Voluntary acts are preceded by electrophysiological (RPs). With spontaneous acts involving no preplanning, the main negative RP shift begins at about200 ms. Control experiments, in which a skin stimulus was timed (S), helped evaluate each subject's error in reporting the clock times for awareness of any perceived event.

I have taken an experimental approach to this question. Freely voluntary acts are preceded by a specific electrical change in the brain that begins 550 ms before the act. Human subjects became aware of intention to act 350-400 ms after RP starts, but 200 ms. before the motor act. The volitional process is therefore initiated unconsciously. But the conscious function could still control the outcome; it can veto the act. Free will is therefore not excluded. These findings put constraints on (...) views of how free will may operate; it would not initiate a voluntary act but it could control performance of the act. The findings also affect views of guilt and responsibility. But the deeper question still remains: Are freely voluntary acts subject to macro-deterministic laws or can they appear without such constraints, non-determined by natural laws and ‘truly free'? I shall present an experimentalist view about these fundamental philosophical opposites. (shrink)

[opening paragraph] -- Clark: The `astonishing hypothesis' which you put forward in your book, and which you obviously feel is very controversial, is that `You, your joys and sorrows, your memories and ambitions, your sense of personal identity and free will are, in fact, no more than the behaviour of a vast assembly of nerve cells. As Lewis Carroll's Alice might have phrased it: `You're nothing but a pack of neurons'.' But it seems to me that this is not so (...) astonishing a statement for a scientist to make. Isn't this what reductionist science has always believed? (shrink)

In this book, which contains several of his key papers as well as new material, he focuses on the problem of consciousness and explains how quantum mechanics...

I have taken an experimental approach to this question. Freely voluntary acts are preceded by a specific electrical change in the brain that begins 550 ms before the act. Human subjects became aware of intention to act 350-400 ms after RP starts, but 200 ms. before the motor act. The volitional process is therefore initiated unconsciously. But the conscious function could still control the outcome; it can veto the act. Free will is therefore not excluded. These findings put constraints on (...) views of how free will may operate; it would not initiate a voluntary act but it could control performance of the act. The findings also affect views of guilt and responsibility. But the deeper question still remains: Are freely voluntary acts subject to macro-deterministic laws or can they appear without such constraints, non-determined by natural laws and ‘truly free'? I shall present an experimentalist view about these fundamental philosophical opposites. (shrink)

An extended examination of Libet's works led to a comprehensive reinterpretation of his results. According to this reinterpretation, the Minimum Train Duration of electrical brain stimulation should be considered as the time needed to create a brain stimulus efficient for producing conscious sensation and not as a basis for inferring the latency for conscious sensation of peripheral origin. Latency for conscious sensation with brain stimulation may occurafterthe Minimum Train Duration. Backward masking with cortical stimuli suggests a 125-300 ms minimum value (...) for the latency for conscious sensation of threshold skin stimuli. Backward enhancement is not suitable for inferring this latency. For determining temporal relations between stimuli that correspond to subjects' reports, theendof cerebral Minimum Train Duration should be used as reference, rather than its onset. Results of coupling peripheral and cortical stimuli are explained by a latency after the cortical Minimum Train Duration, having roughly the same duration as the latency for supraliminal skin stimuli. Results of coupling peripheral stimuli and stimuli to medial lemniscus (LM) are explained by a shorter LM latency and/or a longer peripheral latency. This interpretation suggests a 230 ms minimum value for the latency for conscious sensation of somatosensory near-threshold stimuli. The backward referral hypothesis, as formulated by Libet, should not be retained. Long readiness potentials preceding spontaneous conscious or nonconscious movements suggest that both kinds of movement are nonconsciously initiated. The validity of Libet's measures of W and M moments (Libet et al., 1983a) is questionable due to problems involving latencies, training, and introspective distinction of W and M. Veto of intended actions may be initially nonconscious but dependent on conscious awareness. (shrink)

The problem of free will lies at the heart of modern scientific studies of consciousness. An influential series of experiments by Libet has suggested that conscious intentions arise as a result of brain activity. This contrasts with traditional concepts of free will, in which the mind controls the body. A more recent study by Haggard and Eimer has further examined the relation between intention and brain processes, concluding that conscious awareness of intention is linked to the choice or selection of (...) a specific action, and not to the earliest initiation of action processes. The exchange of views in this paper further explores the relation between conscious intention and brain activity. (shrink)

The idea that our conscious decisions determine our actions has been challenged by a report suggesting that the brain starts to prepare for a movement before the person concerned has consciously decided to move . Libet et al. claimed that their results show that our actions are not consciously initiated. The current article describes two experiments in which we attempted to replicate Libet et al.'s comparison of participants' movement-related brain activity with the reported times of their decisions to move and (...) also the reported times of their decisions of which hand to move. We also looked at the distribution of participants' reports over time to evaluate an alternative explanation of Libet et al.'s results. Although the Readiness Potential was usually present before all of the decisions to move, consistent with the findings of Keller and Heckhausen and Libet et al. , we found that many reported decision times were before the onset of the Lateralized Readiness Potential, which measures hand-specific movement preparation. The latter finding is consistent with the conclusion that the LRP always started after the conscious decision to move. We conclude that even though activity related to movement anticipation may be present before a conscious decision to move, the cortical preparation necessary for the movement to happen immediately may not start until after the conscious decision to move. (shrink)

The original data reported by Benjamin Libet and colleagues are reinterpreted, taking into account the facilitation which is experimentally demonstrated in the first of their series of articles. It is shown that the original data equally well or better support a quite different set of conclusions from those drawn by Libet. The new conclusions are that it takes only 80 ms for stimuli to come to consciousness and that “subjective back-referral of sensations in time” to the time of the stimulus (...) does not occur. (shrink)

The problem of free will arises because of the conflict between two inconsistent impulses, the experience of freedom and the conviction of determinism. Perhaps we can resolve these by examining neurobiological correlates of the experience of freedom. If free will is not to be an illusion, it must have a corresponding neurobiological reality. An explanation of this issue leads us to an account of rationality and the self, as well as how consciousness can move bodies at all. I explore two (...) hypotheses. On the first, freedom is a complete illusion. On the second, it is not an illusion, and there is a corresponding indeterminism at the neurobiological level. This can only occur if there is in fact a quantum mechanical element in the fundamental neurobiology of consciousness. (shrink)

1. Introduction The readiness potential was found to precede voluntary acts by about half a second or more (Kornhuber & Deecke, 1965). Kornhuber (1984) discussed the readiness potential in terms of volition, arguing that it is not the manifestation of an attentional processes. Libet discussed it in relation to consciousness and to free will (Libet et al. 1983a; 1983b; Libet, 1985, 1992, 1993). Libet asked the following questions. Are voluntary acts initiated by a conscious decision to act? Are the physiological (...) facts compatible with the belief that free will determines our voluntary acts? What is the role of consciousness in voluntary action? In this paper I will discuss these questions and the answers that Libet gave to them. (shrink)

How is mind related to matter? This ancient question in philosophy is rapidly becoming a core problem in science, perhaps the most important of all because it probes the essential nature of man himself. The origin of the problem is a conflict between the mechanical conception of human beings that arises from the precepts of classical physical theory and the very different idea that arises from our intuition: the former reduces each of us to an automaton, while the latter allows (...) our thoughts to guide our actions. The dominant contemporary approaches to the problem attempt to resolve this conflict by clinging to the classical concepts, and trying to explain away our misleading intuition. But a detailed argument given here shows why, in a scientific approach to this problem, it is necessary to use the more basic principles of quantum physics, which bring the observer into the dynamics, rather than to accept classical precepts that are profoundly incorrect precisely at the crucial point of the role of human consciousness in the dynamics of human brains. Adherence to the quantum principles yields a dynamical theory of the mind/brain/body system that is in close accord with our intuitive idea of what we are. In particular, the need for a self-observing quantum system to pose certain questions creates a causal opening that allows mind/brain dynamics to have three distinguishable but interlocked causal processes, one micro-local, one stochastic, and the third experiential. Passing to the classical limit in which the critical difference between zero and the finite actual value of Planck's constant is ignored not only eliminates the chemical processes that are absolutely crucial to the functioning of actual brains, it simultaneously blinds the resulting theoretical construct to the physical fine structure wherein the effect of mind on matter lies: the use of this limit in this context is totally unjustified from a physics perspective. (shrink)

Orthodox Copenhagen quantum theory renounces the quest to understand the reality in which we are imbedded, and settles for practical rules describing connections between our observations. Many physicist have regarded this renunciation of our effort describe nature herself as premature, and John von Neumann reformulated quantum theory as a theory of an evolving objective universe interacting with human consciousness. This interaction is associated both in Copenhagen quantum theory and in von Neumann quantum theory with a sudden change that brings the (...) objective physical state of a system in line with a subjectively felt psychical reality. The objective physical state is thereby converted from a material substrate to an informational and dispositional substrate that carries both the information incorporated into it by the psychical realities, and certain dispositions for the occurrence of future psychical realities. The present work examines and proposes solutions to two problems that have appeared to block the development of this conception of nature. The first problem is how to reconcile this theory with the principles of relativistic quantum field theory; the second problem is to understand whether, strictly within quantum theory, a person's mind can affect the activities of his brain, and if so how. Solving the first problem involves resolving a certain non-locality question. The proposed solution to the second problem is based on a postulated connection between effort, attention, and the quantum Zeno effect. This solution explains on the basic of quantum physics a large amount of heretofore unexplained data amassed by psychologists. (shrink)

Commentary on John Searle's Article John Searle presents a philosopher's view of how conscious experience and free action relate to brain function. That view demands an examination by a neuroscientist who has experimentally investigated this issue.

Libet's (2000) arguments in defense of his interpretation of his experimental results are insufficient. The claims of my critical review (Gomes, 2008) do not suffer with his new statements.

A commentary on articles by Klein, Pockett, and Trevena and Miller, in this issue, is given. Average shift in the point of subjective equality , calculated by Klein on Libet's data, and corresponding change in mean shift, calculated by Libet et al. , may be “corrected,” taking as a reference point the end of the minimum train duration. Values obtained, if significant, indicate a latency for conscious sensation of the skin stimulus of at least 230 ms. Pockett's main conclusions are (...) favored, but her explanation of peripheral–lemniscal couplings is found to be unconvincing. Trevena and Miller's article unsuccessfully tries to rescue a dualist interactionist view. Libet's method of timing intentions is thoroughly criticized. (shrink)

This article reviews contributions to The Volitional Brain, some of which defend a libertarian, contra-causal account of free will, while others take a so-called compatibilist view, in which adequate conceptions of human liberty and moral responsibility are claimed to be compatible with naturalistic causality. Siding with compatibilism, this review finds that defenders of libertarian free will place undue weight on the first person feeling of freedom, while discounting scientific evidence that human choices are fully a function of antecedent causes at (...) various levels of description. It is argued that morality, justice, and personal responsibility and efficacy do not require the assumption that persons are first causes, so that we need not fear mechanism when applied to human agency. (shrink)

This article reviews contributions to The Volitional Brain, some of which defend a libertarian, contra-causal account of free will, while others take a so-called compatibilist view, in which adequate conceptions of human liberty and moral responsibility are claimed to be compatible with naturalistic causality. Siding with compatibilism, this review finds that defenders of libertarian free will place undue weight on the first person feeling of freedom, while discounting scientific evidence that human choices are fully a function of antecedent causes at (...) various levels of description. It is argued that morality, justice, and personal responsibility and efficacy do not require the assumption that persons are first causes, so that we need not fear mechanism when applied to human agency. (shrink)