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.Read More
Rethink Priorities has been compiling and analyzing relevant scientific evidence regarding invertebrate consciousness. As explained in a previous post, we selected 53 features potentially indicative of the capacity for valenced experience as criteria for discerning whether invertebrates of 12 biological taxa are conscious or not (see database). However, if a specific feature can effectively operate non-consciously in humans, that function –by itself– may provide no evidence that an individual is conscious. Hence, we investigated which of those 53 features can occur unconsciously in humans. We observe that different noxious stimuli reactions and some simple forms of learning are the most likely to occur unconsciously in humans. These and other findings are presented and discussed in this report.Read More
Invertebrate welfare has been gaining recent traction in the scientific literature and among the effective altruism community. However, whether invertebrates have the capacity to experience pain and pleasure in a morally significant way is still very uncertain. Given this current epistemic state, Rethink Priorities has been compiling and analyzing relevant scientific evidence regarding invertebrate consciousness and exploring criteria that evaluate whether individuals of a given invertebrate species or taxon have valenced experience. These data have been gathered and displayed in this database. In a prior post, we summarized our main findings by feature. Here, we present our results by taxa.Read More
Invertebrate welfare has been gaining recent traction in the scientific literature and among the effective altruism community. However, whether invertebrates have the capacity to experience pain and pleasure in a morally significant way is still very uncertain. Given this current epistemic state, Rethink Priorities has been compiling and analyzing relevant scientific evidence regarding invertebrate consciousness and exploring criteria that evaluate whether individuals of a given invertebrate species or taxon have valenced experience. These data have been gathered and displayed in this database. In this post, the first one of two pieces on our main findings, we present our results by feature.Read More
While invertebrates make up the majority of animal species, our knowledge about their capacity for valenced experience is overlooked compared to existing evidence about vertebrates. In particular, whether invertebrates have the capacity to have valenced experience is uncertain, and hence, it remains unclear whether these organisms have a welfare of their own we should care about.
Rethink Priorities has been systematically exploring this issue during the past months. First, we examined the philosophical difficulties inherent in the detection of instances of morally significant pain and pleasure in nonhumans. Second, given the current epistemic state about invertebrate consciousness, we have been compiling and analyzing relevant scientific evidence regarding this issue. In particular, we investigated the degree to which different features potentially indicative of phenomenal consciousness are found throughout different taxa. In a second post, we described our approach, the rationale of this project, and its limitations. The features we believe to be most relevant for assessing invertebrate sentience are explained in detail in a third, fourth, and fifth post.
In this sixth post, we present our summary of findings, both in narrative form and as a database.Read More
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:
Simple learning abilities, such as classical conditioning, sensitization, and habituation, do not appear to be good evidence of sentience.
Contextual learning and long-term behavior alteration to avoid noxious stimuli are better evidence of sentience.
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.
It’s difficult to study emotions in invertebrates.
Notwithstanding (4), it appears there are striking behavioral and neurochemical similarities between mammalian responses to stressful stimuli and the responses of certain arthropods.
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:
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.
Studying motivational tradeoffs can help us distinguish reflexive, pre-programmed behaviors from more plastic responses.
Comparing cognitive sophistication across dissimilar taxa is extraordinarily difficult.
Notwithstanding (3), many invertebrates, especially arthropods and cephalopods, appear surprisingly intelligent.
The relationship between cognitive sophistication and the capacity for valenced experience is unclear.
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:
Neuron count and brain size are often over-emphasized in superficial discussions of sentience.
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.
Centralized information processing of some kind is probably a necessary condition for consciousness.
Physiological responses to noxious events don’t tell us much about valenced experience.
Simple reactions to noxious events, such as immediate withdrawal, also don’t tell us much about valenced experience.
More complex reactions to noxious events, such as long-term protective behavior, might tell us something about valenced experience.
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.Read More
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.Read More