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Panpsychism is the belief that consciousness is found throughout the universe – not only in humans and animals, but also in trees, plants, and bacteria. Panpsychists believe that some aspects of the mind are present even in elementary particles. The idea that consciousness is widespread attracts many for intellectual and possibly emotional reasons. But can this be verified empirically? Surprising, but possible. This is because one of the most popular scientific theories of consciousness, Integrated Information Theory (IIT), shares many, though not all, of the features of panpsychism.
As the American philosopher Thomas Nagel argued, something is conscious if there is “something as it should be” in the state in which it is. The human brain in the waking state feels like something special.
IIT identifies a unique number, integrated system information, marked with the Greek letter φ (pronounced fi). If φ is equal to zero, the system is not like anything; indeed, the system does not exist as a whole, since it is completely reduced to its constituent components. The more φ, the more conscious the system is and the more irreducible it is. Having received an accurate and complete description of the system, IIT predicts both the quantity and quality of its experience (if any). IIT predicts that due to the structure of the human brain, humans have high φ values, while animals have lower (but positive) values, and classic digital computers have almost none.
The value of φ for a person is not constant. It increases in early childhood as personality develops and may decrease with the onset of dementia and other cognitive impairments. φ will fluctuate during sleep, increasing during sleep and decreasing in deep, dreamless states.
IIT begins by identifying the five true and essential properties of any imaginable conscious experience. For example, experience is defined (exception). This means that the experience is no less than it is (experiencing only the sensation of blue, but not the moving ocean that resembled that color) and no more than it is (say, experiencing the ocean while being aware of the tree crown behind). In the second phase, IIT infers five related physical properties that any system – brain, computer, pine, sand dunes – must exhibit in order to feel something like that. “Mechanism” in IIT is anything that plays a causal role in the system; it could be a logical gate in a computer or a neuron in the brain. IIT claims that consciousness arises only in systems of mechanisms that have a certain structure. To simplify somewhat, this structure should be as integrated as possible – it cannot be accurately described by breaking it down into its component parts. It must also have a causal force on itself, that is, the current state of a given mechanism must limit the future states of not only this particular mechanism, but also the system as a whole.
Given the exact physical description of the system, the theory provides a way to calculate the φ of this system. The technical details of how this is done are complex, but as a result, it is possible, in principle, to objectively measure the φ of the system if you have such an accurate description. (We can calculate the φ of computers because by building them we understand them exactly. Calculating the φ of the human brain is still an estimate.)
The debate about the nature of consciousness may sound like an academic exercise at first glance, but it has real and important implications.
Systems can be assessed at different levels – you can measure the φ of a piece of my brain the size of a sugar cube, or my brain as a whole, or me and you together. Likewise, you can measure the φ of a silicon atom, a particular circuit on a microchip, or a set of microchips that make up a supercomputer. Consciousness, according to the theory, exists for systems for which φ is maximum. It exists for all such systems and only for such systems.
The Φ of my brain is larger than the φ values of any of its parts, but we are going to split it. So I’m conscious. But the φ of me and you together is less than my φ or your φ, so we are not aware of “together.” If, however, future technology could create a tight knot of communication between my brain and yours, then such a brain connection would create a unified mind distributed across the four cortical hemispheres.
Conversely, the φ of a supercomputer is less than the φs of any of the circuits that make up it, so a supercomputer, no matter how large and powerful, has no consciousness. The theory predicts that even if some deep learning system can pass the Turing test, it will be a so-called “zombie” – mimicking consciousness, but not actually conscious.
Thus, like panpsychism, IIT considers consciousness as an internal, fundamental property of reality, which is assessed and, most likely, widespread on the tree of life, since any system with a non-zero volume of integrated information will feel like something. This does not mean that the bee is obese or making plans for the weekend. But the bee may feel some joy when it returns to its hive overgrown with pollen in the sun. When a bee dies, it stops experiencing anything. Likewise, given the enormous complexity of even a single cell with millions of interacting proteins, it can seem like a tiny bit like something.
The debate about the nature of consciousness may seem like an academic exercise at first glance, but it has real and important implications. Obviously, this matters to the way we think about people in vegetative state. Such patients may moan or otherwise move for no reason, but may not be able to purposefully respond to cue commands by moving their eyes or nodding. Can they conscious minds, trapped in their damaged body, perceive but cannot respond? Or are they unconscious?
It is difficult to assess such patients for the presence of consciousness. IIT supporters have developed a procedure by which you can test the consciousness of an unresponsive person. They first created a network of EEG electrodes that can measure the electrical activity of the brain. They then stimulate the brain with a soft magnetic pulse and record its echo. They can then compute a mathematical measure of the complexity of these echoes called the Perturbation Complexity Index (PCI).
In healthy, conscious people – or people with brain damage but clearly conscious – PCI always exceeds a certain threshold. On the other hand, in 100% of cases, if healthy people are asleep, their PCI is below this threshold (0.31). Therefore, it is wise to use PCI as an indicator of the presence of a conscious mind. If the PCI of a person in a steady vegetative state is always measured below this threshold, we can confidently say that this person is not in latent consciousness.
This method is being investigated in a number of clinical centers in the USA and Europe. Other tests are aimed at confirming the predictions made by IIT about the location and timing of the appearance of traces of sensory consciousness in the brains of humans, nonhuman primates and mice.
Unlike panpsychism, IIT’s startling claims can be tested empirically. If they hold out, science may have found a way to cut the knot that has baffled philosophers throughout the history of philosophy.
Christoph Koch is Chief Scientist for the MindScope Program at the Allen Brain Research Institute in Seattle.
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