‘Libet’s delay’ and the philosophy of mind and free will

Question

If you are not familiar with Libet delay and the neuroscience of free will, you can read it below. It seems philosophers are interested in the topic since it relates to the philosophical notions of qualia and sense-data in the philosophy of mind. My question is, if the mind operates quickly and outside the scope of apperception, how do I feel very short touches (less than 500 ms) consciously? What does contemporary philosophy of mind say about this?

Libet used trains of electrical stimulation varying in length from a few milliseconds (thousandths of a second) to over a second, and what he found was this: with short trains of electrical pulses the patients felt nothing, but with longer bursts they said they could feel something like a touch on their arms. Libet showed that it needed half a second of continuous electrical stimulation for the patient to say, ‘I feel it’. It seemed as though the conscious experience came a full half-second after the stimulation began.

The most obvious interpretation (though not necessarily the correct one) was that it takes half a second of neuronal activity to produce consciousness. Libet called this ‘neuronal adequacy for consciousness’. This is very odd. It implies that consciousness must lag far behind the events of the real world and so must be useless in responding to fast-changing events.

If this is true, why don’t we realize it? Libet’s own explanation involves the phenomenon of ‘backward referral’ or ‘subjective antedating’. He argues that consciousness does indeed require half a second of continuous activity in the cortex, but that we do not notice the delay because the events are referred back in time once neuronal adequacy has been reached. This is possible because when a stimulus happens—say a flash of light or a quick touch—there is an immediate effect in the brain called the ‘evoked potential’. According to Libet’s theory, when we consciously feel a touch on the arm, activity builds up in the somatosensory cortex until neuronal adequacy is reached. Once reached, the apparent timing of the touch is referred back to the time of the evoked potential. Otherwise, nothing is felt. In this way no delay in consciousness is ever noticed.

Answer 1

The short answer to this question, is that touches less than 500 msec are NEVER felt consciously. Your body starts reaction to an initially felt touch, but if the touch is not for long enough, it is dismissed as a threat, and consciousness is never informed.

The longer answer is:

Libet's work is very interesting, and the best interpretation of it is that at least SOME parts of our consciousness ARE time-lagged and backdated. His work is seized upon By Daniel Dennett and the other "Delusionists" who assert that ALL of our consciousness (IE, extrapolating well beyond Libet's data) is this sort of backdated manufactured story, such that we either are not really conscious, or that consciousness is irrelevant. However, that is not the only way to interpret Libet's experiments.

An alternative framework can be inferred from Kahneman's Thinking Fast and Slow -- where system 1 in our decision process is over 1000 times faster than system 2, and system 2 is used as a check upon reasoning errors by system 1. This framework is easily translated into conscious/unconscious terms. In this translation, system 1 is analogous to our unconscious neural-net logic processes, and system 2, to our conscious check upon our unconscious. The limits to system 2's throughput mean that almost everything has to be pre-planned, and sometimes executed by system 1, while system 2 (our consciousness) is kept informed of what system 1 is doing, in the most important issues. In this model, letting our consciousness (system 2) know our arm was touched, would not be critical in real time to preparing our neurology to respond and pull away, but our consciousness is informed if the threat lasted long enough to be real.

This alternative concept, of our consciousness as basically an executive manager of a large organization, where the organization discovers things, and starts reacting to them, while informing the executive about the most important events, provides a causal role for consciousness, AND can also accommodate consciousness sometimes being backdated, to create the illusion in the executive's head that the executive initiated everything that the two systems did collectively.

Apply this model to Libet's wrist twitch data, where he observed "reaction potential" about 60% of the time before the subjects reported the intention to twist their wrists -- and one can say that system 1 prepared and planned a wrist twitch, but system 2 (consciousness) vetoed that system 1 proposal 40% of the time. This was Libet's own interpretation of his wrist twitch data. Consciousness remains causal in this two-system, sometimes-time-delayed model.

Answer 2

Caveat

Dcleve has touched upon two works that are popular in contemporary philosophy of mind, Consciousness Explained and Thinking, Fast and Slow. To his, I'll recommend a third reference: A Universe of Consciousness and answer less in the vein of cognitive science, and more in the vein of philosophy.

Short Answer

An exact answer to your question isn't known, and that is because for all that is known in cognitive science about perception and apperception, and all that is speculated about subjective experience by schools of thought such as phenomenology, it is still an open question about how the two relate with some philosophers clinging to theories based on qualia, and other, like Dennett, who reject qualia completely.

Long Answer

The History

Since Wundt opened the first psychological lab in Leibzig in 1879, started a journal, and began calling himself a psychologist, a lot has been learned about perception. And a number of great thinkers including and since Immanuel Kant and his transcendental idealism have put forth theories trying to tie together perception, intuition, and consciousness, but forging a theory by consensus among philosophers of mind has been slow going.

First, let's note that Cartesianism has essentially been defeated, at least the aspect of it that advocates like Descartes himself, that all aspects of the mind are available to introspection. Clearly we have a subconscious mind and somehow our senses become experience in something that might be broadly called intuition. 'Intuition' features prominently in Kant's Critique of Pure Reason. Qualia is the philosophical language that has been used historically to characterize experience into units.

Qualia

And what of these qualia? From the WP article:

Daniel Dennett identifies four properties that are commonly ascribed to qualia.2 According to these, qualia are:

ineffable – they cannot be communicated, or apprehended by any means other than direct experience.
intrinsic – they are non-relational properties, which do not change depending on the experience's relation to other things.
private – all interpersonal comparisons of qualia are systematically impossible.
directly or immediately apprehensible by consciousness – to experience a quale is to know one experiences a quale, and to know all there is to know about that quale.

Do theories of qualia explain how neurons firing become a conscious experience? According to Dennett in his Consciousness Explained, no. In fact, he thinks the whole notion should be scrapped. From page 369:

Some snarls should just be abandoned... That's how it is, in my opinion, with the philosophical topic of qualia, a tormented snarl of increasingly convoluted and bizarre thought experiments.

Neural Correlates of Consciousness

So, if keeping in mind qualia, how do contemporary thinkers talk about this matter? Another strong candidate in theories is the language use of the phrase 'neural correlates of consciousness' (SEP). In essence, we can pair up talking about objective phenomena of neuron firing patterns with introspective statements of experience. This is exactly what those who interpret Libet do when they debate whether our subconscious minds make decisions before our conscious ones and suggest that our decisions are epiphenomenal.

It should be noted, that in this way of thinking, one is essentially advocating a form of physicalism where the mental somehow supervenes on the the physical. In physicalism according to Daniel Stoljar, physicalism is essentially a position, from page 7 of his Physicalism:

(7) Physicalism is true (as a worldview) if and only if every instantiated property is either physical or else is necessitated by some instantiated physical property.

So, to make plain, the physical existence of things is necessary for neurons to fire in such a way that they correlate with subjective experiences, more or less. Those experiences happen only if the physical firings of neurons do.

The How

So, the modern approach to conducting dialog about how neural firing patterns become conscious experience is a primary preoccupation to cognitive scientists and analytic philosophers of mind. Edelman and Tononi in their A Universe of Consciousness have an answer: the dynamic core hypothesis. From WP:

The problem of integrating, or binding, the activity of functionally segregated areas of the brain in order to concentrate attention on a particular activity in a short amount of time (typically 100-250 msecs) after the presentation of a stimulus is explored by means of large-scale simulations. It is shown that this can only happen if some elements interact more strongly among themselves than with the rest of the system including a large amount of reentrancy. These functional clusters are only slowly coming into the range of PET or fMRI scanning technology which commonly require much longer time scales.

At any given time, only a small subset of the neuronal groups in the brain are contributing directly to consciousness and this cluster is called a dynamic core. It represents a single point of view and each different state of consciousness corresponds to a different subset. Some dissociative disorders such as schizophrenia may result in the formation of multiple cores.

In essence, the subconscious becomes conscious when attention is focused on particular activities of the mind that draw from neuronal activity beyond the immediate scope of the whole state of consciousness through reentrant neural activity. In this theory, consciousness is a core group of neural processes that examines the states of other neurons Typically, explanations involve a metaphor using a flashlight that explores a room. So, in the Libet experiment, imagine that brain is a house, and consciousness is a room with a lot of doors and windows. Awareness move around like a flashlight in the room focusing on certain things that make their way into the room from the house.

Let's say you touch something hot. Well, your arm jerks away because of the withdrawal reflex, so your conscious mind doesn't even process that. But, if your hand were held down, eventually, the pain receptors would feed the subconscious mind with an afferent firing pattern, and then your brain would then let that pattern into the "room" and the flashlight would focus on it. In the case of a tooth pain, it might be hard not to focus on it. But, not all firing patterns hijack your attention. Sometimes the perceptual system filters out the experience. One example of that is how a sequence of still frames can be used to create the appearance of animation by a continuous change of images above some threshhold of frequency, usually 24 fps.

From WP, perception:

There is also evidence that the brain in some ways operates on a slight "delay" in order to allow nerve impulses from distant parts of the body to be integrated into simultaneous signals.[55]

Perception is one of the oldest fields in psychology. The oldest quantitative laws in psychology are Weber's law, which states that the smallest noticeable difference in stimulus intensity is proportional to the intensity of the reference; and Fechner's law, which quantifies the relationship between the intensity of the physical stimulus and its perceptual counterpart (e.g., testing how much darker a computer screen can get before the viewer actually notices). The study of perception gave rise to the Gestalt School of Psychology, with an emphasis on holistic approach.

So, the question of how a brief transduction translates into qualia is still being worked out with researchers such as Edelman and Tononi and others like Demasio still working on the details. It is clear that the brain screens out certain happenings from the conscious mind, provides them structure, and constructs a continuous experience of time. Other than that, it's a matter of neurological and psychological nuance that hasn't been fully determined, in no small part because the tools to scan the brain do not capture data at the level of the individual neuron.