Comment author: Gina_Stuessy  (EA Profile) 13 November 2015 06:28:40PM 7 points [-]

All vertebrates have similar physiological pain receptors (, and it seems like there's only a (possible) significant difference in ability to feel pain when you get down to invertebrates, like insects.

Comment author: Adam_Shriver 25 November 2015 02:29:45PM 1 point [-]

"All vertebrates have similar physiological pain receptors ." This might be true, but doesn't really decide the issue. Pain receptors are in the peripheral nervous system, but pain is mediated by the brain. In humans, there are many cases where we have activation in pain receptors without consciously feeling pain (soldiers during battle), and similarly there are many cases where we consciously feel pain without any activation in pain receptors (phantom limb pain, chronic pains). Also, it's worth noting that the link you provide refers to a table in Gary Varner's 1998 book. I'm a former grad student of his, and I don't think even then he would have said the argument for pain is "just as strong," in other groups as in mammals, but he does have an updated table in his 2012 book "Personhood, Ethics, and Animal Cognition" that incorporates some of the points I mentioned above. And, in particular, he writes (p. 123) that "...the argument by analogy for pain in non-human animals is strongest in the case of our fellow mammals, and weaker for all of the other taxa." He does still conclude that the best place to draw the line is between vertebrates and invertebrates, but he's also not saying the arguments are equally strong in al cases.

Comment author: Jeff_Kaufman 13 November 2015 06:07:45PM *  1 point [-]

There's not full agreement among EAs here. Yes, birds and fish are smaller, but some people think mammals matter more.

EDIT: Sorry, I misremembered this. The EAs who think "eat beef instead of chicken" might result in more animal suffering aren't going just from "mammal" status but also from environmental concerns:

I'm somewhat less gung-ho about these numbers than when I first wrote the piece because

  • Brain complexity matters somewhat and isn't incorporated. I think 40 chickens matter many times more than a cow, but not fully 40 times, whereas these figures imply ~40 times more suffering per kg of chicken than kg of beef.

  • In practice, indirect effects dominate, though of course, they're also much harder to figure out. Beef is good if it reduces wild-animal habitat but probably net bad by contributing to climate change. On balance it may be net bad if climate change dominates.

Whatever the sign is of the indirect effects, indirect effects should be more similar across animals than the suffering figures are across animals, since cows and chickens don't differ by ~40 times in their environmental impacts. Hence, these neglected factors should tend to drive the impact estimates (much) closer together.



The reason I preferentially eat chicken, eggs, and seafood, over mammals is twofold:

  • greenhouse gas emissions are 10 fold (or more) less for chicken, fish, and seafood

  • cows and pigs are not only much more intelligent, but also more emotional. I believe that they suffer more because they are smarter.

Having said that, I only buy free range and ethically farmed chicken. I eat mammals too, but very rarely, and only ethically farmed pigs/cows.


Either way, I think this isn't settled.

Comment author: Adam_Shriver 25 November 2015 02:19:06PM 1 point [-]

Though I think that fish and chickens probably feel pain, and that we certainly should base our moral decisions on the assumption that they do feel pain, it also seems pretty clear that there is a stronger argument by analogy in the case of mammals. In particular, the anterior cingulate cortex and the insula cortex play a central role in what is known as the affective dimension of pain in humans and other mammals. The most striking evidence for this is that humans with lesions to these areas will report "feeling pain but no longer finding it unpleasant," but there also is extensive evidence from fMRI on humans and other mammals, single-unit recordings on humans during surgeries (and on other mammals during invasive research), direct stimulation (in the case of the insula) on humans and other mammals, lesion studies on other mammals, and knock-out and knock-in studies on mammalian brain structures.

This is relevant because all and only mammals have these brain structures (the cingulate and insula). There aren't any particular behavioral responses to noxious stimuli that you would see in, say, a mouse, but not in a chicken, which is why I think we should assume that they also consciously feel pain. Nevertheless, it is pretty clear that saying "organism M probably feels pain in a manner similar to humans because M has all of the same brain regions which seem to be doing the same things during noxious stimulation and M also has behavioral similarities" is a stronger argument by analogy than saying "organism M probably feels pain because it has behavioral similarities to humans." So even if the best place to draw the line is between vertebrates and invertebrates, we shouldn't confuse that claim with the claim that the evidence is equally strong in both cases. Whether the evidence is strong enough to outweigh the large difference in numbers between eating beef versus chicken, probably not, though I'm not exactly sure how to weigh the "probability of similarity" from arguments by analogy.