Sentience: The Invention of Consciousness
Oxford University Press, UK, 2022
MIT Press, Boston, 2023

We feel, therefore we are. Conscious sensations ground our sense of self. They are crucial to our idea of ourselves as psychic beings: present, existent, and mattering. But is it only humans who feel this way? Do other animals? Will future machines? Weaving together intellectual adventure and cutting-edge science, Nicholas Humphrey describes his  quest for answers: from his discovery of blindsight in monkeys, and his pioneering work on social intelligence, to breakthroughs in the philosophy of mind. The goal is to solve the hard problem: to explain the wondrous, eerie fact of “phenomenal consciousness” – the redness of a poppy, the sweetness of honey, the pain of a bee-sting. What does this magical dimension of experience amount to, what’s it for, and why has it evolved? He presents here, in full for the first time, a plausible solution, It implies that phenomenal consciousness, far from being primitive, is a relatively late and sophisticated evolutionary development. The implications, for the existence of sentience in nonhuman animals, are startling and provocative.

Advance endorsements

It takes a special kind of person to write illuminatingly about consciousness – a person who is not only steeped in cognitive science, biology, and philosophy, but also has a fertile imagination, an openness to new ideas, and a sensitivity to the richness and variety of experience in humans and other animals. Nicholas Humphrey is such a person, and in his new book he cements his claim to be one of the most insightful writers on this notoriously difficult topic. Sentience is a beautifully written book, full of engaging vignettes, original ideas, and intriguing suggestions. It will fascinate general readers and inspire academic researchers.
 Keith Frankish, author of Mind and Supermind

Nick Humphrey has been a hugely influential figure across the fields of experimental psychology, neuroscience, and philosophy for half a century, and, for my money, is the most inventive psychological thinker of his generation. Taking a long view of his entire scientific career, and peppered with brilliant anecdotes, Sentience crystallises Humphrey's latest thinking on the evolution of consciousness. There are many dazzling insights on offer but, for me, the most eye-catching development is the formulation of a framework for diagnostic sentience-testing, in other words for determining which other animal species are sentient, or even in possession of a sense of self. How staggeringly bold! Imagine what a shock wave such a test would generate, scientifically and philosophically, of course, but also out into the political sphere.
 Paul Broks, author of The Darker the Night, the Brighter the Stars: A Neuropsychologist's Odyssey

A compelling treatise on the evolution of consciousness from one our finest psychologists. Humphrey combines a fascinating, often surprising, and occasionally hilarious scientific autobiography with a raft of well justified ideas about what it takes for an organism to be sentient. His excellent book will challenge you to think about nature's deepest and most personal mystery in a new and thoroughly enlightening way.
 Anil Seth, author of Being You

Nobody has thought more deeply, originally or poetically about animal sentience and the notion of consciousness. In this bold and persuasive book he lays out how he came to his conclusions in a lifetime of studying animal and human minds.
 Matt Ridley, author of The Red Queen and other books

Nicholas Humphrey is a psychologist who has always thought outside the box. In this bold book he goes back to basics, philosophical and biological. It's a provocative and fascinating read, brought to life by the account of his own pioneering work on blindsight.
 Marian Stamp Dawkins, author of Why Animals Matter