In this paper I aim to defend David Rosenthal's higher-order thought theory of consciousness against a prominent objection. The central claim of HOT theory is that a mental state is conscious only if one has the HOT that one is in that state. In broad outline, the objection is that HOT theory is unable to account for cases where the relevant HOTs are false. I consider two variants of the objection, corresponding to two kinds of false HOT: those that merely (...) misrepresent their targets, and those which lack targets altogether. I argue that a satisfactory response to the objection involving the latter, targetless, kind of HOTs, is to deny that one is in any conscious state in virtue of such HOTs. I show how this response is superior to Rosenthal's own response, and defend it against objections. I also argue that my account of targetless HOT cases may be generalized to cover cases of misrepresenting HOTs. (shrink)

Does the self exist? If so, what is its nature? How long do selves last? Galen Strawson draws on literature and psychology as well as philosophy to discuss various ways we experience having or being a self. He argues that it is legitimate to say that there is such a thing as the self, distinct from the human being.

According to unconscious perception hypothesis (UP), mental states of the same fundamental kind as ordinary conscious seeing can occur unconsciously. The proponents of UP often support it with empirical evidence for a more specific hypothesis, according to which colours can be seen unconsciously (UPC). However, UPC is a general claim that admits of many interpretations. The main aim of this paper is to determine which of them is the most plausible. To this end, I investigate how adopting various conceptions of (...) colour and perceptual phenomenal character affects UPC’s resilience to objections. This brings me to the conclusion that the most plausible reading of UPC is the one according to which the phenomenal character of colour perception (i) is constituted by colours qua primitive mind-independent qualities of the environment and (ii) is not essentially tied to consciousness. My conclusion not only identifies the most plausible interpretation of UPC, but also highlights and supports an unorthodox version of the relational theory of perception, which is a perfectly viable yet so far overlooked stance in the debate about unconscious perception. (shrink)

I propose that primary conscious awareness arises from synchronized activity in dendrites of neurons in dorsal thalamic nuclei, mediated particularly by inhibitory interactions with thalamic reticular neurons. In support, I offer four evidential pillars: consciousness is restricted to the results of cortical computations; thalamus is the common locus of action of brain injury in vegetative state and of general anesthetics; the anatomy and physiology of the thalamus imply a central role in consciousness; neural synchronization is a neural correlate of consciousness.

Aristotle, Dignāga, Descartes, Arnauld, Locke, Brentano, Sartre and many others are right about the nature of conscious awareness: all such awareness comports—somehow carries within itself—awareness of itself . This is a necessary condition of awareness being awareness at all: no ‘higher-order’ account of what makes conscious states conscious can be correct. But is very paradoxical: it seems to require that awareness be somehow already present, in such a way as to be available to itself as object of awareness, in order (...) to be constituted as awareness in the first place. Can anything relate to itself in this way? Can there be a relation that is necessarily one-term, reflexive, non-logical , concretely realizable, dynamically real, such that its holding is a necessary condition of the existence of the thing it holds of? It helps to consider the thought this very thought is puzzling. Many accept the reality of the kind of awareness of awareness posited in and , and think it must be not only ‘pre-reflective’ and ‘non-positional’, but also irrelational or non-intentional. But perhaps such awareness of awareness can be fully relational and fully intentional, and can be legitimately said to be its own object or content, even while being pre-reflective and non-positional. (shrink)

People often fail to detect large changes to scenes, provided that the changes occur during a visual disruption. This phenomenon, known as ''change blindness,'' occurs both in the laboratory and in real-world situations in which changes occur unexpectedly. The pervasiveness of the inability to detect changes is consistent with the theoretical notion that we internally represent relatively little information from our visual world from one glance at a scene to the next. However, evidence for change blindness does not necessarily imply (...) the absence of such a representation-people could also miss changes if they fail to compare an existing representation of the pre-change scene to the post-change scene. In three experiments, we show that people often do have a representation of some aspects of the pre-change scene even when they fail to report the change. And, in fact, they appear to ''discover'' this memory and can explicitly report details of a changed object in response to probing questions. The results of these real-world change detection studies are discussed in the context of broader claims about change blindness. (shrink)

Change blindness is the striking failure to see large changes that normally would be noticed easily. Over the past decade this phenomenon has greatly contributed to our understanding of attention, perception, and even consciousness. The surprising extent of change blindness explains its broad appeal, but its counterintuitive nature has also engendered confusions about the kinds of inferences that legitimately follow from it. Here we discuss the legitimate and the erroneous inferences that have been drawn, and offer a set of requirements (...) to help separate them. In doing so, we clarify the genuine contributions of change blindness research to our understanding of visual perception and awareness, and provide a glimpse of some ways in which change blindness might shape future research. (shrink)

In a series of three experiments, we explored the nature of implicit representations in change blindness . Using 3 × 3 letter arrays, we asked subjects to locate changes in paired arrays separated by 80 ms ISIs, in which one, two or three letters of a row in the second array changed. In one testing version, a tone followed the second array, signaling a row for partial report . In the other version, no PR was required. After Ss reported whether (...) a change had been detected and the PR had been completed , they were asked to identify a degraded letter trigram that was either novel, or from a previously shown row . Our findings indicate that when CB occurs, both the pre-change and post-change stimulus information primes despite its unavailability to consciousness. Surprisingly, findings also indicate that when change detection occurs only the post-change information primes. (shrink)

Both visual experience and conscious thought represent external objects, but in visual experience these objects seem present before the mind and available for direct access in a way that they don?t in conscious thought. In this paper, I introduce a couple of challenges that this ?Scene-Immediacy? of visual experience raises for traditional versions of Representationalism. I then identify a resource to which Representationalists can appeal in addressing these challenges: the low-detail fringe of visual experience. I argue that low-detail contents within (...) visual experience provide the mind with a rich access to additional high-detail information, an access that is not found in conscious thought. This access, in turn, speaks to the challenges raised by the Scene-Immediacy of visual experience. Robert Schroer is an Assistant Professor at the University of Minnesota at Duluth. (shrink)

In this paper, I explore and defend the idea that we have epistemic responsibilities with respect to our visual searches, responsibilities that are far more fine-grained and interesting than the trivial responsibilities to keep our eyes open and “look hard”. In order to have such responsibilities, we must be able to exert fine-grained and interesting forms of control over our visual searches. I present both an intuitive case and an empirical case for thinking that we do, in fact, have such (...) forms of control over our visual searches. I then show how these forms of control can be used to aim the visual beliefs that result from our searches towards various epistemic goals. (shrink)

In this paper, I explore and defend the idea that we have epistemic responsibilities with respect to our visual searches, responsibilities that are far more fine‐grained and interesting than the trivial responsibilities to keep our eyes open and “look hard.” In order to have such responsibilities, we must be able to exert fine‐grained and interesting forms of control over our visual searches. I present both an intuitive case and an empirical case for thinking that we do, in fact, have such (...) forms of control over our visual searches. I then show how these forms of control can be used to aim the visual beliefs that result from our searches toward various epistemic goals. (shrink)

Environmental representationalism is the position that phenomenal differences between visual experiences are determined by the representational claims those experiences make about the surrounding environment. Afterimage and phosphene experiences are an important and widely cited objection to this position. In this paper, I defend environmental representationalism from this objection. In particular, I point out several ways in which typical environmental representationalist accounts of these experiences are lacking while developing a more satisfying account which focuses on how the visual system generates its (...) representations as well as on several of the unique temporally-extended features of afterimage/phosphene experiences. (shrink)

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)

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)

People can maintain accurate representations of visual changes without necessarily being aware of them. Here, we investigate whether a similar phenomenon also exists in touch. In Experiments 1 and 2, participants detected the presence of a change between two consecutively-presented tactile displays. Tactile change blindness was observed, with participants failing to report the presence of tactile change. Critically, however, when participants had to make a forced choice response regarding the number of stimuli presented in the two displays, their performance was (...) significantly better than chance . Experiment 3 demonstrated that tactile change detection does not necessarily involve a shift of spatial attention toward the location of change, regardless of whether the change is explicitly detected. We conclude that tactile change detection likely results from comparing representations of the two displays, rather than by directing spatial attention to the location of the change. (shrink)

This paper assesses five main empirical scientific arguments against the reliability of belief formation on the basis of introspecting phenomenal states. After defining ‘reliability’ and ‘introspection’, I discuss five arguments to the effect that phenomenal states are more elusive than we usually think: the argument on the basis of differences in introspective reports from differences in introspective measurements; the argument from differences in reports about whether or not dreams come in colours; the argument from the absence of a correlation between (...) visual imagery ability and the performance on certain cognitive tasks; the argument from our unawareness of our capacity of echolocation; the argument from inattentional blindness and change blindness. I argue that the experiments on which these arguments are based do not concern belief formation on the basis of introspection in the first place or fail to show that it is unreliable, even when limited to introspection of phenomenal states. (shrink)

The paper proposes a way of bridging the gapbetween physical processes in the brain and the ''''felt''''aspect of sensory experience. The approach is based onthe idea that experience is not generated by brainprocesses themselves, but rather is constituted by theway these brain processes enable a particular form of''''give-and-take'''' between the perceiver and theenvironment. From this starting-point we are able tocharacterize the phenomenological differences betweenthe different sensory modalities in a more principledway than has been done in the past. We are also (...) ableto approach the issues of visual awareness andconsciousness in a satisfactory way. Finally weconsider a number of testable empirical consequences,one of which is the striking prediction of thephenomenon of ''''change blindness''''. (shrink)

Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of (...) acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The out- side world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the gov- erning laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Sev- eral lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual “filling in,” visual stability despite eye movements, change blindness, sensory substitution, and color perception. (shrink)

Recently, a number of experiments have emphasized the degree to which subjects fail to detect large changes in visual scenes. This finding, referred to as “change blindness,” is often considered surprising because many people have the intuition that such changes should be easy to detect. Levin, Momen, Drivdahl, and Simons documented this intuition by showing that the majority of subjects believe they would notice changes that are actually very rarely detected. Thus subjects exhibit a metacognitive error we refer to as (...) “change blindness blindness.” Here, we test whether CBB is caused by a misestimation of the perceptual experience associated with visual changes and show that it persists even when the pre- and postchange views are separated by long delays. In addition, subjects overestimate their change detection ability both when the relevant changes are illustrated by still pictures, and when they are illustrated using videos showing the changes occurring in real time. We conclude that CBB is a robust phenomenon that cannot be accounted for by failure to understand the specific perceptual experience associated with a change. (shrink)

Some proponents of the higher-order thought theory of consciousness defend the view that higher-order misrepresentation is possible. In support of this view they have proposed various pieces of empirical evidence. This paper examines one such piece of proposed empirical evidence; Change blindness. CB occurs when a subject fails to detect salient changes in visual scenes. I propose an alternative interpretation of the CB phenomenon on which misrepresentation does not occur. Finally, I examine three lines of reply that might be pursued (...) to defend the claim that CB is evidence of misrepresentation against my interpretation. I conclude that none of the lines of reply succeed in preserving CB as evidence of misrepresentation. The upshot is that, pending further evidence, CB cannot be deployed as empirical evidence in the debate on misrepresentation. (shrink)

According to reductive intentionalism, the phenomenal character of a conscious experience is constituted by the experience's intentional (or representational) content. The goal of this article is to show that a phenomenon in visual perception called change blindness poses a problem for this doctrine. It is argued, in particular, that phenomenal character is not sensitive, as it should be if reductive intentionalism is correct, to fine-grained variations in content. The standard anti-intentionalist strategy is to adduce putative cases in which phenomenal character (...) varies despite sameness of content. This paper explores an alternative anti-intentionalist tack, arguing, by way of a specific example involving change blindness, that content can vary despite sameness of phenomenal character. (shrink)

Verbal narratives provide incomplete information and can be very long, yet readers and hearers often effortlessly fill in the gaps and make connections across long stretches of text, sometimes even finding this immersive. How is this done? In the last few decades, event-indexing situation modeling and complementary accounts of narrative emotion have suggested answers. Despite this progress, comparisons between real-life perception and narrative experience might underplay the way narrative processing modifies our world model, as well as the role of the (...) emotions that do not relate to characters. I reframe narrative experience in predictive processing and neural networks, capturing continuity between fiction, perception, and states like dreaming and imagination, enabled by the flexible instantiation of concepts. In this framework, narrative experience is more clearly revealed as a creative experience that can share some of the phenomenology of dreams. (shrink)

In this event-related potential study a masking technique that prevents conscious perception of words and non-words through attentional distraction was used to reveal the temporal dynamics of word processing under non-conscious and conscious conditions. In the non-conscious condition, ERP responses differed between masked words and non-words from 112 to 160 ms after stimulus-onset over posterior brain areas. The early onset of the word–non-word differences was compatible with previous studies that reported non-conscious access to orthographic information within this time period. Moreover, (...) source localisations provided evidence for automatic activation of prelexical phonological information, whereas no evidence for non-conscious semantic processing was found. When subjects were informed about the masking technique, lexical differences occurred at later time intervals, suggesting conscious access to additional word related information. These results indicate that early visual word processing does not depend entirely on attentional resources, but that non-conscious processing probably is restricted to rather lower-level linguistic information. (shrink)

The authors examine several issues in teaching phenomenology (1) to advanced researchers who are doing qualitative research using phenomenological interview methods in disciplines such as psychology, nursing, or education, and (2) to advanced researchers in the cognitive neurosciences. In these contexts, the term “teaching” needs to be taken in a general and nondidactic way. In the case of the first group, it involves guiding doctoral students in their conception and design of a qualitative methodology that is properly phenomenological. In the (...) case of the second, it is more concerned with explaining the relevance of phenomenology to an audience of experimental scientists via conference presentations or published papers. In both cases, however, the challenge is to make clear to the relevant audience what phenomenology is and how it can relate to what they are doing. (shrink)

Change blindness, the surprising inability of people to detect significant changes between consecutively-presented visual displays, has recently been shown to affect tactile perception as well. Visual change blindness has been observed during saccades and eye blinks, conditions under which people’s awareness of visual information is temporarily suppressed. In the present study, we demonstrate change blindness for suprathreshold tactile stimuli resulting from the execution of a secondary task requiring bodily movement. In Experiment 1, the ability of participants to detect changes between (...) two sequentially-presented vibrotactile patterns delivered on their arms and legs was compared while they performed a secondary task consisting of either the execution of a movement with the right arm toward a visual target or the verbal identification of the target side. The results demonstrated that a motor response gave rise to the largest drop in perceptual sensitivity in detecting changes to the tactile display. In Experiment 2, we replicated these results under conditions in which the participants had to detect tactile changes while turning a steering wheel instead. These findings are discussed in terms of the role played by bodily movements, sensory suppression, and higher order information processing in modulating people’s awareness of tactile information across the body surface. (shrink)

We present a new account of perceptual consciousness, one which gives due weight to the epistemic commitment of normal perception in familiar circumstances. The account is given in terms of a higher-order attitude for which the subject has an immediate perceptual epistemic warrant in the form of an appropriate first-order perception. We develop our account in contrast to Rosenthal's higher-order account, rejecting his view of consciousness in virtue of so-called ‘targetless’ higher-order states. We explain the key notion of an immediate (...) perceptual warrant and show both that it requires the content of the higher-order attitude to match that of the first-order perception, and also that it gives a new perspective on the intimate relationship, rightly emphasised by Rosenthal, between consciousness and a subject's testimony as to ‘how it is with her’. (shrink)

The higher order approach to consciousness attempts to build a theory of consciousness from the insight that a conscious state is one that the subject is conscious of. There is a well-known objection1 to the higher order approach, a version of which is fatal. Proponents of the higher order approach have realized that the objection is significant. They have dealt with it via what David Rosenthal calls a “retreat” (2005b, p. 179) but that retreat fails to solve the problem.

The goal of this study is to characterize observers’ abilities to discriminate between endogenous and exogenous changes. To do so, we developed a new experimental paradigm. On each trial, participants were shown a dot pattern on the screen. Next, the pattern disappeared and participants were to reproduce it. Changes were surreptuously introduced in the stimulus, either by presenting participants anew with the dot pattern they had themselves produced on the previous trial or by presenting participants with a slightly different dot (...) pattern . We analyzed awareness of the changes and behavioral adaptation to them in a dynamical manner. We observe signal attenuation in the presence of endogenous change, dissociation between self-attribution reports and behavioral effect of agency. We discuss the source of this sensitive attenuation as well as the relation between a minimal or core self and an extended, narrative or autobiographical self. (shrink)

Observers have difficulty detecting visual changes. However, they are unaware of this inability, suggesting that people do not have an accurate understanding of visual processes. We explored whether this error is related to participants’ beliefs about the roles of intention and scene complexity in detecting changes. In Experiment 1 participants had a higher failure rate for detecting changes in an incidental change detection task than an intentional change detection task. This effect of intention was greatest for complex scenes. However, participants (...) predicted equal levels of change detection for both types of changes across scene complexity. In Experiment 2, emphasizing the differences between intentional and incidental tasks allowed participants to make predictions that were less inaccurate. In Experiment 3, using more sensitive measures and accounting for individual differences did not further improve predictions. These findings suggest that adults do not fully understand the role of intention and scene complexity in change detection. (shrink)

William Alston’s Theory of Appearing has attracted considerable attention in recent years, both for its elegant interpretation of direct realism in light of the presentational character of perceptual experience and for its central role in his defense of the justificatory force of Christian mystical experiences. There are different ways to account for presentational character, however, and in this article we argue that a superior interpretation of direct realism can be given by a theory of perception as dynamic engagement. The conditions (...) for dynamic engagement are such that there can be no absolute discontinuity between individual perceptual experiences and more public forms of inquiry, and this requirement has radical consequences for the prima facie justificatory force of religious experience. (shrink)

People’s awareness of tactile stimuli has been investigated in far less detail than their awareness of stimuli in other sensory modalities. In an attempt to fill this gap, we provide an overview of studies that are pertinent to the topic of tactile consciousness. We discuss the results of research that has investigated phenomena such as “change blindness”, phantom limb sensations, and numerosity judgments in tactile perception, together with the results obtained from the study of patients affected by deficits that can (...) adversely affect tactile perception such as neglect, extinction, and numbsense. The similarities as well as some of the important differences that have emerged when visual and tactile conscious information processing have been compared using similar experimental procedures are highlighted. We suggest that conscious information processing in the tactile modality cannot be separated completely from the more general processing of spatial information in the brain. Finally, the importance of considering tactile consciousness within the larger framework of multisensory information processing is also discussed. (shrink)

I argue that scientism in general is best understood as the thesis that the boundaries of the natural sciences should be expanded in order to include academic disciplines or realms of life that are widely considered not to belong to the realm of science. However, every adherent and critic of scientism should make clear which of the many varieties of scientism she adheres to or criticizes. In doing so, she should specify whether she is talking about (a) academic or universal (...) scientism, (b) reductive, methodological, epistemological, ontological, moral, or existential, scientism, (c) full or partial scientism, (d) strong or weak scientism, and (e) in the case of moral and existential scientism: replacement or illusion scientism. The strongest version of scientism one could defend is a conjunction of the following theses: strong full epistemological scientism, strong full ontological scientism, strong full Illusion-moral scientism, strong Illusion-existential scientism, and strong full reductive scientism. After a detailed discussion of each of the main varieties of scientism and their interrelations, the paper provides a conceptual map, consisting of two figures, which displays the main varieties of scientism and the relations that obtain between them, primarily, those of implication and mutual exclusion. (shrink)

The topic of this paper is the complex interaction between attention, fixation, and one species of change blindness. The two main interpretations of the target phenomenon are the ‘blindness’ interpretation and the ‘inaccessibility’ interpretation. These correspond to the sparse view (Dennett 1991; Tye, 2007) and the rich view (Dretske 2007; Block, 2007a, 2007b) of visual consciousness respectively. Here I focus on the debate between Fred Dretske and Michael Tye. Section 1 describes the target phenomenon and the dialectics it entails. Section (...) 2 explains how attention and fixation weigh in these debates, and argues that Dretske’s hyper-rich view fails precisely because he overlooks certain effects of attention and fixation. Section 3 explains why Tye’s view is also unsatisfying, mainly because he misconceives the degree of access. Section 4 then puts forward the positive model covariance, which has it that the degree of cognitive access tracks the degree of phenomenology, and contrasts it with Block’s view on the Sperling iconic memory paradigm. The paper ends with a discussion of levels of seeing, which involve crowding, indexing, and other visual phenomena. Change ‘blindness’ is a set of phenomena that was discovered about two decades ago, yet an entirely satisfying understanding is still lacking. To move forward, a more detailed understanding of attention and fixation is called for. (shrink)

Computer vision systems are, on most counts, poor performers, when compared to their biological counterparts. The reason for this may be that computer vision is handicapped by an unreasonable assumption regarding what it means to see, which became prevalent as the notions of intrinsic images and of representation by reconstruction took over the field in the late 1970’s. Learning from biological vision may help us to overcome this handicap.

Changes made during a brief visual interruption sometimes go undetected, even when the object undergoing the change is at the center of the observer's interest and spatial attention. This study examined two potentially important attentional variables in change blindness: spatial distribution, manipulated via set size, and detail level, varied by having the change at either the global or local level of a compound letter. Experiment 1 revealed that both types of change were equally detectable in a single item, but that (...) global change was detected more readily when attention was distributed among several items. Variation of target level probability in Experiment 2 showed further that observers could flexibly set the detail level in monitoring both single and multiple items. Sensitivity to change therefore depends not only on the spatial focus of attention; it depends critically on the match between the detail level of the change and the level-readiness of the observer. (shrink)

Rensink, O’Regan, and Clark (1997) drew attention to the phenomenon of change blindness, in which even large changes can be difficult to notice if made during the appearance of motion transients elsewhere in the image. This article provides a sketch of the events that inspired that article as well as its subsequent impact on psychological science and on society at large.

in Encyclopedia of Consciousness, ed. William P. Banks, Amsterdam: Elsevier, forthcoming in 2009.

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)

This chapter presents an overview of several recent developments in vision science, and outlines some of their implications for the management of visual attention in graphic displays. These include ways of sending attention to the right item at the right time, techniques to improve attentional efficiency, and possibilities for offloading some of the processing typically done by attention onto nonattentional mechanisms. In addition it is argued that such techniques not only allow more effective use to be made of visual attention, (...) but also open up new possibilities for human-machine interaction. (shrink)

Observers inspected normal, high quality color displays of everyday visual scenes while their eye movements were recorded. A large display change occurred each time an eye blink occurred. Display changes could either involve "Central Interest" or "Marginal Interest" locations, as determined from descriptions obtained from independent judges in a prior pilot experiment. Visual salience, as determined by luminance, color, and position of the Central and Marginal interest changes were equalized. -/- The results obtained were very similar to those obtained in (...) prior experiments showing failure to detect changes occurring simultaneously with saccades, flicker, or “mudsplashes” in the visual scene: Many changes were very hard to detect, and Marginal Interest changes were harder to detect than Central Interest changes. -/- Analysis of eye movements showed, as expected, that the probability of detecting a change depended on the eye’s distance from the change location. However a surprising finding was that both for Central and Marginal Interest changes, evenwhen observers were directly fixating the change locations (within 1 degree),more than 40% of the time they still failed to see the changes. It seems that looking at something does not guarantee you “ see” it. (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)

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)