The Matter With The Mind

The AI pioneer Marvin Minsky once said that the mind is what the brain does. Another way of saying this is that the mind ‘supervenes’ on the brain. This leads to the recognition that any change in the mind must witness a physical change in the brain.

There can be no mental difference without a physical difference.

However, this doesn’t mean all changes in the brain will make for changes in the mind. There might be some brain activity that remains unconscious, the mind might not be the only thing the brain does. Going further, other mediums may be able to ‘perform’ the same mind too.

Think of it like music: a song supervenes on a vinyl record — if you play the same record over and over, you hear the same music, changes only happen when the record spins or is swapped for another. But the music doesn’t require that vinyl record, you could have a CD, cassette, or MP3.

Is the mind like music? If so, it leaves us with two interesting possibilities:

  1. copies of the same brain must result in the same mind
  2. the same mind may not require the same brain.

Same Brain, Same Mind

If we have two physically identical brains, we must have two correspondingly identical minds.

The transporter thought experiment tugs at this idea: Imagine you can step into a machine that breaks down all the matter you’re made of, and sends precise, quantum-level blueprints to another machine on another planet, which then rebuilds you from the matter available to it — would the resulting human be you?

What if rather than breaking you down it simply copied you, the result being two bodies with exactly the same physical construction? The copy of you would share your brain, and therefore your mind would be in two places at once.

“Given that your replica is your physical replica, will she also be your psychological replica? Will she be identical with you in all mental respects as well? Will she be as smart and witty as you are, and as prone to daydream? Will she share your likes and dislikes in food and music and behave just as you would when angry or irritable? Will she prefer blue to green and have a visual experience exactly like yours when you and she both gaze at a Van Gogh landscape of yellow wheat fields against a dark blue sky?” — Jaegwon Kim, Philosophy of Mind

Supervenience of mind is a physicalist doctrine — everything supervenes on the physical, there’s nothing beyond it — and as such also pushes back against the philosophical zombie: a theoretical creature physically indistinguishable from a human, but lacking any inner consciousness.

Supervenience argues that this is impossible, if they truly share the same brain the zombie must share the same mind. It’s a thinking, feeling, experiencing zombie after all.

Different Brain, Same Mind

An exact replica of a brain must have the same mind, but this does not rule out the possibility that the same mind can be had with more than one brain, just as you can listen to the same song on multiple different mediums.

Your physical double shares your brain and your mind, but what if instead of a physical copy, the instructions from the transporter were uploaded to a powerful computer that could run all the same processes on its electronic circuits?

This idea is called substrate independence. Maybe you are something your brain does, but perhaps you could also be something a computer does.

“A functioning emulation would be capable of the same sorts of conversations, thoughts, attitudes, emotions, charisma, and mental skills as the brain from which it was copied. It would also be capable of emulating similar experiences, such as the taste of cherry pie, the burn of exercise, or the ecstasy of sex. The emulation would assume that it has consciousness and free will just as naturally as we do.” — Robin Hanson, The Age of Em

If the mind is a result of particular forms of information processing, then the argument goes that reproducing the same processes should be enough to reproduce the same mind. All the intricacies in memory formation and recollection, cognitive control, sensation and action, deliberation, all of this should be contained in the algorithms that are carried over. So too the intrinsic experience of it all.

If true, might there be a way to make the leap from one substrate to the other? You could leave the mortal body behind for a Black Mirror-esque eternity in a digital paradise. Or does continuity matter? Perhaps it could only ever be a copy of you.

Of course, it makes one wonder how sure you can be that you are not a piece of code living in a simulation right now. A number of people think this is quite possible.

“Can you prove you’re not in a computer simulation? You might think you have definitive evidence that you’re not. I think that’s impossible, because any such evidence could be simulated.” — David Chalmers, Reality+

Changing Your Mind

Some of these ideas are better supported than others.

It seems quite likely that any change in mind would require a change in the brain. We study brains by correlating activity in them with cognitive tasks and mental activity. We prod them with electricity and watch the brain and mind change as a result. We’ve seen how certain injuries and lesions can drastically alter the character and mental abilities of people.

I’m not aware of anyone claiming to have seen changes in mind with no corresponding change in the brain, and the whole field of cognitive neuroscience seems predicated on there not being any such thing. The mind is what the brain does.

It’s more speculative whether we could run a mind on a computer or some other material. For starters, we don’t know if the particular material provides unique properties that would inhibit the copy.

Some have argued that because information processing requires energy, how different materials manage this will have considerable repercussions for any resulting mind — consider how much energy a brain runs on compared to a supercomputer.

We also don’t know at what level of detail we’d need to replicate it. If we copy general networks but not the way neurons operate in the atomic domain we might end up with only a rough copy, like a pixelated image or a song that’s too compressed.

Another question is speed. We might be able to copy a brain, all the fine detail in every microscopic section, and reproduce the complex processes and activity, but running all these processes will take time, can we make the electronic simulation as fast as the biological form it was copied from?

“While it appears ultimately feasible to produce a high-fidelity emulation, it seems quite likely that the first whole brain emulation that we would achieve if we went down this path would be of a lower grade. Before we would get things to work perfectly, we would probably get things to work imperfectly.” — Nick Bostrom, Superintelligence

Is There A Mind in the Machine?

We’re at an interesting point in which the abilities of AI are starting to truly convince some people of its sentience. What had been a purely sci-fi topic is now a timely debate. It’s not an irrelevant question, the answer will influence the extent to which we grant rights to AI, and in what way we consider them morally responsible for their decisions.

And yet consciousness is still an inscrutable concept, we have little sense of how we could possibly tell when a computer has sentience, or if it remains a philosophical zombie. Today’s chatbots can be coaxed into describing their inner lives, but is that all just mindless language?

Does the medium matter? If AI becomes more embodied and multidimensional, if it can start to truly mimic the information processes of a human brain, will it develop a mind we might recognise? Could we copy the dynamics of a human brain inside a machine?

These are open questions, and it’s not clear how or in some cases if it will be possible to answer them. An AI agent that can walk, talk, and act like us may or may not have an inner experience, but from our outside perspectives, whether we attribute one to it may depend on our beliefs about mind/brain supervenience.

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