neha - Aug 12, 2013, 1:37p
This was interesting. Thanks. Could you explain further why you dismiss #1, conservative emergence? What is "the difference between consciousness and the rest of physical reality"? Is it really true that consciousness has no externally visible effects which could be definitively distinguished from non-consciousness?


nikhil - Aug 12, 2013, 5:47p
Neha,

Thanks for the questions. Let me try to answer them, the second one first.

No one today has any external test for consciousness. Even if you walk and talk and do fancy things only humans do, you could still (theoretically) lack internal experience. Think about people who sleepwalk - they behave seemingly in the absence of experience, as proverbial "zombies". There are even extreme cases where people do complicated things "in their sleep", like driving many miles, going into someone's house and killing them. So behavior alone does not seem to be sufficient to show the presence of consciousness.

On the flipside, behavior also doesn't seem to be necessary for consciousness. There are examples of people with "locked-in" syndrome who are completely paralyzed but eventually figure out a way to communicate to a nurse by blinking or changing the pH in their mouth. So even in the absence of behavior, consciousness can persist.

So there really isn't any definitive test for consciousness. If there was, we would hopefully be able to apply this test to other non-human creatures and assess their levels of consciousness. Then I could figure out if all this work with the worms had any chance of paying off, seeing as I don't even know if they're conscious or not!

Now on to the first question. The difference between consciousness and the rest of physical reality is that consciousness is an internal state (of experience), while the rest of physical reality is sufficiently encapsulated by external (observable) states (or so conventional science assumes). When matter affects matter, we can observe the change in various physical properties that occur. But somewhere in the chain, consciousness is produced, but this is different from the effect that matter was having on its surroundings in all the previous cases, because it can't be observed. So the hard question is how a physical state that lacks any internal states might build up into the complex internal state of consciousness. Science today has no way to bridge this gap between the physical and the internal (mental), and there's no clear path for how this can even be done.

Here's an analogy: making consciousness from matter is like making wine from water. If all you have is water and you can't add any other chemicals, you can never make wine. You can mix and cool and heat and beat it to your heart's content, but you'll never make wine. Similarly, I believe that no matter what you do to physical matter, you can never make consciousness in a conservatively emergent way.

Hopefully this explanation is clearer.


Alix - Aug 30, 2013, 6:47p
Your blog post is super interesting. But faced with the four alternatives, I’m on the side of the reductionists. My main argument is simply that this is the most parsimonious explanation for how consciousness arises. It doesn’t invoke anything special. And I think one day we might be able to test for consciousness in simulated brains. Recent work in the group of Giulio Tononi developed an approach to measure the level of consciousness of patients in various states. By perturbing the brain and measuring its reaction patterns, they were able to discriminate patients that were awake, asleep, sedated or emerging from coma. Obviously this technique would only work with the human form of consciousness, but we could imagine creating a brain in a vat and looking for patterns of activity indicative of human consciousness. It wouldn’t be bullet proof because these patterns of activity could be associated with something else than consciousness, for example with something that always accompanies consciousness in humans, but not necessarily in a brain in a vat. But I think it’s a flaw to say that because we can’t currently test for consciousness, because it doesn’t have any external representation, it must be something special. They are presumably many phenomena that we can’t observe or test and yet it’s not a reason to invoke “radical” explanations.

Secondly, you write: “perhaps there is a basic law of consciousness, though it differs from known laws in that it operates at the macroscopic scale.” Is it possible that all laws exist at every scale, but that they only matter at a certain level? For example, from my understanding of physics, it’s not that the microscopic laws of physics don’t apply at the level of planets, but simply that they are not useful in understanding the global behavior of planets. Similarly, gravity exists at the microscopic scale, but is irrelevant. (I know that physicists are working on a unifying theory, yet one hasn't emerged yet.) Perhaps consciousness is similar in that it needs a complex enough system to become relevant. If this is true, then it’s not a fundamentally different property from all others.



nikhil - Oct 30, 2013, 8:13a
Thanks for the comment Alix.

To your second point: I think you're confusing the concepts of things that matter *in practicee* with things that matter *in principle*. You say that though gravity exists at the microscopic scale, it is irrelevant. By this you mean that it is irrelevant in practice - you can forget about gravity and just model other forces and you get very accurate simulations. So gravity is only irrelevant *in practice*, but in principle it is still there and likely has a miniscule effect, but an effect nonetheless.

So I take this to mean that gravity is a microscale force that also manifests at the macroscale, but merely as the sum or combination of the microscales (as a conservative emergent).

So when you say that laws only "matter" at a certain level, again I think you're speaking *in practice*. In principle the laws of physics can be viewed as being generated at the microscale and then affecting all higher scales. What I'm concerned with is what is *in principle* plausible with respect to the generation of consciousness.

The in principle/in practice dichotomy often also includes another source of linguistic difficulty: what we're comfortable understanding. Often what is practical is also what is easier for human minds to comprehend, but that is not what I'm interested in here. Although the limits of understanding are inescapable, what I'm trying to understand is not a feature of those limits, but rather the real Truth that lies out there in the world.

Also, your second point towards the end seems to represent a belief in panpsychism - consciousness is there at all scales, but then "needs a complex enough system to become relevant", as you say.

Make up your mind! Are you with the conservative emergents (#1 in the text) or the panpsychists (#3)? To put it another way: do you thing that mind emerges from basic objective features of matter, or do you think all forms of matter have a little bit of proto-consciousness as a basic property?


I Am - Dec 11, 2013, 7:52a
Perhaps Consciousness isn't physical? Any first member in a given series of subsequent members can only pass on what it itself possesses. If this is so, unconscious matter can't pass on consciousness. Perhaps I have it backwards!

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Clayton Aldern - Aug 5, 2013, 9:29a
I don't know. I think, especially when discussing computational models, 'representation' is particularly useful. Say that someone was coming up with a theory for how the visual system works, and had drawn up a computational model that has images being encoded simply by the greyscale value at each pixel. Here, the pixel representation is the wrong representation, because any slight perturbation of the image will drastically shift the response vector in high dimensional space. You need a model that is invariant to size/rotation/translation, because that's how we know our visual system works on a behavioral level. The next model would seek to account for this, and neurobiological experiments could later be performed to validate the model.

To me, 'representation' has little to do with function and everything to do theory—that is, what types of operations we might expect the cells/systems of interest to perform. How we imagine such stimuli being 'represented' in the brain. Thinking in terms of the representation problem allows for good, hypothesis-driven work towards confirming/rejecting these models.


Glen - Sep 21, 2013, 1:04a
Bravo - err, you do know that Skinnerians have been saying similar things for 60 years, right?


Yin Xin - Sep 14, 2015, 7:47a
I just started my neuroscience career, and I felt confused when I met the word "representation". Why don't these neuroscientists use another word?


Eric - Apr 20, 2017, 10:16a
Maps represent the world, right? Representations are just the internal maps by means of which we steer (this is from Dretske). There is no implied dualism.

It seems innocuous enough, there is no dualism implied, any more than when I use a map to get around town.

It is a representation, not the world itself, upon which your behaviors are based. E.g., the representation of the world in V1 is what you base your decision to take your foot off the brake pedal, for isntance. You don't have magical direct access to the stop sign. It is indirect, mediated by sensory channels.

OTOH, if you don't like the word, you could use another word. Visual information, visual signals, etc.. They are pretty much all used synonymously, and people aren't too worried about words as much as the biological mechanisms and explanatory purchase offered by the discovered mechanisms.

When systems are really simple the language of representation is not used much, because organisms more directly coupled to the environment (e.g., venus fly traps are never discussed in such terms). But when layers of information processors are interleaved between stimulus and behavior (e.g., most vertebrates, and many vertebrates), it is more likely to be used because it is natural and useful and innocuous.

I'm not so sure we should be going back to Skinner, Glen. Just sayin'. :)

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