Change/Inattentional Blindness

Peirce and Husserl both realized that our habits and habitual conceptions, though vital to the success of most activities, nevertheless occlude large portions of the experiential canvass. So, unless preparatory work puts us in the right mindset, we risk perceiving the world—not as it is—but rather as we expect it to be. While Peirce and Husserl were predominantly concerned with supplying a better observational basis for inquiries like science, semiotics, and mathematics, I draw on their phaneroscopic/phenomenological tools to combat the (...) addictive and mind-narrowing effects of technology. I go over several examples to show how, when we (try to) rid ourselves of presuppositions and relax the pursuit of efficiency, we enable contemplative possibilities conducive to flourishing and the pursuit of meaning. My overall message is that, in an age when we increasingly depend on devices like Smartphones (and soon VR) to form flat and one-sided worldviews, re-establishing an unmediated contact with our everyday surroundings can have tangible existential benefits, nipping in the bud tyrannical trends as well as wasted lives. (shrink)

Conscious states—state that there is something it is like to be in—seem both rich or full of detail and ineffable or hard to fully describe or recall. The problem of ineffability, in particular, is a longstanding issue in philosophy that partly motivates the explanatory gap: the belief that consciousness cannot be reduced to underlying physical processes. Here, we provide an information theoretic dynamical systems perspective on the richness and ineffability of consciousness. In our framework, the richness of conscious experience corresponds (...) to the amount of information in a conscious state and ineffability corresponds to the amount of information lost at different stages of processing. We describe how attractor dynamics in working memory would induce impoverished recollections of our original experiences, how the discrete symbolic nature of language is insufficient for describing the rich and high-dimensional structure of experiences, and how similarity in the cognitive function of two individuals relates to improved communicability of their experiences to each other. While our model may not settle all questions relating to the explanatory gap, it makes progress toward a fully physicalist explanation of the richness and ineffability of conscious experience—two important aspects that seem to be part of what makes qualitative character so puzzling. (shrink)

It is often claimed that pre-attentive vision has an ‘iconic’ format. This is seen to explain pre-attentive vision's characteristically high processing capacity and to make sense of an overlap in the mechanisms of early vision and mental imagery. But what does the iconicity of pre-attentive vision amount to? This paper considers two prominent ways of characterising pre-attentive visual icons and argues that neither is adequate: one approach renders the claim ‘pre-attentive vision is iconic’ empirically false while the other obscures its (...) ability to do the explanatory work, which motivates positing pre-attentive visual icons in the first place. With this noted, I introduce the notion of an ‘Analogue Map’ and argue that it provides a superior characterisation of pre-attentive vision's iconicity. I then argue that this forces a reassessment of debates which have traditionally presupposed the iconicity of pre-attentive vision, emphasising ramifications for the viability of a format-based perception-thought border. (shrink)

In the contemporary discussions concerning unconscious perception it is not uncommon to postulate that content and phenomenal character are ‘orthogonal’, i.e., there is no type of content which is essentially conscious, but instead, every representational content can be either conscious or not. Furthermore, this is not merely treated as a thesis justified by theoretical investigations, but as supported by empirical considerations concerning the actual functioning of the human cognition. In this paper, I address unconscious color perception and argue for a (...) negative thesis—that the main experimental paradigms used in studying unconscious color perception do not provide support for the position that conscious and unconscious color representations have the same type of content. More specifically, I claim that there is no significant support for the claim that unconscious vision categorically represents surface colors. (shrink)

The idea that attention is necessary for consciousness (the “Necessity Thesis”) is frequently advocated by philosophers and psychologists alike. Experiments involving inattentional and change blindness are thought to support the Necessity Thesis, but they do so only if subjects failing to notice the target stimulus are also not conscious of it. This article uses commonsense phenomenological observations supplemented with empirical data to argue that some subjects failing to notice the target stimulus nonetheless experience its color. Since subjects not noticing the (...) target are commonly assumed to be not attending to it, these scenarios would be instances of consciousness without attention: instead of inattentional and change blindness supporting the Necessity Thesis, they would present counterexamples to it. (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.

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)

In the past two decades a number of arguments have been given in favor of the possibility of phenomenal consciousness without attentional access, otherwise known as phenomenal overflow. This paper will show that the empirical data commonly cited in support of this thesis is, at best, ambiguous between two equally plausible interpretations, one of which does not posit phenomenology beyond attention. Next, after citing evidence for the feature-integration theory of attention, this paper will give an account of the relationship between (...) consciousness and attention that accounts for both the empirical data and our phenomenological intuitions without positing phenomenal consciousness beyond attention. Having undercut the motivations for accepting phenomenal overflow along with having given reasons to think that phenomenal overflow does not occur, I end with the tentative conclusion that attention is a necessary condition for phenomenal consciousness. -/- . (shrink)

Blindsight is a kind of residual vision found in people with lesions to V1. Subjects with blindsight typically report no visual awareness, but they are nonetheless able to make above-chance guesses about the shape, location, color and movement of visual stimuli presented to them in their blind field. A different kind of blindsight, sometimes called type 2 blindsight, is a kind of residual vision found in patients with V1 lesions in the presence of some residual awareness. Type 2 blindsight differs (...) from ordinary visual experience in lacking the particularity, transparency and fine-grainedness often taken to be essential to visual experience, at least in veridical cases. I argue that the case of type 2 blindsight provides a counterexample to the view that these characteristics are essential to veridical visual experience and that this gives us reason to resist the view that visual experience is essentially a perceptual relation to external objects. In the second part of the paper I argue that the case of type 2 blindsight yields important insights into the effects of attentional modulation on perceptual content and that cases of attentional modulation of appearance are not at odds with the view that the phenomenology of visual experience flows from its content. (shrink)

One of the most influential ideas of twentieth-century art history and aesthetics is that vision has a history and it is the task of art history to trace how vision has changed. This claim has recently been attacked for both empirical and conceptual reasons. My aim is to argue for a new version of the history of vision claim: if visual attention has a history, then vision also has a history. And we have some reason to think that at least (...) in certain contexts, visual attention does have a history. (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 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)

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)

Contrary to Block's assertion, “identity-crowding” does not provide an interesting instance of object-seeing without object-attention. The successful judgments and unusual phenomenology of identity-crowding are better explained by unconscious perception and non-perceptual phenomenology associated with cognitive states. In identity-crowding, as in other cases of crowding, subjects see jumbled textures and cannot individuate the items contributing to those textures in the absence of attention. Block presents an attenuated sense in which identity-crowded items are seen, but this is irrelevant to the debate about (...) phenomenal experience of an object in the absence of object-attention. Finally, even unconscious object perception in identity-crowding likely involves an attention-like selective process. (shrink)

We discuss the rational role of highly inattentive experiences, and argue that they can provide rational support for beliefs.

One of the most important issues concerning the foundations ofconscious perception centerson thequestion of whether perceptual consciousness is rich or sparse. The overflow argument uses a form of ‘iconic memory’ toarguethatperceptual consciousnessisricher (i.e.,has a higher capacity) than cognitive access: when observing a complex scene we are conscious of more than we can report or think about. Recently, the overflow argumenthas been challenged both empirically and conceptually. This paper reviews the controversy, arguing that proponents of sparse perception are committed to the (...) postulation of (i) a peculiar kind of generic conscious representation that has no independent rationale and (ii) an unmotivated form of unconscious representation that in some cases conflicts with what we know about unconscious representation. (shrink)

Perceivers generally show a poor ability to detect changes, a condition referred to as “Change Blindness” . They are, in addition, “blind to their own blindness”. A common explanation of this “Change Blindness Blindness” is that it derives from an inadequate, “photographical” folk-theory about perception. This explanation, however, does not account for intra-individual variations of CBB across trials. Our study aims to explore an alternative theory, according to which participants base their self-evaluations on two activity-dependent cues, namely search time and (...) perceived success in prior trials. These cues were found to influence self-evaluation in two orthogonal ways: success-feedback influenced self-evaluation in a global, contextual way, presumably by recalibrating the norm of adequacy for the task. Search time influenced it in a local way, predicting the success of a given trial from its duration. (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)

The book I review, _Sleights of Mind_, aims to illuminate properties of perceptual systems by discussing human susceptibility to magical illusions. I describe how the authors use psychological principles to explain two tricks, spoon bending and the Miser's Dream. I also argue that the book is congenial to the following view of illusions: susceptibility to illusion is the result of evolutionary trade-offs; perceptual systems must make assumptions in order to function at all, but susceptibility to illusion is the byproduct of (...) such assumptions. (shrink)

I argue that perceptual content is always affected by the allocation of one’s attention. Perception attributes determinable and determinate properties to the perceived scene. Attention makes (or tries to make) our perceptual attribution of properties more determinate. Hence, a change in our attention changes the determinacy of the properties attributed to the perceived scene.

This paper discusses several key issues concerning consciousness and human vision. A brief overview is presented of recent developments in this area, including issues that have been resolved and issues that remain unsettled. Based on this, three Hilbert questions are proposed. These involve three related sets of issues: the kinds of visual experience that exist, the kinds of visual attention that exist, and the ways that these relate to each other.

As observers, we generally have a strong impression of seeing everything in front of us at any moment. But compelling as it is, this impression is false – there are severe limits to what we can consciously experience in everyday life. Much of the evidence for this claim has come from two phenomena: change blindness (CB) and inattentional blindness (IB). -/- CB refers to the failure of an observer to visually experience changes that are easily seen once noticed. This can (...) happen even if the changes are large, constantly repeat, and the observer has been informed that they will occur. A related phenomenon is IB – the failure to visually experience an object or event when attention is directed elsewhere. For example, observers may fail to notice an unexpected object that enters their visual field, even if this object is large, appears for several seconds, and has important consequences for the selection of action. -/- Both phenomena involve a striking failure to report an object or event that is easily seen once noticed. As such, both are highly counterintuitive, not only in the subjective sense that observers have difficulty believing they could fail so badly at seeing but also in the objective sense that these findings challenge many existing ideas about how we see. But as counterintuitive as these phenomena are, progress has been made in understanding them. Indeed, doing so has allowed us to better understand the limitations of human perception in everyday life and to gain new insights into how our visual systems create the picture of the world that we experience each moment our eyes are open. (shrink)

An overview is presented of the ways that change blindness has been applied to the study of various issues in perception and cognition. Topics include mechanisms of change perception, allocation of attention, nonconscious perception, and cognitive beliefs. Recent work using change blindness to investigate these topics is surveyed, along with a brief discussion of some of the ways that these approaches may further develop over the next few years.

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)

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)

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)

Our recent opinion article [1] examined what change blindness can and cannot tell us about visual representations. Among other things, we argued that change blindness can tell us a lot about how visual representations can be used, but little about their extent. We and others found the ‘sparse representations’ view appealing (and still do), and initially made the overly strong claim that change blindness supports the conclusion of sparse representations [2,3]. We wrote our article because change blindness continues to be (...) taken as evidence for sparse – or even absent – representations, and we used O’Regan and Noë’s influential paper [4] as an example. However, as has been noted for some time [5–8], this conclusion is logically flawed: lack of ability need not be caused by lack of representation. (shrink)

In this paper we examine to what extent the lengths of the links in an animated articulated figure can be changed without the viewer being aware of the change. This is investigated in terms of a framework that emphasizes the role of attention in visual perception. We conducted a set of five experiments to establish bounds for the sen-sitivity to changes in length as a function of several parameters and the amount of attention available. We found that while length changes (...) of 3% can be perceived when the relevant links are given full attention, changes of over 20% can go unnoticed when attention is not focused in this way. These results provide general guidelines for algorithms that produce or process character motion data and also bring to light some of the potential gains that stand to be achieved with attention-based algorithms. (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)

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)

This past decade has seen a great resurgence of interest in the perception of change. Change has, of course, long been recognized as a phenomenon worthy of study, and vision scientists have given their attention to it at various times in the past (for a review, see Rensink, 2002a). But things seem different this time around. This time, there is an emerging belief that instead of being just another visual ability, the perception of change may be something central to our (...) ‘visual life’, and that the mechanisms that underlie it may provide considerable insight into the operation of much of our visual system. This development may have been sparked by a number of factors: technology that allowed the easy creation of dynamic displays, a feeling in the air that it was time for something new, or it may have simply been a matter of chance. But once underway, this development was fueled by results, results that included both novel behavioral effects and new theoretical insights. Many of these centered around change blindness, the failure of observers to see large changes that are made contingent upon.. (shrink)

The capacity of visual attention/STM can be determined by change-detection experiments. Detecting the presence of change leads to an estimate of 4 items, while detecting the absence of change leads to an estimate of 1 item. Thus, there are two magical numbers in vision: 4 and 1. The underlying limits, however, are not necessarily those of central STM.

By spotlighting the irreducible role of cognitive processes between biology and culture, this synthesis and critique of the universalist tradition in colour science offers a genuine starting-point for all future 'serious inquiry into the relationship between linguistic and non-linguistic aspects of colour classification'.

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)

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)

Scene Perception is the visual perception of an environment as viewed by an observer at any given time. It includes not only the perception of individual objects, but also such things as their relative locations, and expectations about what other kinds of objects might be encountered. -/- Given that scene perception is so effortless for most observers, it might be thought of as something easy to understand. However, the amount of effort required by a process often bears little relation to (...) its underlying complexity. A closer look shows that scene perception is a highly complex activity, and that any account of it must deal with several difficult issues: What exactly is a scene? What aspects of it do we represent? And what are the processes involved? Finding the answers to these questions has proven to be extraordinarily difficult. (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)

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)

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)

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)

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)

High-level allocation of attention is required for detecting changes in images under ‘flicker’ conditions, ie when an original and a modified image are repetitively alternated, with a blank field between each display (R A Rensink, J K O'Regan, J J Clark, 1995 Perception24 Supplement, 26). But how many items can attention ‘grab’ and compare during each display? To determine this capacity, search experiments were carried out under flicker conditions, with displays formed of arrays of rectangles. In half the trials, displays (...) differed by the position of one of the rectangles; in the other half, displays remained the same. Subjects were asked to determine if a change was occurring between the two displays. Performance was measured for several durations of displays and blank fields. In all cases, search showed a clear serial deployment of attention. Comparing the rate of this deployment against the rate of display alternation yielded the number of items compared at a time. Results indicate that, for display durations of less than 100 ms, average capacity is about 1.5 items. Capacity increases somewhat with longer display times, indicating that more items can be stored with increasing display time, or that more items are being grouped into each attentional ‘operand’. (shrink)

My general worry is that Schellenberg’s arguments against naive realism, generalism, and Russellian representationalism do not seem to be successful. Thus her attempt at ruling these views out fails. Her main arguments rely on a shared premise whose plausibility, in the absence of an appropriate theory of particulars, is hard to assess (§2.1). Apart from that, these arguments rely on an under-specified notion of constitution; there seems to be no sense of the term that makes all the premises of her (...) major arguments true without trivializing their conclusions (§2.2). It also seems to me that the challenges that Schellenberg raises for her Russellian opponents, or similar problems, arise for her own view (§3). Finally, Schellenberg believes that an advantage of her view is that it entails the possibility of seeing an object without seeing it as being a certain way. In §4, I argue that it is hard to imagine how one could see without seeing as. (shrink)