This article defends a theory of diffuse attention and distinguishes it from focal attention. My view is motivated by evidence from psychology and neuroscience, which suggests that we can deploy visual selective attention in at least two ways: by focusing on a small number of items, or by diffusing attention over a group of items taken as a whole. I argue that diffuse attention is selective and can be object‐based. It enables a subject to select an object to guide behavior, (...) albeit in a different way than focusing does. (shrink)

In cases of identity crowding, a subject consciously sees items in a figure, even though they are presented too closely together for her to shift attention to each item. Block uses such cases to challenge the view that attention is necessary for consciousness. I argue that in identity crowding cases, subjects really do attend to the items. Specifically, they attend to the figure as a global object that contains the individual items as parts. To support this view, I provide evidence (...) that attention can be directed to a global object or a local object. My response helps to defend the view that attention is necessary for conscious perception. (shrink)

Previous research has successfully used feature integration theory to operationalise the predictions of Perceptual Load Theory, while simultaneously testing the predictions of both models. Building on this work, we test the extent to which these models hold up in a 3D world. In two experiments, participants responded to a target stimulus within an array of shapes whose apparent depth was manipulated using a combination of monoscopic and stereoscopic cues. The search task was designed to test the predictions of feature integration (...) theory, as the target was identified by a single feature or a conjunction of features and embedded in search arrays of varying size, and perceptual load theory, as the task included congruent and incongruent distractors presented alongside search tasks imposing high or low perceptual load. Findings from both experiments upheld the predictions of feature integration theory, regardless of 2D/3D condition. Longer search times in conditions with a combination of monoscopic and stereoscopic depth cues suggests that binding features into three-dimensional objects requires greater attentional effort. This additional effort should have implications for perceptual load theory, yet our findings did not uphold its predictions; the effect of incongruent distractors did not differ between conjunction search trials and feature search trials. Individual differences in susceptibility to the effects of perceptual load were evident and likely explain the absence of load effects. Overall, our findings suggest that feature integration theory may be useful for predicting attentional performance in a 3D world. (shrink)

It has generally been assumed that rapid visual search is based on simple features and that spatial relations between features are irrelevant for this task. Seven experiments involving search for line drawings contradict this assumption; a major determinant of search is the presence of line junctions. Arrow- and Y-junctions were detected rapidly in isolation and when they were embedded in drawings of rectangular polyhedra. Search for T-junctions was considerably slower. Drawings containing T-junctions often gave rise to very slow search even (...) when distinguishing arrow- or Y-junctions were present. This sensitivity to line relations suggests that preattentive processes can extract 3-dimensional orientation from line drawings. A computational model is outlined for how this may be accomplished in early human vision. (shrink)

Previous theories of early vision have assumed that visual search is based on simple two-dimensional aspects of an image, such as the orientation of edges and lines. It is shown here that search can also be based on three-dimensional orientation of objects in the corresponding scene, provided that these objects are simple convex blocks. Direct comparison shows that image-based and scene-based orientation are similar in their ability to facilitate search. These findings support the hypothesis that scene-based properties are represented at (...) preattentive levels in early vision. (shrink)

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

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

Recent work in different fields of cognitive sciences seems to support the idea that in order to explain awareness of visually presented objects some kind of binding mechanism is needed for the correct conjunction of different sensory features into a whole percept. Selective attention is commonly invoked as the key for solving this conjunction problem. Accordingly, the cognitive neurosciences have begun to investigate what kind of neural processing could underlie such a process. I analyse the evidence provided for justifying the (...) existence of a binding problem and I argue against the claim that there is a feature binding problem to be solved in order to explain unity of object awareness. In particular, I question the definition of 'feature' and suggest some possible sources of misunderstanding related to this definition. Finally, I suggest an alternative approach in which perceived object unity does not rely exclusively on attentional conjunction of sensory features: instead of a general and unique mechanism mediating object awareness, I examine evidence that there are at least as many binding mechanisms as potential ways of interacting with visually presented objects. (shrink)

Recent work in experimental psychology and neuroscience has revealed a rather surprising architecture for early (or preattentive) perceptual processes. This paper will describe some of the surprising features of that architecture, and how they bear on recent philosophical debates about the notion of phenomenal consciousness. I will argue that the common sense idea that states of phenomenal consciousness are states of a unitary kind cannot survive confrontation with the details of how our early perceptual processing works. In particular, that architecture (...) forces us to contemplate the prospect of phenomenal consciousness being sundered in two, with states that have phenomenal character making an appearance far before the arrival of anything one could call consciousness or awareness. (shrink)

The perception of the lightness of surfaces has been shown to be affected by information about the spatial configuration of those surfaces and their illuminants. For example, two surfaces of equal luminance can appear to be of very different lightness if one of the two appears to lie in a shadow. How are we to understand the character of the processes that integrate such spatial configuration information so as to yield the eventual appearance of lightness? This paper makes some simple (...) observations about the vocabulary of appearance used in these contexts, and proposes that the end results can be called "phenomenal" in a traditional sense of that word. Processes whose products are phenomenal are next distinguished from processes characterized in other terms: (a) processes of perceptual grouping; (b) processes of perceptual organization; and (c) attentional (as opposed to preattentive) processes. These four categories are conceptually and empirically distinct. In particular, the paper reviews some evidence that appearances as of contours, occlusion, and amodally completed shapes can occur preattentively. Some implications for understanding gestalt grouping processes are briefly discussed. (shrink)

What are the relations between preattentive feature-placing and states of perceptual awareness? For the purposes of this paper, states of "perceptual awareness" are confined to the simplest possible exemplars: states in which one is aware of some aspect of the appearance of something one perceives. Subjective contours are used as an example. Early visual processing seems to employ independent, high-bandwidth, preattentive feature "channels", followed by a selective process that directs selective attention. The mechanisms that yield subjective contours are found very (...) early in this processing. An experiment by Greg Davis and Jon Driver is described; it seems to show that multiple subjective figures can be coded in these preattentive, parallel stages of visual processing. I propose that some of these preattentive states might register the very same differences that, were one aware of them, would be phenomenal differences. Some arguments pro and con on this possibility are assessed. (shrink)