Neurons and Free Will

wiring a neuronA few years ago we noted the remarkable research by Fried, Mukamel, and Kreiman which reproduced and confirmed Libet’s famous research. Libet, in brief, had found good evidence using EEG that a decision to move was formed about half a second before the subject in question became consciously aware of it; Fried et al produced comparable results by direct measurement of neuron firing.

In the intervening years, electrode technology has improved and should now make it possible to measure multiple sites. The scanty details here indicate that Kreiman, with support from MIT, plans to repeat the research in an enhanced form; in particular he proposes to see whether, having identified the formed intention to move, it is then possible to stop it before the action takes place. This resembles the faculty of ‘free won’t’ by which Libet himself hoped to preserve some trace of free will.

From the MIT article it is evident that Kreiman is a determinist and believes that his research confirms that position. It is generally believed that Libet’s findings are incompatible with free will in the sense that they seem to show that consciousness has no effect on our actual behaviour.

That actually sheds an interesting side-light on our view of what free will is. A decision to move still gets made, after all; why shouldn’t it be freely made even though it is unconscious? There’s something unsatisfactory about unconscious free will, it seems. Our desire for free will is a desire to be in control, and by that we mean a desire for the entity that does the talking to be in control. We don’t really think of the unconscious parts of our mind as being us; or at least not in the same way as that gabby part that claims responsibility for everything (the part of me that is writing this now, for example).

This is a bit odd, because the verbal part of our brain obviously does the verbals; it’s strange and unrealistic to think it should also make the decisions, isn’t it? Actually if we are careful to distinguish between the making of the decision and being aware of the decision – which we should certainly do, given that one is clearly a first order mental event and the other equally clearly second order – then it ceases to be surprising that the latter should lag behind the former a bit. Something has to have happened before we can be aware of it, after all.

Our unease about this perhaps relates to the intuitive conviction of our own unity. We want the decision and the awareness to be a single event, we want conscious acts to be, as it were, self- illuminating, and it seems to be that that the research ultimately denies us.

It is the case, of course, that the decisions made in the research are rather weird ones. We’re not often faced with the task of deciding to move our hands at an arbitrary time for no reason. Perhaps the process is different if we are deciding which stocks and shares to buy? We may think about the pros and cons explicitly, and we can see the process by which the conclusion is reached; it’s not plausible that those decisions are made unconsciously and then simply notified to consciousness, is it?

On the other hand, we don’t think, do we, that the process of share-picking is purely verbal? The words flowing through our consciousness are signals of a deeper imaginative modelling, aren’t they? If that is the case, then the words might still be lagging. Perhaps the distinction to be drawn is not really between conscious and unconscious, but between simply conscious and explicitly conscious. Perhaps we just shouldn’t let the talky bit pretend to be the whole of consciousness just because the rest is silent.

Beyond Libet

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!)