Libet’s Loophole: The Fight For Free Will
1) THE FINAL FRONTIER
The issue of free will continues to attract attention in philosophical circles despite the fact that its relationship to its original sparring partner no longer inspires much more than a mere scholarly curiosity. What began as a problem pitting the foreknowledge of God against the existence of a volitional faculty now thrives as a compelling contest between free will and scientific determinism. But relatively recently it seems that this second stage in the centuries old debate over free will has entered an entirely new phase, a phase that might very well represent the final frontier for research into the problem of volition. This phase is marked by a scientific foray into the inner sanctum that is the brain itself.
It is convenient to divide the scientific or post-foreknowledge stage of the free will problem into three distinct, but not discontinuous phases or categories.
- Newtonian: According to a LaPlaceian or mechanistic view of the world, the elaboration of Newtonian science strictly determines all behavior, for man is thought to be a machine which obeys the laws of physics. Early in the last century Newtonian determinism gave way to its post-Newtonian or relativistic successor.
- Quantum: Prediction is based upon probabilities which are restricted by the Heisenberg Uncertainty principle. Quantum fluctuations yield a kind of volitional wash. On the one hand they allow for a future whose horizon of probable outcomes is open. On the other hand they ensure that the random firings of neurons could never be fully under conscious control.
- Cerebral: The primary terrain on which the war of free will is being fought today is the brain itself. For the sake of convenience, I will in this essay bracket the always nagging specter of dualism which haunts the entire framework of the free will problem, that of the ghost in the machine wherein the immaterial mind exists in tandem with the material brain.Daniel Dennett, for instance, takes Libetâ€™s analysis of volition to task for its presupposition of a Cartesian theatre model of the mind in which neurological information is quantized as occurring in specific places at appointed times.1Trying to maintain a phenomenological distance from such a metaphysical problem as dualism in the context of the free will debate however is difficult at best and begs a lot of important questions. Such begging occurs frequently with reference to presupposed entities such as the mind.
My aim in this essay is to evaluate the breathing room available for maintaining belief in free will in light of the experimental results and analysis of Benjamin Libet. I will argue that the persistence of our subjective faith in voluntary action is by no means irrational in response to the evidence generated by his work to date, not all of which is adverse to a freely operating conscious volitional faculty. A fortiori, confidence in the existence of a strong volitional faculty need not, at least not yet, be weakened by concession to any compromise position. The optimism of William James, who once said that his first act of freedom would be to subscribe to a belief in free will, need not be disowned as naÃ¯ve, even for those of us who live in a world which far outstrips in scientific complexity the once audacious Principles of Psychology. Libetâ€™s own position on the freedom of the will, as articulated recently in Mind Time (2004), is more deflationary than it is robust. Constructing a defense of free will based upon a mental capacity to veto signals to act sent from the brain seems like much less than a full endorsement of volition in the fullest and most vigorous sense. Such a capacity provides a loophole for a lukewarm defense of free will, although it does represent a wonderful recovery from the pessimistic trajectory of earlier work on the neurophysiological dimension of the will. From an historical perspective it is quite interesting to note that Antonio Damasio, in his recent book on Spinoza, points out the extent to which any possible account of free will in the Ethics also must rely upon and correlate with prior biological conditions.2 All in all, the mere belief or strong conviction that free will must exist is still a far cry from explaining how it works.
Admittedly, the cloth of what we refer to as free will is woven from only two threads, neither of them very scientific. Logically, free will functions as a sine qua non of our legal culture and moral theology. This is the Augustinian thread, as it was the Bishop of Hippo who first fully formulated a philosophical justification for the faculty of will as a prerequisite for the moral life in conjunction with the reality of evil. Subjectively, we feel that we control a large subset of our actions. It was this latter folk-psychological thread that once prompted Dr. Samuel Johnson to say that while theory seems to weigh against free will; nevertheless, all our experience supports it. Descartes, the seminal figure of modern subject-oriented philosophy, would adapt the Augustinian theory of the will for epistemological purposes in Meditation 4. In his Summa Theologica (II-II, Q. vi, art. 1) St. Thomas Aquinas asserts that a voluntary action requires that the agent possess a knowledge of the telos which explains the act and that the principle of action must be in some way interior to the knowing subject. As with Hamletâ€™s famous but condescending words to Horatio about what could be dreamed of in his myopic philosophy, little could Aquinas dream of what interiority might come to mean in future centuries with the emergence of a neurophysiological understanding of the brain.
The work of Benjamin Libet, building upon the work of Kornhuber and Deecke (1965), demonstrates that the electrocortical correlates of volition can occur prior to our conscious awareness of a choice to act.3 In other words: if neural states located in the prefrontal or other cortices of the brain trigger our actions, then the perception that our actions are consciously caused and initiated by us lacks, or at least loses, credibility. That being the case, it would seem overly recalcitrant to persist uncritically in the belief of the existence of free will. How can our actions be free if their purportedly corresponding brain states, although the extent of such a correspondence is quite an exaggeration, can occur in advance of our willingness to engage in a particular type of behavior? A mere subjective sense that we command our actions, one might legitimately argue, surely cannot survive scientific evidence to the contrary, just as at one time a non-falsifiable reliance upon scriptural authority, what John Haught might characterize as a narrative fixation, could not for long withstand the enlightened onslaught of competent scientific inquiry into the constitution of the universe. A first glance at Libetâ€™s astonishing and counterintuitive results, in violation of the basic priority principle whereby the brain record of an action should not occur prior to our choice to enact it, might tempt one to tamper with a famous line of the existentialist philosopher Jean Paul Sartre. Perhaps we are doomed not to be free. Even William James, despite his facility for turning a phrase, might have to acknowledge that â€œthe future has no ambiguous possibilities hidden in its womb.â€4
To put it strongly: Libetâ€™s work demonstrates that a Readiness Potential or RP can occur in the brain on the average as much as half a second ( 550 milliseconds) or more prior to the seemingly spontaneous performance of an action (e.g. moving a finger). Yet, from what I have read of Libetâ€™s work, it cannot be said for sure that this RP corresponds to or qualifies as the partial brain state configuration of any specific action. Between the onset of an RP and its eventual manifestation in behavior, about 350 to 400 msec. after its onset, experimental subjects became aware (A) of an intermediary intention to perform some specific and supposedly relevant act. In addition, between this intermediary intention to act and the actual performance of the action the subjects would somehow harbor the illusion (I) that they were acting prior to actually doing so. Libetâ€™s counterintuitive result contradicted the expectations of everyone, including that of both Karl Popper and John Eccles as presented in their book entitled The Self and its Brain. Libet thus seemed to reverse the order of possession. The brain does not belong to the self, while the so-called self gets its marching orders from the brain. Despite such a devastating blow to the phenomenology of everyday life, whereby we might swear that some kind of mental force beyond the control of the brain is the precipitant of our actions, Libet, as previously indicated, has found a possibly saving, if limited, volitional resource or loophole. Based upon experimental results, he has identified that the mind can consciously veto an RP and thus stave off what might otherwise be interpreted as a predetermination to act. Aligning with Libetâ€™s loophole is recent work by Schwartz and Begley at UCLA, which has shown that people suffering from obsessive-compulsive neuroses can be trained to consciously resist the overwhelming desire to engage in repetitive self-destructive behaviors.5 Libetâ€™s work thus stands as a challenge and a compromise to our customary intuitively based conception of voluntary action. Darwinâ€™s bulldog, T.H. Huxley, echoes a similar theme to that which would come to the fore a century later in the work of Libet. In a work on animals he wrote that â€œThe feeling we call volition is not the cause of the voluntary act, but simply the symbol in consciousness of that stage of the brain which is the immediate cause of the act.â€6 Earlier still, David Hume in A Treatise of Human Nature defined free will as â€œnothing but the internal impression we feel and are conscious of, when we knowingly give rise to any new motion of our body, or new perception of our mind.â€7
RP – Readiness Potential in brain
A – Awareness of intention to act
I – Illusion of movement in body part
M – Actual Movement
(RP) (A) (I) (M)
550ms. 200 100 0
3) WHERE THEREâ€™S A WILL THEREâ€™S A WAY
Consider the following sporting scenario.
A major league pitcher hurls a baseball towards a batter located 60 feet away at 100 mph. According to a little simple arithmetic, this means that the ball will cross the plate in approximately 1/3 of a second. The competent batter will not swing randomly, for this will produce a result equivalent to swinging blindly. Swinging the bat under game conditions obviously does not qualify as one of those situations which conform to Alan Turingâ€™s famous analysis of the strategic superiority of systematic guessing. The choice of an intelligent swing plane for the bat is made in well less than 1/3 of a second, for balls are seldom thrown without a curve, slide, or dip, thus making it virtually impossible for anyone to precisely guess where the ball is headed from the moment of release.
If the batter chooses the swing plane when the ball is approximately half way toward the plate, then discounting any acceleration or deceleration of the ball, the swing plane choice will occur about 1/6 of a second prior to the ball reaching the plate. In the case of an extremely late swing choice the ball will be that much closer to the plate, in terms of both space and time. In other words this example from everyday sporting life more than adequately shows that spontaneous decisions are not likely to be preceded by any neurologically predetermined configuration of brain states or electrical potential corresponding to the act in question. Even if the brain prepares for the general act of swinging a bat, just as for example Libetâ€™s experimental subjects were well aware that they were awaiting a spontaneous emotional impulse to move a finger, rather than shake a leg, still the brain could have no advance notice of the optimal swing plane relative to an incoming pitch. Plus there is the added very important possibility that the batterâ€™s course of action may be a choice not to act, that is to take the pitch, or to choose unwisely and swing and miss. Therefore, one can reasonably argue that Libetâ€™s result can in no way be generalized so as to dismiss the possibility that the choice of the mind can and often does precede the corresponding brain activity related to the specific act in question. Identity theorists such as Ted Honderich would argue that mental and brain states for an act occur simultaneously.8 The brain surely cannot anticipate when an external force might cause your finger to move without granting to it powers that materialism surely does not allow. On the other hand, if the swinging of the bat itself is used as a measurement baseline, no pun intended, then it is still quite possible that it might very well actually be preceded by an RP. Yet even in this case a more thorough mapping of the brain would be needed in order to pair what is happening in the brain with a subsequent specific act. Detection of an RP just prior to the swinging of the bat does not necessarily signify anything causal. To suggest that it does is to commit the fallacy of post hoc ergo propter hoc. Additionally, Libetâ€™s average of 550 msec. for RPâ€™s preceding spontaneous actions would mean that brain activity in advance of a swing would have originated even prior to the pitch itself. It is true however that the onset of RPâ€™s for premeditated actions or those involving deliberation can be significantly earlier (> 550 msec.) than those which are characterized as spontaneous. But while the general action of swinging the bat can be classified as premeditated, the actual swing plane chosen is undoubtedly more spontaneous.
Libet found that it was possible for subjects to reject the brain directed order to act represented by an RP. Subjects were asked to expect to perform a specific action at a designated time, and also to veto or reject that same action about 100-200 msec. prior to the prearranged time to act. The RP appeared, as expected, but then dipped in intensity at the time coinciding with the conscious decision to veto the act. But if the process to act set in motion by the RP was too far along then such a veto could not prevent the act, which would then proceed automatically. Is a decision not to prevent something from happening sufficient for us to maintain that we freely ordain what we do? While Libet is not happy with the characterization of free will as an obstacle to the otherwise predetermined acts set in motion by our neurophysiology, he does point to what he sees as an interesting resonance between the veto function of the will and the prohibitive content of many of the commandments. Additionally, he argues that if the plethora of immoral desires that plague our conscious lives is the effect of brain stimuli over which we have no conscious control, but we can consciously choose to avert their manifestation in behavior by exercising our option to veto their realization, then there is nothing intrinsically immoral about such desires. What is immoral then, according to his view, would be our allowing such desires to materialize into acts by not stopping them dead in their mental tracks. Like Oscar Wilde, we may be able in principle to resist everything except the temptation which is doled out by the brain.
An important problem with the logic of the entire approach taken by Libet and others is that what is characterized as an act, such as moving a finger, or swinging a bat, can itself just as easily be construed as a composite of submovements or subacts. Even if a subject is instructed to prepare to move a finger at some arbitrary time, nobody consciously wills to perform each and every singular subaction that forms part of a whole act. This alone is sufficient to show that there is a significant degree of the less-than-voluntary even in the exercise of an allegedly freely chosen action. One of several good reasons why the movement of a finger is often selected as an action in experimental situations which purport to test free will is that it does not consist of a jigsaw of parts, and thus might be reasonably classified as a simple muscular action.
RP signals suffer from the following significant defects in relation to free will.
1) The RP does not pinpoint a specific type of action. (Specificity Problem)
2) Discounting the Specificity Problem, the RP still does not account for the differentiation of an action into its component parts. (Mereological Problem â€“ Whole/Part Relation)
Both the Specificity and the Mereological problems challenge any volitional skepticism based solely upon an RP violation of the priority principle, whereby a choice must occur prior to its corresponding brain activity. The existence of the RP certainly is a difficulty to contend with for any traditional volitional apologist, but it still serves as no more than a challenging curiosity to the efficacy of free will in the traditional sense. If the RP is not isomorphic with a specific action or sensitive to a panoply of specific component actions then it is not possible to reasonably argue that it is the cause of any one specific action, whether simple or complex. In addition to the inversion of temporal expectations between choice and brain state, two of the chief philosophical threats of the RP to a traditional interpretation of free will have to do with the principles of consistency and exclusivity. If an action is wildly inconsistent with a fluctuation in the preceding activity of the brain, then no causal efficacy should be attributed to the latter. Additionally, if other candidate causes are available to explain the instigation of an action, then the explanatory power of an RP as the possible cause of the action is diminished. If prior to moving a finger the preceding RP is accompanied by a simultaneous external force applied to the same finger, then the cause of the digital movement would most likely be ascribed to the external physical force rather than to the internal neural fluctuation. Of extreme importance is the fact that a general electrocortical potential (RP) does not come even remotely close to providing a map of the brain for any particular act. For instance, the map of a freely imagined movement is strikingly different than the map which coincides with the movement itself.9 In addition to the neurophysiological data a proper analysis of volition in relation to brain activity requires the contribution of many other brain imaging techniques and methodologies (e.g. magnetic resonance, keeping track of the blood flow and other tracing techniques, PET scans, etc.). We need to know what is going on in all relevant areas of the brain that might have anything to do with consciously willed activity. In addition, there is the further question of what in the brain induces or triggers an RP in the first place. If the RP is not the effect of a brain-directing mental choice, then it must either be the result of a set of preceding brain states, an environmental cause, or some random fluctuation. Much more work is needed in order to reasonably suggest whether an extrapolation of what is going on in the brain prior to a conscious choice to act will further intimidate any desire to persevere as a believer in free will.
Libetâ€™s veto function as a self-willed act would repeat the basic timeline problem if it too were to be anticipated by its own private RP, separate and distinct from the RP which corresponds to the aborted act itself. So far no such separate veto-RP has been detected. Libet contrasts the veto function of overriding an RP with the possibility that the individual might be able to somehow consciously assist or reinforce an RP directive from the brain. Libetâ€™s reasons for so far rejecting such an affirmative post-RP role by the will is that there is no experimental evidence to support it, and also that what he calls â€œautomaticâ€ acts can be performed without the accompaniment of a conscious wish.10
A number of problems can be identified here. Libetâ€™s confirmation of a veto function, which he interprets as overriding a predetermined directive of the brain, is only classified as a negative control function relative to the causal role that the RP is thought to play. Vetoes by a number of subjects were correlated with a drop in the electric potential of the RP, but the RP has never been correlated with any specific act. Nevertheless, since the veto function only occurs after consciousness of a wish to perform an action and is not itself anticipated by its own RP, it is reasonable to view it, not as an explanatory nuisance to an otherwise automated self, but as consistent with our customary conviction that we consciously forge our own destiny. Also recall that a veto function can only cancel an already existing plan to act, which plan, so to speak, can either be the result of a previous brain determination or conscious choice. Libet distinguishes between two types of RPâ€™s. There are those which are associated with deliberative processes and a knowledge of when an act is going to be performed. On the average these occur significantly earlier than his own RP average of 550 msec. for spontaneous decisions to act. I would argue however that Libetâ€™s experimental procedure lacked spontaneity, exhibiting just a lower degree of premeditation or deliberation. While his subjectsâ€™ decisions were spontaneous as to when an action would take place they were not spontaneous as to what type of action was to be performed. One can go further and say that, even from a temporal perspective, the acts were not completely spontaneous since it was assumed that they would occur within a very short period of time. The need to test dozens of patients in order to achieve a reliable timeline average set a pragmatic limit on the amount of time spent with each subject. In authentically spontaneous situations people are not usually being monitored by an experimental apparatus. Perhaps they need to be. Per the baseball scenario, if the choice of a swing plane is genuinely spontaneous and not brain driven, then there does exist a psychosomatic circuitry which allows for the mind to direct the brain and the body. It should come as no surprise however that the brain is capable of preparing the body for action in situations which are not entirely spontaneous. And when we opt to decline to carry out such preparations by the brain, this need not lead to any diminution in the status of the choice signified by a veto relative to choices which are made in the absence of any RP. The choice is equally free in both cases. That an act will be executed automatically if we do not exercise our post-RP veto function quickly enough to prevent it need not be interpreted as a refutation of free will. Nor should the fact that psychology can point to many instances where we suffer from an illusion of freedom. One thing is true. Current neurophysiological research into the motivating source of human behavior gives new meaning to the words of Shakespeare. The fault lies not in our stars, but in ourselves.
3 In this paper I am relying on two recent publications by Libet. Mind Time: The Temporal Factor in Consciousness (Cambridge: Harvard University Press, 2004). â€œDo We Have Free Will?,â€ in the Journal of Consciousness Studies, 6, No. 8-9, 1999, pp. 47-57.