by Quintin Frerichs

One of the most pressing problems in philosophy of mind is solving the so-called ‘problem of other minds‘, the difficulty of proving that agents outside oneself have qualia. A workable solution to the problem of other minds would endow us with the ability to define the moral patienthood of present-day biological entities, evade our solipsistic tendencies, and open the door to truly understanding future nonhuman intelligences, should they prove to be conscious. Even more strangely, it would allow us to evaluate whether dream characters or the products of dissociative identity disorder are separate consciousnesses. Irrevocably proving the existence of qualia in other biological life which lacks the capacity for language and higher-order thought is not, to my knowledge, even conceptually feasible at this time. In the case of two agents with the capacity to communicate and problem solve, however, this solution has been proposed, which requires the agent being tested to prove they have qualia by solving a “phenomenal puzzle”. Crucially, the solution does not require that the two agents experience the same qualia, simply that there exists a mapping between their respective conscious states.

If an agent A wishes to prove the existence of qualia in agent B using the above procedure, then A and B must have the following:

1. A phenomenal bridge (e.g. a biological neural network that connects your brain to someone else’s brain so that both brains now instantiate a single consciousness).
2. A qualia calibrator (a device that allows you to cycle through many combinations of qualia values quickly so that you can compare the sensory-qualia mappings in both brains and generate a shared vocabulary for qualia values).
3. A phenomenal puzzle (as described above).
4. The right set and setting: the use of a proper protocol.

I contend that there may already be a procedure which can be used to generate a reversible phenomenal bridge between two separate minds: a way to make two minds one and subsequently one mind two. Moving in each of these two directions has apparently been demonstrated; by craniopagus twins connected with a thalamic bridge and by corpus callosotomy separating the two cerebral hemispheres. There is tantalizing evidence in each case that consciousness is being fused or fissioned, respectively. In the case of the Hogan sisters, the apparently unitary mind  has access to sensory information from the sensory organs of each cranium. In the case of separating hemispheres there is some debate: alien hand syndrome has suggested the existence of dual consciousness, while other findings have cast doubt on the existence of two separate consciousnesses. While a surgical procedure for separating the hemispheres is as yet permanent, a chemically-induced separation of the hemispheres via the Wada test may provide new avenues for testing the problem of other minds. While some forms of communication (namely language, which is largely left-lateralized) are impaired by the Wada test, other forms such as singing can be left intact. Thus, I believe a combination of Gazzinaga’s procedure and Gómez Emilsson’s phenomenal puzzle approach, in conjunction with a working qualia calibrator, could demonstrate the existence or absence of dual consciousness in the human mind-brain. A version of the Wada test with higher specificity may also be required, to negate some of the characteristic symptoms of confusion, hemineglect, and loss of verbal comprehension.

Phenomenal puzzle solution

The procedure (utilizing the state space of color, with agents L and R corresponding to the left and right hemispheres) would be as follows: 

Note: a difficulty of utilizing the below outlined procedure is determining which hemisphere should serve as the benchmark. While often language ability is dominant in the left hemisphere (especially in right-handed individuals) and therefore eliminated when the left hemisphere is inactivated during the Wada test, this is not always the case. In cases where at least some language ability is preserved in each hemisphere, either can reliably serve as the point of comparison. 

1. Design a phenomenal puzzle, such that the solution corresponds to reporting the number of just noticeable differences required to produce a linear mapping between two locations in the state space of color. 
2. Separate the left and right visual fields (Gazzaniga).
3. Sodium amobarbital is administered to the left internal cardioid artery via the femoral artery and EEG confirms inactivation of the left hemisphere. In the LVF a consent checkbox for performing the experiment is given to the right hemisphere, Y/N checked using the left hand.
4. Similarly, sodium amobarbital is administered to the right internal cardioid artery via the femoral artery and EEG confirms inactivation of the right hemisphere. Consent can be verbally obtained from the left hemisphere. 
5. With both hemispheres activated, qualia calibration on the state space of color is performed (see: A workable solution to the problem of other minds). 
6. With R inactivated, the phenomenal puzzle is presented to L without enough time for L to solve the puzzle.
7. Both hemispheres are activated, and L tells the phenomenal puzzle to LR.
8. L is inactivated and R attempts to solve the puzzle on its own. When R claims to have solved the puzzle (in writing or song most likely), both hemispheres are again reactivated in order to produce LR. R shares its solution with LR.
9. R is inactivated, and L shares the solution to the phenomenal puzzle. If the solution is correct, then R is conscious! 

Point-of-view characterization of above procedure (Under the assumption that both hemispheres are, in fact, conscious):

1. From the perspective of the left brain: A researcher asks “do you consent to the following procedure?” You answer ‘yes’, perhaps wondering if you’ve lost just a part of your computational resources, or created an entirely separate consciousness. A short period of darkness and sedation ensues while consent is obtained from the right brain. Suddenly, the amount of consciousness you’re experiencing expands greatly and new memories are available. The computer screen in front of you rapidly cycles through a series of paired color values. The Qualia Calibrator confirms a match by waiting for consensus of the right motor cortex (in lieu of a button press) and from verbal confirmation of the left hemisphere. It feels like an eye exam at hyper speed: “Color one or color two? Color two or color three?”, but for thousands of colors, many of which you don’t have a name for. Then, you sleep, for some indeterminate amount of time. When you awaken, the researcher explains to you the puzzle to solve. Your consciousness is then expanded again, and you repeat the puzzle to yourself, with the strange feeling that “part of you didn’t know about it”. You go dark again. And when the lights are turn on again, things feel normal, but you have a prominent new memory, the solution to the puzzle. Quickly you check. Take this strange shade of cyan and change it once, twice, three times…yup! That’s the mellow orange you were looking for, and in the same number of “just noticeable differences”.
2. From the perspective of the right brain: You awaken to a scrollable consent form with a checkbox, and a left-handed mouse. Despite your state of relative confusion and lack of verbal fluency, you’re able to understand the form and check the box. Suddenly, your conscious experience expands and your fluency erupts. The computer screen in front of you rapidly cycles through a series of paired color values. The Qualia Calibrator confirms a match by waiting for consensus of the right motor cortex (in lieu of a button press) and from verbal confirmation of the left hemisphere. It feels like an eye exam at hyper speed: “Color one or color two? Color two or color three?”, but for thousands of colors, many of which you don’t have a name for. Again you sleep, your consciousness is briefly expanded, and you learn of the puzzle you are to solve. How did you learn about it? It is weird, you started “repeating” the puzzle to yourself, with the strange feeling that “part of you already had heard it before”. But either way, now you feel like you have heard it really well. Next, it feels like you took a strong sedative and a memory-loss drug at the same time. Now, in this highly impoverished cognitive state, you have to solve a complicated puzzle. To prove that you exist. Ugh. Fortunately, you have help, in the form of an AI which provides the linear mapping you need to discover, provided you answer how many just noticeable differences occur between each set of two points. Half man and machine collaborate to find the solution, and you commit it to memory. Reunited once more, you “share your findings to yourself”. It turns out you’re conscious. The world now knows: the right hemisphere is conscious on its own when the left one is unconscious. Hooray!