Whenever the discussion of a dualist vs materialist model of the mind comes up, one common point made to support the dualist position (that the mind is something other than or more than just the functioning of the brain) is that the brain may not be the origin of the mind, but rather is just the receiver. Often an explicit comparison is made to radios or televisions.

The brain as receiver hypothesis, however, is wholly inadequate to explain the relationship between the brain and the mind, as I will explain below.

As an example of the brain-receiver argument, David Eagleman writes in his book Incognito:

As an example, I’ll mention what I’ll call the “radio theory” of brains. Imagine that you are a Kalahari Bushman and that you stumble upon a transistor radio in the sand. You might pick it up, twiddle the knobs, and suddenly, to your surprise, hear voices streaming out of this strange little box. If you’re curious and scientifically minded, you might try to understand what is going on. You might pry off the back cover to discover a little nest of wires. Now let’s say you begin a careful, scientific study of what causes the voices. You notice that each time you pull out the green wire, the voices stop. When you put the wire back on its contact, the voices begin again. The same goes for the red wire. Yanking out the black wire causes the voices to get garbled, and removing the yellow wire reduces the volume to a whisper. You step carefully through all the combinations, and you come to a clear conclusion: the voices depend entirely on the integrity of the circuitry. Change the circuitry and you damage the voices.

He argues that the Bushman might falsely conclude that the wires in the radio produce the voices by some unknown mechanism, because he has no knowledge of electromagnetic radiation and radio technology.

This point also came up several times in the 600+ comments following my post on the Afterlife Debate. Commenter Luoge, for example, wrote:

“But the brain-as-mediator model has bot yet been ruled out. We can tamper with a TV set and modify its behaviour just as a neurosurgeon can do with a brain. We can shut down some, or all, of its functioning, and we can stimulate to show specific responses. And yet no neurologist is known to have thought that the TV studio was inside the TV set.”

There are two reasons to reject the brain-as-mediator model – it does not explain the intimate relationship between brain and mind, and (even if it could) it is entirely unnecessary.

To deal with the latter point first, I have used the example of the light-fairy. When I flip the light switch on my wall, the materialist model holds that I am closing a circuit, allowing electricity to flow through the wires in my wall to a specific appliance (such as a light fixture). That light fixture contains a light bulb which adds resistance to the circuit and uses the electrical energy to heat an element in order to produce light and heat.

One might hypothesize, however, that an invisible light fairy lives in my wall. When I flip the switch the fairy flies to the fixture where it draws energy from the electrical wires, and then creates light and heat that it causes to radiate from the bulb. The light bulb is not producing the light and heat, it is just a conduit for the light fairy’s light and heat.

There is no way you can prove that my light fairy does not exist. It is simply entirely unnecessary, and adds nothing to our understanding of reality. The physics of electrical circuits do a fine job of accounting for the behavior of the light switch and the light. There is no need to invoke light bulb dualism.

The same is true of the brain and the mind, the only difference being that both are a lot more complex.

More importantly, however, we have enough information to rule out the brain-as-receiver model unequivocally.

The examples often given of the radio or TV analogy are very telling. They refer to altering the quality of the reception, the volume, even changing the channel. But those are only the crudest analogies to the relationship between brain and mind.

A more accurate analogy would be this – can you alter the wiring of a TV in order to change the plot of a TV program? Can you change a sitcom into a drama? Can you change the dialogue of the characters? Can you stimulate one of the wires in the TV in order to make one of the on-screen characters twitch?

Well, that is what would be necessary in order for the analogy to hold.

As we have learned more and more about brain function, we have identified many modules and circuits in the brain that participate in specific functions. During the Afterlife debate I gave a few of my favorite examples.

Disruption of one circuit, for example, can make someone feel as if their loved-ones are imposters, because they do not evoke the usual emotions they should feel.

Disruption of another circuit can make a person feel as if they are not in control of a part of their body – so-called alien hand syndrome.

A stroke that leaves the ownership module intact but unconnected to the paralyzed limb can rarely result in a supernumerary phantom limb – the subjective experience of having an extra limb that you can feel and controlled (but that does not exist).

Seizures are also a profound area of evidence for the mind as brain theory. Synchronous electrical activity in particular parts of the brain can make people twitch and convulse, but also experience smells, sounds, images, feelings, a sense of unreality, a sense of being connected to the universe, an inability to speak, the experience of a particular piece of music, a sense of deja vu, or pretty much anything you can imagine. The subjective experience depends on the part of the brain where the seizure occurs.

There is also copious evidence from strokes and other forms of brain damage. As a practicing neurologist I can examine a patient with a stroke and with a high degree of accuracy predict exactly where the lesion will be in the brain on subsequent imaging. Everything you think, do, and feel has a neuroanatomical correlate in the brain, and if that function is altered or not working, that will predict where the lesion can be found.

The only limitation is the current resolution of our neuroanatomical and circuitry map of the brain. No one denies that the brain is fantastically complex, and that our current models are a long way from capturing this complexity down to its finest level of detail.

I think, however, that non-neuroscientists grossly underestimate the degree to which we have mapped the circuits in the brain. Also, as our technology improves (with the addition of fMRI and transcranial magnetic stimulation, for example) the materialist model of the brain is becoming more successful. If this model were ultimately wrong, then the materialist approach would be running into serious problems. It isn’t. It is a remarkably successful research paradigm.

A dedicated dualist might still argue that each specific mental function requires its own specific receiver. Brain circuits are receiving specific signals. If you stimulate the circuit it acts as if it is receiving the signal. Eventually, this argument leads to a brain that has all the circuitry necessary to produce everything we can observe about mental function – it leads to the light fairy argument, where the light fairy is simply not necessary.

If, on the other hand, the receiver model were correct then it would be reasonable to predict that as we investigate the relationship between brain function and mental function in greater and greater detail, the physical model would break down. We would run into anomalies we could not explain, and it would seem as if the brain does not have the physical complexity to account for the observed mental complexity. None of this is what we find, however.

Conclusion

The brain-as-receiver hypothesis is nothing more than a convenient way for dualists to dismiss evidence for the correlation between brain function and mental function. The hypothesis, however, is dependent upon a gross misunderstanding of the state of our knowledge about brain function, and the intimate connection that has been documented in countless ways between brain function and mental function.

The simplest explanation for the tight correlation between brain and mental function is that the mind is what the brain does. There is no more reason to hypothesize a mind separate from brain than there is to hypothesize that there is a computer fairy that performs all the necessary calculations and then feeds the results to specific circuits in your computer.