Leading scholars continue the debate over whether consciousness causes behavior or plays no functional role in it, discussing the question in terms of neuroscience, philosophy, law, and public policy.

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 rotating spot method of timing subjective events involves the subject’s watching a rotating spot on a computer and reporting the position of the spot at the instant when the subjective event of interest occurs. We conducted an experiment to investigate factors that may impact on the results produced by this method, using the subject’s perception of when they made a simple finger movement as the subjective event to be timed. Seven aspects of the rotating spot method were investigated, using (...) a factorial experiment. Four of these aspects altered the physical characteristics of the computer generated spot or clock face and the remaining three altered the instructions given to the participant. We found compelling evidence that one factor, whether the subject was instructed to report the instant when the finger movement was initiated or the instant when it was completed, resulted in a systematic shift in the response. Evidence that three other factors affect the observed variability in the response was also found. In addition, we observed that there are substantial systematic differences in the responses made by different subjects. We discuss the implications of our findings and make recommendations about the optimal way of conducting future experiments using the rotating spot method. Our overall conclusion is that our results strongly validate the rotating spot method of timing at least the studied variety of subjective event. (shrink)

The duration of “now” is shown to be important not only for an understanding of how conscious beings sense duration, but also for the validity of the phenomenological enterprise as Husserl conceived it. If “now” is too short, experiences can not be described before they become memories, which can be considered to be transcendent rather than immanent phenomena and therefore inadmissible as phenomenological data. Evidence concerning (a) the objective duration of sensations in various sensory modalities, (b) the time necessary for (...) sensations to enter consciousness and (c) the variability in the subjective sense of time's passing under different conditions is used to conclude that the duration of “now” can actually vary under normal conditions from about 10 ms to several seconds and in extreme cases up to several hours. Thus the immanent moment can be long enough to encompass a report of the contents of consciousness, making phenomenology a viable project. A further speculation from the evidence described is that consciousness takes discrete samples of the external world, at a rate inversely proportional to the duration of the “now” moment. (shrink)

The author's version of the electromagnetic field theory of consciousness is stated briefly and then three difficulties with the theory are discussed. The first is a purely technical problem: how to measure accurately enough the spatial properties of the fields which are proposed to be conscious and then how to generate these artificially, so that the theory can be tested. The second difficulty might also be merely technical, or it might be substantive and fatal to the theory. This is that (...) present measurements seem to show a non-constant relationship between brain-generated electromagnetic fields and sensation. The third difficulty involves the basic question of whether consciousness per se has any direct effect on the brain. As an afterword, the disproportionate contribution of synchronously firing neurons to conscious percepts is simply explained in terms of the electromagnetic field theory of consciousness. Susan Pockett Difficulties with the Electromagnetic Field Theory of Consciousness: The author's version of the electromagnetic field theory of consciousness is stated briefly and then three difficulties with the theory are discussed. The first is a purely technical problem: how to measure accurately enough the spatial properties of the fields which are proposed to be conscious and then how to generate these artificially, so that the theory can be tested. The second difficulty might also be merely technical, or it might be substantive and fatal to the theory. This is that present measurements seem to show a non-constant relationship between brain-generated electromagnetic fields and sensation. The third difficulty involves the basic question of whether consciousness per se has any direct effect on the brain. As an afterword, the disproportionate contribution of synchronously firing neurons to conscious percepts is simply explained in terms of the electromagnetic field theory of consciousness. (shrink)

The electromagnetic field theory of consciousness proposes that conscious experiences are identical with certain electromagnetic patterns generated by the brain. While the theory has always acknowledged that not all of the electromagnetic patterns generated by brain activity are conscious, until now it has not been able to specify what might distinguish conscious patterns from non-conscious patterns. Here a hypothesis is proposed about the 3D shape of electromagnetic fields that are conscious, as opposed to those that are not conscious. Seven predictions (...) arising from this hypothesis are described. Existing empirical evidence shows that four of these predictions have already been successfully tested. Requirements for experimental testing of the other three are discussed. (shrink)

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)

Empirical work is reviewed which correlates the presence or absence of various parts of the auditory evoked potential with the disappearance and reemergence of auditory sensation during induction of and recovery from anesthesia. As a result, the hypothesis is generated that the electrophysiological correlate of auditory sensation is whatever neural activity generates the middle latency waves of the auditory evoked potential. This activity occurs from 20 to 80 ms poststimulus in the primary and secondary areas of the auditory cortex. Evidence (...) is presented suggesting that earlier or later waves in the auditory evoked potential do not covary with auditory sensation (as opposed to auditory perception) and it is therefore suggested that they are possibly not the electrophysiological correlates of sensation. (shrink)

Power density spectra and phase synchrony measurements were taken from intracranial electrode grids implanted in epileptic subjects. Comparisons were made between data from the waking state and from the period of unconsciousness immediately following a generalised tonic–clonic seizure. Power spectra in the waking state resembled coloured noise. Power spectra in the unconscious state resembled coloured noise from 1 to about 5 Hz, but at higher frequencies changed in two out of three subjects to resemble white noise. This boosted unconscious gamma (...) power to a higher level than conscious gamma power. For both gamma and beta passbands, synchrony measurements showed more widespread phase synchrony in the unconscious than the conscious state. We conclude that neither gamma activity per se nor phase synchrony per se are neural correlates of consciousness. (shrink)

The duration of “now” is shown to be important not only for an understanding of how conscious beings sense duration, but also for the validity of the phenomenological enterprise as Husserl conceived it. If “now” is too short, experiences can not be described before they become memories, which can be considered to be transcendent rather than immanent phenomena and therefore inadmissible as phenomenological data. Evidence concerning the objective duration of sensations in various sensory modalities, the time necessary for sensations to (...) enter consciousness and the variability in the subjective sense of time's passing under different conditions is used to conclude that the duration of “now” can actually vary under normal conditions from about 10 ms to several seconds and in extreme cases up to several hours. Thus the immanent moment can be long enough to encompass a report of the contents of consciousness, making phenomenology a viable project. A further speculation from the evidence described is that consciousness takes discrete samples of the external world, at a rate inversely proportional to the duration of the “now” moment. (shrink)

Exploring the Illusion of Free Will and Moral Responsibility is an edited collection of new essays by an internationally recognized line-up of contributors. It is aimed at readers who wish to explore the philosophical and scientific arguments for free will skepticism and their implications.

Evidence is summarised for and against the hypothesis that potentiation or facilitation of neural responses during a train of threshold-level stimuli occurred in the experiments reported by Libet et al. . It is concluded that such potentiation probably did occur. Since the main arguments for the existence of subjective backwards referral take it as given that such potentiation did not occur, it is further concluded that the main arguments for the existence of subjective backwards referral fail.