Artificial Consciousness: Does the Substrate Matter?

So far in this series on Artificial Consciousness, I have suggested

• We will use the definition of consciousness that most people have: awareness of the environment and especially of self.
• Consciousness is a matter of degree. That’s certainly true between species, but it’s even true for one individual. We are more aware at some times than others.
• Thinking is essentially symbol-manipulation. When we think about something, we are manipulating symbols about that thing in our minds.  (We are certainly not manipulating the thing itself!)
• Consciousness, or self-awareness, is therefore manipulating symbols about our own symbols.

Now I would like to suggest that it’s the symbols themselves that matter, not the substrate that supports them.

The symbols that we are talking about, of course, are the patterns of neural firings and chemistry in our brains. Suppose medical science were to advance to where new neurons could be created from stem cells. Further suppose that the process were perfected so that an individual neuron could be swapped in for a damaged one and exactly mimic its functioning. Would the patient’s consciousness be affected in any way? It’s obvious that it would not. The new neuron, by supposition, is functioning exactly as the old one did. The patient literally could not be aware that anything had changed. (He could be told, of course, but that’s different.)

A few years later, and advances in nanotechnology have obviated the need for stem cells. Now the neuron can be replaced by something that works exactly the same on the outside (same exchange of neurotransmitters, etc.), but is entirely different on the inside. Again, the patient cannot tell the difference because every cell in his brain, including the artificial one, is functioning exactly as before.

More years go by. Now whole portions of the brain can be replaced by synthetic neurons. Is it not clear that this is just more of the same, and that consciousness is not affected?

One day, the entire brain is decoded, just like the human genome was way back in the 2003. A man visits a brain-scanning center. Every neuron’s connections to other neurons and the other cells of the body, the state of every connection, and every neuron’s own state of excitation are recorded at one instant as he lies on a bed. As he leaves the center, a cinder block falls on his head from some construction taking place ten floors above him. He is rushed to the hospital and becomes the first recipient of an artificial-brain transplant, using the data that were scanned just hours before. His eyes are kept closed, and he is taken back to his bed at the brain-scanning center, where he opens his eyes. He thinks he is getting up from the bed for the first time (right?). He wonders where the stitches on the top of his head came from.

Is he conscious?

If not, what aspect of consciousness does he lack? If so, isn’t his consciousness fully human yet fully artificial?

We have just thought about an artificial consciousness that’s exactly like our own. Next time, we’ll ask what the minimal ingredients are for artificial consciousness.