


How I recognize and describe pain in my previous post is divorced from emotion. I see pain as more fundamental, a sensation more comparable to hunger or oxygen deprivation. I don’t think an animal needs to be emotive to experience pain. I do not know if an earthworm feels sadness, joy, anger, etc. But I assume it experiences discomfort when its cells are being damaged in the same way I assume it experiences hunger when deprived of food. If we want to be technical, my personal interpretation of physical pain is quite similar to nociception, so my argument could be re-phrased to be that it is more conservative to assume a mobile animal is “nociceptive” unless explicitly demonstrated otherwise.

EDIT: I assume the distinction was made because we can reasonably test whether an animal responds to negative stimulus, but we cannot easily determine how it “feels” after the fact. However, I think that has been misconstrued to mean an animal definitively cannot perceive pain if we can only reasonably find that they are nociceptive, and this thinking has paved the way for unethical treatment towards many organisms and potentially trivializes fundamentals of their behavior. “An earthworm does not perceive pain, only nociception”. So? That does not justify mistreatment of these animals (and other living organisms that cannot definitively be proven to feel “pain”) in my eyes, though national legislation, public perception, and laboratory regulations are formatted as if they do. Too many times have I seen people rip the wings off of dragonflies, pour table salt on living snails, crush spiders, disembowel lab beetles, and uproot saplings on the principle that they do not feel pain/are not sentient/are not conscious. That should not make them removed from ethical consideration.

I would be careful about conflating “responding negatively to harm caused to me” and “causing harm to someone else”. I don’t think they are the same thing.

The extreme size dimorphism between males and females in many spider species is a selective response to the fact that females will never pass up a meal, especially if they will have to dedicate additional energy to the production of eggs. She has everything to benefit from the male’s death. The males that survive to live another day (and mate with more females) are the ones small enough to get away after mating. But this has nothing to do with pain, and I would not say it is the equivalency of a beetle consuming its own entrails.

Cannibalism of one’s mate is not uncommon in animals. It has even been observed in highly-social mammals like lions, and I don’t think anyone would argue that they do not feel pain.


Good point. Here’s a question for the thread: How do you regard this research on beetle cyborgs from Singapore?

Is this unethical? Or is it just unappealing? Or is it just unfamiliar? I think we will probably have different responses. (warning, this might be a little disturbing to some people).

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What you describe is not pain, that’s what is logically goes from your posts and why it’s wrong to call described situations as painful, cause what happens is not a pain. And yes, a good point of how to call it.

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I find all of this highly problematic, and without clear answers, as you said in the first post. It all just leads to more questions really!

To watch the video, I feel triggered, and somewhat horrified.
But then this robot video also triggers me in similar ways (at 00:48 at least)
And I have shown this in a lecture in a certain context where I think I actually quite upset some folks. So… I’m not sure I really trust my own or others sense of empathy as a true barometer of justice any more…+Ultimately, if it comes down to a “trolley problem” of beetle vs human, then I would sacrifice the beetle. As I imagine most people would.

This doesn’t make me feel comfortable with experiments on insects though! I guess the core question, and the logic of one beetle vs one human life is more acceptable to me than the premeditated decision to be (potentially) torturing beetles just in case. But this feels essentially, quite weak and more like passing the buck than anything.

Similarly, I’m horrified at the idea of Neuralink being tested on monkeys.
But also prefer the idea of human cyborgs to being slave to an AI overlord…

So yeah, basically, I just feel very conflicted. :)

I also have issue with collecting specimens still (even though I have read many of the arguments for this). The arguments around this issue are similar though…but would probably entail an entire other thread!

p.s. Nice article. Love the term “non-spatiotemporal ingredients” :D

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Damn, that looks like a home video of a pervert. I can’t say I empathize the dino, it’s just a plain awkward scene.

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Yeah… context is key I guess! And expectation.
And how much of the clip is shown.

I’ve shown a small part of this (I think around 00:48) in the context of talking about roboticising taxidermy, human taxidermy(!) and animal ethics and many people were quite upset - they felt it referenced abuse …even if it was a robot.

Another time I showed this and everyone was laughing.
Another time I showed it and one person was laughing. Somewhat awkwardly.

Watching it back now, I still feel slightly triggered at 00:48.
But in any case for the argument here its kind of irrelevant, even if high levels of empathy aren’t triggered by this for you… I’m sure they will be potentially by robots in the coming decades (depending on how robot ethics evolve).

The roboticist involved in the making of Pleo was also the maker of Furby.
He actively set out to try and trigger empathy in children through robotics, to help them learn empathy (he claimed … I think). As I remember though, it lead to people deliberately abusing the Pleo to elicit these reactions…so, didn’t go quite as planned.

Theres a great Radiolab podcast about this -

Slightly worried mention of robot and human taxidermy sounded a little too weird without reference! So - postscript for last comment:-

Robot taxidermy e.g. pet cat drone

Human taxidermy e.g. the philosopher (and early animal rights proponent interestingly) - Jeremy Bentham

Both examples also raising interesting ethical questions similar to the other issues we´re talking about…

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Pedant time: once again, I am too tired and lack the energy to discuss ethics any more so I’ll let the rest of you do it yourselves.

However, @sbushes linked to the famous Backyard Brains control-a-roach experiment.

The guy who runs B Brains was interviewed by Vsauce here and Michael (Vsauce host) asks a few questions before they plant the machine into the insect. One of the replies to the questions was something like this: “yeah we snip the roach antennae during the experiment but roaches have great regenerative capacity, soon the antennae will grow back.”

I’ll let you personally decide whether snipping roach antennae is morally acceptable or wrong. However, one thing is undeniable: Adult roaches cannot molt. Thus they cannot regen their antennae or other external body parts (their regen is linked to molting), and the Backyard Brains guy clearly hasn’t done his research properly (or maybe he has and is just lying). The roaches in the video have long wings and are thus obviously adult (only Ephemeroptera, the “mayflies”, have full wings in an immature stage). By the way the roaches are either Blaberus discoidalis or a hybrid mislabeled as pure discoidalis, mislabeling is rampant in live roach cultures.

Also, some more food for thought from professional entopeople:


Thanks for the link, good review of the science!


Not that I’m much interested in joining into a controversial discussion, but I thought I should offer my own opinion. My personal belief is that any organism whose survival could be enhanced by the experience of physical pain would develop this trait by evolution. Thus, I do think that many arthropods can experience pain (though I’m sure some either don’t experience something recognizable as pain, or is at least very different than what others do experience), but it may be something very different than the mammalian experience of physical pain. My biggest problem with what is called science is that many of its practitioners assume they (either themselves as individuals or as the greater scientific community) know all of what there is to know, but we forget that we that are an animal too, with our own massive biological limitations; there is much that I believe is well beyond our comprehension, and which science does only a partial job at understanding. We must never forget that what we do not know is far greater than what we do know.


Agreed- nice link! (the one).
I would be interested to know which boxes Entognatha, botany + bacteria can/cannot tick on the central diagram if anyone knows?

Pasting it here from the article :

Screenshot 2020-05-31 at 11.55.30
I can’t see anything AFAIK in the list that couldn’t be easily simulated in robotics.
Mind you, I can´t see much in humans that won’t be easily simulated in robotics before long!

As you say @jharkness - current science is limited, as perhaps comparisons to robotics highlight.
Its still, for me, a fascinating and mind-bending topic though- contentious or not + resolvable or not :)
So many unknowns - a wonderful conundrum.


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