The Scale of Feelings: A Theory of Emotional Complexity in the Living World

This essay proposes an original theory of the distribution of emotional complexity in the living world, based on the extension and reinterpretation of Abraham Maslow's (1943) hierarchy of needs to the entire spectrum of living organisms. The central thesis is that a living being's emotional complexity is related to its position in the expanded hierarchy of needs—with a key caveat: this position does not follow a hierarchy between taxonomic classes, but is distributed across species and families, cutting across traditional biological systematics. A corvid or a parrot may rank higher than many mammals; an octopus—a mollusk separated from our evolutionary lineage over 700 million years ago—cognitively and emotionally surpasses many vertebrates. These are not anomalies but the theory's most characteristic and falsifiable predictions. The theory is supported by a systematic review of the scientific literature in comparative neurobiology, cognitive ethology, and evolutionary psychology, with particular reference to the contributions of Stefano Mancuso, Carl Safina, and Jaak Panksepp. The ethical implications of this view of the living world as an emotional community are discussed, with reference to the New York Declaration on Animal Consciousness (2024) and recent legislative developments regarding animal sentience. This Zenodo record contains three language versions: English (main), Italian, and Russian.