Walters, Edgar T. (2018) Defining pain and painful sentience in animals. Animal Sentience 21(14)
Lynne U. Sneddon, Javier Lopez-Luna, David C.C. Wolfenden, Matthew C. Leach, Ana M. Valentim, Peter J. Steenbergen, Nabila Bardine, Amanda D. Currie, Donald M. Broom, and Culum Brown, Fish sentience denial: Muddying the waters
Sentience is essential to most definitions of pain, including a detailed definition invoked by Sneddon et al. to argue that adult and perhaps larval fish feel pain. Because proving painful sentience in non-human animals is not feasible, multiple lines of indirect evidence are needed to implicate pain. This commentary examines the list of 17 criteria used by Sneddon et al. to conclude that fish have conscious pain. The criteria include tests of nociceptive, motivational, and cognitive properties useful for revealing pain-like states that can be understood biologically and be related evolutionarily to human pain. However, additional research is needed to define the crucial aversive component of pain-like states in fish.