Tag Archives: libet

Thinking About the Libet Experiments (Again)

In a way, I hate thinking about how to properly interpret the famous Libet experiments on free will. For those who haven’t heard of them, the experiments are fairly simple. First, the brain is monitored in some way, usually with EEG. Then, the subject is asked to “consciously decide” to wag a finger. There are electrodes on the finger that can detect precisely when the finger moved. Moreover, when the subject “consciously decides” to wag their finger, they are instructed to look at a clock with a fast rotating hand. They are supposed to remember where the clock hand was when they felt like that had consciously decided to wag their finger.

What are the results? Well, the main thrust of the experiments is that Libet would see EEG activity that would reliably predict the movement of the finger before the subject reported even feeling to consciously decide to wag the finger. In other words, before the subject had “consciously decided”, some part of the brain was already active that reliably predicts finger-wagging. They can do this experiment now with more sophisticated techniques, and I think they can use brain activity some 10 seconds before the conscious decision to predict when the finger would wag. Pretty wild stuff, right?

Usually the Libet experiments are interpreted as showing that free will is an illusion and that consciousness is basically a mere side-effect of nonconscious processes. The idea is that the preconscious brain activity is in charge of really deciding to wag the finger. The “conscious decision” to wag the finger is a by-product or side-effect of this preconscious activity. So the idea then is that consciously deciding to do something and then feeling like it was that conscious decision which did the causal work is an illusion. Many theorists like Dan Wegner have thus concluded that consciousness is a retrospective illusion, with no causal efficacy.

Every time I think about the Libet experiments and all these interpretations about free will my head starts to hurt. Somehow it feels super fishy to me to conclude from the experiments that free will is an illusion. Of course, there is a sense in which the Libet experiments do prove the idea of free will to be false. If we thought that, whatever the will is, it can’t be physical or realized in the brain, then yes, the Libet experiments do seem to undermine this idea. Libet’s experiments conclusively show that the brain is a major player (if not the only player) in deciding what we do. If you are a physicalist like me, then this idea is pretty obvious. But I don’t think this immaterial spooky free will concept is really what’s at stake philosophically (although of course theists and dualists will disagree).

What’s at stake in my opinion is whether the Libet experiments call into question the conceptual distinction between voluntary and involuntary actions. Is there a fundamental difference between sneezing when I step into strong sunlight or on deciding to get married? Sneezing is usually understood as an automatic, involuntary reflex. Deciding to marry someone is a classic example of what we call a “voluntary action”. In my opinion, Libet’s experiments don’t call into question the basic legitimacy of this distinction. If even we lived in a perfectly deterministic world, it would still be right to distinguish in humans voluntary and involuntary behavior.

I think what the Libet experiments might show is that there is a neural realizer base for voluntary actions. No surprises there. But what about the idea that the “conscious decision” to wag a finger comes so late? It doesn’t seem to be quick enough to really call the shots for motor control. But I think this comes to the heart of the matter: is the “conscious decision” to wag a finger really the best example of when consciousness exercises control? Wagging a finger and deciding to get married are two radically different kinds of decisions. The first happens over the course of milliseconds, the second can happen over the course of months or years. In my own case, my decision to want to marry Katie was drawn out over a long time period. I really had to stop and reflect deeply about my future with Katie and whether I saw myself being happy with her 50 years in the future.

As a Jaynesian, I like to define consciousness to be a kind of introspective power, a power to reflect on the past, present, or future in ways that transcend the automatic and habitual tendencies of action shared by our animal cousins. Defined in this way, I’m not really sure the decision to wag a finger is really representative of the kind of action planning that consciousness is best suited for. Consciousness as I define it is not suited for millisecond control of finger motion. It’s more relevant for planning a wedding, or deciding to take that new job, or go on vacation. Consciousness as a action-controlling process is less a sensorimotor function as it is a narrotological function. Consciousness thinks in terms of stories. It is a long-term synthetic function. It operates on the longest time-scales in the brain. So finger wagging might just miss consciousness all together. So I’m not sure it’s best to conclude from the Libet experiments that consciousness is just an epiphenomena or mere side-effect that plays no causal role.

Don’t get me wrong though. There is a sense in which even the operations of a narratological consciousness are determinstic insofar as they are realized in brain tissue, and brain tissue of course follows physiological laws without deviation. So there is a sense in which even long-term, narratological conscious processes are “determined” by brain processes. If we could do a long-term Libet-style experiment on the causal precursors of my decision to get married, I’m sure we could find all sorts of precursors. But again, this is only surprising if we thought that the will must be immaterial and free-floating from physical processes. But the fact that consciousness is realized in the brain is no reason to think that sneezing is of the same action type as deciding to get married.  And of course there is whole host of intermediate action types between sneezing (a reflex, really) and getting married. There are certainly a lot of “higher” cognitive functions that are nonconscious, including powers of reasoning and perception. But I think it is crucial to the human sciences that we don’t collapse all these distinctions because of simple experiments like Libet’s. There is an important distinction to be made between voluntary and involuntary, between conscious and nonconscious. And consciousness is not just a synonym for awareness. As I use it, it’s meant to capture that process of reflection and deliberation characteristic of “big” decisions like deciding to get married or whether to take a job.


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Benjamin Libet: A Jaynesian Interpretation

In 1980s, Benjamin Libet performed a psychophysical experiment on voluntary will that has sparked ongoing controversy regarding its interpretation and implications. Take the phenomenon of freely willing your hand to move. This is a phenomenon well-known to us all. Libet’s experiment was aimed at uncovering the extent to which unconscious processes precede the awareness of our decision to freely move. It had long been known that a “readiness potential” precedes voluntary action up to a second before the action takes place, a considerable amount of time neurally speaking. Libet’s reasoning for the experiment was as follows: if the conscious willing of the hand is causally efficacious it should precede or arise around the time when the readiness potential starts. Using a clever timing mechanism, Libet discovered that the readiness potential start 550 ms before the voluntary action and that the conscious willing is reported only 200 ms before the action. There is thus a “lag” or “delay” in consciousness behind the unconscious processing. Libet himself took this as evidence that conscious decisions for action are preceded by unconscious processing and that our traditional notion of the will as a commander is thus mistaken. All the will can do, says Libet, is “veto” an action. Libet concluded that volition is thus largely an illusion, with unconscious processing determining what we are going to do before we have a conscious awareness of making a decision.

But is that the only way to interpret this experiment? Surely not.  In fact, Julian Jaynes’ notion of a “struction” indicates that consciousness actually plays a powerful role in our mental economy, far beyond that of a “veto” function.  In the experiment, the conscious awareness of a decision was timed by a clock mechanism. The subjects were instructed to watch a spot of light revolve and report in clocktime where the spot was at the moment they felt they had decided to move spontaneously. Because the readiness potential always started 350 ms before the subjective decision to move (according to the clock), Libet concludes that the conscious will is not actually making the decision, but only capable of “vetoing” what the unconscious had already decided.

If look closely however, we can see a potential role for consciousness in terms of structions i.e. conscious instructions. Say you are the subject and you are tasked with making a spontaneous move and then reporting the time at which you had decided to move. One would likely narratize this goal in your head, perhaps rehearsing the instructions giving to you by the examiner. This would be the struction that guides your overall behavior in the experiment. Let’s call this conscious instruction to follow the experiment Struction A. Struction A would of course be operative in a temporally extended way throughout the experiment, otherwise you would not be able to obey the instructions of the experimenters. Furthermore, let’s assume that after making a conscious struction, the unconscious mind would need time to “obey” and “carry out” the struction.

This post-struction processing might account for the readiness potential and unconscious processing before the actual decision, but what about the 350 ms delay between the start of the readiness potential and the report of conscious will? Let’s assume that there would be two basic structions in the overall task. Struction A would be the metacognitive operator that guides the overall behavior so as to follow the instructions of the experimenter. Struction B would be the struction which actually gets reported as the conscious decision to move. Given that structions are brain processes, it is not surprising that brain activity would precede Struction B and that brain activity would follow Struction A. Moreover, given that structions are instructions from the narrative mind to the unconscious, it is not surprising that the actual implementation of Struction A takes processing time. But if you look at struction B without accounting for Struction A, it would certainly seem that conscious willing “lags” and never makes decisions itself (except to veto). But if we understand the way in which Struction A keeps the subject focused on the task at hand in a time-extended way, then it becomes clear that Struction A, in some sense, causes the entire half-second processing of the readiness potential, the conscious Struction B, and then the action itself. If you isolate Struction B from Struction A, it seems like consciousness cannot actually initiate decisions, but only “tags along” or gets “referred backwards” so as to seem as if consciousness is making decisions. But if we look at how the temporally extended decision to follow the experimenters directions keeps the subject on task so as to initiate Struction B, we can account for the “preliminary” unconscious processing of the readiness potential for Struction B without losing sight of overall place of conscious structions within the cognitive economy (guiding behavior at the abstract level of propositional attitudes through interiorized narratizing).

In summary, here’s what I think is going on. Struction A is made by the subject. This is a conscious willing, an “instruction” sent to the unconscious or subliminal mind for processing and execution. This instruction sends a command signal to the unconscious to prepare for the tasks of spontaneous decision making and the reporting of time. Unconscious processing takes place in the form of readiness potentials, which was catalyzed by the conscious command (which is experienced as interior narratizing). The unconscious processing initiated by Struction A sets up Struction B, the “spontaneous” willing, which is then reported as the actual spontaneous decision (according to the instructions of the overall experiment). If the subjects had been trained to extend their introspective awareness to include Struction A, then Libet would have concluded that consciousness actually does influence the action, albeit in a time-extended way through abstract executive control (acting and vetoing). But because Libet focuses the conscious report only around Struction B and not the total phenomenological experience, he failed to see how the unconscious readiness potentials which preceded Struction B were themselves preceded by Struction A, which was the conscious instruction to actually carryout the task of spontaneously making a decision.

The general lesson here is that conscious decisions are temporally extended because they operate over longer time periods that half second spontaneity. In fact, spontaneous finger-flicking is not a good model of how conscious volition works. For example, I can consciously instruct myself to raise my arm 10 minutes from now and ff course there will be unconscious processing occurring between the initial struction and when I raise my arm 10 minutes later. But it doesn’t follow that just because unconscious processing occurs before the arm raising that my conscious struction wasn’t the actual impetus for the action.


Filed under Consciousness, Philosophy, Psychology

Thinking about Libet, pt 2

In my last post, I briefly discussed the most pertinent results from Benjamin Libet’s 1982 experiment and some of the implications. In this post, I would like to put on my speculative hat and talk about an alternative to the dichotomy I set up in the previous post I linked.

If you don’t recall, the dichotomy was set up between what appears to happen when we hear a noise behind us and what Libet thought was going on. What seems to be going on is that we consciously hear a sound and then turn around, but Libet proposed that we unconsciously hear it first, turn around, and then our brain performs a “backwards subjective referral” of the event to make it seem like the first scenario is happening. In my last post I said this was a false dichotomy and now I will speculate on what I think is really going on. Bare with me.

Imagine that a human body is sitting in a classroom and attending to the lecturer. All of a sudden this attentive human becomes aware of a door opening behind his back and cocks his head around accordingly in order to see what just interrupted the lecture. All of this activity, including the awareness of the noise of the door opening and the innervation of the appropriate neck and back muscles, all happened within the more-or-less continuous, 3d perceptual space that we all are familiar with.

So, while there are hundreds of potential things to be attentive of in any normal classroom(including the awareness of your own body sitting down), the available cognitive processing power responsible for “shifting the attentional spotlight” allocated almost the entirety of its capacity to the perception of the door opening, probably because of the neural contrast/distinction of such a sudden noise but also because this human body knows from past experience that usually the only things that open doors are other humans and it is this implicit social knowledge imbedded into action-schemas that makes it hard not to notice sudden changes in the social environment.

This contextual social knowledge makes it obvious why more attentional capacity would be allocated to the perception of the door opening rather than say the perception of his body twisting around or the perception of practically anything else in the room, even though the overall body-system never stopped being aware of these things, it is just that the percentage of attentional capacity devoted to the door opening made that particular activity more vivid that anything else upon episodic recollection. With the situation set up in this way, let us try go back to explaining Libet’s half-second delay.

Under my conceptualization, the reason why the neural isomorphic representation of the door opening seems to “echo”(thanks Dennett) around the brain for an “extra” half second past the “necessary” evoked motor potentials is because the brain is essentially “telling a story to itself” about the event. The functionality of this generated “after-the-fact” story comes from the fact that the door-opening-event is now easily fed into a variety of different cognitive systems thanks to the considerably long(in brain terms) half-second of processing necessary to turn such “noisy” sensory data into higher-level “conceptual” representations that implicitly include such linguistic conceptual relativities as self/other, internal/external, etc. important for metaphor-based story telling.

Furthermore, I speculate that evolutionarily speaking, the most advantageous way of putting these high-level representations of low-level sensory-action-data to use would be through an advanced memory/prediction/empathy system. This interrelated triad would be of great advantage in a social atmosphere. Perhaps I will elaborate on this triad a later post, but for now I am done wildly speculating from my armchair.

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Thinking about Libet

In 1982, Benjamin Libet carried out a remarkable study on consciousness that is still being debated by contemporary philosophers and scientists. In today’s post I would like to briefly highlight the results and spell out some implications. Here are the most pertinent results as far as I can see them:

  • In order to “consciously experience” a sensation, it must apparently bounce around the somatosensory cortex, or some other “high-level” area of the cortex for about half a second, probably isolated to the frontal areas(Libet, 1982)
  • “A touch on the skin that the subjects would otherwise have reported feeling was retroactively masked up to half a second later by a stimulation to the cortex”(Blackmore, 2004)

Okay, so how can phenomenological consciousness “drag” half of a second behind the real world when clearly we are able to react much faster than that? The most obvious idea is to say that consciousness has no causal power, it is merely a resultant and not a force (in James’ terms). However, this is at odds with the “hard problem” of consciousness because if our “unconscious” does all the important work, such as reacting to dangerous stimuli in split-second situations, there would have been no evolutionary pressure for phenomenal consciousness to tag along and “dangle” half a second behind the real important things going on in the world, such as a stepping on a snake or braking for a red light.

I believe that I can sketch out a framework that can reasonably explain how consciousness could happen “after the fact”, yet still have enough function that it could easily have evolved in the way that it did given the close-knit social structures of our early hominid ancestors.

Let us look at Blackmore’s example of turning around to look who just opened a door while you are sitting in a classroom. This is what seems to happen:(from blackmore)

Scenario 1

  1. Consciously hear sound
  2. Turn around to look

According to Libet, it should be more like this:

Scenario 2

  1. Unconsciously “hear” sound
  2. Turn around to look
  3. Backwards subjective referral of consciousness to make it seem like Scenario 1 is what actually happened

So how do we extricate ourselves from this mess? I think the first step is to recognize that you are setting up a false dichotomy of sorts by trying to directly reconcile scenarios 1 and 2 as the only two options. Furthermore, we should follow Dennett’s advice and use extreme conceptual caution when using the terms “conscious” and “unconscious”, because the nature of our language necessarily forces an implicit acceptance of the Cartesian Theater whenever we use the language of conscious/unconscious, and it is this intuitive dichotomy that makes it impossible to solve these kinds of philosophical problems using ordinary conceptual frameworks.

However, if we use the framework of enactive perception and attentional theories of consciousness, we will get a better understanding of why trying to decide between either Scenario 1 or 2 will only result in frustration and headaches. In my next post I will discuss an alternative way of looking at this problem. Stay tuned!

Libet, B. 1982 Brain Stimulation in the study of neuronal functions for conscious sensory experiences. Human Neurobiology 1, 235-42

Blackmore, S. 2004 Consciousness: An Introduction

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