Science: Consciousness as Sensation

Neuropsychologist Nicholas Humprey (b. 1943) who is based in Cambridge, is known for his work on evolution of primate intelligence and consciousness. He is author of the recent book, Sentience (2021) giving a radically different perspective of the origin of human consciousness.

Few scientific topics provoke as much debate as the origin and role of human consciousness, the elusive feeling of being alive in the world. There are plenty of theories, of course but none are conclusive due to the essentially non-observability of consciousness. Nonetheless, some theories may strike us as more interesting or logically convincing than others, and in this post, I will highlight one such theory, proposed by the British neuropsychologist, Nicholas Humphrey (b. 1943) who is based in Cambridge, UK.

Humphrey is known for his work on the evolution of primate intelligence and consciousness, and he was the first scientist to demonstrate the remarkable trait called “blindsight” (more on this later). In a series of books and scientific publications, Humphrey has presented a theory to explain why we (and perhaps many other animals) are sentient beings endowed with consciousness. Much of what I will summarize comes from Humphrey’s latest book, Sentience: The Invention of Consciousness (MIT Press, 2023) in which he argues that consciousness is a trait that has evolved to make us feel that life is worth living.  In staking this view, Humphrey departs from the conventional wisdom held by other scientists, that consciousness is simply a cognitive facility of the brain, i.e., something that facilitates certain types of learning, integration, decision making and recognitions. To Humphrey, what is unsatisfactory about this cognitive view is that it tries to invent a role for consciousness in areas of cognition where there’s no obvious need for it. Instead, he argues that we are conscious simply because we could not exist without it (italics paraphrased). In others, consciousness evolved for our own good.

Humphrey’s views owe an intellectual debt to the 18th century Scottish philosopher Thomas Reid who made a distinction between perception and sensation. Perception, Reid wrote, registers information about what is seen in the external world; sensation is the subjective feeling that accompanies perceptions. Sensation, in other words, internalizes what is seen from the outside world into feelings. Without feelings, argues Humphrey, the great achievements of our species – art, poetry, novels, music – would not be possible, so a red rose is just another red object, rather than a lush symbol of love or desire. Ditto for white lilies, which in many cultures, has been a symbol of innocence and purity.

Humphrey’s theory of the mind is largely underpinned by his studies of primate intelligence. He recounts an early experiment while he was a graduate student, where he encountered a caged monkey named Helen. Helen’s visual cortex (the part of the brain that receives, integrates, and processes visual information) had been removed by his graduate supervisor, but her superior colliculus (an ancient brain area involved in visual processing that predates the visual cortex) was still intact. As Humphrey sat beside Helen, waving and trying to interest her, he found that within a few hours, Helen began grasping chunks of apple from his hand, a feat one does not expect of a primate without sight. And one occasion, Humphrey took Helen for walks on a leash in the village near Cambridge. At first, she collided with objects, and with Humphrey, and several times, she fell into a pond. But soon, she learned to navigate her surroundings with remarkable dexterity, such as moving directly across a field to climb a favorite tree or reaching for fruit and nuts Humphrey offered her and only within arm’s length, which suggested that Helen could perceive depth. And in the lab, Helen could find peanuts and currants scattered across a floor strewn with obstacles (once she collected 25 currants from an area of 50 square feet in less than a minute). From these experiments, Humphrey suspected that Helen was making use of visual perceptions without any conscious visual sensations, suggesting that sensation and perception are two independent abilities. The startling ability of Helen was also observed by Humphrey’s supervisor, Larry Weiskrantz in a partially blind man who was able to consistently make accurate guesses about the shape, position, and color of objects in the blind region of his visual field. He named this ability, “blindsight.”

If it is possible to navigate the world with only perceptions, Humphrey asked, why did monkeys and humans evolve to feel varied sensations? What purpose do sensations serve? At first glance, this is a no-brainer – surely, seeing the redness of blood in a wound is “useful” for survival since it prompts us to take quick action to treat the wound. At the same time survival alone cannot be the whole story. What survival value is there in our shared emotions over the symbolism of a red rose? How about feelings poured out in art, in poetry and in music? This is a trickier question though Humphrey suspects that these expressions of feelings also have great survival value for animals that are highly social. Human empathy for example, contributes to social cohesion because without it, we would not be able to put ourselves in the metaphorical shoes of the other. Put another it another way, you can only imagine what it’s like to be someone else if you first know what it’s like to be yourself, and “the more mysterious and unworldly the qualities of phenomenal consciousness, …, and the more significant the self, the greater value people will have placed on their own – and others’ – lives”, Humphrey adds. Seen from this perspective, the whole of the arts is the training ground for humans to “know ourselves”, then know others. Sensations, expressed in art, poetry and songs are the means through which consciousness hone this life critical skill.


This post is an adaption of a New York Magazine article by Nick Romeo entitled “Nicholas Humphrey’s Beautiful Theory of Mind”, published on March 15, 2013.

Leave a Reply