Biomedical subjects

Z Pylyshyn

Publications and source records attributed to Z Pylyshyn.

3 recordsLinked to original sources

PubMed1994

Multiple parallel access in visual attention.

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.

Attention↗

PubMed1989

The role of location indexes in spatial perception: a sketch of the FINST spatial-index model.

This paper hypothesizes a resource-limited mechanism, called a FINST, for individuating or indexing visual features, as distinct from encoding their type or location. FINSTs have the property that they index features in a way that is transparent to their retinal location, and hence under certain conditions succeed in "pointing to" scene locations. The basic assumption is that no operation upon sets of features can occur unless all the features to which the operation applies are first FINSTed. A number of applications of this hypothesis are explored in this paper, including applications to phenomena such as the spatial stability of visual percepts, the ability to track several independently moving targets in parallel, the ability to detect a class of spatial relations requiring the use of "visual routines", various mental imagery phenomena, and the ability to encode complex shapes for recognition. In addition, the possibility is examined that such indexes might be used to bind perceived locations to arguments in motor commands, thereby allowing some forms of perceptual-motor coordination. Several additional assumptions are introduced for this purpose, including the postulation of other indexes (called ANCHORS) for non-visually sensed locations. It is assumed that ANCHORS can be bound to FINSTs, thus allowing cross-referencing of visually detected locations to locations given within a proprioceptive or motor-command frame of reference.

Attention↗

PubMedDate not supplied

Some primitive mechanisms of spatial attention.

Our approach to studying the architecture of mind has been to look for certain extremely simple mechanisms which we have good reason to suspect must exist, and to confirm these empirically. We have been concerned primarily with certain low-level mechanisms in vision which allow the visual system to simultaneously index items at multiple spatial locations, and have developed a provisional model (called the FINST model) of these mechanisms. Among the studies we have carried out to support these ideas are ones showing that subjects can track multiple independent moving targets in a field of identical distractors, and that their ability to track these targets and detect changes occurring on them does not generalize to non-targets or 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 carried out a large number of studies on 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 which is sensitive to attention can occur at multiple precued loci. We believe that taken as a whole the evidence is most parsimoniously accounted for in terms of the hypothesis 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.

Attention↗