A human has their hand cut, and reacts vigorously.
A human has their hand cut, and has no reaction at all.
I do not know for sure whether pain was experienced in the 1st scenario. I can only feel my own pain. However, the 1st scenario is much more likely than the 2nd under the hypothesis that pain was experienced than under the hypothesis that no pain was experienced. So, from Bayes’ rule[1], I should strongly update towards thinking that pain was experienced, and therefore towards the human being sentient.
More broadly, one should update towards believing that a being is sentient if they share properties which are indicators of sentience in humans, such as reacting to damage made to body parts.
“Posterior probability of pain”/”posterior probability of no pain” = “probability of vigorous reaction given pain”/”probability of vigorous reaction given no pain”*”prior probability of pain”/”prior probability of no pain”.
What matters is not that the 1st scenario is much more lilely than the 2nd under the hypothesis that pain is experienced (it clearly is). The relevant question is whether the 1st scenario is much more likely under the hypothesis that pain is experienced than under the hypothesis that pain is not experienced (it’s relation to the second scenario is irrelevant, a red herring). And whether this is actually the case is much less clear.
This is what your footnote equation says too, so I’m not disagreeing with that, but I think the way you presented the argument in the text hides this, and might lead someone to misunderstand what it is they are being asked to judge is ‘much more likely’.
You can make an evolutionary argument for why we would expect an animal to react ‘vigorously’ to sustaining damage, and it is not clear why this evolutionary explanation requires the pain to be ‘experienced’. So someone could make an argument that the likelihood of scenario 1 is high under both hypotheses, in which case it should only cause a small change in your priors.
I thought the post was really interesting, thank you for sharing it! It has updated me towards thinking that there’s a higher chance insects might be sentient. But I think things are still a lot more complicated than suggested by this reply.
Would be interested to hear from those who’ve disagreed with this, since I think I’m just pointing out a mathematical mistake? Interested to be corrected if I’ve got something wrong.
Perhaps would help to give some example numbers. Suppose someone assigns, for an insect:
P(react vigorously given pain experienced) = 1
P(react vigorously given no pain experienced) = 0.5
(These numbers seem defensible to me)
This gives you a Bayes factor of 2, when updating your probability that pain is experienced after seeing evidence that insects react vigorously to some negative stimulus. This is not a ‘strong’ update.
Hi Henry,
Consider these 2 scenarios:
A human has their hand cut, and reacts vigorously.
A human has their hand cut, and has no reaction at all.
I do not know for sure whether pain was experienced in the 1st scenario. I can only feel my own pain. However, the 1st scenario is much more likely than the 2nd under the hypothesis that pain was experienced than under the hypothesis that no pain was experienced. So, from Bayes’ rule[1], I should strongly update towards thinking that pain was experienced, and therefore towards the human being sentient.
More broadly, one should update towards believing that a being is sentient if they share properties which are indicators of sentience in humans, such as reacting to damage made to body parts.
“Posterior probability of pain”/”posterior probability of no pain” = “probability of vigorous reaction given pain”/”probability of vigorous reaction given no pain”*”prior probability of pain”/”prior probability of no pain”.
I think this is a misapplication of Bayes rule.
What matters is not that the 1st scenario is much more lilely than the 2nd under the hypothesis that pain is experienced (it clearly is). The relevant question is whether the 1st scenario is much more likely under the hypothesis that pain is experienced than under the hypothesis that pain is not experienced (it’s relation to the second scenario is irrelevant, a red herring). And whether this is actually the case is much less clear.
This is what your footnote equation says too, so I’m not disagreeing with that, but I think the way you presented the argument in the text hides this, and might lead someone to misunderstand what it is they are being asked to judge is ‘much more likely’.
You can make an evolutionary argument for why we would expect an animal to react ‘vigorously’ to sustaining damage, and it is not clear why this evolutionary explanation requires the pain to be ‘experienced’. So someone could make an argument that the likelihood of scenario 1 is high under both hypotheses, in which case it should only cause a small change in your priors.
I thought the post was really interesting, thank you for sharing it! It has updated me towards thinking that there’s a higher chance insects might be sentient. But I think things are still a lot more complicated than suggested by this reply.
Would be interested to hear from those who’ve disagreed with this, since I think I’m just pointing out a mathematical mistake? Interested to be corrected if I’ve got something wrong.
Perhaps would help to give some example numbers. Suppose someone assigns, for an insect:
P(react vigorously given pain experienced) = 1
P(react vigorously given no pain experienced) = 0.5
(These numbers seem defensible to me)
This gives you a Bayes factor of 2, when updating your probability that pain is experienced after seeing evidence that insects react vigorously to some negative stimulus. This is not a ‘strong’ update.
That’s a verbose way of saying: “looks like it feels pain, probably feels pain”. Invoking Bayes’ Theorem gives the argument a false depth.
Being unnecessarily verbose comes across very negatively in EA communication, important to avoid it