A sentient state is a state that it feels like something to be in. Cows have them, cars don't. Cognitive capacities are a subset of behavioral capacities. Not all behavioral capacities are cognitive (but the distinction is fuzzy). Might the difference have something to do with whether the behaver is sentient?

Like many others, I see Crump et al. (2022) as a milestone for improving upon previous guidelines and for extending their framework to decapod crustaceans. Their proposal would benefit from a firm evolutionary foundation by adding the comparative measurement of life-history complexity as a ninth criterion for attributing sentience to nonhuman animals.

This commentary provides an overview of the practical implications of attributing sentience to protect decapods as food, companion and research animals in the UK context. Recognising their capacity to suffer has implications for humane slaughter in farming and fishing sectors. It should also place a greater duty of care on owners of captive decapods, considering their needs and avoiding unnecessary suffering. The recognition of decapod sentience should also have an impact on their protection as research animals, although research with a potential to cause suffering may be needed to better understand decapods’ capacity to suffer.

Rowan et al use findings from neurobiology, clinical neurology, and general biology to argue for the extensive presence of sentience in animals, but they are wisely cautious concerning when in the phylogenetic scale that emergence occurred.

Crump et al.’s framework is a powerful tool designed to assist decisions on the ethical treatment of decapod crustaceans. However, the question of whether decapods are sentient (i.e., whether they feel), remains open, perhaps indefinitely. More optimistically, we might design experiments that distinguish among different levels of awareness, sometimes viewed as components of sentience. We should strike a balance between assuming that all organisms are sentient and making unnecessary anatomical assumptions about sentience. Refining current experiments may provide concrete insights about awareness in Decapoda and other taxa.

Evidence for sentience in animals distantly related to humans is often sought in observations of behavioral and neural responses to noxious stimuli that would be painful in humans. Most proposed criteria for painful sentience in “lower” animals such as decapod crustaceans have no necessary links to the affective (“suffering”) component of pain. The best evidence for painful affect in animals is learned aversion to stimuli associated with noxious experience, and conditioned preference for contexts associated with relief from aversive consequences of noxious experience, as expressed in voluntary behavior. Such evidence is currently lacking for any invertebrate except octopus.

The rigorous framework for research into potential pain in decapods was successful in allowing legislators in the United Kingdom to evaluate a complex scientific issue. However, it might produce problems for research. I discuss doubts about the usefulness of the eight criteria. Some have yet to receive any investigation and others do not allow much inference about pain. In addition, some existing studies are not covered in the framework. Most worrying, however, is the potential for stifling future research of novel areas that are excluded from the framework.

This target article has three parts. The first briefly reviews the thinking about nonhuman animals’ sentience in the Western canon: what we might know about their capacity for feeling, leading up to Bentham’s famous question “can they suffer?” The second part sketches the modern development of animal welfare science and the role that animal-sentience considerations have played therein. The third part describes the launching, by Compassion in World Farming, of efforts to incorporate animal sentience language into public policy and regulations concerning human treatment of animals.

Treves et al. (2019) make a convincing case that conservation efforts need to go beyond an anthropocentric worldview. Implementing that vision, however, will require human advocates to represent nonhuman interests. Where will the knowledge of those interests come from? How can humans know what is in the best interest of another animal, a plant, or an ecosystem? We discuss how the values embedded in current scientific practices may be ill-suited to representing nonhuman interests and we offer some ideas for correcting these shortcomings.

Each of the criteria for determining which should be given moral standing has its shortcomings. The criterion of cognitive is especially weak. That research on comparative cognition may default to the simplest account is not grounds for abandoning this scientific practice. Instead, we should dissociate scientific evidence of cognitive ability from moral obligation. In addition to the criteria suggested by Mikhalevich & Powell for including species in welfare protections, I would suggest a very old one — the ability to physically move.