Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Opinion: Estimating Invertebrate Sentience, published by Jason Schukraft on the Effective Altruism Forum. Write a Review Introduction Between May 2018 and June 2019 Rethink Priorities completed a large project on the subject of invertebrate sentience.[1] We investigated the best methodology to approach the question, outlined some philosophical difficulties inherent in the project, described the features most relevant to invertebrate sentience, compiled the extant scientific literature on the topic, summarized our results, and ultimately produced an invertebrate welfare cause profile. We are currently in the process of identifying concrete interventions to improve invertebrate wellbeing, with a report on the welfare of managed honey bees due out in mid-November and a report on the welfare of farmed snails nearing completion. One thing we did not do was publish explicit numerical estimates of the probability that various groups of invertebrates are sentient. Our team discussed publishing such estimates many times, but these discussions generated considerable internal disagreement. Two members of the (four person) team believed that publishing explicit sentience estimates was a bad idea. The other two members felt that it was a good idea. In the end, we settled on the following compromise: several months after the completion of the invertebrate sentience project, we would publish an unofficial opinion piece in which each of us could share her/his own reasoning on the subject and, if so desired, her/his own estimates.[2] This post fulfills that compromise. In it, the 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. What follows are the personal opinions of individual researchers. Officially, Rethink Priorities does not have a position on the explicit probability that various invertebrates are sentient. Daniela R. Waldhorn 1. Vertebrates There is an ample and detailed body of empirical data which justifies believing that non-human vertebrates are sentient. In particular, there is solid neuro-anatomical, physiological and behavioral evidence that vertebrates like cows and chickens are conscious. There is also a growing trend to recognize that these animals do not only experience physical suffering (and pleasure) but also have emotional lives (see e.g. Marino, 2017; Proctor et al., 2013). Based on existing evidence and the generalized acceptance of the Cambridge Declaration on Consciousness (2012)[3], my overall conclusions regarding the probabilities of consciousness for these animals are presented as follows: 2. Invertebrates When we consider invertebrates, the debate about whether they are conscious becomes much more complex. First, it must be conceded that the numerous invertebrate species and their diversity impose severe constraints to justifiable generalizations about the presence of consciousness in this group of animals. Second, the scientific literature about sentience in invertebrates is not only scarce but fragmentary–that is to say, the extent to which invertebrates have been investigated varies. Thus, there are some particular species about which there is a comparatively great deal of knowledge (e.g., fruit flies), whereas much less research has focused on individuals of ot...