Tag Archives: explanatory gap

Closing the Gap

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mind the gapA better neurophysiology, the answer to the Hard Problem? Kirchhoff and Hutto propose a slightly different way forward.

The Hard Problem, of course, is about reconciling the physical description of a conscious event with the way it feels from inside. This is the ‘explanatory gap’. Most of us these days are monists of one kind or another; we believe the world ultimately consists of one kind of thing, usually matter, without a second realm of spirits or other metaphysical entities on top. Some people would, accordingly seek to reduce the mental to the physical, perhaps even eliminating the mental so that our monism can be tidy ((I’m a messy monist myself). Neurophysiology, as formulated by Varela and briefly described in Kirchhoff and Hutto’s paper, does not look for a reduction, merely an explanation.
It does this by putting aside any idea of representations or computations; instead it proposes a practical research programme in which introspective reports of experience are matched with scans or other physical investigations. By elucidating the structure of both experience and physical event, the project aims to show how the two sides of experience constrain each other.

This, though, doesn’t seem enough for Kirchhoff and Hutto. Researching the two sides of the matter together is fine, but how will it ever show constraints, or generate an explanation? it seems it will be doomed to merely exhibiting correlation. Moreover, rather than resolving the explanatory gap, this approach seems to consolidate it.
These are reasonable objections, but I don’t think it’s quite as hopeless as that. The aspiration must surely be that the exploration comes together by exhibiting, not just correlation, but an underlying identity of structure? We might hope that the physical structure of the visual cortex tells us something about our colour space and visual experience that matches the structure of 0ur direct experience of colour, for example, in such a way that the mysterious quality of that experience is attenuated and eventually even dispelled. Other kinds of explanation might emerge. When I take off my glasses and look at the surface of brightly lit swimming pool, I see a host of white circles, all the same size and filled with the suggestion of a moire pattern, bobbing daintily about. In a pre-scientific era, this would have been hard to account for, but now I know it is entirely the result of some facts about the shape of my eyes and the lenses in them, and phenomenological worries don’t even get started. It could be that neurophilosophy can succeed in offering explanations good enough to remove the worries that currently exist. The great thing about it, of course, is that even if that hope is philosophically misplaced, elucidating the structure of experience from both ends is a very worthwhile project anyway, one that can surely only yield valuable new understanding.

However, what Kirchhoff and Hutto propose is that we go a little further and abolish the gap. Instead of affirming the separateness of the physical and the phenomenal, they suggest, we should recognise that they represent to different descriptions of a single thing.

That might seem a modest adjustment, but they also assert that the phenomenal character of experience actually arises not from the mere physics, but from the situation of that experience, taking place in an enactive, embodied context. So if we hold a book, we can see it; if we shut our eyes, we continue to feel it; but we also have a more complex engagement with it from our efforts to hold up what we know is a book, the feel of pages, and so on. There’s all sorts of stuff going on that isn’t the mere physical contact, and that’s what yields the character of the experience.

I see that, I think, but it’s a little odd. If we imagine floating in a sensory deprivation tank and gazing at a smooth, uniform red wall, we seem to be free of a lot of the context we’d normally have and on this view it’s a bit hard to see where the phenomenal intensity would be coming from (perhaps from the remembered significance of red?) We might suspect that Kirchhoff and Hutto are getting their phenomenal content smuggled in with the more complex phenomenal experience that they implicitly demand by requiring context, an illicit supplement that remains unexplained.

On this, why not let a thousand flowers grow; go ahead and develop explanations according to any exploratory project you prefer, and then we’ll have a look. Some of them might be good even if your underlying theory is wrong.
I think it is, incidentally. For me the explanatory gap is always misconstrued; the real gap is not between physics and phenomenology, it’s between theory and actuality, something that shouldn’t puzzle us, or at least not in the way it always does.

A Different Gap

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gapWe’re often told that when facing philosophical problems, we should try to ‘carve them at the joints’. The biggest joint on offer in the case of consciousness has seemed to be the ‘explanatory gap’ between the physical activity of neurons and the subjective experience of consciousness. Now, in the latest JCS, Reggia, Monner, and Sylvester suggest that there is another gap, and one where our attention should rightly be focussed.

They suggest that while the simulation of certain cognitive processes has proceeded quite well, the project of actually instantiating consciousness computationally has essentially got nowhere.  That project, as they say, is affected by a variety of problems about defining and recognising success. But the real problem lies in an unrecognised issue: the computational explanatory gap. Whereas the explanatory gap we’re used to is between mind and brain, the computational gap is between high-level computational algorithms and low-level neuronal activity. At the high level, working top-down, we’ve done relatively well in elucidating how certain kinds of problem-solving, goal-directed kinds of computation work, and been able to simulate them relatively effectively.  At the neuronal, bottom-up level we’ve been able to explain certain kinds of pattern-recognition and routine learning systems. The two different kinds of processing have complementary strengths and weaknesses, but at the moment we have no clear idea of how one is built out of the other. This is the computational explanatory gap.

In philosophy, the authors plausibly claim, this important gap has been overlooked because in philosophical terms these are all ‘easy problem’ matters, and so tend to be dismissed as essentially similar matters of detail. In psychology, by contrast, the gap is salient but not clearly recognised as such: the lower-level processes correspond well to those identified as sub-conscious, while the higher-level ones match up with the reportable processes generally identified as conscious.

If Reggia, Monner and Sylvester are right, the well-established quest for the neural correlates of consciousness has been all very well, but what we really need is to bridge the gap by finding the computational correlates of consciousness. As a project, bridging this gap looks relatively promising, because it is all computational. We do not need to address any spooky phenomenology, we do not need to wonder how to express ‘what it is like’, or deal with anything ineffable; we just need to find the read-across between neural networking and the high-level algorithms which we can sort of see in operation. That may not be easy, but compared to the Hard Problem it sounds quite tractable. If solved, it will deliver a coherent account right from neural activity through to high-level decision making.

Of course, that leaves us with the Hard Problem unsolved, but the authors are optimistic that success might still banish the problem. They draw an analogy with artificial life: once it seemed obvious that there was a mysterious quality of being alive, and it was unclear how simple chemistry and physics could ever account for it. That problem of life has never been solved in terms, but as our understanding of the immensely subtle chemistry of living things has improved, it has gradually come to seem les and less obvious that it is really a problem. In a similar way the authors hope that if the computational explanatory gap can be bridged, so that we gradually develop a full account of cognitive processes from the ground-level firing of neurons up to high-level conscious problem-solving, the Hard Problem will gradually cease to seem like something we need to worry about.

That is optimistic, but not unreasonably so, and I think the new perspective offered is a very interesting and plausible one. I’m convinced that the gap exists and that it needs to be bridged: but I’m less sure that it can easily be done.  It might be that Reggia, Monner, and Sylvester are affected in a different way by the same kind of outlook they criticise in philosophers: these are all computational problems, so they’re all tractable. I’m not sure how we can best address the gap, and I suspect it’s there not just because people have failed to recognise it, but because it is also genuinely difficult to deal with.

For one thing, the authors tend to assume the problem is computational. It’s not clear that computation is of the essence here. The low-level processes at a neuronal level don’t look to be based on running any algorithm – that’s part of the nature of the gap. High-level processes may be capable of simulation algorithmically, but that doesn’t mean that’s the way the brain actually does it. Take the example of catching a ball – how do we get to the right place to intercept a ball flying through the air?  One way to do this would be some complex calculations about perspective and vectors: the brain could abstract the data, do the sums, and send back the instructions that result. We could simulate that process in a computer quite well. But we know – I think – that that isn’t the way it’s actually done: the brain uses a simpler and quicker process which never involves abstract calculation, but is based on straight matching of two inputs; a process which incidentally corresponds to a sub-optimal algorithm, but one that is good enough in practice. We just run forward if the elevation of the ball is reducing and back if it’s increasing. Fielders are incapable of predicting where a ball is going, but they can run towards the spot in such a way as to be there when the ball arrives.  It might be that all the ‘higher-level’ processes are like this, and that an attempt to match up with ideally-modelled algorithms is therefore categorically off-track.

Even if those doubts are right, however, it doesn’t mean that the proposed re-framing of the investigation is wrong or unhelpful, and in fact I’m inclined to think it’s a very useful new perspective.

 

Closing the Gap

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Picture: mind the gap. One way of setting up the vexed question of qualia is to claim that there is an explanatory gap between what science tells us about our sensory organs and nervous system on the one hand, and actual real experience on the other.  Nothing in the biological/physical story, it’s claimed, tells us what the redness of a rose or the smell of violets is actually like, and nothing of that kind ever could. The two aspects of the experience do not connect with each other.  In the latest JCS, Michael Pauen sets out to show us that that supposed gap does not exist.

He attacks from four angles.  First, the thought-experiments put forward to point out the gap are inconsistent: second, they require the first-person view to have a special privilege which it hasn’t; third, the arguments for the gap are circular, resting on the same intuition they set out to vindicate. Finally, he offers a historical argument to show that apparent gaps of a similar kind have disappeared in the past as our scientific understanding grew: there’s no reason to think that this one too will stop seeming plausible when we understand things better.

We’ve often discussed the thought-experiments in question.  There’s Mary, brought up in monochrome but knowing all the science, who nevertheless knows something more, it’s claimed, when she sees what redness is really like. There are the ‘zombies’, creatures exactly like us in every physical detail and consequently in behaviour too, yet having no real experiences: the possibility of such beings, if you accept it, proving that there’s more than just physics going on. There are also the many variants of the inverted spectrum, where what I experience when I see blue is what you experience when you see red; our inability to discover or communicate this difference once again proving the existence of the gap.

What’s inconsistent about all that? Pauen introduces a new kind of zombie (Another new kind of zombie? There must be a dozen kinds in the literature already.) .  These are part-time zombies.  Some of the time they do have subjective experience just like us, at other times, as it were, the lights go out for a while.  The intermittent nature of their experience doesn’t affect their behaviour, of course, because ex hypothesi zombies are all exactly like their non-zombie equivalents in all physical matters. Moreover, because their zomboid episodes leave no physical traces in their brains, they can’t remember whether or not they had experiences at any given time. For that matter, we can’t tell whether we are part-time zombies ourselves, because we wouldn’t remember in either case. In fact, we can’t tell whether we ever did have subjective experience: so the theory of the gap ultimately undermines our reasons for believing in the gap in the first place.

This is a useful argument: still, I think Pauen may underestimate how far committed dualists might be prepared to go in digging in on this issue. Why has the experience got to leave physical traces in the brain, they might ask – I might just remember it spiritually. Pauen in reply would no doubt point out that such a spiritual memory could never have physical effects, so nothing they say with a physical mouth or write with a physical hand could ever have been caused by those ineffable experiences.  This is certainly an uncomfortable position for the dualists to be in, but it really only expands and dramatises the bind they were already in about the acausal nature of qualia, and you could argue that it’s only a little worse than the problems about interaction with the physical world which dualists have always faced. Somehow they seem to live with it.

Pauen’s second argument is meant to show that there’s no privileged first-person access to qualia: what does that actually mean? It’s obvious that you can’t, strictly, see things from my perspective without being me: but the explanatory gap also requires that there are facts about my experience (facts, presumably, about what it is like) that you can never get to know from the third-person perspective (if you could get to know everything from the third-person view there would be no gap). Pauen argues that if the subjects can recognise qualia, there must be some resulting difference in their epistemic or functional dispositions: these in turn will be recognisable from the third-person point of view. Contrariwise, if there is no functional difference, the subjects themselves will be unable to recognise the qualia, because the mere ability to do so would itself constitute a functional difference. Although I think he’s right about this, I think he has again assumed more agreement than some would be prepared to give.  I suppose most people these days are broadly functionalist in a general sense, but not everyone would accept that the ability to recognise the presence or absence of qualia has anything to do with functional dispositions, if that is to be read as referring to functional dispositions of physical matter. It’s tough to see how it could be otherwise, but there are mouths ready to bite that bullet.

Why is that? Why do people live with positions that involve such bad, unresolved philosophical problems? I think the dualists might say: look Michael, we know this is severely problematic – they don’t call it the hard problem for nothing – but what can we do? These qualia are right there, immediately obvious. It’s as if you’d come up with some really cogent arguments to show we had no heads, arguments we couldn’t fault. In those circumstances we’re forced to say, sorry Michael, but we just have not been decapitated – we just haven’t – so for the time being we’re going to have to work on the assumption that there’s something wrong with your case for acephaly even though just at the moment we can’t give you an unproblematic alternative.

Ah, but that plays into Pauen’s hands, because his third argument addresses the strength of the intuition behind qualia. He points out, quite rightly, I think, that we generally start with a strong feeling that there is something it is like; then the various arguments get presented to validate this intuition.  But on examination all of the arguments rest in the end on the same intuition. It is logically open to us to just deny that Mary learns anything new, to deny the possibility of zombies, and dismiss the issue of the inverted spectrum as meaningless. No argument compels us to do otherwise, it’s just that the same basic intuition is supposed to lead us in the other direction. Intuitions, Pauen points out, don’t prove anything.

That’s right of course, but there are a couple of things to be said. The first is that I don’t think the advocates of qualia actually suppose they’re putting forward a tight logical case. The arguments are, as it were, ostensive, they don’t deduce the existence of qualia, they simply display it.  What we’re offered is not really arguments so much as what Dennett calls ‘intuition pumps’, less powerful but legitimate tools if used properly.

Second, in calling them ‘intuitions’, Pauen sells these impressions a bit short. There are intuitions and intuitions: here we’re not talking about a hunch that people have qualia, we’re talking about having qualia right in your face, having them in the most direct and unmediated manner – a manner which some might even argue had a special immunity from error (I can be wrong about the fact that I’m seeing a rose, but can’t be wrong about the fact that I seem to be seeing a rose (Eric Schwitzgebel might have something to say about that though)). For those who believe in them, qualia may be ineffable, but they’re also undeniable in a unique way denied to mere feelings about things are likely to be.

Or so you may think: but Pauen’s last argument is the historical one that things which one seemed irreducible to us have often ended up being perfectly explicable once we knew a bit more about the underlying science. In general Pauen is arguing against the view that there is an explanatory gap  in principle, but here his argument also implicitly rebuts those who, like Colin McGinn, never claimed qualia were mysterious in themselves, only forever mysterious to us. I don’t suppose anyone ever changed their mind because the opposition’s retelling of events convinced them they were on the wrong side of history, but I found Pauen’s account, which takes up a substantial part of the paper, enlightening. Besides Fechner and Du Bois-Reymond he picks out Descartes for particular attention, and it was refreshing to see him given fair and accurate treatment for once instead of being blamed for imaginary theatres and what have you.

On this general historical argument I again think Pauen is basically right. It is already possible to explain many aspects of vision in ways which tend to reduce the sense of ineffability a bit, and no doubt this will continue to develop. But that may not do the job of dispelling all the magic.  Part of the sensation of mystery about qualia, I suspect, does come from a certain mere bogglement over the difference between first and third person view; and a large part comes from the inexplicable haecceity of the world and even worse, of ourselves. These things are not going to stop bothering people any time soon.