Over a long career, Libet has conducted experiments that have shown, in clear and concrete ways, how the brain produces conscious awareness.

On the phenomenological view, a minimal form of self-consciousness is a constant structural feature of conscious experience. Experience happens for the experiencing subject in an immediate way and as part of this immediacy, it is implicitly marked as my experience. For the phenomenologists, this immediate and first-personal givenness of experiential phenomena must be accounted for in terms of a pre-reflective self-consciousness. In the most basic sense of the term, selfconsciousness is not something that comes about the moment one attentively inspects (...) or reflectively introspects one's experiences, or in the instant of self-recognition of one's image in the mirror, or in the proper use of the first-person pronoun, or in the construction of a self-narrative. Rather, these different kinds of self-consciousness are to be distinguished from the pre-reflective self-consciousness which is present whenever I am living through or undergoing an experience, i.e., whenever I am consciously perceiving the world, whenever I am thinking an occurrent thought, whenever I am feeling sad or happy, thirsty or in pain, and so forth. (shrink)

Most ?theories of consciousness? are based on vague speculations about the properties of conscious experience. We aim to provide a more solid basis for a science of consciousness. We argue that a theory of consciousness should provide an account of the very processes that allow us to acquire and use information about our own mental states ? the processes underlying introspection. This can be achieved through the construction of information processing models that can account for ?Type-C? processes. Type-C processes can (...) be specified experimentally by identifying paradigms in which awareness of the stimulus is necessary for an intentional action. The Shallice (1988b) framework is put forward as providing an initial account of Type-C processes, which can relate perceptual consciousness to consciously performed actions. Further, we suggest that this framework may be refined through the investigation of the functions of prefrontal cortex. The formulation of our approach requires us to consider fundamental conceptual and methodological issues associated with consciousness. The most significant of these issues concerns the scientific use of introspective evidence. We outline and justify a conservative methodological approach to the use of introspective evidence, with attention to the difficulties historically associated with its use in psychology. (shrink)

Laboratoire de Neurosciences Cognitives et Imagerie Ce´re´brale (LENA), Hoˆpital de La Salpeˆtrie`re, Centre National de la Recherche Scientifique (CNRS).

This paper will argue that there is no such thing as introspective access to judgments and decisions. It won't challenge the existence of introspective access to perceptual and imagistic states, nor to emotional feelings and bodily sensations. On the contrary, the model presented in Section 2 presumes such access. Hence introspection is here divided into two categories: introspection of propositional attitude events, on the one hand, and introspection of broadly perceptual events, on the other. I shall assume that the latter (...) exists while arguing that the former doesn't (or not in the case of judgments and decisions, at least). Section 1 makes some preliminary points and distinctions, and outlines the scope of the argument. Section 2 presents and motivates the general model of introspection that predicts a divided result. Section 3 provides independent evidence for the conclusion that judgments and decisions aren't introspectable. Section 4 then replies to a number of objections to the argument, the most important of which is made from the perspective of so-called "dual systems theories" of belief formation and decision making. The upshot is a limited form of eliminativism about introspection, in respect of at least two core categories of propositional attitude. (shrink)

Cognitive science has wholeheartedly embraced functional brain imaging, but introspective data are still eschewed to the extent that it runs against standard practice to engage in the systematic collection of introspective reports. However, in the case of executive processes associated with prefrontal cortex, imaging has made limited progress, whereas introspective methods have considerable unfulfilled potential. We argue for a re-evaluation of the standard ‘cognitive mapping’ paradigm, emphasizing the use of retrospective reports alongside behavioural and brain imaging techniques. Using all three (...) sources of evidence can compensate for their individual limitations, and so triangulate on higher cognitive processes. (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)

This is a prepublication version of the final chapter from the Blackwell Companion to Consciousness. In it I re-examine the basic conditions required for a study of conscious experiences in the light of progress made in recent years in the field of consciousness studies. I argue that neither dualist nor reductionist assumptions about subjectivity versus objectivity and the privacy of experience versus the public nature of scientific observations allow an adequate understanding of how studies of consciousness actually proceed. The chapter (...) examines the sense in which the experimenter is also a subject, the sense in which all experienced phenomena are private and subjective, the different senses in which a phenomenon can nevertheless be public and observations of it objective, and the conditions for intra-subjective and intersubjective repeatability. The chapter goes on to re-examine the empirical method and how methods used in psychology differ from those used in physics. I argue that a reflexive understanding of these relationships supports a form of “critical phenomenology” that fits consciousness studies smoothly into science. (shrink)

As is the case with other concepts about mental affairs, the concept of introspection has many different interpretations. Some seem to consider introspecting a perceptive act and others see it as a thinking activity . For the present purpose, we will claim it as a common understanding in all such theories that introspection presupposes consciousness . States of consciousness, broadly discussed in the philosophical and empirical literature as first order states of consciousness, are states in which a subject is aware (...) of some or other object, thought, or feeling. Introspective states, however, are states in which a subject directs his or her attention towards their own conscious state. According to this understanding which we claim is a widespread one introspection can exist only in conscious subjects, and, furthermore, it is by way of introspection that a subject can learn about having this or that experience. To avoid misunderstandings, we wish to underline that the claim is not that experiencing as such is dependent upon such acts of introspection. On the contrary, we believe that a subject can have all kinds of intero- and exteroceptive experiences, directing attention towards the represented object . It is only when the subject directs attention not towards the object as such but towards the very state of being conscious of the object that he or she is introspective. (shrink)

Benjamin Libet compared the perceived time of direct brain stimulation to the perceived time of skin stimulation. His results are among the most controversial experiments at the interface between psychology and philosophy. The new element that I bring to this discussion is a reanalysis of Libet's raw data. Libet's original data were difficult to interpret because of the manner in which they were presented in tables. Plotting the data as psychometric functions shows that the observers have great uncertainty about the (...) relative timing of events, as seen the shallow psychometric slopes. A second indication of uncertainty comes from Libet's use of three response categories, A first; B first; and A and B simultaneous. The large number of “perceptually simultaneous” responses provides a further measure of the difficulty of the judgment. There are thus a very broad range of stimulus delays in which the subject is unable to make an accurate ordering response. These points provide evidence that there is no compelling reason to invent exotic or ad hoc mechanisms to account for Libet's data since the uncertainty window is large enough to allow simple mechanism such as memory shifts. Libet argued that his data provide evidence for a backward referral in time. I argue that even though Libet's own data are weak, there are good arguments for a backward referral mechanism to help the subject make sense out of the tangled chaos of asynchronous information associated with experienced events. (shrink)

To study whether the distinction between introspective and non-introspective states of mind is an empirical reality or merely a conceptual distinction, we measured event-related potentials elicited in introspective and non-introspective instruction conditions while the observers were trying to detect the presence of a masked stimulus. The ERPs indicated measurable differences related to introspection in both preconscious and conscious processes. Our data support the hypothesis that introspective states empirically differ from non-introspective states.

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)

A seminal experiment found that the reported time of a decision to perform a simple action was at least 300 ms after the onset of brain activity that normally preceded the action. In Experiment 1, we presented deceptive feedback (an auditory beep) 5 to 60 ms after the action to signify a movement time later than the actual movement. The reported time of decision moved forward in time linearly with the delay in feedback, and came after the muscular initiation of (...) the response at all but the 5-ms delay. In Experiment 2, participants viewed their hand with and without a 120-ms video delay, and gave a time of decision 44 ms later with than without the delay. We conclude that participants' report of their decision time is largely inferred from the apparent time of response. The perception of a hypothetical brain event prior to the response could have, at most, a small influence. (shrink)

This paper addresses whether we have transparent accurate access to our own conscious experience. It first sketches the origin and social history of this issue in the seventeenth century, when the trust one can have in self- knowledge was disputed in the religious, social and scientific domains. It then reviews evidence that our conscious experience is disunified in several ways and has two levels, can be opaque to us, and contains much that is non-explicit; and that attending to one's experience (...) not only affects and changes it, but may also bring about specific content and phenomenal experience. Quite apart from trusting other people's introspective reports, we cannot trust ourselves even in knowing our own consciousness. Finally, several ways of coping with the problems produced by these characteristics are suggested. (shrink)