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How Could We Recognize Pain in an Octopus? Part 1

The views expressed are those of the author and are not necessarily those of Scientific American.


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At the level of personal experience, there is nothing that seems easier to understand than pain. When I jam my finger in a doorway, I have no difficulty at all recognizing the sensation that results. But this superficial simplicity covers up a world of complexity at the level of brain mechanisms, and the complexities are even greater when we try to identify pain in other people or other species of animals. Some of the complexities are purely scientific, but others are caused by moral or philosophical issues getting mixed up with scientific issues.

My provocation for writing this post was a blog post called Do Octopuses Feel Pain?, by Katherine Harmon, who writes the blog Octopus Chronicles, It’s basically a nice article—there’s nothing objectionable about it—but it pressed one of my buttons. She made a number of important points, and altogether what she wrote is well worth reading, but nevertheless the result left me with a feeling of dissatisfaction, as do most scientific discussions about pain in animals. I’d like to try to explain where that discomfort comes from.

In her blog post, Harmon listed three elements that are involved in feeling pain: (1) nociception, that is, having mechanisms in the body that are capable of detecting damage and transmuting it into neural signals; (2) the experience of pain; (3) the ability to communicate pain information from sensation to perception. I’m not sure I understand the third aspect, but I take it to mean the ability to transform nociception into experience.

In any case, the essence of pain as most people understand it is aspect 2. Most people think of pain as a particular type of experience—as something that happens inside our minds and can only be observed by ourselves.

But as philosophers are well aware, there’s a big problem with that approach. The problem with thinking of pain as a private experience is that it leaves us helpless to identify pain in other people, much less in other species of animals. If it is unobservable from the outside, how could we possibly know whether it exists? This is what philosophers call the Problem of Other Minds.

The standard solution, implicit in most scientific discussions of pain, is that the more closely an animal resembles us, the safer we are in attributing experiences like ours to it. Other people have bodies and brains very similar to ours—the argument goes—so we can safely assume that they have pains like ours, especially when they tell us about them. Some types of animals, particularly mammals, have brain structures and nociceptive systems so similar to ours that it seems only reasonable for them to have pain experiences like ours. And so on.

But here’s the thing. That solution just doesn’t work. It is wrong even for mammals and other people, and if you try to apply it to octopuses or lobsters, it doesn’t produce anything except bafflement.

To help you see why the similarity-to-us approach is off the mark, I’d like to present you with four simple thought experiments. I claim that the pain-as-experience and similarity-to-us theory gives answers to them that most people will feel are wrong. If we don’t have clear answers to these sorts of scenarios, we will not be in a good position to make use of scientific data about octopi or other animals—maybe not even data about ourselves. I have my own answers to them, which I’ll explain in a followup post.

Here are the four thought experiments:

1. Suppose we are confronted with aliens from another planet, who are broadly humanoid in appearance, with two arms, two legs, an erect bipedal stance, and a head with two eyes and a mouth. They speak a language, but it does not translate easily into English, and it is unclear whether they have any word that corresponds to “pain”. Suppose also that their internal organs are completely different from ours, and in particular their nervous systems bear no resemblance to ours on any level. Imagine that we poke one of these aliens in the arm with a needle, and see that the alien jerks back its arm, scrunches up its face, and lets out a screech. Should we conclude that the alien is experiencing pain?

2. Same story, but suppose now that we are dealing with a humanoid-appearing robot rather than an alien. Should we conclude that the robot is experiencing pain? If you give a different answer for the robot than for the alien, can you justify it?

3. Suppose we are dealing with an ordinary human, a man named Wally Wallace. He claims to be in constant excruciating pain, but we cannot see any evidence of it in his behavior. He seems completely relaxed; he laughs and jokes; he moves without any appearance of constraint; he seems happy. Nevertheless he says that he is in agony. Of course he might be lying, but is there any possibility that he is telling the truth? What would it take to convince you?

4. The reverse scenario. Suppose Sally Sanders has a broken leg. She claims that she doesn’t feel any pain at all, but she is pale and moves stiffly; she gasps and winces whenever anything touches the injured area; she seems to move in a way that keeps the injured area from touching things. Nevertheless she says that she is pain-free. Of course she might be lying, either to herself or to us, but is there any possibility that she is telling the truth?

If you find this challenging, I hope you won’t be too distressed about it. The fact is that pain is a complicated thing. In humans it involves a mixture of sensory perception, motivation, and evaluation—a combination of brain activity, “experience” (whatever that is), and behavior. Applying such an intricate concept to a species that we don’t understand very well is never going to be easy.

Image: Anneli Salo

William Skaggs About the Author: William Skaggs is a neuroscientist whose experimental work has focused on the role of the hippocampus in learning, memory, and spatial navigation, but he is interested in several other areas of science as well, especially the study of consciousness. He has ambitions to be a science writer, and has contributed extensively to Wikipedia under the name "Looie496", mainly by writing articles about the nervous system. Follow on Twitter @weskaggs.

The views expressed are those of the author and are not necessarily those of Scientific American.



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Comments 11 Comments

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  1. 1. jtdwyer 10:59 am 09/20/2013

    I presume that if an octopus senses pain (local tissue damage) it will physically withdraw from the source of injury.

    I really don’t see a puzzle here, unless you’re referring to emotional distress. In that case, you’ll have to rely on the judgement of a psychologist…
    <%)

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  2. 2. looie496 11:37 am 09/20/2013

    @jtdwyer: Even a plant might physically withdraw from the source of an injury. The word “pain” implies more than that. — Bill Skaggs

    Link to this
  3. 3. larkalt 12:23 pm 09/20/2013

    Perhaps our concept of “feeling pain” is a mental construct that makes sense to us in terms of how our brains operate and how other humans’ brains operate. We extend it to animals when they do things that look like pain.
    But it doesn’t necessarily have any meaning outside of human minds and brains.

    Link to this
  4. 4. looie496 12:32 pm 09/20/2013

    @larkalt: If pain doesn’t have any meaning outside of humans minds and brains, then is there anything wrong about torturing a dog or cat? — Bill Skaggs

    Link to this
  5. 5. larkalt 12:46 pm 09/20/2013

    @looie496 We extend the concept of pain to other creatures more or less based on their similarity to us, their gestures etc. And with it, more or less, our ethical standards.
    Why mention dogs and cats, when pigs are more intelligent? Most people don’t mind eating chopped pig, and don’t give any thought to the pig’s experience. That shows you how subjective our ethics are.

    Link to this
  6. 6. jtdwyer 1:57 pm 09/20/2013

    Bill Skaggs,
    My dictionary refers to pain in the sense of physical sensation; “mental or emotional suffering or torment”;
    obtuse applications such as ‘I’m taking great pains to explain such a simple matter to you’.

    As I explained, the physical sensation of pain can be detected in other people and animals by a basic response – to escape the source of pain.

    IMO, you do not adequately explain what you mean by “The word “pain” implies more than that.” What are you referring to? Please define what “much more than that” is implied, in your opinion…

    If you’re asking whether octopuses suffer from “mental or emotional suffering or torment”, then the answer may simply be that we have no way of communicating such abstract concepts with octupuses – unless you assert that they feel fear as we do and respond by ejecting ink, or that they change colors for some purpose other than avoiding predators.

    Perhaps some correlation between octopus and human brain activity indicating some specific emotional states could be established by brain imaging studies – but I doubt it. I suggest that you refer to http://en.wikipedia.org/wiki/Anthropomorphism

    Link to this
  7. 7. looie496 2:20 pm 09/20/2013

    @jtdwyer: I am less concerned about what pain truly is (which I think is a meaningless question) than about the thought process by which people attribute pain to an entity. The fact that plants and simple machines can show withdrawal from noxious inputs, but most people don’t attribute pain to them, means that people must be basing their judgements on something more than this. — Bill Skaggs

    Link to this
  8. 8. larkalt 2:45 pm 09/20/2013

    Plants usually react very slowly. If they reacted faster we probably would attribute pain to them.
    People know what’s living, nonliving, and killed. Children probably learn the difference, very young. We have a mental category for tools and machines, which doesn’t include pain.
    But someone who was unfamiliar with machines might attribute pain to a robot.

    Link to this
  9. 9. subterra 1:33 am 09/21/2013

    1. If the alien has internal organs, we can probably conclude that it is a biological organism of some sort, even if the organs don’t resemble ours. If it has arms and legs and moves about, we can probably conclude that it is an animal of some sort. If it speaks a language, even one that does not translate well, we can probably conclude that it possesses some sort of awareness as well as the ability to manipulate abstract symbols in a complex manner. Since you speak of aliens in the plural, we can probably conclude that it is a social being. Therefore, it would be adaptive if these particular beings were able to detect damage incurred to their organs while moving about, and to quickly and easily communicate such to other members of their social group. Withdrawing from the source of damage and emitting a sharp noise (and maybe a few curses) is consistent with this, as well as consistent with a human experience of what we call “pain,” so equating the two is reasonable though not completely certain.

    2. This is meaningless without a much more precise definition of “robot.” Are we talking about the arm that welds bumpers to cars, or about Kryten, the robot on Red Dwarf?

    3. Wally isn’t communicating pain in the way that humans generally do, rather he is nonverbally communicating wellness and comfort. Most other humans would likely conclude that he is pulling their leg.

    4. It is given that Sally has a broken leg, and her nonverbal clues suggest extreme discomfort. Pain. The more adaptive (and thus likely) group behavior would be to give much greater weight to the nonverbal clues than to the verbal statements of lack of pain, so what is really important here is the effect of perceived pain on group behavior.

    Link to this
  10. 10. larkalt 8:44 am 09/22/2013

    “what is really important here is the effect of perceived pain on group behavior.”

    That brings up a good point – a pain perception may evolve so that group members can communicate about pain to others. Especially when a species uses sophisticated language skills to communicate.
    Octopuses aren’t generally social so perhaps that means they don’t have a pain perception.

    Link to this
  11. 11. larkalt 9:01 am 09/22/2013

    “a pain perception may evolve so that group members can communicate about pain to others”
    And if group members help others in pain or they need to say “Don’t pull on my hair! That hurts”.

    Link to this

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