This is the ninth post in the Moral Weight Project Sequence, which provides an overview of the research Rethink Priorities conducted between May 2021 and October 2022 on making resource allocation decisions across species. The goal of this post is to help animal welfare grantmakers assess the relative value of improvements to the lives of some commercially-important insects.

This is the eighth post in the Moral Weight Project Sequence, which provides an overview of the research Rethink Priorities conducted between May 2021 and October 2022 on making resource allocation decisions across species. In this post, Senior Research Manager Bob Fischer briefly recaps the research team’s understanding of welfare ranges and their proposed way of using them. The post also summarizes the methodology and responds to some questions and objections.

This is the seventh post in the Moral Weight Project Sequence, which provides an overview of the research Rethink Priorities conducted between May 2021 and October 2022 on making resource allocation decisions across species. In this post, Senior Research Manager Bob Fischer warns against dismissing research just because its findings suggest "the Equality Result" (i.e. that certain species can realize roughly the same amount of welfare as humans).

This is the sixth post in the Moral Weight Project Sequence, which provides an overview of the research Rethink Priorities conducted between May 2021 and October 2022 on making resource allocation decisions across species. In this post, Joe Gottlieb summarizes his full report on phenomenal unity and cause prioritization. He concludes that there is not enough empirical evidence to assume that certain species “house” multiple welfare subjects per individual.

This is the fifth post in the Moral Weight Project Sequence, which provides an overview of the research Rethink Priorities conducted between May 2021 and October 2022 on making resource allocation decisions across species. This post assesses the hypothesis that brains have many conscious subsystems, which could affect how we ought to make tradeoffs between members of different species.

This is the fourth post in the Moral Weight Project Sequence. The aim of the sequence is to provide an overview of the research that Rethink Priorities conducted between May 2021 and October 2022 on interspecific cause prioritization—i.e., making resource allocation decisions across species. The aim of this post is to summarize our full report on the use of neuron counts as proxies for moral weights.

This is the third post in the Moral Weight Project Sequence. The aim of the sequence is to provide an overview of the research that Rethink Priorities conducted between May 2021 and October 2022 on interspecific cause prioritization. The aim of this post is to suggest a way to quantify the impact of assuming hedonism on welfare range estimates.

This is the second post in the Moral Weight Project Sequence. The aim of the sequence is to provide an overview of the research that Rethink Priorities conducted between May 2021 and October 2022 on interspecific cause prioritization—i.e. making resource allocation decisions across species. The aim of this post is to provide an overview of the Welfare Range Table, which records the results of a literature review covering over 90 empirical traits across 11 farmed species.

This post is the first in the Moral Weight Project Sequence. The aim of the sequence is to provide an overview of the research that Rethink Priorities conducted between May 2021 and October 2022 on interspecific cause prioritization—i.e., making resource allocation decisions across species. The aim of this post is to introduce the project and explain how EAs could use its results.

This report is a postscript to "The relative Importance of the severity and duration of pain,” and addresses whether the order of negative and positive experiences matter. For example, is pain worse if it occurs at the end of an individual’s life?

How should effective altruists decide whether to prioritize interventions that alleviate severe but relatively brief suffering or instead those that alleviate longer-lasting but less severe suffering? When one pain is longer-lasting but less intense than a second pain, the most straightforward way to compare how much disutility they cause is to multiply how much longer by how much less severe the first pain is than the second pain. This report investigates whether this mathematical approach is sufficient for making cause prioritization decisions, requires some amendments, or is fundamentally flawed.

Are there differences in the characteristic intensity ranges of valenced experience across species? This question is important because the answer to it could affect the way we wish to spend our scarce resources helping different types of animals, including humans. For example, if the pains and pleasures of trout and salmon are but pale reflections of the pains and pleasures of cows and pigs, then in many instances we may be able to do more good helping mammals rather than fish.

Differences in the intensity range of valenced experience across species may affect how we ought to allocate resources to help different types of animals. Humans and other mammals likely share a roughly similar intensity range. It is unlikely that any species of animal possesses an intensity range that is exclusively extraordinarily mild. Some aspects of cognitive sophistication appear to be positively correlated with intensity range; other aspects of cognitive sophistication appear to be negatively correlated with intensity range. Affective complexity generally appears to be positively correlated with intensity range. There is as yet no good objective measure of valence intensity, though there is much interesting work ongoing in this area.

Considering differences in the subjective experience of time may affect the proportion of resources we wish to allocate to different species. I’ve recently written two pieces on the subject. Counting somewhat conservatively, the two posts total more than 23,000 words. In this (much shorter) post I attempt to succinctly introduce the topic and convey my main conclusions. The aim is to create a digestible overview of my current thinking that imposes a smaller time burden on readers.

The subjective experience of time is a morally significant aspect of well-being. Critical flicker-fusion frequency (CFF) has occasionally been suggested as a proxy for the subjective experience of time. CFF, a measure of visual temporal resolution, is the threshold at which a rapidly flickering light appears to glow steadily. CFF thresholds have been measured in more than 70 different species across 30+ orders and 3 phyla. Values range from ~7 Hz to ~200 Hz. Putatively similar animals sometimes possess very different CFF thresholds. I tentatively estimate there is a ~40% chance that CFF values roughly track the subjective experience of time under ideal conditions.

The subjective experience of time refers to how slow or fast time appears to pass for an individual. Animals with faster rates of subjective experience undergo more subjective moments per objective unit of time than animals with slower rates of subjective experience. Roughly speaking, animals with faster rates of subjective experience perceive the world as if it were slowed down compared to the perceptions of animals with slower rates of subjective experience. Based on human reports of alterations in the subjective experience of time, as well as general differences in behavior, neurology, and temporal resolution across animals, I estimate there is a ~70% chance that there exist morally relevant differences in the subjective experience of time across species.

An animal’s capacity for welfare is how good or bad its life can go. An animal’s moral status is the degree to which an animal’s experiences or interests matter morally. It’s plausible that animals differ in their capacity for welfare and/or their moral status. These differences could affect the way we ought to allocate resources across interventions and/or cause areas. Unfortunately, measuring capacity for welfare and moral status is tremendously difficult. When donors or researchers choose to focus on cause areas or interventions that target certain species rather than others, they are often implicitly making judgments about the comparative value of different animals (including humans). Without a model for quantifying differences in comparative value, such judgments are apt to be guided by imperfect and likely unreliable heuristics.

Understanding differences in capacity for welfare and moral status could significantly affect the way we wish to allocate resources among interventions and cause areas. For instance, some groups of animals that exhibit tremendous diversity, such as fish or insects, are often treated as if all members of the group have the same moral status and capacity for welfare. Further investigation could compel us to prioritize some of the species in these groups over others. More generally, if further investigation suggested we have been overestimating the moral value of mammals or vertebrates compared to the rest of the animal kingdom, we might be compelled to redirect many resources to invertebrates or non-mammal vertebrates. To understand the importance of these considerations, we must first develop a broad conceptual framework for thinking about this issue.

In this post, four members of Rethink Priorities’ invertebrates team—Daniela R. Waldhorn, Marcus A. Davis, Peter Hurford, and Jason Schukraft—outline their views on the value, feasibility, and danger of quantitative estimates of invertebrate sentience. Marcus and Peter provide numerical estimates of sentience for each of the taxa we investigated for our invertebrate sentience project, Daniela offers a qualitative ranking of the same taxa, and Jason argues that we are not yet in a position to deliver estimates that are actionable and robust enough to outweigh the (slight but non-negligible) harm that publishing such estimates prematurely might engender.

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?