The conclusions drawn by Benjamin Libet from his work with collegues on the timing of somatosensorial conscious experiences has met with a lot of praise and criticism. In this issue we find three examples of the latter. Here I attempt to place the divide between the two opponent camps in a broader perspective by analyzing the question of the relation between physical timing, neural timing, and experiential timing. The nervous system does a sophisticated job of recombining and recoding messages from (...) the sensorial surfaces and if these processes are slighted in a theory, it might become necessary to postulate weird operations, including subjective back-referral. Neuroscientifically inspired theories are of necessity still based on guesses, extrapolations, and philosophically dubious manners of speech. They often assume some neural correlate of consciousness as a part of the nervous system that transforms neural activity in reportable experiences. The majority of neuroscientists appear to assume that the NCC can compare and bind activity patterns only if they arrive simultaneously at the NCC. This leads to a search for synchrony or to theories in terms of the compensation of differences in neural delays . This is the main dimension of the Libet discussion. Examples from vision research, such as “temporal-binding-by-synchrony” and the “flash-lag” effect, are then used to illustrate these reasoning patterns in more detail. Alternatively one could assume symbolic representations of time and space that are not coded in their own dimension . Unless such tags are multiplexed with the quality message , one gets a binding problem for tags. One of the hidden aspects of the discussion between Libet and opponents appears to be the following. Is the NCC smarter than the rest of the nervous system, so that it can solve the problems of local sign and timing on its own, or are these pieces of information coded symbolically early on in the system? A supersmart NCC appears to be the assumption of Libet's camp . The wish to distribute the smartness evenly across all stages of processing in the nervous system appears to motivate the opponents. I argue that there are reasons to side with the latter group. (shrink)

Benjamin Libet has argued that electrophysiological signs of cortical movement preparation are present before people report having made a conscious decision to move, and that these signs constitute evidence that voluntary movements are initiated unconsciously. This controversial conclusion depends critically on the assumption that the electrophysiological signs recorded by Libet, Gleason, Wright, and Pearl are associated only with preparation for movement. We tested that assumption by comparing the electrophysiological signs before a decision to move with signs present before a decision (...) not to move. There was no evidence of stronger electrophysiological signs before a decision to move than before a decision not to move, so these signs clearly are not specific to movement preparation. We conclude that Libet’s results do not provide evidence that voluntary movements are initiated unconsciously. (shrink)

Neuroscience has begun to elucidate the mechanisms of volition, decision-making, and action. Some have taken the progress neuroscience has made in these areas to indicate that we are not free to choose our actions . The notion that we can consciously initiate our behavior is a crucial tenet in the concept of free will, and closely linked to how most individuals view themselves as persons. There is thus reason to inquire if the aforementioned inference drawn by some might be too (...) hasty. While there is much evidence appearing to indicate that consciousness does not influence behavior—including evidence indicating that neural activity precedes a decision by several seconds, neural activity predicts what action an individual will perform, and that individuals infer when they decided to act after an action was performed—this evidence seems to suffer methodological issues. Additionally, there are empirically supported interpretations of the aforementioned data consistent with the idea that individuals can consciously control their actions. This paper therefore concludes that neuroscience does not currently substantiate the idea that we cannot consciously initiate or control our actions. (shrink)

The target article sought to question the common belief that our decisions are often biased by unconscious influences. While many commentators offer additional support for this perspective, others question our theoretical assumptions, empirical evaluations, and methodological criteria. We rebut in particular the starting assumption that all decision making is unconscious, and that the onus should be on researchers to prove conscious influences. Further evidence is evaluated in relation to the core topics we reviewed (multiple-cue judgment, deliberation without attention, and decisions (...) under uncertainty), as well as priming effects. We reiterate a key conclusion from the target article, namely, that it now seems to be generally accepted that awareness should be operationally defined as reportable knowledge, and that such knowledge can only be evaluated by careful and thorough probing. We call for future research to pay heed to the different ways in which awareness can intervene in decision making (as identified in our lens model analysis) and to employ suitable methodology in the assessment of awareness, including the requirements that awareness assessment must be reliable, relevant, immediate, and sensitive. (shrink)

Prior to the initiation of spontaneous movement, evoked potentials can be seen to precede awareness of the impending movement by several hundreds of milliseconds, meaning that this recorded neural activity is the result of unconscious processing. This study investigates the neural representations of impending movement with and without awareness. Specifically, the relationship between awareness and ‘idling’ cortical oscillations in the beta range was assessed. It was found that, in situations where there was awareness of the impending movement, pre-movement evoked potentials (...) were associated with a decrease in beta range oscillations. In contrast, when awareness of the impending movement was not present, the onset of the pre-movement potential was associated with tonic levels of beta range oscillations. A model is considered where by distributed neural activity remains outside of conscious awareness through the persistence of tonic slow wave cortical oscillations. (shrink)

Striking experimental results by Benjamin Libet and colleagues have had an impor- tant impact on much recent discussion of consciousness. Some investigators have sought to replicate or extend Libet’s results (Haggard, 1999; Haggard & Eimer, 1999; Haggard, Newman, & Magno, 1999; Trevena & Miller, 2002), while others have focused on how to interpret those findings (e.g., Gomes, 1998, 1999, 2002; Pockett, 2002), which many have seen as conflicting with our commonsense picture of mental functioning.

The first priority of this response is to address Libet's rebuttal of my reinterpretation of his data. Then, because many authors have commented on various aspects of the debate, the rest of the response is organized in terms of subject matter, not as replies to each individual commentator. First, I reply to an objection expressed by two separate commentators to part of my reinterpretation of those of Libet's data supposedly supporting backward referral. This leads to a brief discussion of the (...) whole concept of backward referral. The relevance of the flash-lag illusion to possible measurement errors in the Libet/Trevena and Miller paradigm is addressed next. Finally, I have a few words to say on the relationship between quantum mechanical ontology and free will. (shrink)

Four experiments examined how accurately participants can report the times of their own decisions. Within an auditory reaction time task, participants reported the time at which the tone was presented, they decided on the response, or the response key was pressed. Decision time reports were checked for plausibility against the actual RTs, and we compared the effects of experimental manipulations on these two measures to see whether the reported decision times showed appropriate effects. In addition, we estimated the amount of (...) error associated with individual decision time reports by checking how often participants’ decision time reports were implausibly early or late , and by using several quantitative models. Overall, the results suggest that decision time reports are not very accurate but they may be usable for some purposes. (shrink)

Neuroscientific studies have shown that brain activity correlated with a decision to move can be observed before a person reports being consciously aware of having made that decision . Given that a later event cannot cause an earlier one , such results have been interpreted as evidence that decisions are made unconsciously . We argue that this interpretation depends upon an all-or-none view of consciousness, and we offer an alternative interpretation of the early decision-related brain activity based on models in (...) which conscious awareness of the decision to move develops gradually up to the level of a reporting criterion. Under this interpretation, the early brain activity reflects sub-criterion levels of awareness rather than complete absence of awareness and thus does not suggest that decisions are made unconsciously. (shrink)

The idea that intentions make the difference between voluntary and non-voluntary behaviors is simple and intuitive. At the same time, we lack an understanding of how voluntary actions actually come about, and the unquestioned appeal to intentions as discrete causes of actions offers little if anything in the way of an answer. We cite evidence suggesting that the origin of actions varies depending on context and effector, and argue that actions emerge from a causal web in the brain, rather than (...) a central origin of intentional action. We argue that this causal web need not be confined to the central nervous system, and that proprioceptive feedback might play a counterintuitive role in the decision process. Finally we argue that the complex and dynamic origins of voluntary action and their interplay with the brain’s propensity to predict the immediate future are better studied using a dynamical systems approach. (shrink)

The major findings by Libet et al. are briefly summarized. The criticisms and alternative proposals by Trevena and Miller, Pockett, and Gomes are analyzed and found to be largely unwarranted.

People have intuitively assumed that many acts of volition are not influenced by unconscious information. However, the available evidence suggests that under suitable conditions, unconscious information can influence behavior and the underlying neural mechanisms. One possibility is that stimuli that are consciously perceived tend to yield strong signals in the brain, and this makes us think that consciousness has the function of sending such strong signals. However, if we could create conditions where the stimuli could produce strong signals but not (...) the conscious experience of perception, perhaps we would find that such stimuli are just as effective in influencing volitional behavior. (shrink)

S. Pockett and G. Gomes discuss a possible bias in the method by which Libet's subjects estimated the time at which they became aware of their intent to move their hands. The bias, caused by sensory delay processing the clock information, would be sufficient to alter Trevena and Miller's conclusions regarding the timing of the lateralized readiness potential. I show that the flash-lag effect would compensate for that bias. In the last part of my commentary I note that the other (...) target articles do not examine the most interesting aspect of Libet's unfashionable views on free will. I point out that Libet's views are less strange than they at first appear to be. (shrink)

This issue of Consciousness and Cognition presents four target articles and eight commentaries on the target articles. The present article presents comments on those commentaries, grouped into backward referral and volition categories. Regarding backward referral: I disagree with my fellow commentators and take the unpopular position of defending Libet's notion of backward referral. I join my fellow commentators in critiquing Libet's notion of a 500-ms delay. I examine several of the hypotheses suggested by other commentators for why cortical and lateral (...) meniscus stimulation give very different timing results. I suggest a simple experiment to help discriminate among the hypotheses. I comment on why temporal reordering is more likely to occur late rather than early in mental processing. Regarding Libet's volition experiments, I ask what is the root of the controversy, given the general agreement on the data. I agree with a commentator that Libet's chronotheology rather than his chronoscience is the cause of much of the controversy. Rather than joining others in criticizing Libet for his chronotheology I point out that he is making a respectable philosophical point regarding nondeterministic Free Will, but one that is easily misunderstood. I discuss two ways by which Libet's viewpoint can be brought into mainstream science. (shrink)

Trevena and Miller provide further evidence that readiness potentials occur in the brain prior to the time that participants claim to have initiated a voluntary movement, a contention originally forwarded by Libet, Gleason, Wright, and Pearl . In their examination of this issue, though, aspects of their data lead them to question whether their measurement of the initiation of a voluntary movement was accurate. The current article addresses this concern by providing a direct analysis of biases in this task. This (...) was done by asking participants to make subjective timing decisions regarding a stimulus that could be measured objectively. Our findings suggest that their timing task was indeed biased such that participants' tend to report events as happening approximately 70 ms later than they actually happened. Implications for the original Libet et al. claims are discussed. (shrink)

The belief in free will has been frequently challenged since Benjamin Libet published his famous experiment in 1983. Although Libet’s experiment is highly dependent upon subjective reports, no study has been conducted that focused on a first-person or introspective perspective of the task. We took a neurophenomenological approach in an N = 1 study providing reliable and valid measures of the first-person perspective in conjunction with brain dynamics. We found that a larger readiness potential is attributable to more frequent occurrences (...) of self-initiated movements during negative deflections of the slow cortical potentials . These negative deflections occur in parallel with an inner impulse reported by an expert meditator which may in turn lead to a voluntary act. We demonstrate in this proof-of-principle approach that the first-person perspective obtained by an expert meditator in conjunction with neural signal analysis can contribute to our understanding of the neural underpinnings of voluntary acts. (shrink)

We explored the neural mechanisms allowing humans to report the subjective onset times of conscious events. Magnetoencephalographic recordings of neural oscillations were obtained while human subjects introspected the timing of sensory, intentional, and motor events during a forced choice task. Brain activity was reconstructed with high spatio-temporal resolution. Event-time introspection was associated with specific neural activity at the time of subjective event onset which was spatially distinct from activity induced by the event itself. Different brain regions were selectively recruited for (...) introspection of different event types, e.g., the bilateral angular gyrus for introspection of intention. Our results suggest that event-time introspection engages specific neural networks to assess the contents of consciousness. Subjective event times should therefore be interpreted as the result of complex interactions between introspection and experience networks, rather than as direct reproduction of the individual’s conscious state or as a mere post hoc interpretation. (shrink)

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)

The paper investigates possible readings of the later Heisenberg's remarks on the nature of quantum states. It discusses, in particular, whether Heisenberg should be seen as a proponent of the epistemic conception of states – the view that quantum states are not descriptions of quantum systems but rather reflect the state assigning observers' epistemic relations to these systems. On the one hand, it seems plausible that Heisenberg subscribes to that view, given how he defends the notorious "collapse of the wave (...) function" by relating it to a sudden change in the epistemic situation of the observer registering a measured result. On the other hand, his remarks on quantum probabilities as "potentia" or "objective tendencies" are difficult to reconcile with such a reading. The accounts that are attributed to Heisenberg by the different possible readings considered are subjected to closer scrutiny; at the same time, their respective virtues and problems are discussed. _German_ Diese Arbeit untersucht mögliche Lesarten von Heisenbergs späten Bemerkungen über die Natur von Quantenzuständen. Insbesondere wird die Frage diskutiert, ob Heisenberg als Vertreter der epistemischen Auffassung von Quantenzuständen gelten kann – der Idee, dass Quantenzustände nicht Beschreibungen der objektiven Eigenschaften von Quantensystemen sind sondern die epistemischen Beziehungen von Beobachtern zu diesen Systemen widerspiegeln. Einerseits erscheint es plausibel, dass Heisenberg dieser Sichtweise zustimmt, wenn man sich ansieht, wie er den berüchtigten,,Kollaps der Wellenfunktion" verteidigt, indem er ihn mit einer plötzlichen Änderung in der Kenntnis des ein Messergebnis registrierenden Beobachters in Zusammenhang bringt. Andererseits sind seine Bemerkungen über quantenmechanische Wahrscheinlichkeiten als,,Potentia" oder,,objektive Tendenzen" mit einer solchen Lesart nur schwer in Einklang zu bringen. Die Positionen, die Heisenberg den verschiedenen möglichen Lesarten zufolge vertritt, werden eingehenden Untersuchungen unterzogen; gleichzeitig werden ihre jeweiligen Vorzüge und Probleme diskutiert. (shrink)

The temporal granularity of consciousness may be far less fine than the real-time information processing mechanisms that underlie our sensitivity to small temporal differences. It is suggested that conscious time perception, like space perception, is subject to errors that belie a unitary underlying representation. E. R. Clay's concept of the “specious present,” an extended moment represented in consciousness, is suggested as an alternative to the more common notion of instantaneous experience that underlies much reasoning based on the “time of arrival” (...) in consciousness. (shrink)

We report two experiments in which participants had to judge the time of occurrence of a stimulus relative to a clock. The experiments were based on the control condition used by Libet, Gleason, Wright, and Pearl [Libet, B., Gleason, C. A., Wright, E. W., & Pearl, D. K. . Time of conscious intention to act in relation to onset of cerebral activities : The unconscious initiation of a freely voluntary act. Brain 106, 623–642] to correct for any bias in the (...) estimation of the time at which an endogenous event, the conscious intention to perform a movement, occurred. Participants’ responses were affected systematically by the sensory modality of the stimulus and by the speed of the clock. Such findings demonstrate the variability in judging the time at which an exogenous event occurs and, by extension, suggest that such variability may also apply to the judging the time of occurrence of endogenous events. The reliability of participants’ estimations of when they formed the conscious intention to perform a movement in Libet et al.’s study is therefore questionable. (shrink)

Mental timing studies may be influenced by powerful cognitive illusions that can produce an asymmetry in their rate of progress relative to neuronal timing studies. Both types of timing research are also governed by a temporal asymmetry, expressed by the fact that the direction of causation must follow time's arrow. Here we refresh our earlier suggestion that the temporal asymmetry offers promise as a means of timing mental activities. We update our earlier analysis of Libet's data within this framework. Then (...) we consider the surprises which often occur on those rare occasions when neural timing experiments parallel mental timing work exactly. Together, these surprises and asymmetries prescribe a relentlessly meticulous and fully transparent exposition of timing methods, terms, and concepts which shuns plausible narratives, even when buttressed by rigorous formal models, unless guided by apposite empirical evidence. (shrink)

Climate policy decisions are decisions under uncertainty and are, therefore, based on a range of future climate scenarios, describing possible consequences of alternative policies. Accordingly, the methodology for setting up such a scenario range becomes pivotal in climate policy advice. The preferred methodology of the Intergovernmental Panel on Climate Change will be characterised as ,,modal verificationism"; it suffers from severe shortcomings which disqualify it for scientific policy advice. Modal falsificationism, as a more sound alternative, would radically alter the way the (...) climate scenario range is set up. Climate science's inability to find robust upper bounds for future temperature rise in line with modal falsificationism does not disprove that methodology, rather, this very fact prescribes even more drastic efforts to curb CO2 emissions than currently proposed. (shrink)

We report two experiments in which participants had to judge the time of occurrence of a stimulus relative to a clock. The experiments were based on the control condition used by Libet, Gleason, Wright, and Pearl [Libet, B., Gleason, C. A., Wright, E. W., & Pearl, D. K. . Time of conscious intention to act in relation to onset of cerebral activities : The unconscious initiation of a freely voluntary act. Brain 106, 623–642] to correct for any bias in the (...) estimation of the time at which an endogenous event, the conscious intention to perform a movement, occurred. Participants’ responses were affected systematically by the sensory modality of the stimulus and by the speed of the clock. Such findings demonstrate the variability in judging the time at which an exogenous event occurs and, by extension, suggest that such variability may also apply to the judging the time of occurrence of endogenous events. The reliability of participants’ estimations of when they formed the conscious intention to perform a movement in Libet et al.’s study is therefore questionable. (shrink)

Some psychologists and philosophers have argued that neuroscience is importantly relevant to our moral responsibility practices, especially to our practices of praise and blame. For consider: on an unprecedented scale, contemporary neuroscience presents us with a mechanistic account of human action. Furthermore, in uential studies – most notoriously, Libet et al. (1983) – seem to show that the brain decides to do things (so to speak) before we consciously make a decision. In light of these ndings, then – or so (...) some have argued – we ought to revise our practices of praise and blame. In the current paper, I argue that this conclusion is unwarranted. The reason is that the argument for it depends on controversial non-empirical premises, premises we need not accept. I suggest, however, that neuroscience does bear on our moral responsibility practices in one important, if less revisionary, way. In particular, neuroscience o ers a new kind of evidence for determining when agents should be held exempt from our normal moral responsibility practices. (shrink)

Scientific experiments which try to examine free will are faced with various critical arguments — both philosophical and methodological. In this article I will present the most important and the most interesting critical arguments attacking two the most influential experiments: Benjamin Libet experiment and John‐Dylan Haynes experiment. In the first part of the article I will consider a particular criticism of Libet paradigm, which loses its importance in context of Haynes paradigm. Next I will present critical arguments which attack both (...) Haynes and Libet experiments (and probably all other psychophysiological experiments facing free will problem). Because of this analysis I will consider informative value of presented experiments in context of existence of free will. (shrink)

: Behavioral actions can attain their intended result either when all possible details and intervening factors are controlled in advance by the action plan, or when only the final outcome is taken into account while the rest is left for on-line correction. Both ways have numerous advantages and disadvantages. The former can be applied only in very simple instances and therefore, puts very strong limits on the complexity of behavior. The latter can be used for action plans of practically unlimited (...) complexity. Such movements are free because they are determined not by their environmental conditions but by their future result. To perform them, however, the executive system must admit its principal inability to predict and control everything in advance. This produces high emotional load, that is, the anxiety to meet uncertain and uncontrollable environments. Humans avoid this feeling of uncontrollability by developing doctrines like Divine Providence or the modern neuroscientific determinism. Such doctrines are based on intuitively plausible identification of causality with necessity and predictability. To claim the principal predictability of the world , they invent arguments denying the freedom of voluntary actions. (shrink)