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.

动物福利科学应用中最大的问题之一是我们对不同个体进行比较的能力，包括物种内和物种间。尽管福利科学提供了衡量个体动物福利的方法，但还没有确定的方法来比较个体之间的衡量标准。在这篇论文中，我将这个问题诊断为不确定性之一——给出的数据有多个结论，这些结论来自我们无法区分的两个变化来源：潜在目标变量（福利经验）的变化和测量指标与目标。然后我描述了一些可能的比较方法，这些方法基于相似性假设的使用，这些假设在不同情况下有或多或少的理由，以及在无法进行直接比较时我们可能使用的替代方法。最后，我们进行福利比较的所有可用选项都是不完美的，我们需要根据具体情况做出明确的决定，以决定哪些最适合手头的任务，同时承认它们的潜在局限性。我们对感知生物学的理解的未来发展将有助于加强我们进行比较的方法。