James of Seattle clued me in to a thought experiment described by Dr. Anna Schapiro in a Twitter thread.
It’s very similar to one discussed in a new preprint paper: Do action potentials cause consciousness? Like all good thought experiments, it exercises and challenges our intuitions. In this case, it forces us to contemplate how we think consciousness actually works. The paper authors claim it challenges major theories of consciousness. I don’t think it does, but you might feel differently.
- Let’s say we’re able to record the voltage spikes from every neuron in your brain for 30 seconds. (This can actually be done for small numbers of neurons, but let’s assume we can somehow do it for all 86 billion.) During the 30 seconds, you wave to yourself in a mirror.
- Now, let’s further assume we can use the recording to induce the same spikes in those neurons in the same order. We do this using voltage clamps on each neuron. (Again voltage clamping is currently doable for small numbers of neurons (fascinating example), but let’s assume we can do it for all 86 billion.) So we run the recording, inducing the spikes in your neurons in the same order. During the sequence, are you seeing yourself wave in the mirror? (In Schapiro’s poll, 70% thought they would be.)
- Okay, let’s suppose we have the technology to block the neurotransmitters in all of your synapses, and we do so. We’re now going to run the recording, inducing the spikes in the same neurons in the same order. Still seeing yourself waving? (Only 28% of Schapiro’s respondents thought so.)
- Now we physically distribute your neurons to labs throughout the world. We send instructions on exactly when, in a precisely timed operation, they’re supposed to induce spikes in the neurons they receive. When those instructions are followed in all the labs, are you still conscious of yourself waving in the mirror? (24%)
- Finally, it turns out someone screwed up on the time zones, so the ordering in 4 got messed up. Still seeing yourself waving? (11%)
So when in this sequence do you think consciousness disappears, if ever?
According to the paper authors, many of the major theories of consciousness, such as global workspace, higher order thought, or recurrent processing, are committed to you being conscious through all the steps, although I suspect the proponents of those theories would argue that their theories are more context specific than that. The paper authors also assert that integrated information theory, with its causal structure requirements, and their own Dendritic Information Theory, will have bailed by step 3.
When considering this, I think it’s important to ask Daniel Dennett’s hard question: And then what happens? To be conscious of something, I think, involves more than just the immediate processing. It’s being in the moment with your memories, recognizing with your learned associations, and then remembering it afterward. It’s having the episode be part of your episodic stream of consciousness.
With that in mind, I think there is a chance of still being conscious in step 2. But step 3 is where we unquestionably mess with the causal dynamics. At that point, consciousness in the sense described above seems absent. But as usual it comes down to exactly how we define consciousness.
In step 1, you’re presumably fully aware of where you are and what you’re doing. In step 2, you might be confused about exactly what’s happening, but with your synapses still working, you should remember that you’ve already done this once, and might remember the second time after it’s done.
But in step 3, when we block the synapses, you no longer have the ability to remember the previous attempts. (Remember, memories are thought to be stored in the varying strengths of synaptic connections.) If it makes sense to say you know anything, you think this is the first time you’ve done the waving. And most importantly, assuming we unblock your synapses afterward, you won’t have any memory of the run in step 3. From your perspective, you will have blacked out during that period, maybe similar to the experience of an epileptic patient having a seizure. If we call that state “conscious”, it seems completely separate from your overall autobiographical consciousness.
But isn’t it reasonable to assume that some kind of experience takes place in step 3? What exactly do we mean by “experience”? If we can’t be changed by the sequence, in what manner is it really an experience?
Perhaps most importantly, what test could we ever do to establish there was still a consciousness present in step 3? We couldn’t trust any self report, behavioral indicators, or brain scan patterns, because those would just be from the recording playing back. And again, you’d have no memory of it afterward, so couldn’t self report your experience after the fact. We’d have an epiphenomenal version of consciousness, something with no causal effects.
If step 3 isn’t conscious, then steps 4 and 5 are moot. But if we do retain consciousness in step 3, the paper authors note that electromagnetic field theories of consciousness should bail at step 4, when all the neurons are now too distant to affect each other purely through the field. If we still think consciousness is present at step 4, it’s hard for me to see the rational for deciding it’s absent in step 5.
What do you think? Where do you draw the line? And why? And do you see any issues with the one I drew?