You are welcome! Rethink Priorities (RP) has a research agenda on valuing impacts across species, and Hannah Tookey from RP commented the following on 6 January 2026. “We don’t currently have anything scheduled on this topic [“projects decreasing the uncertainty of interspecies comparisons of expected hedonistic welfare”], but we regularly review project ideas and may consider working on something like this a little later in the year. Dedicated funding would certainly make it more likely that we could prioritize this work”.

Thanks for the context, Jamie! That makes sense to me. I would still be curious to know about concrete decisions that were significantly influenced by the Pulse project. Its impact seems less tangible to me than that of RP's research targeting particular cause areas. However, this could easily be because I am less familiar with movement building efforts.

I [Jim] think maybe we should be more uncertain about inter-species tradeoffs than you seem to be, here.

I agree I have underestimated the uncertainty in comparisons between the individual (expected hedonistic) welfare per unit time of different species. I now recommend decreasing this uncertainty.

I continue to recommend funding the Centre for Exploratory Altruism Research’s (CEARCH’s) High Impact Philanthropy Fund (HIPF), which I estimate decreases 5.07 billion soil-animal-years per $. I recommend even more investigating whether soil nematodes have positive or negative lives.

After the post above, I recommended research informing how to increase the welfare of soil animals (for example, my top recommendation quoted above) over pursuing whatever land use change interventions naively seem to achieve that the most cost-effectively. I have little idea about whether funding HIPF (as recommended in the 1st sentence quoted above), or any other way of changing land use increases or decreases welfare. I am very uncertain about what increases or decreases soil-animal-years, and whether soil animals have positive or negative lives.

I currently recommend decreasing the uncertainty about how the (expected hedonistic) welfare per unit time of different organisms and digital systems compares with that of humans. I am now more pessimistic about research informing how to increase the welfare of soil animals. I have very little idea about whether existing interventions which robustly increase the welfare of humans or non-soil animals increase or decrease animal welfare due to potentially dominant uncertain effects on soil animals. Likewise, I do not know whether hypothetical interventions which robustly increased the welfare of soil animals would increase or decrease welfare due to potentially dominant uncertain effects on soil microorganisms.

I recommend research informing how to increase the welfare of soil animals over pursuing whatever land use change interventions naively seem to achieve that the most cost-effectively.

I currently recommend decreasing the uncertainty about how the (expected hedonistic) welfare per unit time of different organisms and digital systems compares with that of humans. I am now more pessimistic about the above. I have very little idea about whether existing interventions which robustly increase the welfare of humans or non-soil animals increase or decrease animal welfare due to potentially dominant uncertain effects on soil animals. Likewise, I do not know whether hypothetical interventions which robustly increased the welfare of soil animals would increase or decrease welfare due to potentially dominant uncertain effects on soil microorganisms.

I have also estimated the total welfare of animal populations, trees, and bacteria and archaea assuming individual (expected hedonistic) welfare per fully-happy-organism-year is proportional to "metabolic energy consumption per unit time at rest at 25 ºC"^"exponent". I had recommended research informing how to increase the welfare of soil animals, but I am now more pessimistic about this. I currently think it is better to focus on decreasing the uncertainty about how the individual welfare per unit time of different organisms and digital systems compares with that of humans.

You are welcome! I have now estimated the total welfare of animal populations, trees, and bacteria and archaea assuming individual welfare per fully-healthy-organism-year is proportional to "metabolic energy consumption per unit time at rest"^"exponent". I had recommended research informing how to increase the welfare of soil animals, but I am now more pessimistic about this. I currently think it is better to focus on decreasing the uncertainty about how the individual welfare per unit time of different organisms and digital systems compares with that of humans.

Relatedly, here is an illustration of why I think individual welfare per fully-healthy-animal-year could be proportional to "metabolic energy consumption per unit time at rest"^"exponent".

I have now estimated the total welfare of animal populations, trees, and bacteria and archaea based on the assumption above. I had recommended research informing how to increase the welfare of soil animals, but I am now more pessimistic about this. I currently think it is better to focus on decreasing the uncertainty about how the welfare per unit time of different organisms and digital systems compares with that of humans. 

Thanks for the reply, Sophie!

You are welcome!

It sounds broadly akin to how I'm inclined to address Pascal's Mugging cases (treat the astronomical stakes as implying proportionately negligible probability).

Makes sense. I see Pascal's muggings as instances where the probability of the offers is assessed indepently of their outcomes. In contrast, for any distribution with a finite expected value, the expected value density (product between the PDF and value) always ends up decaying to 0 as the outcome increases. In meta-analyses, effect sizes, which can be EVs under a given model, are commonly weighted by the reciprocal of their variance. Variance tends to increase with effect size, and therefore larger effect sizes are usually weighted less heavily.

People sometimes point to Holden Karnofsky's post Why we can’t take expected value estimates literally (even when they’re unbiased) to justify not relying on EVs (here are my notes on it from 4 years ago). However, the post does not broadly argue against using EVs. I see it as a call for not treating all EVs the same, and weighting them appropriately.