In its classical form, epiphenomenalism is the view that conscious mental events have no physical effects: while physical events cause mental events, the opposite is never true. Unlike classical epiphenomenalism, contemporary forms do not hold that conscious men­ tal states always lack causal efficacy, only that they are epiphenomenal relative to certain kinds of action, ones we pre-theoretically would have thought consciousness to causally contribute to. Two of these contemporary, empirically based challenges to the efficacy of the mental are the (...) focus of this chapter. The first, originating in research by Libet, has been interpreted as showing that the neural events initiating voluntary actions precede our conscious willing of them, meaning the conscious will cannot be what causes them. The second challenge, originating in studies by Milner and Goodale, consist of instances in which the content of visual consciousness and motor action dissociate, casting doubt on the intuitive view that visual consciousness guides visually based motor action. (shrink)

Accurate perception of moving objects would be useful; accurate visually guided action is crucial. Visual motion across the scene influences perceived object location and the trajectory of reaching movements to objects. In this commentary, I propose that the visual system assigns the position of any object based on the predominant motion present in the scene, and that this is used to guide reaching movements to compensate for delays in visuomotor processing.

Is the position of a moving target ? I argue that we should regard moving targets as the natural (veridical) position references. Motion is probably perceptually absolute, whereas position and time are relative quantities, as in physics. According to this view, processing delays are incorporated in the abstract local signs of motion signals. The flash-lag effect is one case in point.

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 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)

This paper is concerned with the role of conscious agency in human action. On a folk-psychological view of the structure of agency, intentions, conceived as conscious mental states, are the causes of actions. In the last decades, the development of new psychological and neuroscientific methods has made conscious agency an object of empirical investigation and yielded results that challenge the received wisdom. Most famously, the results of Libet’s studies on the ‘readiness potential’ have been interpreted by many as evidence in (...) favor of a skeptical attitude towards conscious agency. It is questionable, however, whether action initiation should be regarded as the touchstone of conscious agency. I shall argue that the traditional folk-psychological view, but also some of the objections leveled against it, rest in part on an over-simplified conception of the structure of agency, that neglects both the role of control processes after action initiation and the role of planning processes before action initiation. Taking these processes into account can lead to a reassessment of the relation between intentions and action and of the role of conscious agency in action production. (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)

Proximal intentions are intentions to do something at once. Are they ever among the causes of actions? Can agents “veto” or retract proximal intentions and refrain from acting on them in certain experimental settings? When, in controlled studies, do proximal intentions to press a button, for example, arise? And when does the agent's consciousness of these intentions arise? This article explores these questions—and evaluates some answers that have been offered—in light of the results of some recent research in neuroscience. Methods (...) for timing the onset of proximal intentions and onsets of consciousness of such intentions also receive special attention. (shrink)

Recent findings indicate that complex cognitive functions are organized at a global level in the brain and rely on large-scale information processing requiring functional integration of multiple disparate neural assemblies. The critical question of the integration of distributed brain activities is whether the essential integrative role can be attributed to a specific structure in the brain or whether this ability is inherent to the cognitive network as a whole. The results of the present study show that mean values of the (...) running correlation function in frontal-temporal EEG pairs with one electrode in the anterior cingulate cortex are significantly higher than the same values in other frontal-temporal pairs. These findings indicate a particular role of the ACC in large-scale communication, which could reflect its unique integrative functions in cognitive processing. (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)

Evidence for motion extrapolation at motion offset is scarce. In contrast, there is abundant evidence that subjects mentally extrapolate the future trajectory of weak motion signals at motion offset. Further, pointing movements overshoot at motion offset. We believe that mental and sensorimotor extrapolation is sufficient to solve the problem of perceptual latencies. Both present the advantage of being much more flexible than motion extrapolation.

Reinterpretations of Libet's results have received support from most commentaries. Libet's arguments against alternative hypotheses are contested. Latency depends on intensity. Integration of intensity and duration explains the Minimum Train Duration. Analogies of Libet's timing of intentions with control experiments indicate biases of opposite signs, according to intramodal or intermodal results. Rosenthal's view of nonconscious intentions becoming conscious after a delay is favored. Compatibilist free will is discussed.

Illusionism is a prominent hypothesis about action control, according to which acts that we consider voluntary are nevertheless caused by unconscious brain events, and thus our subjective experience of consciously willing them is ultimately illusory. Illusionism can be understood as either an ontological thesis or a phenomenological claim, but both versions are vulnerable to a line of attack based on the role of long-term planning in action control. According to this objection, the evidence upon which illusionism rests is confined to (...) short-term intentions, so it is not sufficient to justify broader conclusions on the causal inefficacy of conscious will. In this essay we reconstruct the logic of this objection against illusionism, clarify why surveying folk intuitions on conscious distal intentions is essential to the debate, and present a study in which the role of conscious planning in intentionality judgment is clearly revealed. We also present other relevant findi... (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)

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)

Spontaneous actions are preceded by brain signals that may sometimes be detected hundreds of milliseconds in advance of a subject's conscious intention to act. These signals have been claimed to reflect prior unconscious decisions, raising doubts about the causal role of conscious will. Murakami et al. (2014. Nat Neurosci 17: 1574–1582) have recently argued for a different interpretation. During a task in which rats spontaneously decided when to abort waiting, the authors recorded neurons in the secondary motor cortex. The neural (...) activity and relationship to action timing was parsimoniously explained using an integration-to-bound model, similar to those widely used to account for evidence-based decisions. In this model, the brain accumulates spontaneously occurring inputs voting for or against an action, but only commits to act once a certain threshold is crossed. The model explains how spontaneous decisions can be forecast (partially predicted) by neurons that reflect either the input or output of the integrator. It therefore presents an explicit hypothesis capable of rejecting the claim that such predictive signals imply unconscious decisions. We suggest that these results can inform the current debate on free will but must be considered with caution. (shrink)