‘Sentience’ sometimes refers to the capacity for any type of subjective experience, and sometimes to the capacity to have subjective experiences with a positive or negative valence, such as pain or pleasure. We review recent controversies regarding sentience in fish and invertebrates and consider the deep methodological challenge posed by these cases. We then present two ways of responding to the challenge. In a policy‐making context, precautionary thinking can help us treat animals appropriately despite continuing uncertainty about their sentience. In a scientific context, we can draw inspiration from the science of human consciousness to disentangle conscious and unconscious perception (especially vision) in animals. Developing better ways to disentangle conscious and unconscious affect is a key priority for future research.

The performance of natural behavior is commonly used as a criterion in the determination of animal welfare. This is still true, despite many authors having demonstrated that it is not a necessary component of welfare – some natural behaviors may decrease welfare, while some unnatural behaviors increase it. Here I analyze why this idea persists, and what effects it may have. I argue that the disagreement underlying this debate on natural behavior is not one about which conditions affect welfare, but a deeper conceptual disagreement about what the state of welfare actually consists of. Those advocating natural behavior typically take a “teleological” view of welfare, in which naturalness is fundamental to welfare, while opponents to the criterion usually take a “subjective” welfare concept, in which welfare consists of the subjective experience of life by the animal. I argue that as natural functioning is neither necessary nor sufficient for understanding welfare, we should move away from the natural behavior criterion to an alternative such as behavioral preferences or enjoyment. This will have effects in the way we understand and measure welfare, and particularly in how we provide for the welfare of animals in a captive setting.

There are many decision contexts in which we require accurate information on animal welfare, in ethics, management, and policy. Unfortunately, many of the methods currently used for estimating animal welfare in these contexts are subjective and unreliable, and thus unlikely to be accurate. In this paper, I look at how we might apply principled methods from animal welfare science to arrive at more accurate scores, which will then help us in making the best decisions for animals. I construct and apply a framework of desiderata for welfare measures, to assess the best of the currently available methods and argue that a combined use of both a whole-animal measure and a combination measurement framework for assessing welfare will give us the most accurate answers to guide our action.

Human neural organoid research is advancing rapidly. As Greely (2021) notes in the target article, this progress presents an “onrushing ethical dilemma.” We can’t rule out the possibility that suff...

The keeping of captive animals in zoos and aquariums has long been controversial. Many take freedom to be a crucial part of animal welfare and, on these grounds, criticise all forms of animal captivity as harmful to animal welfare, regardless of their provisions. Here, we analyse what it might mean for freedom to matter to welfare, distinguishing between the role of freedom as an intrinsic good, valued for its own sake and an instrumental good, its value arising from the increased ability to provide other important resources. Too often, this debate is conducted through trading intuitions about what matters for animals. We argue for the need for the collection of comparative welfare data about wild and captive animals in order to settle the issue. Discovering more about the links between freedom and animal welfare will then allow for more empirically informed ethical decisions regarding captive animals.

One of the biggest problems in applications of animal welfare science is our ability to make comparisons between different individuals, both within and across species. Although welfare science provides methods for measuring the welfare of individual animals, there’s no established method for comparing measures between individuals. In this paper I diagnose this problem as one of underdetermination—there are multiple conclusions given the data, arising from two sources of variation that we cannot distinguish: variation in the underlying target variable (welfare experience) and in the relationship of measured indicators to the target. I then describe some of the possible methods of making comparisons, based on the use of similarity assumptions that will have greater or lesser justification in different circumstances, and the alternative methods we may use when direct comparisons are not possible. In the end, all our available options for making welfare comparisons are imperfect, and we need to make explicit context-specific decisions about which will be best for the task at hand while acknowledging their potential limitations. Future developments in our understanding of the biology of sentience will help strengthen our methods of making comparisons.