Archive for May, 2011

Picture: dials. Libet’s famous experiments are among the most interesting and challenging in neuroscience; now they’ve been taken further. A paper by Fried, Mukamel and Kreiman in Neuron (with a very useful overview by Patrick Haggard) reports on experiments using a number of epilepsy patients where it was ethically possible to implant electrodes and hence to read off the activity of individual neurons, giving a vastly more precise picture than anything achievable by other means. In other respects the experiments broadly followed the design of Libet’s own, using a similar clock-face approach to measure the time when subjects felt they decided to press a button. Libet discovered that a Readiness Potential (RP) could be detected as much as half a second before the subject was conscious of deciding to move; the new experiments show that data from a population of 250 neurons in the SMA (the Supplementary Motor Area) were sufficient to predict the subject’s decision 700 ms in advance of the subject’s own awareness, with 80% accuracy.

The more detailed picture which these experiments provide helps clarify some points about the relationship between pre-SMA and SMA proper, and suggest that the sense of decision reported by subjects is actually the point at which a growing decision starts to be converted into action, rather than the beginning of the decision-forming process, which stretches back further. This may help to explain the results from fMRI studies which have found the precursors of a decision much earlier than 500 ms beforehand. There are also indications that a lot of the activity in these areas might be more concerned with suppressing possible actions than initiating them – a finding which harmonises nicely with Libet’s own idea of ‘free won’t’ – that we might not be able to control the formation of impulses to act, but could still suppress them when we wanted.

For us, though, the main point of the experiments is that they appear to provide a strong vindication of Libet and make it clear that we have to engage with his finding that our decisions are made well before we think we’re making them.

What are we to make of it all then? I’m inclined to think that the easiest and most acceptable way of interpreting the results is to note that making a decision and being aware of having made a decision are two different things (and being able to report the fact may be yet a third). On this view we first make up our minds; then the process of becoming aware of having done so naturally takes some neural processing of its own, and hence arrives a few hundred milliseconds later.

That would be fine, except that we strongly feel that our decisions flow from the conscious process, that the feelings we are aware of, and could articulate aloud if we chose, are actually decisive. Suppose I am deciding which house to buy: house A involves a longer commute while house B is in a less attractive area. Surely I would go through something like an internal argument or assessment, totting up the pros and cons, and it is this forensic process in internal consciousness which causally determines what I do? Otherwise why do I spend any time thinking about it at all – surely it’s the internal discussion that takes time?

Well, there is another way to read the process: perhaps I hold the two possibilities in mind in turn: perhaps I imagine myself on the long daily journey or staring at the unlovely factory wall. Which makes me feel worse? Eventually I get a sense of where I would be happiest, perhaps with a feeling of settling one alternative and so of what I intend to do. On this view the explicitly conscious part of my mind is merely displaying options and waiting for some other, feeling part to send back its implicit message. The talky, explicit part of consciousness isn’t really making the decision at all, though it (or should I say ‘I’?) takes responsibility for it and is happy to offer explanations.

Perhaps there are both processes in involved in different decisions to different degrees. Some purely rational decisions may indeed happen in the explicit part of the mind, but in others – and Libet’s examples would be in this category – things have to feel right. The talky part of me may choose to hold up particular options and may try to nudge things one way or another, but it waits for the silent part to plump.

Is that plausible? I’m not sure. The willingness of the talky part to take responsibility for actions it didn’t decide on and even to confect and confabulate spurious rationales, is very well established (albeit typically in cases with brain lesions), but introspectively I don’t like the idea of two agents being at work I’d prefer it to be one agent using two approaches or two sets of tools – but I’m not sure that does the job of accounting for the delay which was the problem in the first place…

(Thanks to Dale Roberts!)

Picture: Paul Churchland. There is a lot of interesting stuff over at the The Third Annual Online Consciousness Conference; I particularly enjoyed Paul Churchland’s paper Consciousness and the Introspection of Apparent Qualitative Simples (pdf), which is actually a fairly general attack on the proponents of qualia, the irreducibly subjective bits of experience.  Churchland is of course among the most prominent, long-standing and robust of the sceptics; and it seems to me his scepticism is particularly pure in the sense that he asks us to sign up to very little beyond faith in science and distrust of anything said to be beyond its reach. He says here that in the past his arguments have been based on three main lines of attack: the conditions actually required for a reduction of qualia; the actual successes of science in explaining sensory experience, and the history of science and the lessons to be drawn from it. Some of those arguments are unavoidably technical to some degree; this time he’s going for a more accessible approach and, as it were, coming for the qualophiles on their own ground.

The attack has two main thrusts. The first is against Nagel, who in his celebrated paper What is it like to be a bat? claimed that it was pointless to ask for an objective account of matters that were quintessentially subjective. Well, to begin with, says Churchland, it’s not the case that we’re dealing with two distinct realms here: objective and subjective overlap quite a bit. Your subjective inner feelings give you objective information about where your body is, how it’s moving, how full your stomach is, and so on. You can even get information about the exhausted state of certain neurons in your visual cortex by seeing the floaty after-image of something you’ve been staring at.  Now that in itself doesn’t refute the qualophiles’ claim, because they go on to say that nevertheless, the subjective sensations themselves are unknowable by others. But that’s just nonsense. Is the fact that someone else feels hungry unknowable to me? Hardly: I know lots of things about other people’s feelings: my everyday life involves frequent consideration of such matters. I may not know these things the way the people themselves know them, but the idea that there’s some secret garden of other people’s subjectivity which I can never enter is patently untrue.

I think Churchland’s aim is perhaps slightly off there: qualophiles would concede that we can have third-person knowledge of these matters: but in our own experience, they would say, we can see there’s something over and above the objective element, and we can’t know that bit of other people’s feelings: for all we’ll ever know, the subjective feelings that go along with feeling hungry for them might be quite different from the ones we have.

But Churchland has not overlooked this and addresses it by moving on to the bat thought-experiment itself. Nagel claims we can’t know how it feels to be a bat, he says, but this is because we don’t have a bat’s history. Nagel is suggesting that if we have all the theoretical information about bat sensitivity we should know what being a bat is like: but these are distinct forms of knowledge, and there’s no reason why the possession of one should convey the other. What we lack is not access to a particular domain of knowledge, but the ability to have been a bat. The same unjustified claim that theoretical knowledge should constitute subjective knowledge is at the root of Jackson’s celebrated argument about Mary the colour scientist, says Churchland: in fact we can see this in the way Jackson equivocates between two senses of the word ‘know': knowing a body of scientific fact, and ‘knowing how’ to tell red from green.

The second line of attack is directed against Chalmers, and it’s here that the simples of the title come in. Chalmers, says Churchland, claims that a reductive explanation of qualia is impossible because subjective sensations are ultimately simples – unanalysable things which offer no foothold to an inter-theoretical reduction.  The idea here is that in other cases we reduce away the idea of, say, temperature by analysing its properties in terms of a different theoretical realm, that of the motion of molecules. But we can’t do that for subjective qualities. Our actual experiences may consist of complex combinations, but when we boil it down enough we come to basic elements like red. What can we say about red that we might be able to explain in terms of say neurons? What properties does red have?  Well, redness, sort of. What can we say about it? It’s red.

Churchland begins by pointing out that our experiences may turn out to be more analysable than we realise. Our first taste of strawberry ice cream may seem like a simple, elemental thing, but later on we may learn to analyse it in terms of strawberry flavour, creaminess, sweetness, and so on. This in itself does not prove that there isn’t a final vocabulary of simples lurking at the bottom, of course. But, asks Churchland, how will I know when I’ve hit bottom?  Since every creature’s ability to discriminate is necessarily limited, it’s inevitable that at some point it’s going to seem as if I have gone as far as I could possibly go – but so what? Even temperature probably seemed like a simple unanalysable property once upon a time.

Moreover, aren’t these unanalysable properties going to be a bit difficult to handle? How do we ever relate them to each other or even talk about them? Of course, the fact that qualia have no causal properties makes this pretty difficult already. If they don’t have any causal effects, how can they explain anything? Qualophiles say they explain our conscious experience, but to do that they’d need to be registered or apprehended or whatever, and how can that happen if they never cause anything? As an explanation, this is ‘a train wreck’.

Churchland is quite right that all this is a horrible mess, and if Chalmers were offering it as a theory it would be fatally damaged. But we have to remember that Chalmers is really offering us a problem: and this is generally true of the qualophiles. Yes, they might say, all this stuff is impossible to make sense of; it is a train wreck, but you know, what can we do because there they are, those qualia, right in front of your nose. It’s pretty bad to put forward an unresolved mystery, but it would be worse to deny one that’s palpably there.

On the point about simples, Churchland has a point too: but there does seem to be something peculiarly ungraspable here. Qualia seem to be a particular case of the perpetual give-away argument; whatever happens in the discussion someone will always say ‘the trouble is, I can imagine all that being true, and yet I can still reasonably ask: is that person really having the same experience as me?’ So we might grant that in future Churchland will succeed in analysing experience is such a way that he’ll be able to tell from a brain scan what someone is experiencing, conclusions that they will confirm in great detail: we can give him all that and still feel we don’t know whether what we actually experience as red is what the subject experiences as blue.

Churchland thinks that part of the reason we continue to feel like this is that we don’t appreciate just how good some of the scientific explanations are already, let alone how good they may become. To dramatise this he refers back to his earlier paper on Chimerical colours (pdf).  It turns out that the ‘colour spindle’ which represents all possible colours is dealt with in the brain by a neuronal area which follows the Hurvich-Jameson model. The interesting thing about this is that the H-J model is larger than the spindle: so the model actually encodes many impossible colours, such as a yellow as dark as black. Presumably if we stimulated these regions with electrodes, we should experience these impossible colours.

But wait! There is a way to hit these regions without surgery, by selectively exhausting some neurons and then superimposing the after-image on a coloured area. See the paper for an explanation and also a whole series of practical examples where, with a bit of staring, you can experience colours not in nature.

These are well worth trying, although to be honest I’m not absolutely sure whether the very vivid results seem to me to fall outside the colour spindle: I think Churchland would say I’m allowing my brain to impose sceptical filtering – because some mental agent in the colour processing centre of my brain doesn’t believe in dark yellow, for example, he’s whispering in my ear that hey, it’s really only sort of brown, isn’t it?

For Churchland these experiments show that proper science can make predictions about our inner experience that are both remarkable and counter-intuitive, but which are triumphantly borne out by experience. I do find it impossible not to sympathise with what he says. But I can also imagine a qualophile pointing out that the colour spindle was supposed to be a logically complete analysis of colour in terms of three variables: so we might argue that these chimerical colours are evidence that analyses of sensory experience and the reductions that flow from them tend to fail and that the realm of colour qualia, quite contrary to the appraently succesful reduction embodied inthe colour spindle, is actually unconstrained and undefinable.  And why are these experiments so exciting, the qualophile might ask, if not because they seem to hold out the promise of new qualia?

Picture: Gladraeli. As Gilbert and Sullivan had it,

…every boy and every girl
That’s born into the world alive
Is either a little Liberal
Or else a little Conservative!

Now indeed it seems that right-wing brains are measurably different from left-wing ones.

Well, alright, it’s not as simple as that, but as this review (via)of an interesting piece of research reports, in one sample of young adults, self-reported political conservatives tended to have a larger right amygdala, whereas self-reported liberals tend to have a larger anterior cingulate cortex. Strictly speaking we are probably not entitled to deduce anything from this, but if we want to jump to conclusions we can assume that a larger amygdala is associated with greater levels of distrust and hostility, while a larger anterior cingulate cortex is associated with greater tolerance of conflict and uncertainty. It’s easy to imagine that a more distrustful (perhaps we should say ‘sceptical’) personality, with a more pessimistic view of human nature, might be associated with generally more right-wing views. I’m not so sure about the interpretation of the other finding, but I suppose a greater tolerance of conflict and uncertainty might be associated with less support for established authority and traditional mores, and so with a generally more leftish slant. I suppose we would expect, in line with the often-observed tendency to drift to the right as one ages, that the amgydala would swell and the anterior cingulate cortex shrink as time went by?

It’s generally fairly plausible that political views correlate to at least some degree with personality traits. It’s often suggested that introversion tends to go with a more conservative outlook, for example. It’s certainly the case that political leanings are more about direction of travel than about specific policies: pretty well everyone alive now is a raving lefty in terms of the medieval political outlook (though even then there were outbursts of radicalism, of course). Conservative opinion which once would fight to the death defending the divine right of kings finds itself, four hundred years later, defending the mercantile individualist values it once regarded as the enemy. For that matter I’ve just been reading a few of Trollope’s novels, and it seems pretty clear that the Duke of Omnium’s coalition government would find its successor in Westminster today not just unacceptably but almost incomprehensibly left-wing, even though in theory the governments have a broadly similar mixture of conservative and liberal opinion.

It’s strange that Kanai’s research identifies two different measures of political leaning. It doesn’t seem to me that trusting and liking people is exactly the same thing as tolerating conflict. The existence of two independent axes suggests that there are actually four different positions. As well as the die-hard right and the entrenched left, we have on the one hand people who favour hard-nosed policies but attach no value to authority and convention; while on the other hand we have people who prefer generous and supportive systems but want to combine them with traditional and conforming ways of behaving. Neither seems at all hard to imagine: I know people who would fit both those descriptions tolerably well. Perhaps our existing political set-up misses out on the full geometry: if so it might be a little worrying because it would imply that perhaps there are problems and solutions which are really quite important but remain partly invisible to us on our one-dimensional view?

If the normal right-left spectrum is so inadequate (and I think many people would say it is, and that there are really not just two axes involved, but several), how come we’re lumbered with it? It’s not that surprising that when one group is in power many of its opponents band together and sink their differences in the joint project of turning the rascals out; and when the tables are turned it’s the new opposition that benefits from the same effect. Over time it seems plausible this would lead to the crystallisation of two broad groupings; and the theme of those who have established wealth and power, and hence tend to like theoretical arguments against change, versus those who have less and so are predisposed to like reforming and revolutionary sentiments, seems well adapted to be the thread along which the parties ultimately take shape.

Fine for politics, but I can’t see how that would explain a similar dichotomy in the brain, unless there’s something more fundamental going on. Could there be some kind of game-theoretical account, in which, say, big-amygdala people do well out of their hard-nosed attitudes and reproduce successfully up to the point where they become a majority of the population, at which point the level of distrust undermines social cohesion and fully offsets the benefits to new ‘selfish’ entrants, so the advantage begins to accrue to the cingulate cortexers who can cope with a bit of dissent and disorder, who then do better until their generosity and trust begins to be exploited by a selfish minority and so on until some kind of balance is reached?

Maybe it’s not genetic, though: perhaps it has to do with birth order? It is said that first-born children tend to endorse authority and take on the role of parental deputy, while for subsequent children there are more rewards in being the first non-conformist than in being a mere second deputy. Perhaps these influences create differential growth in differing parts of the brain (alas, no data on birth order)?

Having jumped repeatedly from one conclusion to another like an excitable frog, I find myself in an unfamiliar part of the pond, so I shall retreat, taking with me only the wild speculation that much of the theory and rhetoric of politics might in fact resemble the bizarre confabulations produced by some patients to give a superficial appearance of conscious volition to behaviour whose actual origins in deep mental hard-wiring or cognitive deficits are actually quite unknown to them.