Prominent among the arguments against the legalization of assisted suicide is the contention that legalization will have a disproportionately adverse, or “disparate,” impact on various vulnerable groups. There are many versions of this argument, with different advocates of this argument focusing on different vulnerable groups, and some advocates confusedly blending slippery slope and social justice concerns. Also, the weight placed on this argument by its various advocates is not uniform, with some including the argument in a list of multiple, apparently (...) similarly persuasive, reasons for not legalizing assisted suicide, while others place significant reliance on it and yet others advance the argument without any clear indication of its importance. Nonetheless, the various versions share a common core: One reason assisted suicide should not be legalized is that members of certain vulnerable groups are more likely to be pressured into requesting it, whether directly by those hostile or indifferent to their interests, or indirectly by social circumstances, such as an inability to pursue other healthcare choices. (shrink)

Prominent among the arguments against the legalization of assisted suicide is the contention that legalization will have a disproportionately adverse, or “disparate,” impact on various vulnerable groups. There are many versions of this argument, with different advocates of this argument focusing on different vulnerable groups, and some advocates confusedly blending slippery slope and social justice concerns. Also, the weight placed on this argument by its various advocates is not uniform, with some including the argument in a list of multiple, apparently (...) similarly persuasive, reasons for not legalizing assisted suicide, while others place significant reliance on it and yet others advance the argument without any clear indication of its importance. Nonetheless, the various versions share a common core: One reason assisted suicide should not be legalized is that members of certain vulnerable groups are more likely to be pressured into requesting it, whether directly by those hostile or indifferent to their interests, or indirectly by social circumstances, such as an inability to pursue other healthcare choices. (shrink)

Prior to passage of the Oregon Death with Dignity Act, opponents of assistance in dying argued that legalization would have serious harmful consequences. Specifically, they argued that the quality and availability of palliative care would decline, that the harms of legalization would affect certain vulnerable groups disproportionately, that legal assisted dying could not be confined to the competent terminally ill who voluntarily request assistance, and that the practice would result in frequent abuses. Data from Oregon's decade-long experience decisively refute the (...) first three predictions. As to abuses, the record is not quite as clear, but if an appropriate framework for analysis is utilized, the most reasonable conclusion is that the risks of abuse do not outweigh the benefits of legalization. To the extent projected harmful consequences are relevant to the debate over legalization, Oregon's experience argues in favor of legalization of assistance in dying. (shrink)

Even if there is a common morality, many would argue that it provides little guidance in resolving moral disputes, because universally accepted norms are both general in content and few in number. However, if we supplement common morality with commonly accepted factual beliefs and culture-specific norms and utilize coherentist reasoning, we can limit the range of acceptable answers to disputed issues. Moreover, in the arena of public policy, where one must take into account both legal and moral norms, the constraints (...) on acceptable answers will narrow the extent of reasonable disagreement even further. A consideration of the debate over legalization of assisted dying supports this claim. (shrink)

: There is a concern that genetic engineering will exacerbate existing social divisions and inequalities, especially if only the wealthy can afford genetic enhancements. Accordingly, many argue that justice requires the imposition of constraints on genetic engineering. However, it would be unwise to decide at this time what limits should be imposed in the future. Decision makers currently lack both the theoretical tools and the factual foundation for making sound judgments about the requirements of justice in a genetically transformed society. (...) Moreover, focusing on the uncertain inequities of the future may result in failure to give priority to more pressing inequities of the present. Especially in a country that recently has enacted tax legislation that will widen existing wealth disparities, concern about the distant threat of a genetic aristocracy appears misplaced. (shrink)

: Common morality theory must confront apparent counterexamples from the history of morality, such as the widespread acceptance of slavery in prior eras, that suggest core norms have changed over time. A recent defense of common morality theory addresses this problem by drawing a distinction between the content of the norms of the common morality and the range of individuals to whom these norms apply. This distinction is successful in reconciling common morality theory with practices such as slavery, but only (...) at the cost of underscoring the limits of common morality theory, in particular its inability to resolve disputes about the moral status of entities. Given that many controversies in bioethics center on the disputed status of various entities, such as embryos and nonhuman animals, this is an important limitation. Nonetheless, common morality theory still can be a useful resource in diminishing moral conflict on issues that do not involve disputes over moral status. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Gonzales v. Oregon and the Politics of MedicineRonald A. Lindsay (bio)Throughout 2005, the morbid joke on Capitol Hill was that the twin inevitabilities of "death and taxes" had been replaced by "death politics and taxes." There seemed to be some truth in this observation given the highly publicized intervention by some members of Congress in the Schiavo case and the continuing controversy over government regulation of end-of-life care. (...) The Supreme Court's recent decision in Gonzales v. Oregon (74 U.S.L.W. 4068 (17 January 2006)) has resolved one of the critical issues relating to this controversy by holding that a physician may prescribe controlled substances to provide assistance in dying if such a practice is authorized by state law and not expressly prohibited by federal law. However, other issues remain. In fact, the Court's decision has underscored some of the reasons why there is not only continuing controversy over end-of-life care, but also over other aspects of the practice of medicine. First, it is apparent there is no consensus among health care professionals about the precise boundaries of the legitimate practice of medicine. Second, the regulation of the practice of medicine traverses ill-defined legal territory. In particular, there is significant uncertainty concerning the implications of some regulations as well as the allocation of regulatory authority between and within state and federal governments. This uncertainty leaves substantial room for political maneuvers.Before discussing the politics of medicine, it is worth looking at the regulation of controlled substances in some detail both because this review will provide the necessary background for understanding the ruling in Gonzales v. Oregon and because it will illustrate the uncertainty resulting from multiple sources of regulatory authority.Federal and State Regulation of Controlled SubstancesSince the Pure Food and Drug Act of 1906, the federal government has regulated certain aspects of the distribution and administration of drugs deemed susceptible to abuse. The current primary vehicle for federal regulation is the Comprehensive Drug Abuse Prevention and Control Act, enacted in 1970, of which Title II is known as the Controlled Substances Act (CSA) (21 U.S.C. § 801 et seq.). A [End Page 99] "controlled" substance is just that, a substance that is regulated under the CSA. The CSA classifies controlled substances in five categories or schedules based on their potential for abuse, their accepted medical use, and the risks associated with their use under medical supervision. Schedule I substances have a high potential for abuse and have no currently accepted use in medical treatment. Schedule II-V substances are approved for medical use but are subject to a descending hierarchy of restrictions on their use. To give a lawful prescription for a controlled substance, a physician must be registered with the appropriate federal agency, currently the Drug Enforcement Administration (DEA). Moreover, to be valid, such a prescription must be issued for "a legitimate medical purpose" (21 U.S.C. § 830(b)(3)(A)(ii)).There is little dispute that the primary purposes of the CSA are to control drug abuse and to eliminate illicit trafficking in drugs. In accomplishing these objectives, there is a division of responsibility among various federal agencies, in particular the Department of Health and Human Services and the Department of Justice. Of particular relevance to the controversy in Gonzales v. Oregon is the Attorney General's authority to revoke a physician's registration for prescribing controlled substances if the physician's registration would be inconsistent with the public interest.All 50 states have their own statutes and regulations that address various aspects of the distribution and administration of controlled substances. Most states have adopted versions of the model Uniform Controlled Substances Act, which largely mimics federal law, but several states have placed additional restrictions on a physician's ability to prescribe controlled substances, including time limits on the validity of a prescription and limits on the quantity of a drug that can be prescribed. States are the primary, but by no means the exclusive, source of regulation of medical practice in general. States license physicians, establish boards and agencies to regulate the actions of physicians, and promulgate rules and guidelines to which physicians... (shrink)

few areas of public policy have been fraught with as much controversy as bioethics. Each novel development in biomedical technology seems to spark rancorous disputes. Those averse to new technologies often express the concern that the new technology is 'unnatural' or requires us to 'play God'. Slogans such as 'Frankenfoods' and 'sanctity of life' substitute for reasoned argument. This is an ambitious book that seeks to reframe the debates surrounding current controversies in bioethics. Carefully examining and dissecting claims made by (...) many policy-makers and ethicists on topics such as assistance in dying, genetic engineering, and embryonic stem cell research, bioethicist Ronald A Lindsay shows that all too often these claims are based on instinctive reactions, beliefs that lack factual support, and religious or ideological dogma. After describing in detail the proper way to approach and resolve a dispute in bioethics, Lindsay proceeds to analyse several different cutting-edge issues. Through his insightful analysis, Lindsay demonstrates how to achieve pragmatic, progressive solutions to these controversies. An antidote for misguided thinking, "Future Bioethics" illuminates the way forward to bioethics policies appropriate for the 21st century. (shrink)

When looking at a scene, observers feel that they see its entire structure in great detail and can immediately notice any changes in it. However, when brief blank fields are placed between alternating displays of an original and a modified scene, a striking failure of perception is induced: identification of changes becomes extremely difficult, even when changes are large and made repeatedly. Identification is much faster when a verbal cue is provided, showing that poor visibility is not the cause of (...) this difficulty. Identification is also faster for objects mentioned in brief verbal descriptions of the scene. These results support the idea that observers never form a complete, detailed representation of their surroundings. In addition, results also indicate that attention is required to perceive change, and that in the absence of localized motion signals it is guided on the basis of high-level interest. (shrink)

Five aspects of visual change detection are reviewed. The first concerns the concept of change itself, in particular the ways it differs from the related notions of motion and difference. The second involves the various methodological approaches that have been developed to study change detection; it is shown that under a variety of conditions observers are often unable to see large changes directly in their field of view. Next, it is argued that this “change blindness” indicates that focused attention is (...) needed to detect change, and that this can help map out the nature of visual attention. The fourth aspect concerns how these results affect our understanding of visual perception—for example, the implication that a sparse, dynamic representation underlies much of our visual experience. Finally, a brief discussion is presented concerning the limits to our current understanding of change detection. (shrink)

One of the more powerful impressions created by vision is that of a coherent, richly-detailed world where everything is present simultaneously. Indeed, this impression is so compelling that we tend to ascribe these properties not only to the external world, but to our internal representations as well. But results from several recent experiments argue against this latter ascription. For example, changes in images of real-world scenes often go unnoticed when made during a saccade, flicker, blink, or movie cut. This "change (...) blindness" provides strong evidence against the idea that our brains contain a picture-like representation of the scene that is everywhere detailed and coherent. (shrink)

'Principles Of Mental Imagery' offers a broad, balanced, and up-to-date introduction to the major findings of this research and identifies five general principles that can account for most of them. It considers the development of experimental techniques that have solved many of the challenging methodological problems inherent in imagery research and includes recent experimental findings not covered in other imagery books..

Large changes that occur in clear view of an observer can become difficult to notice if made during an eye movement, blink, or other such disturbance. This change blindness is consistent with the proposal that focused visual attention is necessary to see change, with a change becoming difficult to notice whenever conditions prevent attention from being automatically drawn to it. -/- It is shown here how the phenomenon of change blindness can provide new results on the nature of visual attention, (...) including estimates of its capacity and the extent to which it can bind visual properties into coherent descriptions. It is also shown how the resultant characterization of attention can in turn provide new insights into the role that it plays in the perception of scenes and events. (shrink)

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this _change blindness_ can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and (...) to cast new light on the way that it is?and is not?involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of _seeing_. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a _virtual representation_, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This _sensing_ is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself?the mechanisms involved when _scrutinizing_ items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved. (shrink)

A set of visual search experiments tested the proposal that focused attention is needed to detect change. Displays were arrays of rectangles, with the target being the item that continually changed its orientation or contrast polarity. Five aspects of performance were examined: linearity of response, processing time, capacity, selectivity, and memory trace. Detection of change was found to be a self-terminating process requiring a time that increased linearly with the number of items in the display. Capacity for orientation was found (...) to be about 5 items, a value comparable to estimates of attentional capacity. Observers were able to filter out both static and dynamic variations in irrelevant properties. Analysis also indicated a memory for previously-attended locations. These results support the hypothesis that the process needed to detect change is much the same as the attentional process needed to detect complex static patterns. Interestingly, the features of orientation and polarity were found to be handled in somewhat different ways. Taken together, these results not only provide evidence that focused attention is needed to see change, but also show that change detection itself can provide new insights into the nature of attentional processing. (shrink)

Experiments are presented showing that visual search for Mueller-Lyer (ML) stimuli is based on complete configurations, rather than component segments. Segments easily detected in isolation were difficult to detect when embedded in a configuration, indicating preemption by low-level groups. This preemption—which caused stimulus components to become inaccessible to rapid search—was an all-or-nothing effect, and so could serve as a powerful test of grouping. It is shown that these effects are unlikely to be due to blurring by simple spatial filters at (...) early visual levels. It is proposed instead that they are due to more sophisticated processes that rapidly bind contour fragments into spatially-extended assemblies. These results support the view that rapid visual search cannot access the primitives formed at the earliest stages of visual processing; rather, it can access only higher-level, more ecologically-relevant structures. (shrink)

It is suggested that the relationship between visual attention and conscious visual experience can be simplified by distinguishing different aspects of both visual attention and visual experience. A set of principles is first proposed for any possible taxonomy of the processes involved in visual attention. A particular taxonomy is then put forward that describes five such processes, each with a distinct function and characteristic mode of operation. Based on these, three separate kinds—or possibly grades—of conscious visual experience can be distinguished, (...) each associated with a particular combination of attentional processes. (shrink)

It has often been assumed that when we use vision to become aware of an object or event in our surroundings, this must be accompanied by a corresponding visual experience (i.e., seeing). The studies reported here show that this assumption is incorrect. When observers view a sequence of displays alternating between an image of a scene and the same image changed in some way, they often feel (or sense) the change even though they have no visual experience of it. The (...) subjective difference between sensing and seeing is mirrored in several behavioral differences, suggesting that these are two distinct modes of conscious visual perception. (shrink)

Over the centuries, magicians have developed extensive knowledge about the manipulation of the human mind—knowledge that has been largely ignored by psychology. It has recently been argued that this knowledge could help improve our understanding of human cognition and consciousness. But how might this be done? And how much could it ultimately contribute to the exploration of the human mind? We propose here a framework outlining how knowledge about magic can be used to help us understand the human mind. Various (...) approaches—both old and new—are surveyed, in terms of four different levels. The first focuses on the methods in magic, using these to suggest new approaches to existing issues in psychology. The second focuses on the effects that magic can produce, such as the sense of wonder induced by seeing an apparently impossible event. Third is the consideration of magic tricks—methods and effects together—as phenomena of scientific interest in their own right. Finally, there is the organization of knowledge about magic into an informative whole, including the possibility of a science centered around the experience of wonder. (shrink)

We show that early vision can use monocular cues to rapidly complete partially-occluded objects. Visual search for easily detected fragments becomes difficult when the completed shape is similar to others in the display; conversely, search for fragments that are difficult to detect becomes easy when the completed shape is distinctive. Results indicate that completion occurs via the occlusion-triggered removal of occlusion edges and linking of associated regions. We fail to find evidence for a visible filling-in of contours or surfaces, but (...) do find evidence for a "functional" filling-in that prevents the constituent fragments from being rapidly accessed. As such, it is only the completed structures—and not the fragments themselves—that serve as the basis for rapid recognition. (shrink)

When brief blank fields are placed between alternating displays of an original and a modified scene, a striking failure of perception is induced: the changes become extremely difficult to notice, even when they are large, presented repeatedly, and the observer expects them to occur (Rensink, O'Regan, & Clark, 1997). To determine the mechanisms behind this induced "change blindness", four experiments examine its dependence on initial preview and on the nature of the interruptions used. Results support the proposal that representations at (...) the early stages of visual processing are highly volatile, and that focused attention is needed to stabilize them sufficiently to support the perception of change. (shrink)

Our visual experience of the world is one of diverse objects and events, each with particular colors, shapes, and motions. This experience is so coherent, so immediate, and so effortless that it seems to result from a single system that lets us experience everything in our field of view. But however appealing, this belief is mistaken: there are severe limits on what can be visually experienced. -/- For example, in a display for air-traffic control it is important to track all (...) moving items. For a single item, this can be done without problem. Three or four can also be tracked, although some degree of effort may be needed. As the number is increased further, accurate tracking becomes more and more difficult—and eventually, impossible. Performance is evidently affected by a factor within the observer which enables certain kinds of perception to occur, but is limited in some way. This factor is generally referred to as attention. -/- At various times, attention has been associated with clarity of perception, intensity of perception, consciousness, selection, or the allocation of a limited “resource” enabling various operations (see Hatfield, 1998). During the past several decades, considerable progress has been achieved by focusing on the idea of selection (Broadbent, 1982). In particular, attention can be productively viewed as contingently selective processing. This can be embodied in various ways by various processes—there need not be a single quantity identified with all forms of attention, or a single site where it operates (Allport, 1993; Tsotsos, 2011). Although “paying attention” is often considered to be a unitary operation, it may simply refer to the control of one or more selective processes, ideally in a co-ordinated way. While this view has some cost in terms of conceptual simplicity, it can help make sense of a large set of phenomena. -/- This article surveys several of the major issues in our understanding of attention and how it relates to perception. It focuses on vision, since many—if not all—considerations are similar for all sensory modalities, and the level of understanding achieved in this domain is currently the most advanced. (shrink)

Human vision briefly retains a trace of a stimulus after it disappears. This trace—iconic memory—is often believed to be a surrogate for the original stimulus, a representational structure that can be used as if the original stimulus were still present. To investigate its nature, a flicker-search paradigm was developed that relied upon a full scan (rather than partial report) of its contents. Results show that for visual search it can indeed act as a surrogate, with little cost for alternating between (...) visible and iconic representations. However, the duration over which it can be used depends on the type of task: some tasks can use iconic memory for at least 240 ms, others for only about 190 ms, while others for no more than about 120 ms. The existence of these different limits suggests that iconic memory may have multiple layers, each corresponding to a particular level of the visual hierarchy. In this view, the inability to use a layer of iconic memory may reflect an inability to maintain feedback connections to the corresponding representation. (shrink)

Traditionally, vision science and information/data visualization have interacted by using knowledge of human vision to help design effective displays. It is argued here, however, that this interaction can also go in the opposite direction: the investigation of successful visualizations can lead to the discovery of interesting new issues and phenomena in visual perception. Various studies are reviewed showing how this has been done for two areas of visualization, namely, graphical representations and interaction, which lend themselves to work on visual processing (...) and the control of visual operations, respectively. The results of these studies have provided new insights into aspects of vision such as grouping, attentional selection and the sequencing of visual operations. More generally yet, such results support the view that the perception of visualizations can be a useful domain for exploring the nature of visual cognition, inspiring new kinds of questions as well as casting new light on the limits to which information can be conveyed visually. (shrink)

Recent advances in the field of creative cognition have helped to reveal the cognitive structures and processes that are involved in creative thinking and imagination. This article begins by reviewing recent studies of creative imagery that have explored the emergent properties of mental images. The geneplore model of creative cognition, which describes how preinventive structures such as creative mental images are generated and interpreted, is then discussed. In discussing this model and its implications, a distinction is made between aspects of (...) creative imagery that reflect conscious, deliberate control and those that reflect the absence of such control, as illustrated particularly by the emergence of unanticipated structures in imagined forms. The intentional, structured qualities of creative thinking are then contrasted with its spontaneous, unstructured qualities. The article concludes by discussing the recent topics of chaotic cognition and creative realism and how they bear on the general issue of balancing structured and unstructured processes in creative endeavors. (shrink)

The human experience is punctuated by times of crisis. Some crises are experienced at a personal level (e.g., the diagnosis of a life-threatening disease), organizational level (e.g., a business facing bankruptcy), and still others are experienced on a societal or global level (e.g., COVID-19 pandemic). Although crises can be deeply troubling and anxiety provoking, they can also serve as an important catalyst for creative action and innovative outcomes. This is because during times of crisis our typical forms of reasoning and (...) action may no longer serve us. It is precisely during such times that new ways of thought, action and leadership are needed. A key question for researchers to consider is:Why and how times of crisis serve as an impetus for creative actions and outcomes?The purpose of this paper is to address this question. I open by briefly discussing the features of a crisis. I then introduce an empirically testable, process model that outlines various pathways, factors, and outcomes associated with different ways people and organizations respond during times of crisis. I close by briefly outlining future directions for creativity theory and research. (shrink)

We show that cast shadows can have a significant influence on the speed of visual search. In particular, we find that search based on the shape of a region is affected when the region is darker than the background and corresponds to a shadow formed by lighting from above. Results support the proposal that an early-level system rapidly identifies regions as shadows and then discounts them, making their shapes more difficult to access. Several constraints used by this system are mapped (...) out, including constraints on the luminance and texture of the shadow region, and on the nature of the item casting the shadow. Among other things, this system is found to distinguish between line elements (items containing only edges) and surface elements (items containing visible surfaces), with only the latter deemed capable of casting a shadow. (shrink)

The past few years have seen a resurgence of interest in the scientific study of magic. Despite being only a few years old, this “new wave” has already resulted in a host of interesting studies, often using methods that are both powerful and original. These developments have largely borne out our earlier hopes (Kuhn et al., 2008) that new opportunities were available for scientific studies based on the use of magic. And it would seem that much more can still be (...) done along these lines. -/- But in addition to this, we also suggested that it might be time to consider developing an outright science of magic—a distinct area of study concerned with the experience of wonder that results from encountering an apparently impossible event1. To this end, we proposed a framework as to how this might be achieved (Rensink and Kuhn, 2015). A science can be viewed as a systematic method of investigation involving three sets of issues: (i) the entities considered relevant, (ii) the kinds of questions that can be asked about them, and (iii) the kinds of answers that are legitimate (Kuhn, 1970). In the case of magic, we suggested that this could be done at three different levels, each focusing on a distinct set of issues concerned with the nature of magic itself: (i) the nature of magical experience, (ii) how individual magic tricks create this experience, and (iii) organizing knowledge of the set of known tricks in a more comprehensive way (Rensink and Kuhn, 2015). Our framework also included a base level focused on how the methods of magic could be used as tools to investigate issues in existing fields of study. -/- Lamont (2010) and Lamont et al. (2010) raised a number of concerns about the possibility of such a science, which we have addressed (Rensink and Kuhn, 2015). More recently, Lamont (2015) raised a new objection, arguing that although base-level work (i.e., applications of magic methods) might be useful, there is too little structure in magic tricks for them to be studied in a systematic way at the other levels, ruling out a science of magic. We argue here, however, that although this concern raises some interesting challenges for this science, it does not negate the possibility that it could exist, and could contribute to the study of the mind. (shrink)

This paper critically appraises the applied action-guide approach to bioethics and finds it wanting in two ways: it is tethered to a social contract view of the doctor-patient relationship that is largely incompatible with experiences of illness and care; and, as a formalist doctrine, it lacks critical edge and tends toward accommodationism. An alternative approach is recommended that involves interpreting moral experience by means once associated with the rhetorical arts — practical reasoning, hermeneutics, casuistry, and thick description.

Papers presented at a symposium on philosophy and medicine at the Institute for the Medical Humanities at the University of Texas Medical Branch in 1974 were published in the inaugural volume of this series.

Several studies (e.g., Becklen & Cervone, 1983; Mack & Rock, 1998; Neisser & Becklen, 1975) have found that observers attending to a particular object or event often fail to report the presence of unexpected items. This has been interpreted as inattentional blindness (IB), a failure to see unattended items (Mack & Rock, 1998). Meanwhile, other studies (e.g., Pashler, 1988; Phillips, 1974; Rensink et al., 1997; Simons, 1996) have found that observers often fail to report the presence of large changes in (...) a display when these changes occur simultaneously with a transient such as an eye movement or flash of the display. This has been interpreted as change blindness (CB), a failure to see unattended changes (Rensink et al., 1997). In both cases there is a striking failure to report an object or event that would be quite visible under other circumstances. And in both cases there is a widespread (although not universal) belief that the underlying cause has to do with the absence of attention. The question then arises as to how these effects might be related. Is CB the same thing as IB? If not, what is the relation between them? And given that these phenomena deal with failures of subjective perception, what can they teach us about the nature of our visual experience? In particular, what can they teach us about the role played by visual attention? (shrink)

In the not-too-distant past, vision was often said to involve three levels of processing: a low level concerned with descriptions of the geometric and photometric properties of the image, a high level concerned with abstract knowledge of the physical and semantic properties of the world, and a middle level concerned with anything not handled by the other two. The negative definition of mid-level vision contained in this description reflected a rather large gap in our understanding of visual processing: How could (...) the here-and-now descriptions of the low levels combine with the enduring knowledge of the high levels to produce our perception of the surrounding world? A number of experimental and theoretical efforts have been made over the past few decades to solve this "mid-level crisis". One of the more recent of these is based on the phenomenon of change blindness—the difficulty in seeing a large change in a scene when the transients accompanying that change no longer convey information about its location (Rensink, O'Regan, & Clark, 1997; Rensink, 2000a). Phenomenologically, this effect is quite striking: the change typically is not seen for several seconds, after which it suddenly snaps into awareness. During the time the change remains "invisible", there is an apparent disconnection of the low-level descriptions (which respond to the change) from subjective visual experience (which does not). As such, this effect would seem to have the potential to help us understand how mid-level mechanisms might knit low- and high-level processes into a coherent representation of our surroundings. -/- It is argued here that this potential can indeed be realized, and that change blindness can teach us much about the nature of mid-level vision.3 A number of studies are first reviewed showing that the perception of a scene does not involve a steady buildup of detailed representation: rather, it is a dynamic process, with focused attention playing one of the main roles, viz., forming coherent object representations whenever needed. It is then argued that change blindness can also shed considerable light on the nature of focused attention itself, such as its speed, capacity, selectivity, and ability to bind together visual properties into coherent structures. (shrink)