Throughout the text, fundamental questions concerning the nature of visual perception are addressed.

Like most people, I used to think of my conscious life as like a stream of experiences, passing through my mind, one after another. But now I’m starting to wonder, is consciousness really like this? Could this apparently innocent assumption be the reason we find consciousness so baffling?

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)

O'Regan & Noë make plausible that perception involves mastery of sensory-motor dependencies. Their rejection of qualia, however, is less persuasive; as is their view that we see only what we are attending to. At times they seem to oppose “internal representation” in general; I argue that they should in fact only be rejecting crude conceptions of brain picturing.

Change blindness—our inability to detect changes in a stimulus—occurs even when the change takes place gradually, without disruption (Simons et al., 2000). Such gradual changes are more difficult to detect than changes that involve a disruption. In this experiment, we extend previous findings to the domain of facial expressions of emotions occurring in the context of a realistic scene. Even with changes occurring in central, highly relevant stimuli such as faces, gradual changes still produced high levels of change blindness: Detection (...) rates were three times lower for gradual changes than for displays involving disruption, with only 15% of the observers perceiving the gradual change within a single trial. However, despite this high rate of change blindness, changes on faces were significantly better detected than color changes occurring on non facial objects in the same scene. (shrink)

In recent years, a pair of intriguing phenomena has caused researchers working on vision and visual attention to reevaluate many of their assumptions. These phenomena, which have come to be called change blindness (CB) and inattentional blindness (IB), have led many to the conclusion that ordinary perceivers labor under a ``grand illusion'' concerning perception - an illusion that is..

One of the striking, even amusing, spectacles to be enjoyed at the many workshops and conferences on consciousness these days is the breathtaking overconfidence with which laypeople hold forth about the nature of consciousness Btheir own in particular, but everybody =s by extrapolation. Everybody =s an expert on consciousness, it seems, and it doesn =t take any knowledge of experimental findings to secure the home truths these people enunciate with such conviction.

Mack and Rock show evidence that no consciousperception occurs without a prior attentiveact. Subjects already executing attention taskstend to neglect visible elements extraneous tothe attentional task, apparently lacking evenbetter-than-chance ``implicit perception,''except in certain cases where the unattendedstimulus is a meaningful word or has uniquepre-tuned salience similar to that ofmeaningful words. This is highly consistentwith ``enactive'' notions that consciousnessrequires selective attention via emotional subcortical and limbic motivationalactivation as it influences anterior attentionmechanisms. Occipital activation withoutconsciousness suggests that motivated search,enacted through the organism's (...) subcorticalmotivational functions, is needed beforevisual stimulation engenders consciousness.This enactive view – that searching for,rather than receiving or processing input isthe basis of consciousness – was slow ingaining acceptance lacking empirical evidenceof this kind, combined with thestimulus-response assumption that brain eventssubserving perceptual consciousness must resultfrom transformation of perceptual input ratherthan from the organism's self-regulatedactivity as manifested through subcorticalactivity. Implicit perception occurring withword priming is ``paradoxical'' according to Mackand Rock, suggesting late selection forattention after extensive unconsciousprocessing, while most trials involvingnonverbal rather than verbal images mightsuggest earlier selection, sinceunattended objects are unseen, apparently evenimplicitly. This paper argues that anteriorand subcortical motivational mechanisms play animportant role in early selection; posteriormechanisms then unconsciously enhance signals;if data survive early gating andcorticothalamic enhancement, then still further anterior-limbic loops motivatedlyactivate ``image schemas'' resonating withposterior nonconscious processing; at thatpoint, consciousness occurs. (shrink)

& Awareness of change within a visual scene only occurs in subjects were aware of, replicated those attentional effects, but the presence of focused attention. When two versions of a.

Several recent findings support the notion that changes in the environment can be implicitly represented by the visual system. S. R. Mitroff, D. J. Simons, and S. L. Franconeri (2002) challenged this view and proposed alternative interpretations based on explicit strategies. Across 4 experiments, the current study finds no empirical support for such alternative proposals. Experiment 1 shows that subjects do not rely on unchanged items when locating an unaware change. Experiments 2 and 3 show that unaware changes affect performance (...) even when they occur at an unpredictable location. Experiment 4 shows that the unaware congruency effect does not depend simply on the pattern of the final display. The authors point to converging evidence from other methodologies and highlight several weaknesses in Mitroff et al.’s theoretical arguments. It is concluded here that implicit representation of change provides the most parsimonious explanation for both past and present findings. (shrink)

Evidence from many different paradigms (e.g. change blindness, inattentional blindness, transsaccadic integration) indicate that observers are often very poor at reporting changes to their visual environment. Such evidence has been used to suggest that the spatio-temporal coherence needed to represent change can only occur in the presence of focused attention. In four experiments we use modified change blindness tasks to demonstrate (a) that sensitivity to change does occur in the absence of awareness, and (b) this sensitivity does not rely on (...) the redeploy- ment of attention. We discuss these results in relation to theories of scene percep- tion, and propose a reinterpretatio n of the role of attention in representing change. (shrink)

I contend that Alva Noë’s Enactive Approach to Perception fails to give an adequate account of the periphery of attention. Noë claims that our peripheral experience is not produced by the brain’s representation of peripheral items, but rather by our mastery of sensorimotor skills and contingencies. I offer a two-pronged assault on this account of the periphery of attention. The first challenge comes from Mack and Rock’s work on inattentional blindness, and provides robust empirical evidence for the semantic processing (and (...) hence representation) of some wholly unattended stimuli. The second challenge draws on LaBerge’s theory of attention to provide a substantial advantage to peripheral representations, saving time whenever we shift the focus of our attention to something which had been in the periphery, allowing us to respond to that thing more quickly than would be possible if Noë’s account of perception were correct. (shrink)

In response to new research into the phenomena of inattentional blindness and change- blindness, several philosophers and vision researchers have proposed a novel form of scepticism: they contend that we do not have the conscious experience that we think we have. I will show that this claim is not supported by the evidence usually cited in support of it, and I expose what I believe to be the underlying error motivating this position: the belief that consciousness is either focal (what (...) occupies the focus of attention) or non- existent. Once we appreciate the phenomenology of the periphery of attention, we see that we have the resources to place the problematic phenomena in our peripheral. (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)

Change blindness—our inability to detect changes in a stimulus—occurs even when the change takes place gradually, without any disruption (Simons et al., 2000). Such gradual changes are more difficult to detect than changes that involve a disruption. Using this method, David et al. (in press) recently showed substantial blindness to changes that involve facial expressions of emotion. In this experiment, we show that people who failed to detect any change in the displays were (1) nevertheless influenced by the changing information (...) in subsequent recognition decisions about which facial expression they had seen, and (2) that their confidence in their decisions was lower after exposure to changing vs. static displays. The findings therefore support the notion that undetected changes that occur in highly salient stimuli may be causally efficacious and influence subsequent behaviour. Implications concerning the nature of the representations associated with undetected changes are discussed. (shrink)

In O'Regan & Noë's (O&N's) account for the phenomenal experience of seeing, awareness is equated to what is within the current focus of attention. They find no place for a distinction between phenomenal and access awareness. In doing so, they essentially present a dualistic solution to the mind-brain problem, and ignore that we do have phenomenal experience of what is outside the focus of attention.

This paper investigates a new species of skeptical reasoning about visual experience that takes its start from developments in perceptual science (especially recent work on change blindness and inattentional blindness). According to this skepticism, the impression of visual awareness of the environment in full detail and high resolution is illusory. I argue that the new skepticism depends on misguided assumptions about the character of perceptual experience, about whether perceptual experiences are 'internal' states, and about how best to understand the relationship (...) between a person's or animal's perceptual capacities and the brain-level or neural processes on which they depend. I propose a conception of perceptual experience as a form of skillful engagement with the environment on the part of the whole person or animal. (shrink)

This paper looks at two puzzles raised by the phenomenon of inattentional blindness. First, how can we see at all if, in order to see, we must first perceptually attend to that which we see? Second, if attention is required for perception, why does it seem to us as if we are perceptually aware of the whole detailed visual field when it is quite clear that we do not attend to all that detail? We offer a general framework for thinking (...) about perception and perceptual consciousness that addresses these questions and we propose, in addition, an informal account of the relation between attention and consciousness. On this view, perceptual awareness is a species of attention. (shrink)

Experiments on scene perception and change blindness suggest that the visual system does not construct detailed internal models of a scene. These experiments therefore call into doubt the traditional view that vision is a process in which detailed representations of the environment must be constructed. The non-existence of such detailed representations, however, does not entail that we do not perceive the detailed environment. The “grand illusion hypothesis” that our visual world is an illusion rests on (1) a problematic “reconstructionist” conception (...) of vision, and (2) a misconception about the character of perceptual experience. (shrink)

Recent results showing that large changes in a scene are not noticed if they occur at the same time as a global visual disturbance caused by saccades, flicker, "mudsplashes", or film cuts, are generally explained in terms of a theory in which it is assumed that the observer's internal representation of the outside world is very sparse, containing only what the observer is currently processing. The present paper presents some clarifications of the theory, and some new implications and predictions that (...) arise from it. (shrink)

Any theory of experience which postulates that brain mechanisms generate "raw feel" encounters the impassable "explanatory gap" separating physics from phenomenology.

Recently a number of studies have shown that under certain circumstances, very large changes can be made in a picture without observers noticing them. What characterizes the experiments showing such "Change Blindness" in visual scenes is the fact that the changes are arranged to occur simultaneously with some kind of extraneous, brief disruption in visual continuity, such as the large retinal disturbance produced by an eye saccade, a shift of the picture, a brief flicker, a "mudsplash", an eye blink, or (...) a film cut in a motion picture sequence. These phenomena are attracting an increasing amount of attention from experimental psychologists and from philosophers, because they suggest that humans' internal representation of the visual world is much sparser than usually thought. (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.

Experiments on scene perception and change blindness suggest that the visual system does not construct detailed internal models of a scene. These experiments therefore call into doubt the traditional view that vision is a process in which detailed representations of the environment must be constructed. The non-existence of such detailed representations, however, does not entail that we do not perceive the detailed environment. The “grand illusion hypothesis” that our visual world is an illusion rests on (1) a problematic “reconstructionist” conception (...) of vision, and (2) a misconception about the character of perceptual experience. (shrink)

The contributors to this volume seek to answer this question by exploring how analytic and holistic processes contribute to our perception of faces, objects, ...

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.

A striking blindness to changes in real-world scenes can be induced using a variety of techniques (e.g., saccade-, blink-, or flicker-contingent change). The strength and robustness of this phenomenon points towards the involvement of mechanisms central to visual perception. It is proposed here that this induced change blindness can be explained by an..

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.

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 front of them. 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 proposal 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)

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)

Methods. We employed a "flicker" technique, in which an original and a modified image (each of duration 240 ms) continually alternated, with a blank field (duration 80 ms) between each display. Images were all of real-world scenes. One of three kinds of change (appearance/disappearance, color, or translation) was made to an object or region in each scene. Changes were large and easily seen under normal conditions. Subjects viewed the flicker display, and pressed a key when they noticed the change.

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)

We suggest that the sensorimotor “theory” of vision is really an unstructured collection of separate ideas, and that much of the evidence cited in its favor at best supports only a subset of these ideas. As an example, we note that work on change blindness does not “vindicate” (or even speak to) much of the sensorimotor framework. Moreover, the ideas themselves are not always internally consistent. Finally, the proposed framework draws on ideas initially espoused by James Gibson, but does little (...) to differentiate itself from those earlier views. For even part of this framework to become testable, it must specify which sources of evidence can support or contradict each of the component hypotheses. (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)

b>—Several paradigms (e.g. change blindness, inattentional blindness, transsaccadic integra- tion) indicate that observers are often very poor at reporting changes to their visual environment. Such evidence has been used to suggest that the spatio-temporal coherence needed to represent change can only occur in the presence of focused attention. However, those studies almost always rely on explicit reports. It remains a possibility that the visual system can implicitly detect change, but that in the absence of focused attention, the change does not (...) reach awareness and consequently is not reported. To test this possibility, we used a simple change detection paradigm coupled with a speeded orien- tation discrimination task. Even when observers reported being unaware of a change in an item’s orientation, its nal orientation effectively biased their response in the orientation discrimination task. Both in aware and unaware trials, errors were most frequent when the changed item and the probe had incongruent orientations. These results demonstrate that the _nature _of the change can be represented in the absence of awareness. (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)

In this paper I argue that a recently discovered set of visual illusions sheds new light on the nature of time consciousness. In particular, I argue that these illusions put strong pressure on a view I call Temporal Atomism that otherwise might have seemed quite attractive. According to temporal atomism if you were to fix which non-temporal properties are experienced as well as the temporal properties of your experience itself, you would also have fixed which temporal properties are experienced. While (...) it has been claimed before that views like temporal atomism are confused, and face conceptual as well as empirical problems, my argument based on the newly discovered illusions provides a new and more straightforward challenge: temporal atomism either has to give up its crucial motivations, or it can not even so much as make sense of the content of the subject’s visual experience. I end with brief suggestions concerning how the results of this paper bears on further philosophical debates about time consciousness, change blindness, and the role of attention in perceptual experience. (shrink)