Invertebrate Welfare Cause Profile

More than 99.9% of animals are invertebrates. There is modest evidence that some large groups of invertebrates, especially cephalopods and arthropods, are sentient. The effective animal activism community currently allocates less than 1% of total spending to invertebrate welfare. That share should rise so that we can better understand invertebrate sentience and investigate the tractability of improving invertebrate welfare.

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Features Relevant to Invertebrate Sentience, Part 3

Executive Summary

In this, the final of three posts on features potentially relevant to invertebrate sentience, we assess 9 learning indicators, 4 navigational skills, and 7 mood state behaviors. Here are some high-level takeaways:

  1. Simple learning abilities, such as classical conditioning, sensitization, and habituation, do not appear to be good evidence of sentience.

  2. Contextual learning and long-term behavior alteration to avoid noxious stimuli are better evidence of sentience.

  3. It’s plausible that the evolutionary role of consciousness is to produce an integrated and egocentric spatial model of the world to guide an animal as it navigates a complex environment.

  4. It’s difficult to study emotions in invertebrates.

  5. Notwithstanding (4), it appears there are striking behavioral and neurochemical similarities between mammalian responses to stressful stimuli and the responses of certain arthropods.

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Features Relevant to Invertebrate Sentience, Part 2

Executive Summary

In this, the second of three posts on features potentially relevant to invertebrate sentience, we assess 5 drug responses, 5 motivational tradeoffs, and 5 feats of cognitive sophistication. Here are some high-level takeaways:

  1. Research that analyzes the effects of analgesics, antidepressants, and anxiolytics on invertebrates—especially self-administration studies—has the potential to reveal important evidence about various invertebrates’ capacity for valenced experience.

  2. Studying motivational tradeoffs can help us distinguish reflexive, pre-programmed behaviors from more plastic responses.

  3. Comparing cognitive sophistication across dissimilar taxa is extraordinarily difficult.

  4. Notwithstanding (3), many invertebrates, especially arthropods and cephalopods, appear surprisingly intelligent.

  5. The relationship between cognitive sophistication and the capacity for valenced experience is unclear.

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Features Relevant to Invertebrate Sentience, Part 1

Executive Summary

In this, the first of three posts on features potentially relevant to invertebrate sentience, we assess 10 anatomical and evolutionary features and 5 types of noxious stimuli reactions. Here are some high-level takeaways:

  1. Neuron count and brain size are often over-emphasized in superficial discussions of sentience.

  2. Nociceptors (specialized peripheral sensory cells used by the body to detect potentially harmful stimuli) are found in a diverse range of animals including fruit flies, sea hares, and nematodes. The possession of nociceptors may be a necessary condition for painful experience, but it is not a sufficient condition.

  3. Centralized information processing of some kind is probably a necessary condition for consciousness.

  4. Physiological responses to noxious events don’t tell us much about valenced experience.

  5. Simple reactions to noxious events, such as immediate withdrawal, also don’t tell us much about valenced experience.

  6. More complex reactions to noxious events, such as long-term protective behavior, might tell us something about valenced experience.

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Invertebrate Sentience: A Useful Empirical Resource

Rethink Priorities reviewed the scientific literature relevant to invertebrate sentience. We selected 53 features potentially indicative of the capacity for valenced experience and examined the degree to which these features are found throughout 18 representative biological taxa. These data have been compiled into an easily sortable database that will enable animal welfare organizations to better gauge the probability that (various species of) invertebrates have the capacity for valenced experience. This essay details what we’ve done, why, and the strengths and weaknesses of our approach.

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Detecting Morally Significant Pain in Nonhumans: Some Philosophical Difficulties

Other humans merit moral concern. We think many nonhumans merit moral concern too. But how do we know? And which nonhumans? Chimpanzees? Chickens? Bumblebees? Protozoa? Roombas? Rocks? Where and how do we draw a line?

What would it take to justifiably believe that some nonhuman experiences pain (or pleasure) in a morally significant way?1 This is a tough question, but it is incredibly important to get right. Humans constitute a very, very small fraction of the animal kingdom. If other vertebrate animals experience morally significant pain, then much of our engagement with these animals is deeply immoral. If invertebrate animals experience morally significant pain, then, given the sheer number of invertebrates,2 an almost incomprehensible amount of morally significant suffering occurs beyond the ken of normal human attention. And if the capacity to experience morally significant pain is not restricted to organic entities, then human civilizations of the future may be capable of producing exponentially more sentient entities than presently exist.

On the other hand, if many, most, or all nonhumans do not experience morally significant pain, then it could be a waste of resources to try to change their condition. Given that there are millions of humans currently experiencing morally significant pain (for whom these resources would be a great aid), the opportunity cost of wasting time, talent, and money on nonhumans appears tremendous.

Figuring out where and whether to allocate resources to help nonhumans is of significant interest to Rethink Priorities. This post is our first in a series on morally significant pain in invertebrates.

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