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Y Tsal

Publications and source records attributed to Y Tsal.

16 recordsLinked to original sources
PubMed2000

Object features, object locations, and object files: which does selective attention activate and when?

The representation within which attention operates was investigated in 3 experiments. The task was similar to that of R. Egly, J. Driver, and R. D. Rafal (1994). Participants had to detect the presence of a target at 1 of 4 ends of 2 shapes, differing in color and form. A precue appeared at 1 of the 4 possible corners. The 2 shapes occupied either the same or different locations in the cuing and target displays. The results showed that the cued object location was attended whether or not space was task relevant, whereas the cued object features (color and form) were attended only when these were task relevant. Moreover, when object file continuity was maintained through continuous movement, attention was found to follow the cued object file as it moved while also accruing to the cued location.

Adult↗
PubMed2000

Attending to an object's color entails attending to its location: support for location-special views of visual attention.

Van der Heijden, Kurvink, de Lange, de Leeuw, and van der Geest (1996) argued that the results supporting the location-special view obtained by Tsal and Lavie (1988) were due to uncontrollable shifts of fixation, rather than reflecting the properties of the attentional system. In the present study, we present an improved variation of the Tsal and Lavie (1988) paradigm and reassert our claim that location is a special dimension. Subjects were presented with circular arrays of six letters of different colors. Three of the letters were enclosed by (Experiment 1) or superimposed on (Experiments 2, 3, and 4) different colored shapes. The subjects were instructed to report the (target) shape with a given color (e.g., report whether the red shape was a square, a circle, or a triangle) and then either freely report letters from the array (Experiments 1, 2, and 4) or identify a prespecified target letter (Experiment 3). In all four experiments, performance was substantially better for the letter that appeared in the location of the to-be-reported shape (location letter) than for the letter that shared its color (color letter). We conclude that attending to the stimulus color entails directing attention to its location.

Adult↗
PubMed1999

A salient distractor does not disrupt conjunction search.

Leading theories of attention posit that bottom-up and top-down factors simultaneously affect attentional priority in visual search. Recent evidence, however, suggests that subjects may rely exclusively on top-down guidance when searching for a target defined by a specific known feature (Bacon & Egeth, 1994). In the present experiment, we addressed this issue in a conjunction search task. We investigated how searching for a green O among green Ts and red Os is affected by the presence of a distractor with a unique shape (green X), color (blue O), or both (blue X). We showed that the salient distractor does not disrupt performance on target-present trials, but produces a large interference on target-absent trials. We conclude that salience-based and top-down processes are alternative modes of guidance, rather than joint contributors in the allocation of attentional priority.

Attention↗
PubMed1999

Effects of attention on localization of stimuli in the visual field.

Subjects localized a small letter that appeared inside one of three large circles that was either validly or invalidly cued. The results indicated that, although unattended stimuli were localized fairly accurately, attention still improved localization. Moreover, the results revealed a greater dispersion of localization responses along the horizontal axis and also showed that mislocalization of attended peripheral stimuli is biased toward the periphery.

Adult↗
PubMed1996

Inattention magnifies perceived length: the attentional receptive field hypothesis.

Five experiments demonstrated that a briefly presented vertical line is judged as longer when it is unattended relative to when it is attended. This effect was obtained in estimating the length of 1 of 5 possible lines (Experiment 1) and in matching the length of a test line to a criterion line (Experiments 3 and 4). The directional effect of attention was eliminated when participants estimated the length difference between 2 simultaneously presented lines (Experiment 2). An additional matching experiment (Experiment 5) demonstrated similar lengthening effects for unattended lines and for unattended distances separated by vertically displaced dots. It is proposed that the metric for unattended stimuli is composed of large attentional receptive fields and that the final output is mediated by rounding up processes, so that the unattended line is systematically perceived as longer than the attended one.

Attention↗
PubMed1994

English and Hebrew letter report by English- and Hebrew-reading subjects: evidence for stimulus control, not hemispheric asymmetry.

Three experiments were conducted using tachistoscopic circular displays of English and/or Hebrew letters that were equidistant from a fixation point. It was found that: (1) Irrespective of native language, English or Hebrew, subjects initiate their reports of English letters from the upper left quadrant and of Hebrew letters from the upper right quadrant of the display. In addition, subsequent letter reports come mostly from the same quadrant. (2) Although Experiments 1 and 2 indicated that direction of reporting might be a function of display language, Experiment 3 provided data to show that direction of reporting was a function of the position of the first response and not the display letter language that engaged that response, nor the display language of adjacent letters. It was suggested that the typical asymmetries reported in the literature, such as right visual field superiority for word stimuli, are the result of a particular set of stimulus conditions (e.g., hemifield presentations) and response requirements (e.g., reaction time and correct recognition). When stimulus conditions and response requirements are made compatible with previously overlearned behaviors, the potential influences of cerebral asymmetries are overshadowed by external stimulus control.

Adult↗
PubMed1994

Effects of attention on perception of features and figural organisation.

Four studies are reported that demonstrate effects of attention on early perceptual processes. These studies show that directing attention to stimulus location influences perceived brightness, perceived length, and the overall organisation of the Müller-Lyer figure and ambiguous figures. Since in all four studies the dependent measure was dissociated from the attentional instructions, the results are not open to traditional criticism of late-selection advocates, and therefore provide strong support for early-selection views of attention.

Attention↗
PubMed1994

Attention reduces perceived brightness contrast.

The effects of attention on brightness perception was investigated in four experiments. In the first three, subjects estimated the brightness of a briefly presented small grey square by selecting a number that corresponded to one of four possible squares varying on a lightness-darkness dimension. In the last experiment, subjects matched the brightness of two peripheral squares, one attended and one unattended. When the stimulus appeared on a white background (Experiments 1, 2, and 4a) it was judged as brighter when attention was directed to its location than when attention was diverted to another location. When the stimulus appeared on a dark background (Experiments 3 and 4b), the opposite pattern of results was obtained: the attended stimulus was judged as darker than the unattended one. These results show that attention reduces the perceived contrast between the stimulus and its background, suggesting that attention enables subjects to provide a more veridical judgement of stimulus brightness by limiting processing resources to the square itself, at the expense of the surrounding background. As attention produced a directional brightness effect rather than just an improvement in report accuracy, the results can be attributed to early perceptual processing effects, hence providing support for early selection views of attention.

Adult↗
PubMed1994

The role of segmentation in prospective and retrospective time estimation processes.

In five experiments, we investigated the effects of the segmentation level of an interval on its perceived duration. A prospective paradigm and an absolute time estimation method were used in two experiments, and in two others we used a retrospective paradigm and a comparative estimation method. A positive relationship was obtained between segmentation level of the estimated interval and its perceived duration under retrospective-comparative conditions for both auditory and tactual stimuli, but no relationship was found under prospective-absolute conditions. The paradigm, estimation method, and segmentation level were jointly manipulated in the fifth experiment. The impact of segmentation was significant under retrospective (both absolute and comparative) and close to significant under prospective-comparative conditions. These findings suggest that high-priority events are perceived and coded as contextual changes and that the impact of segmentation on time estimation is mediated by memory processes.

Adult↗
PubMed1994

The role of attention in illusory conjunctions.

In five experiments, we investigated the effects of attention on illusory conjunctions formed between features of unrelated objects. The first three experiments used a weak manipulation of attention and found that illusory conjunctions formed either among features receiving high attentional priority or among features receiving low attentional priority were not more frequent than were conjunctions formed between mixed features of different attentional priority. The last two experiments used a strong manipulation of attention and failed to reveal any evidence of true illusory conjunctions. The results are inconsistent with the feature-integration theory, which predicts that when attention is focused on a subset of items, illusory conjunctions ought to occur within and outside of the attended subset, but not between the attended and unattended items.

Attention↗
PubMed1994

Perceptual load as a major determinant of the locus of selection in visual attention.

In this paper, we propose that the debate concerning the locus of attentional selection can be resolved by specifying the conditions under which early selection is possible. In the first part, we present a theoretical discussion that integrates aspects from structural and capacity approaches to attention and suggest that perceptual load is a major factor in determining the locus of selection. In the second part, we present a literature review that examines the conditions influencing the processing of irrelevant information. This review supports the conclusion that a clear physical distinction between relevant and irrelevant information is not sufficient to prevent irrelevant processing; early selection also requires that the perceptual load of the task be sufficiently high to exceed the upper limit of available attentional resources.

Attention↗
PubMed1993

Location dominance in attending to color and shape.

Four experiments investigated whether Ss direct attention to stimulus location when attempting to attend to its color or shape. In the first 2 experiments a given property (location, color, or shape) of a letter cue instructed Ss whether to report any letters from a subsequent display. Regardless of which property was relevant, Ss reported letters adjacent to the cue and not those similar to its color or shape. In the last 2 experiments, the varied location of a cue was irrelevant to the task, whereas its varied color instructed Ss to report a letter in a given location or of a given shape. Targets adjacent to the cue were reported faster than those remote from the cue. The results suggest that attempting to attend to any aspect of a stimulus entails directing attention to its location.

Adult↗
PubMed1983

Movements of attention across the visual field.

Vocal reaction times were measured for targets presented at three distances from fixation. The targets were preceded by a cue, and the time interval between the cue and the target (stimulus-onset asynchrony; SOA) was varied. For each peripheral distance, the reaction time function initially declined as SOA was increased and then reached asymptote. The further the target from fixation, the longer the SOA at which the function reached asymptote. The asymptotic SOA values were taken as a measure of the time it takes attention to reach a given target. Comparisons of these values for the three peripheral distances permitted estimating the velocity of attention movements. These measurements suggest that when summoned by a peripheral cue, attention travels through space at a constant velocity of about 1 degree per 8 msec.

Attention↗