Philosopher’s Corner: The role of qualia in neuroscience

By Yaseen Jamal

YaseenPhilosopher David Chalmers has famously argued that neuroscience, in its current state, cannot comprehensively explain human consciousness. He admits that it can account for mechanical functions of the brain, such as cognitive integration of information, sensory processing, speech production, motor control, discrimination of stimuli, etc., and he labels this task the “easy problem” of consciousness. The consistency of these functions with current physics, chemistry, and biology seems clear and scientific research about such functions is already underway.

Chalmers also believes, however, that there is a “hard problem” of consciousness, which relates to the phenomenal, or subjective, properties of experience. According to him, the “hard problem” represents an impassible obstacle for neuroscience. He argues that the metaphysical features of the mind are entirely inconsistent with a physical worldview.

These phenomenal properties are termed qualia, and exclusively refer to the sensations, perceptions, affects, or “raw feels” that flavor our world and constitute the richness of human experience. For example, the redness of red, the raw feeling of pain, the particular taste of aged cheese, or the emotional state of anger are all subjective properties that demand explanation. How can it be that physical bodies experience anything at all?

Typically, qualia are defined by four characteristics. Qualia are private, meaning they cannot be known unless they are experienced through the first-person perspective. Qualia are intrinsic, which indicates that they are self-sufficient and independent of other items in experience. Qualia are also ineffable, signifying that the experience of qualia cannot be sufficiently conveyed through words alone. Finally, qualia are immediately accessible through consciousness, which means that knowledge of qualia is direct and certain, as opposed to knowledge of the physical world, which is indirect and logically deduced. Qualia, defined in this way, represent the most significant hurdle to materialistic explanations of consciousness because physical objects do not share these properties.

This definition, unfortunately, leads us down a murky path towards dualism, a philosophical position which asserts that there are two kinds of real substances: the physical substance out of which the universe is composed, and the non-physical substance out of which the mind is composed. Dualists, such as René Descartes, the 16th century French philosopher who coined the phrase, “I think, therefore I am,” would argue that the brain represents the nexus of these two substances.

The dualist position appears outdated and filled with deeper questions, the most prominent being the interaction problem: How might the two substances interact with each other? Surely the interaction cannot be physical nor can it be non-physical, so we must posit a third kind of substance to facilitate the interaction, which only leads to further regress.

Apart from this problem, the dualist position is unfalsifiable, escapes scientific analysis, and clearly does not offer the most parsimonious account of consciousness. Essentially, dualism identifies the most difficult questions about the brain and resorts to a childish replacement of intelligent explanation with an ambiguous metaphysical placeholder, hermetically sealing the explanatory gap with magic.

To scientists, this should seem like an unacceptable position that does not need to be taken seriously. Neuroscience must provide a reasonable account of qualia that is consistent with a scientific worldview. Philosopher Daniel Dennett took on this challenge in 1991, when he utilized an impressive volume of research in neuroscience, psychology, evolutionary biology, and especially computer science to develop a scientific theory of consciousness in his book, Consciousness Explained.

In essence, Dennett argued against the idea of a “Cartesian Theater,” the dualist model of consciousness in which sequences of neuronal firing somehow cross a finish line and result in a grand theatrical production of conscious experience that is observed by the metaphysical self. In its place, Dennett proposes the multiple drafts model of consciousness. His theory radically differs from the traditional understanding of the mind, and his discussion is detailed, scientific, and apparently comprehensive. Best of all, he does not purport to prove that materialism is true, but rather, he claims that the multiple drafts model is what a materialistic explanation would look like if consciousness is indeed a physical phenomenon.

Though I cannot adequately explain the model here, I want to point out an important outcome of his theory. Dennett ultimately concludes that qualia, as defined by David Chalmers, do not exist. He asserts that the phenomenal features of the perceived world are not actually qualia, but only seem like qualia, and that there is no “hard problem” of consciousness. Where Chalmers would argue that his experience consists of properties that are ineffable, private, intrinsic, and exclusively immediate, Dennett would respond by saying that it only seems like Chalmers’ experience has those properties. It is important to note that Dennett does not deny that humans have phenomenal experiences. Rather, he suggests that human brains are ill-equipped for the task of introspectively examining their phenomenal experiences, and he repeatedly emphasizes the idea that humans can be wrong about what they think they experience.

Still, the debate is ongoing, there is no definitive proof for either dualism or materialism, and we may never know whether qualia really exist or not. At this point in our discussion, it might be tempting to rule out the relevance of qualia in neuroscience. After all, if qualia do exist, they would be metaphysical and wholly inaccessible to scientific study, and if they don’t exist, then they can be thrown out of the discussion entirely.

I think this is a hasty conclusion. Granted, qualia, or the properties of experience which seem like qualia, need not be studied directly by neuroscience. This task is best left to phenomenology, the branch of philosophy that aims to describe the conscious experience and its underlying structure of perception. In relation to the goals of neuroscience, however, first-person descriptions of qualia can serve as valuable sources of information that might improve our understanding of the mind/brain, and, in turn, enhance our ability to treat and diagnose brain-related illnesses. Despite their ineffability, qualia can still be described or alluded to using analogies, metaphors, thought experiments, or examples, even though the full nature of the experience will not be conveyed.

Consider the issue of anesthesia awareness. Out of every 1,000 patients sedated with anesthesia, approximately one to two individuals will “wake up” during their operation, feeling the pains of flesh being cut, hearing the voices of the operating team, or facing the discomfort of a breathing tube in their throat without being able to move, speak, or otherwise indicate to the doctors that they are indeed conscious. This can be a severely traumatic experience with the potential to trigger Post-Traumatic Stress Disorder for many patients.

The mechanisms of anesthesia are not yet fully understood, and it still unclear how anesthetics interrupt the continuity of the conscious experience. We cannot yet measure the degree of awareness in anesthetized patients nor do we precisely know which neuronal systems, in relation to conscious perception, are affected by the drugs. Perhaps first-person descriptions of experience from patients who have suffered from anesthesia awareness can offer an additional source of information that might supplement our knowledge about the mechanical effects of anesthesia on the brain.

Interestingly, first-person accounts of qualia might also inspire novel routes of research in neuroscience. For example, researchers at the Albert-Ludwigs-University of Frieburg in Germany examined the link between visual contrast perception and depression. They were partially motivated by subjective reports of altered color perception from depressed patients, as well as by the lingual relation between depression and color (ex. feeling blue). By using pattern electroretinogram (PERG), the researchers found a strong correlation between retinal contrast gain and severity of depression. This suggests that behavioral or mood disorders indeed have some effect on the conscious perception of color.

In this way, perhaps detailed, first-person descriptions of experience from high-functioning autistic patients or schizophrenics can offer an additional source of information that might improve our clinical understanding of these ailments or inspire novel paths of scientific inquiry. Alternatively, these descriptions would be essential should neuroscience aim to fully understand the effects of pharmacological treatments for psychiatric disorders. At the moment, it appears that reductionist attitudes might have some limitations that are worth considering, and that there may be some pragmatic benefits for neuroscience from the use of subjective accounts of qualia.

Still, it is possible that the neuroscience of the future could fully understand the mind solely through a mechanical understanding of the brain without any need for the first-person perspective. But until that time comes, I think that qualia will retain their potential to serve as a useful concept in neuroscience research, regardless of whether they exist or not.


Tye, Michael, “Qualia”, The Stanford Encyclopedia of Philosophy (Fall 2013 Edition), Edward N. Zalta (ed.), URL =

Dennett, Daniel, Consciousness Explained, Boston, Little Brown & Co., (1991), print.

Lang, Joshua, “Awakening”, The Atlantic (January 2013), URL=

Bubl, E., et al. (2010). Seeing Gray When Feeling Blue? Depression Can Be Measured in the Eye of the Diseased. Biol. Psychiatry 68: 205-208. DOI: 10.1016/j.biopsych.2010.02.009.


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