Conscious experience is one of the most difficult and thorny problems in psychological science. Its study has been neglected for many years, either because it was thought to be too difficult, or because the relevant evidence was thought to be poor. Bernard Baars suggests a way to specify empirical constraints on a theory of consciousness by contrasting well-established conscious phenomena - such as stimulus representations known to be attended, perceptual, and informative - with closely comparable unconscious ones - such as (...) stimulus representations known to be preperceptual, unattended, or habituated. Adducing data to show that consciousness is associated with a kind of global workplace in the nervous system, and that several brain structures are known to behave in accordance with his theory, Baars helps to clarify many difficult problems. (shrink)
The standard behavioral index for human consciousness is the ability to report events with accuracy. While this method is routinely used for scientific and medical applications in humans, it is not easy to generalize to other species. Brain evidence may lend itself more easily to comparative testing. Human consciousness involves widespread, relatively fast low-amplitude interactions in the thalamocortical core of the brain, driven by current tasks and conditions. These features have also been found in other mammals, which suggests that consciousness (...) is a major biological adaptation in mammals. We suggest more than a dozen additional properties of human consciousness that may be used to test comparative predictions. Such homologies are necessarily more remote in non-mammals, which do not share the thalamocortical complex. However, as we learn more we may be able to make “deeper” predictions that apply to some birds, reptiles, large-brained invertebrates, and perhaps other species. (shrink)
Conscious perception, like the sight of a coffee cup, seems to involve the brain identifying a stimulus. But conscious input activates more brain regions than are needed to identify coffee cups and faces. It spreads beyond sensory cortex to frontoparietal association areas, which do not serve stimulus identification as such. What is the role of those regions? Parietal cortex support the ‘first person perspective’ on the visual world, unconsciously framing the visual object stream. Some prefrontal areas select and interpret conscious (...) events for executive control. Such functions can be viewed as properties of the subject, rather than the object, of experience – the ‘observing self’ that appears to be needed to maintain the conscious state. (shrink)
Most early studies of consciousness have focused on human subjects. This is understandable, given that humans are capable of reporting accurately the events they experience through language or by way of other kinds of voluntary response. As researchers turn their attention to other animals, “accurate report” methodologies become increasingly difficult to apply. Alternative strategies for amassing evidence for consciousness in non-human species include searching for evolutionary homologies in anatomical substrates and measurement of physiological correlates of conscious states. In addition, creative (...) means must be developed for eliciting behaviors consistent with consciousness. In this paper, we explore whether necessary conditions for consciousness can be established for species as disparate as birds and cephalopods. We conclude that a strong case can be made for avian species and that the case for cephalopods remains open. Nonetheless, a consistent effort should yield new means for interpreting animal behavior. (shrink)
Neural Darwinism (ND) is a large scale selectionist theory of brain development and function that has been hypothesized to relate to consciousness. According to ND, consciousness is entailed by reentrant interactions among neuronal populations in the thalamocortical system (the ‘dynamic core’). These interactions, which permit high-order discriminations among possible core states, confer selective advantages on organisms possessing them by linking current perceptual events to a past history of value-dependent learning. Here, we assess the consistency of ND with 16 widely recognized (...) properties of consciousness, both physiological (for example, consciousness is associated with widespread, relatively fast, low amplitude interactions in the thalamocortical system), and phenomenal (for example, consciousness involves the existence of a private flow of events available only to the experiencing subject). While no theory accounts fully for all of these properties at present, we find that ND and its recent extensions fare well. (shrink)
Can we make progress exploring consciousness? Or is it forever beyond human reach? In science we never know the ultimate outcome of the journey. We can only take whatever steps our current knowledge affords. This paper explores today's evidence from the viewpoint of Global Workspace theory. First, we ask what kind of evidence has the most direct bearing on the question. The answer given here is ‘contrastive analysis’ -- a set of paired comparisons between similar conscious and unconscious processes. This (...) body of evidence is already quite large, and constrains any possible theory . Because it involves both conscious and unconscious events, it deals directly with our own subjective experience, as anyone can tell by trying the demonstrations in this article. (shrink)
In the last decade, careful studies of the living brain have opened the way for human consciousness to return to the heights it held before the behavioristic coup of 1913. This is illustrated by seven cases: the discovery of widespread brain activation during conscious perception; high levels of regional brain metabolism in the resting state of consciousness, dropping drastically in unconscious states; the brain correlates of inner speech; visual imagery; fringe consciousness; executive functions of the self; and volition. Other papers (...) in this issue expand on many of these points. . In the past, evidence based on subjective reports was often neglected . It is still true that brain evidence has greater credibility than subjective reports, no matter how reliable. What is new is increasing convergence between subjective experiences and brain observations. For that reason it is no longer rare to see the word 'consciousness' and 'subjectivity' in major science journals. No one so far has discovered a gulf dividing mind and brain. On the contrary, the new evidence supports the central role of consciousness as it was regarded over more than two millenia of written thought. In a sense this was predictable. Nature is full of unexpected convergences -- between fruit fly genes and the human body, between the arc of a tennis ball and the orbit of Mars, and between consciousness and the brain. These convergences show once again the remarkable unity of the observable universe. (shrink)
When “divided attention” methods were discovered in the 1950s their implications for conscious experience were not widely appreciated. Yet when people process competing streams of sensory input they show both selective processesandclear contrasts between conscious and unconscious events. This paper suggests that the term “attention” may be best applied to theselection and maintenanceof conscious contents and distinguished from consciousness itself. This is consistent with common usage. The operational criteria for selective attention, defined in this way, are entirely different from those (...) used to assess consciousness. To illustrate the scientific usefulness of the distinction it is applied to Posner's brain model of visual attention. It seems that features that are often attributed to attention—like limited capacity—may more accurately be viewed as properties of consciousness. (shrink)
In humans, conscious perception and cognition depends upon the thalamocortical complex, which supports perception, explicit cognition, memory, language, planning, and strategic control. When parts of the T-C system are damaged or stimulated, corresponding effects are found on conscious contents and state, as assessed by reliable reports. In contrast, large regions like cerebellum and basal ganglia can be damaged without affecting conscious cognition directly. Functional brain recordings also show robust activity differences in cortex between experimentally matched conscious and unconscious events. This (...) basic anatomy and physiology is highly conserved in mammals and perhaps ancestral reptiles. While language is absent in other species, homologies in perception, memory, and motor cortex suggest that consciousness of one kind or another may be biologically fundamental and phylogenetically ancient. In humans we infer subjective experiences from behavioral and brain evidence. This evidence is quite similar in other mammals and perhaps some non-mammalian species. On the weight of the biological evidence, therefore, subjectivity may be conserved in species with human-like brains and behavior. (shrink)
This paper explores a remarkable convergence of ideas and evidence, previously presented in separate places by its authors. That convergence has now become so persuasive that we believe we are working within substantially the same broad framework. Taylor's mathematical papers on neuronal systems involved in consciousness dovetail well with work by Newman and Baars on the thalamocortical system, suggesting a brain mechanism much like the global workspace architecture developed by Baars (see references below). This architecture is relational, in the sense (...) that it continuously mediates the interaction of input with memory. While our approaches overlap in a number of ways, each of us tends to focus on different areas of detail. What is most striking, and we believe significant, is the extent of consensus, which we believe to be consistent with other contemporary approaches by Weiskrantz, Gray, Crick and Koch, Edelman, Gazzaniga, Newell and colleagues, Posner, Baddeley, and a number of others. We suggest that cognitive neuroscience is moving toward a shared understanding of consciousness in the brain. (shrink)
When are psychologists entitled to call a certain theoretical construct "consciousness?" Over the past few decades cognitive psychologists have reintroduced almost the entire conceptual vocabulary of common sense psychology, but now in a way that is tied explicitly to reliable empirical observations, and to compelling and increasingly adequate theoretical models. Nevertheless, until the past few years most cognitive psychologists and neuroscientists avoided dealing with consciousness. Today there is an increasing willingness to do so. But is "consciousness" different from other theoretical (...) entities like "working memory" or "mental imagery"? Some argue that under no circumstances can empirical science speak of consciousness as such, while others claim that the scientific goal is "knowing what it is like to be a bat" --- to share an organism's conscious experience . The Bat Criterion is ominously reminiscent of the protracted debate on the consciousness of ants and amoebas that caused so much uneasiness in psychology around 1900. It seems to demand that we first solve the mind-body problem as a condition of doing sensible science, and thereby creates the risk of endless, fruitless controversy. The endless philosophical debate about consciousness helped trigger the Behaviorist revolution about 1913, which threw out the baby of consciousness with the bathwater of perennial, circular debate. We've been that way; let's not go back to it. This paper maintains that the position of behavioristic denial is far too restrictive, but that the Bat Criterion is far too demanding --- that in fact, we only need to specify comparable pairs of psychological phenomena that differ only in the fact that one member of any pair is conscious, while the other is not. This "method of contrastive analysis" is a generalization of the experimental method, with consciousness as a variable whose interaction with other psychological and biological phenomena can be assessed in standard ways. As usual in science, this strategy is pragmatic: If it appears to yield sensible results, it can be a stepping-stone toward further understanding . This paper describes five sets of well-established pairs of phenomena that meet these criteria. Others are presented elsewhere, with more of a theoretical interpretation . Here I simply want to show that any adequate theory of conscious experience must satisfy these demanding but achievable empirical constraints. (shrink)
1.1 Bilateral damage to the thalamus abolishes waking consciousness. The critical site of this damage is believed to be a relatively small cluster of neurons, about the size of a pencil eraser on either side of the brain's midline, called the Intra-Laminar Nuclei (ILN) because they are located inside the white layers (laminae) that divide the two thalami into their major groupings of nuclei. The fact that bilateral damage to the ILNs abolishes consciousness is very unusual. There is no other (...) site in the brain that has this property, except the reticular formation in the brain stem. In contrast, huge chunks of cortex can be damaged without abolishing the STATE of consciousness. (Cortical damage does change the CONTENTS of consciousness, of course). (shrink)
After suggesting an operational definition for fringe experiences—as opposed to clearly conscious and clearly unconscious phenomena—we examine three empirical cases: The tip-of-the-tongue experience, the fringe experience of "wrongness," and the case of conscious focus on abstract, hard-to-image conscious contents. In each case, Mangan′s four major claims are explored in some detail. Most tasks seem to involve a combination of conscious experiences, complex unconscious representations, and multiple fringe experiences. The chief disagreement from this analysis involves vague experiences that are generally believed (...) to be focal: The case of currently topical abstract concepts, which are not reported as conscious images or percepts. In the interest of caution, it may be better to speak of "conscious access" to focal abstract concepts, rather than "conscious experience" of such concepts. There may be other vague but focally conscious phenomena, such as an intention to act, the signal for executing a prepared action, and so on. Mangan′s points are generally supported, with some qualifications. (shrink)
The life sciences in the 20th century were guided to a large extent by a reductionist program seeking to explain biological phenomena in terms of physics and chemistry. Two scientists who figured prominently in the establishment and dissemination of this program were Jacques Loeb in biology and Ivan P. Pavlov in psychological behaviorism. While neither succeeded in accounting for higher mental functions in physical-chemical terms, both adopted positions that reduced the problem of consciousness to the level of reflexes and associations. (...) The intellectual origins of this view and the impediment to the study of consciousness as an object of inquiry in its own right that it may have imposed on peers, students, and those who followed is explored. (shrink)
Since the advent of behaviorism the question of volition or "will" has been largely neglected. We consider evidence indicating that two identical behaviors may be quite distinct with respect to volition: For instance, with practice the details of predictable actions become less and less voluntary, even if the behavior itself does not visibly change. Likewise, people can voluntarily imitate involuntary slips they have just made. Such examples suggest that the concept of volition applies not to visible behavior per se, but (...) to the control system that guides behavior. Involuntary events include both automatisms and counter voluntary actions such as slips . An adequate theory of voluntary control must account for the entire set of such pairs of voluntary/involuntary contrasts. The problem of volition highlights core psychological issues. Voluntary acts are consistent with one′s current dominant goals. Volition and consciousness are intimately related. Consciousness of an action seems to recruit unconscious resources that help in planning, executing, and monitoring a voluntary act. Conversely, losing conscious access to an action seems to produce a loss of voluntary control. However, voluntary actions are not wholly conscious. It appears that we only need conscious access to nonroutine choice-points in the flow of control; routine aspects are handled unconsciously. The goals that guide voluntary acts often encounter conflict, either from reality or from other goals, and emotions are widely believed to result from appraisals of such conflicts . Finally, there is a close connection between countervoluntary slips and the symptoms of clinical pathology, which involve a loss of voluntary control over speech, action, feeling, imagery, or thought. A modern version of William James′ ideomotor theory is proposed, based on Global Workspace theory . The theory shows how a conscious goal image could activate unconscious plans and automatisms that shape a voluntary act. Conscious feedback from the act serves to communicate success or failure to many unconscious routines, which may then adapt cooperatively to shape future actions. (shrink)
The metacognitive stance of Smith et al. risks ignoring sensory consciousness. Although Smith et al. rightly caution against the tendency to preserve the uniqueness of the human mind at all costs, their reasoned stance is undermined by a selective association of consciousness with high-level cognitive operations. Neurobiological evidence may offer a more general, and hence more inclusive, basis for the systematic study of animal consciousness.
Surgical patients under anesthesia can wake up unpredictably and be exposed to intense, traumatic pain. Current medical techniques cannot maintain depth of anesthesia at a perfectly stable and safe level; the depth of unconsciousness may change from moment to moment. Without an effective consciousness monitor anesthesiologists may not be able to adjust dosages in time to protect patients from pain. An estimated 40,000 to 200,000 midoperative awakenings may occur in the United States annually. E. R. John and coauthors present the (...) scientific basis of a practical ''consciousness monitor'' in two articles. One article is empirical and shows widespread and consistent electrical field changes across subjects and anesthetic agents as soon as consciousness is lost; these changes reverse when consciousness is regained afterward. These findings form the basis of a surgical consciousness monitor that recently received approval from the U.S. Food and Drug Administration. This may be the first practical application of research on the brain basis of consciousness. The other John article suggests theoretical explanations at three levels, a neurophysiological account of anesthesia, a neural dynamic account of conscious and unconscious states, and an integrative field theory. Of these, the neurophysiology is the best understood. Neural dynamics is evolving rapidly, with several alternative points of view. The field theory sketched here is the most novel and controversial. (shrink)
The world of our experience consists at all times of two parts, an objective and a subjective part . . . The objective part is the sum total of whatsoever at any given time we may be thinking of, the subjective part is the inner 'state' in which the thinking comes to pass.
?In everday language, the word ?attention? implies control of access to consciousness, and we adopt this usage here. Attention itself can be either voluntary or automatic. This can be readily modeled in the theory. Further, a contrastive analysis of spontaneously self?attributed vs. self?alien experiences suggests that ?self? can be interpreted as the more enduring, higher levels of the dominant context hierarchy, which create continuity over the changing flow of events. Since context is by definition unconscious in GW theory, self in (...) this sense is thought to be inherently unconscious as well. This proposal is consistent with a great deal of objective evidence. However, aspects of self may become known through ?conscious self-monitoring,? a process that ??is useful for self-evaluation and self?control. The results of conscious self-monitoring are combined with self?evaluation criteria, presumably of social origin, to produce a stable ?self?concept?, which functions as a supervisory system within the larger self organization. (shrink)
