Neural Antecedents of Decision: Some Phenomenological Skepticism

Web-happy philo-types are by now familiar with the recent study on “Unconscious determinants of free decisions in the human brain” by Soon et al., published in Nature Neuroscience. The study, which expands on the famous experiments performed by Benjamin Libet, purportedly demonstrates a seven second gap between the onset of neural activity involved in making a choice and the subject’s awareness of the choice. The details are discussed, among other places, at Not Exactly Rocket Science, Mixing Memory, NeuroLogica, and Conscious Entities; some interesting comments also at Alexander Pruss's blog. Essentially, participants were asked to press one of two buttons, and to take note of the letter showing on a screen in front of them at the instant they first become aware of having made a decision (Libet’s original experiments asked subjects to remember the position of a hand on a clock); all the while, fMRI scans were recording their brain activity. The comparison, then, is between two heterogeneous sorts of things: neural events, and conscious awareness.

One problem I have with these experiments is that they seem to assume a temporally thin notion of consciousness. Neural processes take time, which is why you can measure how long they go on before an action is carried out. They are temporally thick processes. But conscious awareness is apparently assumed to be instantaneous: we know the exact moment we become aware of something. This is a temporally thin notion: there is no gap in time between the instant we become aware of something and the instant we become aware that we are aware of it or, as in the set-up of the experiment, between the instant we make a choice and the instant we become aware of having made the choice. One obvious reply is to deny that there is any problem here, given a basic assumption that “becoming aware” and “becoming conscious” are synonymous. Surely there is an instant when I am conscious of my decision, say, or conscious of the position of the hand on a clock face (or the letter on a screen). And there is no real sense in which we can speak of something like being aware of such things without also being conscious of them.

But this sounds dubious. What these experiments measure, after all, is not simply when the subjects become aware of a decision. Instead, they measure when the subjects become conscious of that awareness. This is a reflexive process. But is there reason to think that the reflexiveness itself does not take up time?

To complicate matters, there are two reflexive processes going on. On the one hand, the subjects must become conscious of making a decision. On the other, they must become conscious of the letter on the screen at the instant that they become conscious of making a decision. This sounds like a fairly complex process to me, though maybe I am wrong. In any case, though, the process has got to take at least some time to perform. (That there is likely also some temporal gap between seeing the letter on the screen and registering that one has seen it complicates this even further.) What I am suggesting, in other words, is that there might be two temporal gaps that the experiments do not address sufficiently. First, there might be a gap between becoming conscious of a decision and becoming conscious of that consciousness. Second, there might be a gap between becoming conscious of that consciousness and associating this second-order consciousness with the awareness of a particular letter on a screen.

I worry about this, particularly, because the reflexive process is not involved in normal decision making. I either continue typing, or I stop to scratch my nose. But I do this without the second-order consciousness. I cannot, looking back at my action, pinpoint the exact instant when I decided to scratch my nose; normally, I cannot upon reflection even establish that I ever made such a decision, but this fact does not undermine my experience of having made the decision nevertheless. (This suggests, to me, that we may be better off not treating decisions, choices, or volitions as if they were events, and instead recognize them as interpretative abstractions.) So what I am questioning here is the idea that being aware of making a decision—in the normal way in which we experience making decisions in everyday situations—is really connected to the sort of consciousness of deciding that these experiments look at. What they are looking at is the process by means of which we thematize our decisions in consciousness; but this is neither something we normally do, nor is it something that seems central to our awareness of ourselves as deciding.

To top it off, I wonder to what extent the results of these experiments are even transferable to our everyday decisions. The subjects are specifically asked to pay attention to their decision and note the instant when they become conscious of it. But this is not something we normally do. Try it. Right now. Decide to scratch your nose, and then scratch it. When I do this, it feels weird: there is a doubling effect going on, as if I am performing the same action twice. In Searle’s terminology, the decision to scratch my nose is a prior intention, while the mental process involved in the actual nose-scratching is the intention in action. The prior intention in such simple actions is completely redundant. So if you are specifically looking for it, this seems to just distort what it is you normally do when you make decisions. When we ask people to locate the temporal instant at which they make a decision, we are asking them to do something extremely unusual, and the experimental data obtained from such exercises seems unlikely to be telling us very much about normal human decisions making; it might be telling us not what is going on in the brain when we make decisions, but what is going on in the brain when we try to catch ourselves making decisions, which is going to be a very different and very slippery task.

I am not just trying to be skeptical. What I am curious about is just the claim the scientists performing experiments like these seem to be making, i.e., the claim that we can scientifically study the relation between neural processes and consciousness or, at least, that we can do this given current technologies without either distorting or oversimplifying the precise thing we are studying. I am perfectly sure that we can study the neural processes. But it is not at all clear that we have the tools for scientifically studying consciousness. Why, then, should we think scientifically studying the relation—particularly the temporal relation—between the two a currently plausible proposal? These experiments are certainly interesting for all sorts of reasons; I am uncertain that the light they claim to shed on conscious choice is one of them.