The Clearest Candidates

Abstract

Abstract Debate in recent years has shifted from vertebrates towards invertebrates, where sentience candidature is more contestable. Octopuses are often regarded as sentient due to their large brains and impressive intelligence. Yet we should be aware of the possibility of decouplings between intelligence, brain size, and sentience in the animal kingdom. Precautions to safeguard animal welfare should be driven by markers of sentience. Yet even when we restrict our focus to markers of sentience, octopuses are clearly sentience candidates. A review in 2021 considered the evidence of sentience in cephalopod and decapod crustaceans, constructing a framework based on eight theoretically well-motivated criteria. It reported with high confidence that octopuses satisfied at least seven of the eight criteria. The question of exactly when enough evidence has amassed to imply a realistic possibility of sentience that it would be irresponsible to ignore is a difficult judgement. The coleoid cephalopods and decapods of the Pleocyemata suborder are clear sentience candidates, whereas decapods of the Dendrobranchiata suborder are investigation priorities.