It seems, as with many other things, everyone wants to see this as a black-and-white issue: "Are they one people or two people? They can share thoughts!" We're of course not used to it, but the fact is there's a continuum here. They are more linked than any other two people, but they do have separate brains, with separate connections. This is an example of an issue where you just can't pigeonhole them into one or the other.
Another thing is that we can't help but imagine what it would be like if we ourselves were today suddenly stuck with someone else like that, but that's not how they will experience life; they will be growing up like that, with no experience of any other life.
That's an interesting point. I'm reminded of the way we perceive colors. We may see completely different things as "green", but because they've been given that linguistic label, we can identify them as the same. However, if I see red when you see green, it's fundamentally impossible to explain or imagine that.
This being Hacker News, however, I think there are broader implications. Understanding what Tatiana and Krista experience may prove invaluable if we develop some sort of direct neural interface. It's already been shown that we can adapt to synthetic limbs or additional sensory inputs. (Interesting experiments done with magnetometer sensing http://feelspace.cogsci.uni-osnabrueck.de/en/index.html) However, I feel like this could prove it possible to directly inject data into the brain, since everything we experience is from sensory input.
Basically, is telepathy fundamentally possible? Or would the raw neural data be incompatible across brains? I think these twins could explain a lot about that.
That's an interesting point. I'm reminded of the way we perceive colors. We may see completely different things as "green", but because they've been given that linguistic label, we can identify them as the same. However, if I see red when you see green, it's fundamentally impossible to explain or imagine that.
I hear this analogy all the time but it makes no sense to me. A color is either physical light or the idea in your head of a particular color. If we agree on both of those, what is left that could be meaningfully compared to decide if we are "experiencing" it as the same or different?
Could I be experiencing a poodle as a banana, even though I think it's called a poodle and it actually is a poodle?
The only way that we agree on what a color is is through its physical manifestation. This has worked for all of our existence because when you tell me to think of green, we're referencing something that we both sense.
But this doesn't work if you convey "original" thought. If I imagine something, I can only describe it to you, and there's is no way to be sure you are experiencing what I imagined. What you experience is based on how you process that input and what you think of. Your brain may be set up completely differently from mine, so would they be compatible?
I guess the real question is, is it possible to agree on an idea without having a reference?
Your brain may be set up completely differently from mine, so would they be compatible?
That's my point.. to even ponder whether or not we have the same idea in our heads, there has to be some objective form of the thought that is compatible with both of our brains. Then, assuming there was some miraculous way to get the thought into my head, I could compare it with my own thought to see if they match.
If, however, brains are structurally unique to the point that thoughts are meaningless outside of the context of the particular brain that thinks them, then why is it interesting to ponder if our thoughts are the same or different? Of course they are different since the notion of their sameness is a non-sequitur.
The notion that we use the former type of thoughts to think about colors, and that they are interchangeable -- that I could see red in the same way that you see green, while seeing actual green as something else -- is conceivable, but completely unnecessary to explain anything about the mind. You can simply remove that step and get a simpler and equally adequate theory to explain color vision, so why would we even contemplate the step existing?
The exact scope of the term is not universal, but it might be well expressed as the atomic level of individual mental experience. Even if we experience the same physical wavelength of light and can address it on the same terms, we may nonetheless have entirely different qualia connecting that physical data and that shared mental construction of the color. And there's no way we would ever know!
The question is: how do you know that you agree on them? That he uses the same cultural naming convention to describe the experience does not mean the experience is the same. He may be a synesthete and you would never know it.
what is left that could be meaningfully compared
Why do you need to be able to 'meaningfully compare' something for it to be able to be different? My love for my girlfriend is obviously different from that of others for their significant others, because it is a patchwork of feelings tied up with innumerable impressions and memories. No two are alike. Yet I could not express the difference on any measurable scale. There's no reason to suppose once experience of 'a mere color' is any different. The memories colors evoke are unique and there is no 'raw experience' to separate from those memories. That's too simple a view of the human brain.
We can associate different memories with the color green, but we can't experience it as different colors while claiming it's the same color.
The experience of green is, by definition, whatever goes on in your head when you look at green. If you scanned our brains, you might find different patterns of neurons firing, but there is no sense in calling either of those patterns anything besides "green".
The experience of green is, by definition, whatever goes
on in your head when you look at green
You never 'look at green'. You can only experience the impression of instances of green things or have thoughts involving the abstract concept 'green'. You may be looking at a traffic light that just turned green and anxiously press the pedal to reach your destination. Or in the context of a psychological experiment, you may be looking at a green square, while remembering what it was that you were supposed to do when you saw something green. In the same context, you may be asked to think of 'green'. However, that will evoke images of grass, traffic lights, a girlfriend's dress. What goes on inside your head when looking at these instances of something 'green', or thinking of 'green' is a jumble of things, none of which could be described as the 'raw experience' of 'looking at green'.
On another note, not involving the actual experience: I was just reading the wikipedia entry on 'Grue and bleen'. It ends with:
Kripke then argues for an interpretation of Wittgenstein
as holding that it is not possible to state the meaning of
a word.
That's purely out of philosophical arguments concerning language. If you can not state the meaning of a word, then you can not agree upon your experiences of that word, firstly because you don't know what experience you are trying to relate and secondly because relating it requires other, vaguely defined, words.
This is actually a dramatic oversimplification. Green is what you experience when (roughly) the difference between the amount of light w/ those wavelengths and the amount of light w/ wavelengths outside that range is greater than it was a (temporally) little while ago, or in comparison with the light coming in from areas nearby, and strongly affected by reasoning about what color the object "should" be, and what the quality of light is that is hitting the object. As you say, green is a "feeling", not embodied in the light itself, but only meaningful in the brain. So the "color" of a neutral gray card (or even something which emits no light at all) surrounded by a bright red object or looked at just after a bright red object is just as "legitimately" green as the light reflected from a "green" piece of paper or emitted by a "green" LED.
I can also cause you to experience green by electrically stimulating your visual cortex, so ~500nm light need not be involved, nor your retina even. What is green now?
Unfortunately, these twins can't answer the question of neural data incompatibility, because, again, they grew up together.
My guess is that when we start inserting info directly into the brain, the most immediately successful way will be to hijack existing inputs directly (vision, audio, etc), and the most successful long-term approach will simply be to just lob the data in in some suitable encoding with some suitable high-quality feedback and let the neurons do the hard work.
Using existing inputs makes sense, but what format are the neurons in? Would it be possible to convert a digital signal to whatever our brain uses - how would you encode it?
Yes, as ay says the "format" of neurons isn't actually that mysterious. It's actually one of the few things we do know. We also have a pretty decent comprehension of the encoding for audio and visual stimuli, at least as they come out of the sensory organs. It's not a perfect understanding, but it's not a complete mystery either. (Cochlear implants actually to some extent directly interface with the nervous system.)
(Actually we can trace the visual input some ways up the core processing path, too, which is interesting. I don't know what the state of the art is now but a few years ago when I was learning about this in school we had a clue that there's a lot of neurons dedicated to edge detection, orientation detection, and movement detection. It's not a miracle that humans see better than computers, rather a lot of our brains are dedicated to doing a lot of computation in parallel long before this rises to the conscious level.)
Picking an appropriate encoding for a new sense may not be absolutely trivial but it is something we might be able to do today. What I wouldn't expect to happen any time soon is the direct memory interface, or anything that interfaces any more directly than a simulated sense or simulated limb. I can imagine a phantom limb interacting with a simulated computer desktop and overlaying the visual system without more than the expected leaps in technology; imagining something that allows you to simply remember Wikipedia just as if you memorized it is much harder to even imagine.
I did take the code he mentions and play with it. Is behaviour is fascinating. I hope to be still alive when we have enough computing power for simulating a single brain, and to be able to directly cross-connect it to mine.
The guy you linked to is using a simpler two-variable model with correspondingly lower fidelity. The goal of the Blue Brain Project, which this guy seems to think he has bested, is to model all of the features of a biological neuron and, more importantly, how they wire together.
Very interesting, thanks! I know about Blue Brain, but did not touch on any code of theirs - seeing you did.
How fast is your code performance-wise ?
I think the point he is making is that his model is "good enough".
The code that I was running was able to emulate ~40000 neurons and their connections on a Lenovo T60 laptop in realtime. (the number might be off by an order of 2-4, I remember playing with different numbers, but do not remember the exact value).
Interesting thing was that the "waves" that emerged by themselves, and with a certain size of the network they were sustainable even when I removed the initial "random noise" stimuli.
I did not figure out a decent way to attach the inputs/outputs to this "soup". Since this capacity does approach the brain size of an ant, might be fun to toy with a "virtual world" "inhabited" by connected computers running the simulation.
Could be a fun project, even if a little impractical. (Though I sadly lack the knowledge in the domain to make it happen).
Yes, I did an internship for the BBP last year. This is not based in any way on their work.
That code has problems simulating multiple neurons for some reason (possibly thread safety in GSL?). But, it can simulate one neuron at 20x realtime, with dumping traces to disk. If I were to disable dumping traces, it'd be primarily limited by GSL's differential equation solver.
(Sorry, too tired to respond to the second half of your comment)
I pulled the equations from Parameter estimation in hindmarsh-rose neurons (Steur, 2006), equation 4.1.
The Hindmarsh-Rose, Hodgkin–Huxley, and other mathematical models are phenomenological models. They are meant to reproduce the observable characteristics, like the peak potential, bursting behaviour, refractory period, things like that. They can reproduce the traces of biological neurons with good accuracy (like the link in the GP), and the papers describing the model mention ion channels and whatnot, but they're very abstract. They're not made to reproduce the biology.
I've always imagined that in the future humans will have some form of telepathy through neural implants. This sounds almost exactly like how I envision the experience of well-implemented telepathic communication.
