Note: This article was also published on the Scientific American blog.
Header image is The Voyage of Life: Old Age by Thomas More, taken from this website.
What is consciousness? In a sense, this is one of the greatest mysteries in the universe. yet in another, it’s not an enigma at all. If we define consciousness as the feeling of what it’s like to subjectively experience something, then there is nothing more deeply familiar. Most of us know what it’s like to feel the pain of a headache, to empathize with another human being, to see the color blue, to hear the soaring melodies of a symphony, and so on. In fact, as philosopher Galen Strawson insightfully pointed out in a New York Times opinion piece, consciousness is “the only thing in the universe whose ultimate intrinsic nature we can claim to know.”
This is a crucial point. We don’t have direct access to the outer world. Instead we experience it through the filter of our consciousness. We have no idea what the color blue really looks like “out there,” only how it appears to us “in here.” Furthermore, as some cognitive scientists like Donald Hoffman have argued in recent years, external reality is likely to be far different from our perceptions of it. The human brain has been optimized, through the process of evolution, to model reality in the way that’s most conducive to its survival, not in the way that most faithfully represents the world.
Science has produced an outstandingly accurate description of the outer world, but it has told us very little, if anything, about our internal consciousness. With sufficient knowledge of physics, I can calculate all the forces acting on the chair in front of me, but I don’t know what “forces” or “laws” are giving rise to my subjective experience of the chair.
A neuroscientist might argue that the electrochemical activity in a given region of my brain mediates my perception of the chair, but as philosopher Joseph Levine has claimed, there seems to be an “explanatory gap” between the physical events in my nervous system and the sensation of subjective experience. It seems that my consciousness of, say, the color of the chair is categorically different from the electrical impulses fired by the neurons in my brain that detect color. Similarly, it is very difficult, if not impossible, to explain how the feeling of pain reduces to the stimulation of certain fibers in my nervous system. Bridging this explanatory gap is known as the “hard problem of consciousness.”
Over the millennia, thinkers in both the East and West have contemplated a variety of solutions to the hard problem of consciousness, many of which upend our traditional views on the nature of reality. The Yogacara school of Buddhism endorses idealism, the belief that everything is consciousness. René Descartes, arguably the first Western philosopher to write about consciousness, consciousness, asserted the dualist perspective that the mind is fundamentally separate from physical matter.
But all of this is indeed philosophy. Centuries-old debates about the metaphysics of the mind and universe are unlikely to make progress anytime soon. Is there any way that we can better elucidate consciousness scientifically? Or are the core questions of consciousness intrinsically restricted to the domain of philosophy?
This summer, I had the privilege of interning at the Qualia Research Institute (QRI), a San Francisco–based research nonprofit that is dedicated to discovering the science of consciousness (qualia are subjective experiences). Its approach rests on two core philosophical assumptions: The first is “qualia formalism,” which claims that our subjective experience has a mathematical structure. The second is “valence realism,” the view that we can objectively measure the so-called valence of conscious experience—that is, how pleasant an experience feels.
These ideas serve as the foundation for QRI’s “symmetry theory of valence.” The theory claims that if a subjective experience can be represented as some kind of a mathematical object, then the symmetry of that object corresponds to how pleasant the experience is.
In physics, a symmetry is broadly defined as any kind of invariance under a transformation—in other words, a property of a system that doesn’t get altered when a change is applied to that system. There are the symmetries that we are familiar with in everyday life—for example, a square looks exactly the same when it is rotated 90 degrees. Then there are slightly more abstract symmetries, such as those of a harmonious musical chord, whose frequency patterns remain invariant when they are shifted by a fixed amount of time.
The frequency over time of a consonant musical chord (C and G notes). The curve repeats itself every t seconds, where t is a value known as the “period.” Image taken from here.
Furthermore, the symmetry theory of valence yields some concrete, testable predictions. In particular, stimulating the brain at harmonious frequencies via transcranial magnetic stimulation, a technology that sends a series of magnetic pulses through the skull, should induce states of higher emotional valence. Similarly, stimulation of the vagus nerve, which relays information between the brain and the rest of the body, should feel more pleasant when it is synchronized with harmonious music.
Recently, Selen Atasoy, a neuroscientist now at the University of Oxford, developed a paradigm that may turn out to be incredibly useful for testing the theory, as well as for quantifying emotional valence in general. Atasoy’s method hinges on the notion that the connectome—or the structure of all the connections—of the brain resonates at certain natural frequencies. That is, as we can see in the images below, “connectome-specific harmonic waves” (CSHWs) of neuronal activity cycle around the brain at these frequencies.
Connectome-specific harmonic waves cycling around the brain at the natural resonant frequencies of the connectome. Images taken from here.
QRI claims that emotional valence corresponds to the weighted sum of the consonance, dissonance and noise in the harmonics of a given brain state. We calculate the dissonance between CSHWs in a way that’s similar to computing the dissonance of a combination of musical notes. Like sound, brain harmonics with alike frequencies (i.e. frequencies falling within a “critical bandwidth”) and high amplitudes will cause mutual dissonance, and the total dissonance is equivalent to the sum of the dissonance between all possible pairs of harmonics.
We can calculate the dissonance between CSHWs by determining their spatiotemporal proximity. In particular, harmonics that overlap with each other in a short interval of time would be highly unpleasant. By subtracting the dissonance and noise from the brain state, we obtain the amount of consonance.
With this information, we can visualize the “consonance-dissonance-noise signature” of the brain and subsequently map out the valence of a person’s subjective experience. In the images below, the amount of consonance in a brain is represented by the thickness of the blue arrows connecting two brain harmonics, and the level of dissonance is symbolized by the thickness of the red arrows. A harmonic has a greater weight or amplitude if the black circle next to it is larger. The diagram on the left has greater consonance, hence the corresponding brain feels more pleasure. The diagram on the right has a lot of dissonance, and therefore the corresponding brain experiences more pain.
QRI is still in the very early stages of testing the symmetry theory of valence, and it needs funding to run scientific trials on human subjects. If the theory proves to be correct, it will have groundbreaking implications for mental well-being and our understanding of consciousness. With an objective framework for determining the brain states that are associated with high and low emotional valence, we can design therapeutics and interventions that dramatically improve the quality of subjective experience. Hence we could treat mental disorders such as depression more effectively than status quo antidepressants while also enhancing the baseline mood for healthy people.
You may notice that the symmetry theory of valence doesn’t directly solve the hard problem of consciousness. It is meant to explain the valence of experience, not the nature of experience and how, if at all, it emerges from the brain. Valence, however, is arguably the defining feature of consciousness. Indeed, it seems that there is nothing more fundamental to consciousness than the felt-sense of whether the experience is good or bad.
Without this, the experience wouldn’t matter, at least not intrinsically.Indeed, it seems that there is nothing more fundamental to consciousness than the subjective feeling of an experience. QRI has one of the few theories that makes empirical claims about the mathematical structure that corresponds to valence. Consequently, it has a much more tractable approach to consciousness than past philosophical speculation. With this perspective, QRI may carry the keys to unlocking the answer to a profound enigma—that we’ve known all along.