Do we need a new Moral Weights Project?

By NickLaing @ 2025-06-30T17:47 (+83)

Is now the time to add to RP’s great work?
 

 


Rethink’s Moral weights project (MWP) is immense and influential. Their work is the most cited “EA” paper written in the last 3 years by a mile - I struggle to think of another that comes close. Almost every animal welfare related post on the forum quotes the MWP headline numbers - usually not as gospel truth, but with confidence. Their numbers carry moral weight[1] moving hearts, minds and money towards animals.

To oversimplify, if their numbers are ballpark correct then...

  1. Farmed animal welfare interventions outcompete human welfare interventions for cost-effectiveness under most moral positions.[2]

  2.  Smaller animal welfare interventions outcompete larger animal welfare if you aren’t risk averse.


There are downsides in over-indexing on one research project for too long, especially considering a question this important. The MWP was groundbreaking, and I hope it provides fertile soil for other work to sprout with new approaches and insights. Although the concept of “replicability”  isn't quite as relevant here as with empirical research, I think its important to have multiple attempts at questions this important. Given the strength of the original work, any new work might be lower quality - but perhaps we can live with that. Most people would agree that more deep work needs to happen here at some stage, but the question might be is now the right time to intentionally invest in more?
 

Arguments against more Moral Weights work

  1. It might cost more money than it will add value
  2. New researchers are likely to land land on a similar approaches and numbers to RP so what's the point?[3]
  3. RP’s work is as good as we are likely to get, why try again and get a probably worse product?
  4. We don’t have enough new scientific information since the original project to meaningfully add to the work.
  5. So little money goes to animal welfare work  now anyway, we might do more harm than good at least in the short term if new research pushes in the other direction from RP's work. 


Steps I’d like to see in a new project[4]

  1. Form a diverse group of experts, including some more cynical of animal sentience and moral worth along with pro animal-welfare scientists.

  2. Start basically from scratch, making efforts not to rely too much on RP’s work[5]

  3. Exclude those who worked directly on the RP project
  4. Make efforts to include experts from outside the EA sphere


Full disclosure, I’m not unbiased here. As I’ve written I think RP may have favored animals at a number of critical junctures. The project was spearheaded by animal welfare campaigners, neuron counts were largely disregarded, and their behavioral score system meant that tiny weights were very unlikely. I also think its a little strange that RP don’t seem to have changed their numbers or processes on further inspection and criticism[6]. Often by now a project that complex would have evolved and changed in some respects. Of course none of this means that they are wrong, and I like many have updated heavily in favour of animal welfare work on the basis of their excellent work.

What do you think - is now the time to intentionally plan and fund more moral weights work?
 

  1. ^

    Zero apologies for the pun

  2. ^

     See Rethink’s own moral parliament https://parliament.rethinkpriorities.org/

  3. ^

    IMO this would still be useful information if independent people ended up using similar messages.

  4. ^

     I realise these might be hard practically

  5. ^

     Difficult to be sure, given the lack of other work.

  6. ^

     Either self-reflection or external criticism

Bob Fischer @ 2025-07-01T18:01 (+34)

Hi Nick. Thanks for the kind words about the MWP. We agree that it would be great to have other people tackling this problem from different angles, including ones that are unfriendly to animals. We've always said that our work was meant to be a first pass, not the final word. A diversity of perspectives would be valuable here.

For what it’s worth, we have lots of thoughts about how to extend, refine, and reimagine the MWP. We lay out several of them here. In addition, we’d like to adapt the work we’ve been doing on our Digital Consciousness Model for the MWP, which uses a Bayesian approach. Funding is, and long has been, the bottleneck—which explains why there haven’t been many public updates about the MWP since we finished it (apart from the book, which refines the methodology in notable ways). But if people are interested in supporting these or related projects, we’d be very glad to work on them.

I’ll just add: I’ve long thought that one important criticism of the MWP is that it’s badly named. We don’t actually give “moral weights,” at least if that phrase is understood as “all things considered assessments of the importance of benefiting some animals relative to others” (whether human or nonhuman). Instead, we give estimates of the differences in the possible intensities of valenced states across species—which only double as moral weights given lots of contentious assumptions. 

All things considered assessments may be possible. But if we want them, we need to grapple with a huge number of uncertainties, including uncertainties over theories of welfare, operationalizations of theories of welfare, approaches to handling data gaps, normative theories, and much else besides. The full project is enormous and, in my view, is only feasible if tackled collaboratively. So, while I understand the call for independent teams, I’d much prefer a consortium of researchers trying to make progress together.

Hugh P @ 2025-06-30T21:34 (+24)

Someone should commission new moral weights work in the next year


I’d like to see it expanded to even smaller animals if possible, like @Vasco Grilo🔸 asks here.

Vasco Grilo🔸 @ 2025-07-01T11:16 (+3)

Thanks for pointing that out, Hugh! I would like Rethink Priorities (RP) to get mainline welfare ranges nematodes, microorganisms (protists, archaea, and bacteria), and plants. From Table S1 of Bar-on et al. (2018), there are 10^21 nematodes, 10^27 protists, 10^29 archaea, 10^30 bacteria, and 10^13 trees. I think effects on nematodes, and maybe microorganisms are the driver of the overall effects of the vast majority of interventions.

Beyond Singularity @ 2025-07-01T01:13 (+19)

I'm not an expert on moral weights research itself, but approaching this rationally, I’m strongly in favour of commissioning an independent, methodologically distinct reassessment of moral weights—precisely because a single, highly-cited study can become an invisible “gravity well” for the whole field.

Two design suggestions that echo robustness principles in other scientific domains:

  1. Build in structured scepticism.
    Even a small team can add value if its members are explicitly chosen for diverse priors, including at least one (ideally several) researchers who are publicly on record as cautious about high animal weights. The goal is not to “dilute” the cause, but to surface hidden assumptions and push every parameter through an adversarial filter.
  2. Consider parallel, blind teams.
    A light-weight version of adversarial collaboration: one sub-team starts from a welfare-maximising animal-advocacy stance, another from a welfare-sceptical stance. Each produces its own model and headline numbers under pre-registered methods; then the groups reconcile differences. Where all three sets of numbers (Team A, Team B, RP) converge, we gain confidence. Where they diverge, at least we know which assumptions drive the spread.

The result doesn’t have to dethrone RP; even showing that key conclusions are insensitive to modelling choices (or, conversely, highly sensitive) would be valuable decision information for funders.

In other words: additional estimates may not be “better” in isolation, but they increase our collective confidence interval—and for something as consequential as cross-species moral weights, that’s well worth the cost.

NickLaing @ 2025-07-01T03:33 (+4)

Thanks for fleshing this out more, both of your design suggestions make a lot of sense to me. You also stated one of my major concerns far better than I did.

"A single, highly-cited study can become an invisible “gravity well” for the whole field."

Jason @ 2025-07-01T22:44 (+18)

Does anyone know roughly what this would cost, either financially or in terms of what the people involved would be doing counterfactually?

(Obviously the amount would depend on the precise scope of work, but given that funding seems to be the bottleneck, throwing a range out there might sharpen the discussion.)

Michael St Jules 🔸 @ 2025-06-30T19:46 (+18)

I'm not sure it needs a whole other large project, especially one started from scratch. You could just have a few people push further on these points, which seem like the most likely cruxes:

  1. Further developing and defending measures that scale with neuron counts.
  2. Assessing animals on normative stances besides expectational hedonistic utilitarianism.
  3. Defending less animal-friendly responses to the two envelopes problem (see prior writing and the comments here, here, here, here, here and here).
  4. EDIT, also: Assessing the probability that invertebrates of interest (and perhaps other animals of interest) can experience excruciating or unbearable pain, as effectively all-consuming pain an animal would be desperate and take incredible risks to avoid.

And then have them come up with their own models and estimates. They could mostly rely on the studies and data RP collected on animals, although they could check the ones that seem most cruxy, too.

JoelMcGuire @ 2025-07-01T17:56 (+6)

Someone should commission new moral weights work in the next year

 

The moral weights of animals seems like one of the most important inputs into cause prioritization. The difference between whether we use RP weights or neuron count is the difference between whether the present contains more happiness than suffering, and potentially whether humanity has been overall good or bad for wellbeing. 

This also poses challenges to the future. Averting catastrophes is profoundly insufficient if the default trajectory for wellbeing is negative (and potentially worsening). Indeed, if the default trajectory is negative (and we have no good ways of changing it) we can imagine the universe giving a sigh of relief if we were filtered out of the cosmic pool of awareness. 

Given the profound importance for cause prioritization -- if the present is overall negative for wellbeing I think it implies we should focus much, much more on making the future and present go well than go long -- we should have several independent well resourced attempts to answer the question of "how do we weigh the wellbeing of animals versus humans?" 

Stijn Bruers 🔸 @ 2025-07-01T09:07 (+5)

I'd like to see a few more surveys on moral weights, with larger samples of both animal welfare experts and lay people, than this small one (n=100) I conducted in Belgium https://brill.com/view/journals/jaae/7/1/article-p91_6.xml

David_Moss @ 2025-07-01T18:07 (+6)

I agree. We proposed some surveys on this topic here and here. And we did some very limited work conceptually replicating earlier surveys here.

Rick Baker @ 2025-07-02T19:54 (+3)

Someone should commission new moral weights work in the next year

I strongly agree with the author’s point about the danger of relying too heavily on one study, especially given the importance of moral weights in estimating cost effectiveness. I also think that there is value in reexamining moral weights within GHD (eg health relative to income).

Leroy Dixon @ 2025-07-02T14:15 (+3)

Someone should commission new moral weights work in the next year

I think any study should be replicated, and RP's moral weights is no exception. Having different frameworks can allow us to get upper and lower bound estimates. I'm sure even the lower bounds would not be negligible when multiplied by the number of animals in factory farms

david_reinstein @ 2025-07-02T23:28 (+2)

Someone should commission new moral weights work in the next year

Most of the reasons stated below by others. In general, multiple independent investigations boosts credibility. Not sure whether it needs to be in the next year given resource constraints, but sooner is better. 

Marius L T @ 2025-07-02T14:10 (+1)

Someone should commission new moral weights work in the next year

 

There are many judgement calls in this type of work. A new moral weights project will give useful information about how robust results are.