No abstract

It is widely accepted that there exists a region or locus of maximal resource allocation in visual perception -sometimes referred to as the spotlight of attention. We have argued that even if there is a single locus of processing, there must be multiple loci of parallel access -several places in the visual field must be indexed at once and these indexes can be used to determine where attention is allocated. We have carried out a variety of studies to support these ideas, including experiments showing that subjects can track multiple independent moving targets in a field of identical distractors, that the enhanced ability to detect changes occurring on these targets does not accrue to nontargets nor to items lying inside the convex polygon that they form (so that a zoom-lens of attention does not fit the data). We have used a visual search paradigm to show that (serial or parallel) search can be confined to a subset of indexed items and the layout of these items is of little importance. We have also studied the phenomenon known as subitizing and have shown that subitizing occurs only when items can be preattentively individuated and in those cases location precuing has little effect, compared with when counting occurs, which suggests that subitizing may be carried out by counting active indexes rather than items in the visual field. And finally we have run studies showing that a certain motion effect that is sensitive to attention can occur at multiple precued loci. We believe that this evidence suggests that there is an early preattentive stage in vision where a small number of salient items in the visual field are indexed and thereby made readily accessible for a variety of visual tasks.

Over 30 years of research using Posner's spatial cueing paradigm has shown that selective attention operates on representations of spatial locations, leading to space-based theories of attention. Manipulations of stimuli and methods have shown this paradigm to be sensitive to several types of object-based representations-providing evidence for theories incorporating object-based attentional selection. This paper critically evaluates the evidence demanding object-based explanations that go beyond positing spatial representations alone, with an emphasis on identifying and interpreting successes and failures in obtaining object-based cueing effects. This overview of current evidence is used to generate hypotheses regarding critical factors in the emergence and influence of object representations-their generation, strength, and maintenance-in the modulation of objectbased facilitatory and inhibitory cueing effects.Keywords Selective attention . Object-based . Spacebased . Facilitation . IOR Many different experimental paradigms have been used to investigate the role of objects in visual selection (see Bichot, 1999, andScholl, 2001, for reviews). Through converging operations, strong evidence has emerged revealing that object-based representations can mediate attentional selection. Examples of such paradigms include studies of the attentional blink within and between objects (e. Mari-Beffa, Houghton, Estevez, & Fuentes, 2000;Tipper, Brehaut, & Driver, 1990), visual marking (e.g., Watson & Humphreys, 1998, visual search in multiple-object displays (e.g., Enns & Rensink, 1990;Goldsmith, 1998;Grossberg, Mingolla, & Ross, 1994;Rensink & Enns, 1995;Treisman, 1982;Wolfe & Bennett, 1997), and spatial cueing (e.g., Egly, Driver, & Rafal, 1994;Tipper, Driver, & Weaver, 1991). In each of these literatures, positing that attention operates on representations of objects has provided more thorough and satisfying explanations of data than would simply assuming that attention operates on spatial representations alone. The present review concentrates on evidence for claims of object-based selection from studies using the spatial cueing paradigm. Why spatial cueing?A key motivation for focusing on spatial cueing is that claims have emerged that object-based spatial cueing We gratefully acknowledge Janice J. Snyder for inspiring a comprehensive table-based approach to integrating research findings. This paper benefited greatly from the review process and we thank the editor and the reviewers for their contribution.

The in situ optical properties and electrocatalytic performance of representative water-oxidation catalyst have been considered.

Editor:Abstract. We used cascade-correlation to model human cognitive development on a well studied psychological task, the balance scale. In balance scale experiments, the child is asked to predict the outcome of placing certain numbers of equal weights at various distances to the left or fight of a fulcrum. Both stage progressions and information salience effects have been found with children on this task. Cascade-correlation is a generative connectionist algorithm that constructs its own network topology as it learns. Cascade-correlation networks provided better fits to these human data than did previous models, whether rule-based or connectionist. The network model was used to generate a variety of novel predictions for psychological research.