Online research in philosophy

I propose a new argument showing that conscious vision sometimes depends constitutively on conscious attention. I criticise traditional arguments for this constitutive connection, on the basis that they fail adequately to dissociate evidence about visual consciousness from evidence about attention. On the same basis, I criticise Ned Block's recent counterargument that conscious vision is independent of one sort of attention (‘cognitive access'). Block appears to achieve the dissociation only because he underestimates the indeterminacy of visual (...) consciousness. I then appeal to empirical work on the interaction between visual indeterminacy and attention, to argue for the constitutive connection. (shrink)

Reflection on the fine-grained information required for visual guidance of action has suggested that visual content is non-conceptual. I argue that in a common type of visually guided action, namely the use of manipulable artefacts, vision has conceptual content. Specifically, I show that these actions require visual attention and that concepts are involved in directing attention. In acting with artefacts, there is a way of doing it right as determined by the artefact’s conventional use. (...) class='Hi'>Attention must reflect our understanding of the function and appropriate ways to use these artefacts, understanding that requires possession of the relevant concept. As a result, we attend to the artefact’s relevant functional properties. In these cases, attention is structured by concepts. This discussion has a bearing on the dual visual stream hypothesis. While it is often held that the two visual streams are functionally independent, the argument of this essay is that the constraints on attention suggest a functional interaction between them. (shrink)

Although much of vision appears to be effortless and all-encompassing, there nevertheless exist limits to what it can do. Consider, for example, air traffic control, where it is imperative to keep track of all moving items in a display (corresponding to the airplanes in an airspace). If only a single item is present, it can generally be tracked without problem. It is also possible to track four or five items simultaneously, although some effort is needed. But for twenty or thirty (...) items, even a maximal effort will not suffice, and the task must be shared among several controllers. What appears to be happening in such cases is that visual perception is constrained by a consciously-controlled factor within the observer, a factor that enables certain kinds of processing to take place, but which is limited in the extent to which it can be applied. This factor is referred to as visual attention. (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 nature of attention is one of the oldest and most central problems in psychology. A huge amount of research has been produced on this subject in the last half century, especially on attention in the visual modality, but a general explanation has remained elusive. Many still view attention research as a field that is fundamentally fragmented. This book takes a different perspective and presents a unified theory of visual attention: the TVA model. The (...) TVA model explains the many aspects of visual attention by just two mechanisms for selection of information: filtering and pigeonholing. These mechanisms are described in a set of simple equations, which allow TVA to mathematically model a large number of classical results in the attention literature. The theory explains psychological and neuroscientific findings by the same equations; TVA is a complete theory of visual attention, linking mind and brain. Aimed at advanced students and professional researchers, Principles of Visual Attention contains a detailed review of the most important research done on attention in vision, spanning cognitive psychology, brain imaging, patient studies, and recordings from single cells in the visual cortex. The book explains the TVA model and shows how it accounts for attentional effects observed across all the research areas described. Principles of Visual Attention offers a uniquely integrated view on a central topic in cognitive neuroscience. (shrink)

Models of saccade generation and visual selective attention must explain how and why particular targets are selected. Findlay & Walker do an excellent job of explaining the how of visual selection, but not the why. For a salience map to be more than a description of the relative importance of potential targets, there must be some account of the learning and inheritance that fashion its peaks and troughs. Point of gaze is not necessarily region of attention, (...) and it may be premature to downgrade the role of covert attention in models of visual selection. (shrink)

The systematic review of key topics and the multitude of perspectives make this book an ideal primary or ancillary text for graduate courses in perception, vision, consciousness, or philosophy of mind.

John Campbell argues that visual attention to objects is the means by which we can refer to objects, and that this is so because conscious visual attention enables us to retrieve information about a location. It is argued here that while Campbell is right to think that we visually attend to objects, he does not give us sufficient ground for thinking that consciousness is involved, and is wrong to assign an intermediary role to location. Campbell’s view (...) on sortals is also queried, as is his espousal of the so-called Referential View of Experience. (shrink)

As many as two million people in the United Kingdom repeatedly see people, animals, and objects that have no objective reality. Hallucinations on the border of sleep, dementing illnesses, delirium, eye disease, and schizophrenia account for 90% of these. The remainder have rarer disorders. We review existing models of recurrent complex visual hallucinations (RCVH) in the awake person, including cortical irritation, cortical hyperexcitability and cortical release, top-down activation, misperception, dream intrusion, and interactive models. We provide evidence that these can (...) neither fully account for the phenomenology of RCVH, nor for variations in the frequency of RCVH in different disorders. We propose a novel Perception and Attention Deficit (PAD) model for RCVH. A combination of impaired attentional binding and poor sensory activation of a correct proto-object, in conjunction with a relatively intact scene representation, bias perception to allow the intrusion of a hallucinatory proto-object into a scene perception. Incorporation of this image into a context-specific hallucinatory scene representation accounts for repetitive hallucinations. We suggest that these impairments are underpinned by disturbances in a lateral frontal cortex–ventral visual stream system. We show how the frequency of RCVH in different diseases is related to the coexistence of attentional and visual perceptual impairments; how attentional and perceptual processes can account for their phenomenology; and that diseases and other states with high rates of RCVH have cholinergic dysfunction in both frontal cortex and the ventral visual stream. Several tests of the model are indicated, together with a number of treatment options that it generates. Key Words: Blindness; Charles Bonnet; cholinergic; cortical release; delirium; dementia; dream intrusion; hallucination; Perception and Attention Deficit (PAD) model; schizophrenia. (shrink)

Commentators agree that the Perception and Attention Deficit (PAD) model is a promising model for accounting for recurrent complex visual hallucinations (RCVH) across several disorders, though with varying detailed criticisms. Its central tenets are not modified, but further consideration of generative models of visual processing and the relationship of proto-objects and memory systems allows the PAD model to deal with variations in phenomenology. The commentaries suggest new ways to generate evidence that will test the model.

Unilateral neglect stems from a relatively selective impairment of exogenous, or stimulus-related, orienting of attention. This neuropsychological evidence parallels “change blindness” experiments, in which normal individuals lack awareness of salient details in the visual scene as a consequence of their attention being exogenously attracted by a competing event, suggesting that visual consciousness requires the integrity of exogenous orienting of attention.

This book contains a rich, interdisciplinary collection of articles by some of the pioneers of contemporary research on attention.

The Perception and Attention Deficit (PAD) model of visual hallucinations is as limited in generality as other models. It does, however, raise an interesting hypothesis on the role of attentional biases among proto-objects. The prediction that neither impaired attention nor impaired sensory activation alone will produce hallucinations should be addressed in future studies by analysing partial correlations between putative causes and hallucinatory effects.

In three experiments, participants' visual span was measured in a comparative visual search task in which they had to detect a local match or mismatch between two displays presented side by side. Experiment 1 manipulated the dif®culty of the comparative visual search task by contrasting a mismatch detection task with a substantially more dif®cult match detection task. In Experiment 2, participants were tested in a single-task condition involving only the visual task and a dual-task condition in (...) which they concurrently performed an auditory task. Finally, in Experiment 3, participants performed two dual-task conditions, which differed in the dif®culty of the concurrent auditory task. Both the comparative search task dif®culty (Experiment 1) and the divided attention manipulation (Experiments 2 and 3) produced strong effects on visual span size. q 2001 Elsevier Science B.V. All rights reserved. (shrink)

A common objection to representationalism is that a representationalist view of phenomenal character cannot accommodate the effects that shifts in covert attention have on visual phenomenology: covert attention can make items more visually prominent than they would otherwise be without altering the content of visual experience. Recent empirical work on attention casts doubt on previous attempts to advance this type of objection to representationalism and it also points the way to an alternative development of the (...) objection. (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.

This somewhat odd paper argues against a representational view of visual experience using an intricate "inversion" type thought experiment involving double vision: two subjects could represent external space in the same way while differing phenomenally due to different "spread" in their double images. The spatial structure of the visual field is explained not by representation of external space but functionally, in terms of the possible locations of an attentional spotlight. -/- I'm fond of the ideas in this paper (...) but doubt I'll be returning to it soon. (shrink)

'Epistemological constructivism' holds that vision is mediated by background preconceptions and is theory-laden. Hence, two persons with differing theoretical commitments see the world differently and they could agree on what they see only if they both espoused the same conceptual framework. This, in its turn, undermines the possibility of theory testing and choice on a common theory-neutral empirical basis. In this paper, I claim that the cognitive sciences suggest that a part of vision may be only indirectly penetrated by cognition (...) in a way that does not threaten retrieval of information from a visual scene in a bottom-up way. That blocks the constructivist epistemological thesis. However, since spatial attention, which can be cognitively driven, seems to permeate all stages of visual processes, one is led to conclude that there is no part of vision immune to direct cognitive interference. Against this, I elaborate on the role of spatial attention and argue that it does influence vision in a top-down manner, but it does so only in an indirect way. I then argue that the existence of visual processes that are only indirectly penetrated by cognition undermines the epistemological conclusions of constructivism. (shrink)

We tested Collerton et al.'s model of visual hallucinations by re-examining a data set for correlations between visual hallucinations and measures of attentional function in schizophrenia patients. These data did not support their model. We suggest that cortical hyperexcitability plays an important role in hallucinations, and propose an alternative model that links evidence for cortical hyperexcitability with abnormal neural dynamics.

Pylyshyn's effort in establishing the cognitive impenetrability of early vision is welcome. However, his view about the role of attention in early vision seems to be oversimplified. The allocation of focal attention manifests its effect among multiple stages in the early vision system, it is not just confined to the input and the output levels.

We assemble here in this time and place to discuss the thesis that conscious attention can provide knowledge of reference of perceptual demonstratives. I shall focus my commentary on what this claim means, and on the main argument for it found in the first five chapters of Reference and Consciousness. The middle term of that argument is an account of what attention does: what its job or function is. There is much that is admirable in this account, and (...) I am confident that it will be the foundation, the launching-pad, for much future work on the subject. But in the end I will argue that Campbell’s picture makes the mechanisms of attention too smart: smarter than they are, smarter than they could be. If we come to a more realistic appraisal of the skills and capacities of our sub-personal minions, the “knowledge of reference” which they yield will have to be taken down a notch or two. (shrink)

I have two goals in this paper. First, I want to show by example that inferences about theoretical entities are relatively contingent affairs. Previously accepted conceptual metaphors in science set both the general form of new theories and our acceptance of the theories as plausible. In addition, they determine how we define the relevant parameters in investigating phenomena in the first place. These items then determine how we conceptualize things in the world. Second, and maybe more importantly, I want to (...) solve a puzzle that falls out of our current explication of attention, namely why we have it. Given the now widely accepted view that our brains are massively parallel, it is difficult to see why we should have evolved attentional mechanisms at all. Why gate when we can already process what we transduce in parallel? Here I answer that puzzle and suggest a perspective on attention that makes it a bit easier to understand, although this perspective also entails that we have to revise how we individuate experimental protocols and relevant data. (shrink)

This study investigated attention to a spatial location using a new spatial preparation task. Participants responded to a target dot presented in the center of a display and ignored a distractor dot presented to the right or left of the center. In an attempt to vary the level of preparatory attention directed to the target, the distractor dot was presented prior to the onset time of the target and the relative frequency of distractor dots to target dots within (...) a block of trials was varied. The results from the first three experiments showed that when instructions induce weak preparatory attention to the target location, response times to a target on target-only trials increase substantially as the percentage of trials containing a distractor increases from 0 to 75%. In Experiments 2 and 3, instructions and display saliency were used to induce strong preparatory attention to the target location, resulting in almost constant response times across distractor percentages. Experiment 4 varied percentage of target trials in the absence of distractors, with the result that response times decreased as target trial percentage increased. Accounts of these data by early ''activity-based'' and late ''criterion-based'' attention theories are compared, and the early theory is given a more detailed description within the context of a cognitive neuroscience theory of attention. (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)

John McDowell (in Mind and World) and Bill Brewer (in Perception and Reason) argue that the content of our perceptual experience is conceptual in the following sense. It is of the type of content that could be the content of a judgement – that is, a content which results from the actualization of two (or more) conceptual abilities. Specifically, they suggest that the conceptual abilities actualized in experience are demonstrative abilities, and thus the resulting content is of the type we (...) may express by means of sentences of the form ‘this is thus’. In this paper I argue that we cannot construe experiential contents in this way. I first outline a construal of the ability to think about a thing being thus which is based on Brewer's discussion of conceptual experiential contents, and which I take to be the best construal available to the conceptualist. I then show that on this construal the demonstrative abilities that account for our experience of properties require intentional focused attention to the relevant properties. The conceptualist is thus committed to holding that we experience only the properties we are intentionally attending to, and I argue that this is implausible. The interest in examining Brewer's conceptualist construal of experiential content and pointing out its shortcoming is not limited merely to an interest in whether there is a workable conceptualist account of experiential content. I suggest that certain aspects of Brewer's construal capture important (and often neglected) aspects of our perceptual experience, and that understanding why the account fails can contribute to our understanding of both experiential content and demonstrative thought. (shrink)

I present an account of how agents can know what they are doing when they intentionally execute object-oriented actions. When an agent executes an object-oriented intentional action, she uses perception in such a way that it can fulfil a justificatory role for her knowledge of her own action and it can fulfil this justificatory role without being inferentially linked to the cognitive states that it justifies. I argue for this proposal by meeting two challenges: in an agent's knowledge of her (...) action perception can only play an enabling role (and no justificatory role) for the agent's knowledge and if perception has a justificatory role, then the agent's knowledge must be inferential. (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)

A “multifactorial” model should accommodate a psychological perspective, aiming to relate the phenomenology of complex visual hallucinations not only to neurobiological findings but also an understanding of the patient's psychological problems and situation in life. Greater attention needs to be paid to the role of the “lack of insight” patients may have into their hallucinations and its relationship to cognitive impairment.

Reply to John Campbell's contribution to a symposium on *The Contents of Visual Experience*.

This paper examines the status of unattended visual stimuli in the light of recent work on the role of attention in visual perception. Although the question of whether attention is required for visual experience seems very interesting, this paper argues that there currently is no good reason to take a stand on the issue. Moreover, it is argued that much of the allure of that question stems from a continued attachment to the defective ‘inner picture (...) view’ of experience and a mistaken notion that the ultimate goal of vision is to produce visual experience. The paper considers a promising general account of the content and structure of vision and presents reasons for not taking that account to be committed to any substantive claims about the experiential status of unattended visual stimuli. Also addressed are the active nature of vision and the role of vision in enabling our ecological success. These considerations highlight that visual experience is not the whole of vision and that a much more important question about unattended visual stimuli than whether they are consciously experienced is what contribution they make to how we interact with the world. (shrink)

A range of arguments are presented to demonstrate that (1) human visual orientations are conceptually constituted (concept?bound); (2) the concept?boundedness of visual orientations does not require a cognitivist account according to which a mental process of ?inference? or of ?interpretation? must be postulated to accompany a purely ?optical? registration of ?wavelengths of light?, ?photons?, or contentless ?information'; (3) concept?bound visual orientations are not all instances of ?seeing as?, contrary to some currently prominent cognitivist accounts; (4) the dispute (...) between cognitivist and realist accounts about the phenomenon of ?seeing as? is spurious, and is based upon a confusion about the fundamental analytical distinction made by Wittgenstein between ?seeing? and ?seeing as'; (5) ?perceiving?, ?seeing?, and ?seeing as? are but three of a large array of verbs of human visual orientation, and are not ?master categories? under which one can subsume these other modalities; (6) one cannot deduce a continuity of human visual orientation from a continuity of photon?photoreceptor interaction, a point we characterize as the ?staggered character? of human visual orientations; (7) detailed attention to the grammars of the diverse verbs of human visual orientation can open up a domain of study which we here refer to as a ?praxiology of perception'; (8) the nature of such an inquiry can be illustrated with exemplary reference to the analysis of the properties of ?noticing? as embedded in courses of practical action; and (9) such arguments, which claim that existing perceptual theories overly homogenize what is involved in visual orientations to the world, parallel those of Stroll, who proposes that standard accounts of ?what is perceived? overly homogenize the perceptible environment. (shrink)

The oral eye is a metaphor for the dominance of global designer capitalism. It refers to the consumerism of a designer aesthetic by the ‘I’ of the neoliberalist subject, as well as the aural soundscapes that accompany the hegemony of the capturing attention through screen cultures. An attempt is made to articulate the historical emergence of such a synoptic machinic regime drawing on Badiou, Bellmer, Deleuze, Guattari, Lacan, Rancière, Virilio, Ziarek, and Žižek to explore contemporary art (post-Situationism) and (...) class='Hi'>visual cultural education. jagodzinski develops the concept of an ‘avant-garde without authority,’ ‘self-refleXion’ and ‘in(design)’ to further the questions surrounding the posthuman as advanced by theorists such as Hansen, Stiegler and Ziarek’s ‘force’ of art. (shrink)

The “top-down” and “bottom-up” approaches have been thought to exhaust the possibilities for doing cognitive neuroscience. We argue that neither approach is likely to succeed in providing a theory that enables us to understand how cognition is achieved in biological creatures like ourselves. We consider a promising third way of doing cognitive neuroscience, what might be called the “neural dynamic systems” approach, that construes cognitive neuroscience as an autonomous explanatory endeavor, aiming to characterize in its own terms the states and (...) processes responsible for brain-based cognition. We sketch the basic motivation for the approach, describe a particular version of the approach, so-called ‘Dynamic Causal Modeling’ (DCM), and consider a concrete example of DCM. This third way, we argue, has the potential to avoid the problems that afflict the other two approaches. (shrink)

Recent developments in psychology and neuroscience suggest away to link the mental phenomenon of visual awareness with specific neural processes. Here, it is argued that the feed-forward activation of cells in any area of the brain is not sufficient to generate awareness, but that recurrent processing, mediated by horizontal and feedback connections is necessary. In linking awareness with its neural mechanisms it is furthermore important to dissociate phenomenal awareness from visual attention or decision processes.

Mole's (2008 [this issue]) argument that consciousness is a necessary concomitant of attention rests on the question of what is being attended in spatial attention. His answer is space. Some authors, including ourselves, claim that the fact that the processing of unseen objects can be modulated by spatial attention (e.g. Kentridge et al., 1999; 2004; 2008; Marzouki et al., 2007; Sumner et al., 2006) demonstrates that visual attention is not a sufficient precondition for visual (...) awareness. Mole, however, contends that as space, rather than any object that might occupy that space, is what is being attended, these experiments do not constitute evidence for a dissociation between attention and consciousness. We disagree. To understand the source of this disagreement we need to understand the various processes encompassed by the term 'attention' and to consider experimental evidence illustrating how these processes operate. We review evidence that spatial attention can be deployed with the specific goal of determining the properties of objects occupying the attended region of space. One might, for example, attend to a location with the goal of determining the colour of objects occupying that space as efficiently as possible. Mole's assumption that all that is attended in spatial attention is space is not consistent with this evidence. We conclude that attention can be directed at objects by mechanisms of so- called 'spatial attention' without those objects necessarily eliciting conscious visual experience and hence that attention is not a sufficient precondition for visual awareness. (shrink)

Recent advances in our understanding of visual perception have shown it to be a far more complex and counterintuitive process than previously believed. Several important consequences follow from this. First, the design of an effective statistical graphics system is unlikely to succeed based on intuition alone; instead, it must rely on a more sophisticated, systematic approach. The basic elements of such an approach are outlined here, along with several design principles. An overview is then given of recent advances in (...) our understanding of visual perception, including rapid perception, visual attention, and scene perception. It then is argued that the mechanisms involved can be successfully harnessed to allow data to be displayed more effectively than at present. Several directions of development are discussed, including effective use of visual attention, the display of dynamic information, and the effective use of nonattentional and nonconscious perceptual systems. (shrink)

Recent neural models clarify many properties of mental imagery as part of the process whereby bottom-up visual information is influenced by top-down expectations, and how these expectations control visual attention. Volitional signals can transform modulatory top-down signals into supra-threshold imagery. Visual hallucinations can occur when the normal control of these volitional signals is lost.

Corballis suggests that apes lack voluntary control over their vocal production. However, recent evidence implicates voluntary control of vocalizations in apes, which suggests that intentional control of vocal communication predates the hominid-pongid split. Furthermore, the ease with which apes in captivity manipulate the visual attention of observers implies a common cognitive basis for joint attention in humans and apes.

The notion that visual attention can operate over visual objects in addition to spatial locations has recently received much empirical support, but there has been relatively little empirical consideration of what can count as an `object' in the ®rst place. We have investi- gated this question in the context of the multiple object tracking paradigm, in which subjects must track a number of independently and unpredictably moving identical items in a ®eld of identical distractors. What types of (...) feature clusters can be tracked in this manner? In other words, what counts as an `object' in this task? We investigated this question with a technique we call target merging: we alter tracking displays so that distinct target and distractor loca- tions appear perceptually to be parts of the same object by merging pairs of items (one target with one distractor) in various ways ± for example, by connecting item locations with a simple line segment, by drawing the convex hull of the two items, and so forth. The data show that target merging makes the tracking task far more dif®cult to varying degrees depending on exactly how the items are merged. The effect is perceptually salient, involving in some conditions a total destruction of subjects' capacity to track multiple items. These studies provide strong evidence for the object-based nature of tracking, con®rming that in some contexts attention must be allocated to objects rather than arbitrary collections of features. In addition, the results begin to reveal the types of spatially organized scene components that can be independently attended as a function of properties such as connectedness, part struc- ture, and other types of perceptual grouping. q 2001 Elsevier Science B.V. All rights reserved. (shrink)

Most everyday tasks involve multiple modalities, which raises the question of how the processing of these modalities is coordinated by the cognitive system. In this paper, we focus on the coordination of visual attention and linguistic processing during speaking. Previous research has shown that objects in a visual scene are fixated before they are mentioned, leading us to hypothesize that the scan pattern of a participant can be used to predict what he or she will say. We (...) test this hypothesis using a data set of cued scene descriptions of photo-realistic scenes. We demonstrate that similar scan patterns are correlated with similar sentences, within and between visual scenes; and that this correlation holds for three phases of the language production process (target identification, sentence planning, and speaking). We also present a simple algorithm that uses scan patterns to accurately predict associated sentences by utilizing similarity-based retrieval. (shrink)

Because the visual system cannot process all of the objects, colors, and features present in a visual scene, visual attention allows some visual stimuli to be selected and processed over others. Most research on visual attention has focused on spatial or location-based attention, in which the locations occupied by stimuli are selected for further processing. Recent research, however, has demonstrated the importance of objects in organizing (or segregating) visual scenes and guiding (...) attentional selection. Because of the long history of spatial attention research, theories of spatial attention are more mature than theories of other visual processes, such as object segregation and object attention. In the present paper, I outline a biased competition account of object segregation and attention, following similar accounts that have been developed for spatial attention (Desimone and Duncan, 1995). In my biased competition account, I seek to understand how some objects can be segregated and selected over other objects in a complex visual scene. Under this account, there are two sources of visual information that allow an object to be processed over other objects: bottom-up information carried by the physical stimulus and top-down information based on an observer's goals. I use the biased competition account to combine many diverse findings from the object segregation and attention literatures into a common framework. (shrink)

In three experiments, subjects attempted to track multiple items as they moved independently and unpredictably about a display. Performance was not impaired when the items were briefly (but completely) occluded at various times during their motion, suggesting that occlusion is taken into account when computing enduring perceptual objecthood. Unimpaired performance required the presence of accretion and deletion cues along fixed contours at the occluding boundaries. Performance was impaired when items were present on the visual field at the same times (...) and to the same degrees as in the occlusion conditions, but disappeared and reappeared in ways which did not implicate the presence of occluding surfaces (e.g. by imploding and exploding into and out of existence, instead of accreting and deleting along a fixed contour). Unimpaired performance did not require visible occluders (i.e. Michotte’s tunnel effect) or globally consistent occluder positions. We discuss implications of these results for theories of objecthood in visual attention. (shrink)

Inverting a face impairs perception of its features and recognition of its identity. Whether faces are special in this regard is a current topic of research and debate. Kanizsa studied the role of facial features and environmental context in perceiving the emotion and identity of upright and inverted faces. He found that observers are biased to interpret faces in a retinal coordinate frame, and that this bias is readily overruled by increased realism of facial features, but not easily overruled by (...) environmental context. An additional factor contributing to a retinal coordinate-frame interpretation may be the ambiguous nature of the face stimuli. Since his facial expressions are interpretable both upright and inverted, they may in both orientations activate an endogenous attentional process for faces. We present visual search and change-blindness experiments that explore how inversion, negation, and facial emotion affect visual attention to static faces. We find that attention to faces is impaired by inversion and negation. We also find that the parts of the face that receive greater attention can be influenced by the emotional expression of the face. We propose to extend these experiments to dynamic faces. To this end, we develop a theory of the visual representation of dynamic faces, in which faces are represented by classes of `spacetime fragments'-moving regions of the face with high informational content. We then present ideas for future experiments which are motivated by the spacetime fragment theory, and which should serve to constrain its further development. (shrink)

This commentary considers experimental material – some new, some from earlier studies – challenging the model presented by Findlay & Walker. It concentrates on the role of voluntary and involuntary visual attention versus fixation in saccade control and on the generation of antisaccades, reflexive prosaccades, and corrective saccades. The data of a large number of subjects are presented to show the systematic relationship between voluntary saccade generation, error production, and error correction in an antisaccade task.

The notion that visual attention can operate over visual objects in addition to spatial locations has recently received much empirical support, but there has been relatively little empirical consideration of what can count as an `object' in the ®rst place. We have investigated this question in the context of the multiple object tracking paradigm, in which subjects must track a number of independently and unpredictably moving identical items in a ®eld of identical distractors. What types of feature (...) clusters can be tracked in this manner? In other words, what counts as an `object' in this task? We investigated this question with a technique we call target merging: we alter tracking displays so that distinct target and distractor locations appear perceptually to be parts of the same object by merging pairs of items (one target with one distractor) in various ways ± for example, by connecting item locations with a simple line segment, by drawing the convex hull of the two items, and so forth. The data show that target merging makes the tracking task far more dif®cult to varying degrees depending on exactly how the items are merged. The effect is perceptually salient, involving in some conditions a total destruction of subjects' capacity to track multiple items. These studies provide strong evidence for the object-based nature of tracking, con®rming that in some contexts attention must be allocated to objects rather than arbitrary collections of features. In addition, the results begin to reveal the types of spatially organized scene components that can be independently attended as a function of properties such as connectedness, part structure, and other types of perceptual grouping. q 2001 Elsevier Science B.V. All rights reserved. (shrink)

Pylyshyn claims that if a system is cognitively penetrable, its function depends in a semantically coherent way to the organism's goals and beliefs. He rejects evidence of attentional modulation observed in neurons within the visual system, claiming that any modulation seen is not logically related to goals and behavior. I present some of this evidence and claim that it is connected in exactly the way Pylyshyn requires and thus it refutes his main thesis.

Although the study of visual perception has made more progress in the past 40 years than any other area of cognitive science, there remain major disagreements as to how closely vision is tied to general cognition. This paper sets out some of the arguments for both sides (arguments from computer vision, neuroscience, Psychophysics, perceptual learning and other areas of vision science) and defends the position that an important part of visual perception, which may be called early vision or (...) just vision, is prohibited from accessing relevant expectations, knowledge and utilities - in other words it is cognitively impenetrable. That part of vision is complex and articulated and provides a representation of the 3-D surfaces of objects sufficient to serve as an index into memory, with somewhat different outputs being made available to other systems such as those dealing with motor control. The paper also addresses certain conceptual and methodological issues, including the use of signal detection theory and event-related potentials to assess cognitive penetration of vision. A distinction is made among several stages in visual processing. These include, in addition to the inflexible early-vision stage, a pre-perceptual attention allocation stage and a post-perceptual evaluation, memory-accessing, and inference stage which provide several different highly constrained ways in which cognition can affect the outcome of visual perception. The paper discusses arguments that have been presented in both computer vision and psychology showing that vision is "intelligent" and involves elements of problem solving". It is suggested that these cases do not show cognitive penetration, but rather they show that certain natural constraints on interpretation, concerned primarily with optical and geometrical properties of the world, have been compiled into the visual system. The paper also examines a number of examples where instructions and "hints" are alleged to affect. (shrink)

This chapter argues that attention is a distinctive mode of consciousness, which plays an essential functional role in making information accessible for use in the rational control of thought and action. The main line of argument can be stated quite simply. Attention is what makes information fully accessible for use in the rational control of thought and action. But what makes information fully accessible for use in the rational control of thought and action is a distinctive mode of (...) consciousness. Therefore, attention is a distinctive mode of consciousness. In a slogan: attention is rational-access consciousness. (shrink)

This paper defends and develops the structuring account of conscious attention: attention is the conscious mental process of structuring one’s stream of consciousness so that some parts of it are more central than others. In the first part of the paper, I motivate the structuring account. Drawing on a variety of resources I argue that the phenomenology of attention cannot be fully captured in terms of how the world appears to the subject, as well as against an (...) atomistic conception of attention. In the second part of the paper, I show how the structuring account can be made precise: attention causes and causally sustains phenomenal relations to hold between the parts of the stream of consciousness; most importantly the relation of one part being peripheral to another. I end by pointing out consequences for both the scientific study of attention as well as for several areas of central philosophical interest. (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..