A guide to the growing scientific consensus on animal sentience — which species feel pain, have emotions, and experience subjective states, and how we know.
Animal sentience science has advanced dramatically in recent decades. The traditional view that pain and emotional experience require a cortex similar to the human cortex has been challenged by evidence that subcortical brain structures are sufficient for affective experience. This means that birds, fish, and potentially some invertebrates may have richer inner lives than previously assumed. The scientific debate has shifted from whether animals feel pain to questions about the intensity and character of that experience in different taxa. Policy and ethics are beginning to catch up: more jurisdictions now include fish in animal welfare legislation, and invertebrate sentience is receiving serious scientific attention.