Biomedical subjects

S Yantis

Publications and source records attributed to S Yantis.

At least 19 recordsLinked to original sources

PubMed1997

Visual attention: control, representation, and time course.

Three central problems in the recent literature on visual attention are reviewed. The first concerns the control of attention by top-down (or goal-directed) and bottom-up (or stimulus-driven) processes. The second concerns the representational basis for visual selection, including how much attention can be said to be location- or object-based. Finally, we consider the time course of attention as it is directed to one stimulus after another.

Attention↗

PubMed1997

Perceptual grouping in space and time: evidence from the Ternus display.

We report three experiments investigating the effect of perceptual grouping on the appearance of a bistable apparent-motion (Ternus) display. Subjects viewed a Ternus display embedded in an array of context elements that could potentially group with the Ternus elements. In contrast to several previous findings, we found that grouping influenced apparent motion perception. In Experiment 1, apparent motion perception was significantly affected via grouping by shape similarity, even when the visible persistence of the elements was controlled. In Experiment 2, elements perceived as moving without context were perceived as stationary without context were perceived as moving when grouped with moving elements perceived as stationary without context were perceived as moving when grouped with moving context elements. We argue that grouping in the spatial and temporal domains interact to yield perceptual experience of apparent-motion displays.

Adult↗

PubMed1996

Attentional capture by abrupt onsets: new perceptual objects or visual masking?

The authors have shown that an object appearing abruptly in a previously blank location is efficiently detected in visual search when it is embedded in an array of objects without abrupt onset (term no-onset stimuli). In these experiments, no-onset stimuli appeared well before the onset stimulus but were camouflaged by additional line segments rendering the stimuli unidentifiable. B. S. Gibson (1996) claims that the availability of the no-onset stimuli was delayed relative to that of the abrupt onset stimulus because of forward masking. The authors show that forward masking is unlikely to be a significant factor in their experiments, and 3 new experiments are reported that undermine Gibson's masking account. Observed differences in the efficiency with which onset and no-onset stimuli are processed in visual search are due to attentional capture by new perceptual objects and to a relatively sluggish process of updating existing object representations.

Attention↗

PubMed1995

Allocating visual attention: tests of a two-process model.

Observers require less time to identify a visual target when its location is cued in advance than when it is not cued, and the magnitude of the improvement depends on the validity of the cue. According to J. Jonides's (1983) 2-process model, there exist 2 possible modes of attentional readiness: a focused-attention mode and a diffuse-attention mode. Observers are assumed to enter the focused-attention mode on a proportion of trials that matches the validity of the cue and to enter the diffuse-attention mode on the remaining trials. The present experiment tested and rejected the response time mixture prediction of the 2-process model. An instance of the class of 1-process models in which perceptual objects are sampled in parallel according to the validity of the cue was evaluated. A stochastic simulation of the model yielded results that paralleled those of the experiment.

Adult↗

PubMed1994

Stimulus-driven attentional capture: evidence from equiluminant visual objects.

Previous work has shown that abrupt visual onsets capture attention. Possible attention. Possible mechanisms for this phenomenon include (a) a luminance-change detection system and (b) a mechanism that detects the appearance of new perceptual objects. Experiments 1 and 2 revealed that attention is captured in visual search by the appearance of a new perceptual object even when the object is equiluminant with its background and thus exhibits no luminance change when it appears. Experiment 3 showed that a highly salient luminance increment alone is not sufficient to capture attention. These findings suggest that attentional capture is mediated by a mechanism that detects the appearance of new perceptual objects.

Attention↗

PubMed1994

Object continuity in apparent motion and attention.

Recent theories of attention have emphasized the role of object-based representations in visual selection. One defining property of any object is spatiotemporal continuity. The present experiments show that the continuity property may underlie two seemingly unrelated perceptual phenomena: attentional capture by abrupt visual onset and the appearance of bistable apparent motion displays. In Experiment 1, observers carried out two visual tasks. In the first task, they reported the appearance of a bistable apparent-motion (or Ternus) display. Whether group or element motion was perceived depended on the duration of the blank interval between successive frames. In the second task, subjects engaged in visual search for a prespecified target, and one each trial one element was briefly flickered off and back on. The degree to which that element captured attention also depended on the duration of the temporal gap. The time course of the gap duration effect in the visual search task was very similar to that for the Ternus display. In Experiment 2, we ruled out the possibility that the presence of an abrupt offset caused the results of Experiment 1. It is argued that the apparent motion and attentional capture phenomena examined here may reflect the operation of the same underlying mechanism: in both cases, a sufficiently long temporal gap disrupts spatiotemporal continuity, thereby fundamentally changing the perceived organization of the display.

Attention↗

PubMed1994

Visual motion and attentional capture.

Previous work has shown that abrupt visual onsets capture attention. This occurs even with stimuli that are equiluminant with the background, which suggests that the appearance of a new perceptual object, not merely a change in luminance, captures attention. Three experiments are reported in which this work was extended by investigating the possible role of visual motion in attentional capture. Experiment 1 revealed that motion can efficiently guide attention when it is perfectly informative about the location of a visual search target, but that it does not draw attention when it does not predict the target's position. This result was obtained with several forms of motion, including oscillation, looming, and nearby moving contours. To account for these and other results, we tested a new-object account of attentional capture in Experiment 2 by using a global/local paradigm. When motion segregated a local letter from its perceptual group, the local letter captured attention as indexed by an effect on latency of response to the task-relevant global configuration. Experiment 3 ruled out the possibility that the motion in Experiment 2 captured attention merely by increasing the salience of the moving object. We argue instead that when motion segregates a perceptual element from a perceptual group, a new perceptual object is created, and this event captures attention. Together, the results suggest that motion as such does not capture attention but that the appearance of a new perceptual object does.

Attention↗

PubMed1993

Stimulus-driven attentional capture and attentional control settings.

Jonides and Yantis (1988) found that abrupt-onset singletons capture attention in visual search when onset is orthogonal to the target's defining and reported attributes and that color and brightness singletons do not. They concluded that abrupt onset may be unique in capturing visual attention. Folk, Remington, and Johnston (1992) challenge this conclusion and argue that (a) the occurrence of attentional capture is contingent on the adoption of an appropriate attentional control setting by the observer and (b) properties other than onset (in particular, color) can capture attention involuntarily. In this article, each of these claims is critically evaluated, and it is argued that the results reported by Folk et al., though important, do not definitively corroborate either one. The available evidence concerning stimulus-driven attentional capture is summarized, and 3 empirical generalizations that characterize the evidence are advanced.

Attention↗

PubMed1993

Dividing attention between color and shape: evidence of coactivation.

When attention is divided between spatially distinct objects, the time to detect a target decreases when two or more targets are present. This redundancy gain can be accounted for by an interactive race model (Mordkoff & Yantis, 1991) in which separate decisions are made about each object, but environmental contingencies among the objects can influence decision times. In the present study, we examined whether the model also accounts for performance when attention must be divided between stimulus attributes other than spatial location. Subjects made target-present responses when displays included a prespecified color, a prespecified letter, or both target features. The data violated the predictions of all separate-activations models, including the interactive race model. Two control experiments ruled out an alternative account based on task complexity. We conclude that coactivation occurs when target attributes from two separable dimensions are simultaneously present, but not when target attributes come from the same dimension. A modular hybrid of race and coactivation models is tentatively proposed.

Adult↗

PubMed1992

Multielement visual tracking: attention and perceptual organization.

Two types of theories have been advanced to account for how attention is allocated in performing goal-directed visual tasks. According to location-based theories, visual attention is allocated to spatial locations in the image; according to object-based theories, attention is allocated to perceptual objects. Evidence for the latter view comes from experiments demonstrating the importance of perceptual grouping in selective-attention tasks. This article provides further evidence concerning the importance of perceptual organization in attending to objects. In seven experiments, observers tracked multiple randomly moving visual elements under a variety of conditions. Ten elements moved continuously about the display for several seconds; one to five of them were designated as targets before movement initiation. At the end of movement, one element was highlighted, and subjects indicated whether or not it was a target. The ease with which the elements in the target set could be perceptually grouped was systematically manipulated. In Experiments 1-3, factors that influenced the initial formation of a perceptual group were manipulated; this affected performance, but only early in practice. In Experiments 4-7, factors that influenced the maintenance of a perceptual group during motion were manipulated; this affected performance throughout practice. The results suggest that observers spontaneously grouped the target elements and directed attention toward this coherent but nonrigid virtual object. This supports object-based theories of attention and demonstrates that perceptual grouping, which is usually conceived of as a purely stimulus-driven process, can also be governed by goal-directed mechanisms.

Adult↗

PubMed1992

Involuntary attentional capture by abrupt onsets.

The extent to which brief abrupt-onset visual stimuli involuntarily capture spatial attention was examined in five experiments. The paradigm used was intended to maximize the opportunity and incentive for subjects to ignore abrupt-onset distractor stimuli in nontarget locations. Subjects made a speeded two-choice response to a target letter appearing in one of four boxes. An abrupt-onset visual stimulus, easily discriminable from the target, was flashed briefly prior to the presentation of a target. In separate blocks, the flash stimulus marked the box in which the target would subsequently appear (SAME), a different box (DIFF), fixation (CENTER), or all four boxes (ALL). Prior to each block, subjects were informed of the flash-target relationship. In all five experiments, response time was elevated in the DIFF, CENTER, and ALL conditions. The interference effect was larger for the DIFF condition and persisted for longer flash-target SOAs. These results suggest that, under appropriate conditions, spatial attention can be involuntarily drawn to abrupt-onset events despite the intention of subjects' to ignore them.

Attention↗

PubMed1991

An interactive race model of divided attention.

Two classes of models have been proposed to explain how redundant information extracted from separate sources comes to activate a single response. Each provides a fundamentally different account of why responses to redundant signals are typically faster than those to either signal alone (the redundant-signals effect). Independent race models assume that a race occurs between perceptual codes on independent channels and that only the winner activates the response. Coactivation models assume that there is some form of energy or activation-strength summation, with information being pooled across channels prior to decision. An intermediate class of models is introduced and a specific exemplar, the interactive race model, is tested in a series of redundant-target detection experiments. In particular, we examine the effects on performance of two types of contingency that have previously been overlooked as sources of task-relevant information. The results reveal that response times are significantly influenced by both interstimulus and stimulus-response contingencies. The interactive race model provides a natural account of these findings as well as several otherwise puzzling results in the divided-attention literature.

Adult↗

PubMed1991

Analyses of multinomial mixture distributions: new tests for stochastic models of cognition and action.

Mixture distributions are formed from a weighted linear combination of 2 or more underlying basis distributions [g(x) = sigma j alpha j fj(x); sigma alpha j = 1]. They arise frequently in stochastic models of perception, cognition, and action in which a finite number of discrete internal states are entered probabilistically over a series of trials. This article reviews various distributional properties that have been examined to test for the presence of mixture distributions. A new multinomial maximum likelihood mixture (MMLM) analysis is discussed for estimating the mixing probabilities alpha j and the basis distributions fj(x) of a hypothesized mixture distribution. The analysis also generates a maximum likelihood goodness-of-fit statistic for testing various mixture hypotheses. Stochastic computer simulations characterize the statistical power of such tests under representative conditions. Two empirical studies of mental processes hypothesized to involve mixture distributions are summarized to illustrate applications of the MMLM analysis.

Arousal↗

PubMed1991

Mechanisms of attentional selection: temporally modulated priority tags.

When a single abrupt onset appears in a multielement display, it captures attention. When multiple onset elements occur, they have conditional priority over no-onset elements such that a limited number of onsets can be serviced with high priority in visual search (Yantis & Johnson, 1990). We report three experiments in which we assess two possible mechanisms for attentional prioritization: a priority queue into which a fixed number of high-priority elements are placed for early servicing during search, and a mechanism that temporarily tags all high-priority elements for early servicing or more frequent sampling. We manipulated the visual quality or inter-letter confusability of the stimuli to prolong encoding and/or comparison operations; this manipulation led to a decrease in the estimated number of elements serviced with high priority. We conclude that a mechanism incorporating temporally decaying priority tags is implicated in servicing multiple abrupt onsets in visual search.

Adult↗

PubMed1990

Abrupt visual onsets and selective attention: voluntary versus automatic allocation.

The hypothesis that abrupt visual onsets capture attention automatically, as suggested by Yantis and Jonides (1984) was tested in four experiments. A centrally located cue directed attention to one of several stimulus positions in preparation for the identification of a target letter embedded in an array of distractor letters. In all experiments, one stimulus (either the target or one of the distractors) had an abrupt onset; the remaining letters did not. The effectiveness of the cue was manipulated (varying either its duration or its predictive validity) to test whether abrupt onsets capture attention even when subjects are in a highly focused attentional state. Results showed that onsets do not necessarily capture attention in violation of an observer's intentions. A mechanism for partially automatic attentional capture by abrupt onset is proposed, and the diagnosticity of the intentionality criterion for automaticity is discussed.

Adult↗

PubMed1990

On the locus of visual selection: evidence from focused attention tasks.

Early and late selection models of attention disagree about whether visual objects are identified before or after selection, with recent evidence of interference from to-be-ignored stimuli favoring late selection over early selection accounts. However, these tests may not have permitted optimal attentional focusing. In 4 experiments subjects identified an attentionally cued target letter embedded among distractors. Only minimal effects of information appearing in to-be-ignored locations were observed. This striking efficiency of selection provides support for early selection theories and calls into question some late selection theories holding that stimuli throughout the display are immediately and fully identified prior to attentional selection. In order to explain the larger pattern of results across a variety of focused- and divided-attention paradigms, a hybrid model is advanced with a flexible locus for visual selection.

Adult↗

PubMed1990

Mechanisms of attentional priority.

When a single abrupt onset occurs in a multielement visual display, it captures attention, possibly by generating an attentional interrupt that designates onsets as being of high priority. In 3 experiments, the mechanisms subserving attentional priority setting were investigated. Subjects searched for a prespecified target letter among multiple distractor letters, half of which had abrupt onsets and half of which did not. The target, when present, was equally often an onset element and a no-onset element. Several models for attentional priority, differing in how many onset elements have priority over no-onset elements, were assessed. The data support a model in which approximately 4 onset stimuli are processed before any no-onset stimuli are processed. Two attentional priority mechanisms are proposed: (a) queuing of a limited number of high-priority elements and (b) temporally modulated decay of attentional priority tags.

Adult↗

PubMed1990

Detecting conjunctions of color and form in parallel.

Certain theories of visual attention assume that at least one processing stage must be serial when the target of search is defined as the conjunction of two or more separable features. To explain why conjunction-search response times do not always form linearly increasing functions of display size, recent versions of this general model have posited the existence of an early parallel process that guides the serial stage toward display elements that are likely targets. Other models have relaxed the seriality assumption, allowing for a limited number of parallel decisions. In the three experiments reported here, a redundant-target detection task was used with conjunctively defined targets and display sizes of two (Experiment 1), one or two (Experiment 2), and six (Experiment 3). In all three experiments, strong evidence for parallel processing was observed. The implications for models of elementary visual processes are discussed.

Attention↗