Set Of Distractors Research Articles

Priming of luminance-defined motion direction in visual search

Features that we have recently attended to strongly influence how we allocate visual attention across a subsequently viewed visual scene. Here, we investigate the characteristics of any such repetition effects during visual search for Gabor patch targets drifting in the odd direction relative to a set of distractors. The results indicate that repetition of motion direction has a strong effect upon subsequent allocation of attention. This was the case for judgments of a target's presence or absence, of a target's location, and of the color of a target drifting in the odd direction. Furthermore, distractor repetition on its own can facilitate search performance on subsequent trials, indicating that the benefits of repetition of motion direction are not confined to repetition of target features. We also show that motion direction need not be the target-defining dimension throughout a trial block for motion priming to occur, but that priming can build up with only one presentation of a given target direction, even within blocks of trials where the target may, unpredictably, be defined by a different feature (color, in this case), showing that dimensional-weighting accounts cannot, on their own, account for motion direction priming patterns. Finally, we show by randomizing the set size between trials that priming of motion direction can decrease search rates in visual search.

Priming of luminance-defined motion direction in visual search

Features that we have recently attended to strongly influence how we allocate visual attention across a subsequently viewed visual scene. Here, we investigate the characteristics of any such repetition effects during visual search for Gabor patch targets drifting in the odd direction relative to a set of distractors. The results indicate that repetition of motion direction has a strong effect upon subsequent allocation of attention. This was the case for judgments of a target’s presence or absence, of a target’s location, and of the color of a target drifting in the odd direction. Furthermore, distractor repetition on its own can facilitate search performance on subsequent trials, indicating that the benefits of repetition of motion direction are not confined to repetition of target features. We also show that motion direction need not be the target-defining dimension throughout a trial block for motion priming to occur, but that priming can build up with only one presentation of a given target direction, even within blocks of trials where the target may, unpredictably, be defined by a different feature (color, in this case), showing that dimensional-weighting accounts cannot, on their own, account for motion direction priming patterns. Finally, we show by randomizing the set size between trials that priming of motion direction can decrease search rates in visual search.

Ultrastructural and elemental spectrum analysis of distraction osteogenesis reconstruction for cleft palate on rhesus model

teady of distractor in two set directions: arallel to the Y axis or the extension xis. Thereby, to promote intramembraous ossification, speed up bone formation nd elevate the quality of bone formation. esults: Distractor set parallel to Y axis erformed better than the extension axis. onclusions: This study provides a theretical basis for the position of distract quipment and distraction orientations in linical application. cknowledgement. This study was suported by Scientific and Technologial Development Programme of Jilin rovince Scientific and Technological ureau. NO.20040508

A new look at novelty effects: Guiding search away from old distractors

We examined whether search is guided to novel distractors. In Experiment 1, subjects searched for a target among one new and a variable number of old distractors. Search displays in Experiment 2 consisted of an equal number of new, old, and familiar distractors (the latter repeated occasionally). We found that eye movements were preferentially directed to a new distractor on target-absent trials and that subjects tended to immediately fixate a new distractor after leaving the target on target-present trials. In both cases, first fixations on old distractors were consistently less frequent than could be explained by chance. We interpret these patterns as evidence for negative guidance: Subjects learn the visual features associated with the set of old distractors and then guide their search away from these features, ultimately resulting in the preferential fixation of novel distractors.

The N2pc component in ERP and the lateralization effect of language on color perception

This study examined the electrophysiological bases of the effect of language on color perception. In a visual search task, a target was presented to the left or right visual field. The target color was either from the same category as a set of distractors (within-category condition) or from a different category (between-category condition). For both category conditions, the targets elicited a clear N2pc (N2-posterior-contralateral) component in the event-related potential (ERP) in the contralateral hemisphere. In the left hemisphere only, the N2pc amplitude for the between-category condition was larger than that for the within-category condition. These results indicate that the N2pc could be used as an index to describe the lateralization effect of language on color perception.

Attention has memory: priming for the size of the attentional focus

Repeating the same target's features or spatial position, as well as repeating the same context (e.g. distractor sets) in visual search leads to a decrease of reaction times. This modulation can occur on a trial by trial basis (the previous trial primes the following one), but can also occur across multiple trials (i.e. performance in the current trial can benefit from features, position or context seen several trials earlier), and includes inhibition of different features, position or contexts besides facilitation of the same ones. Here we asked whether a similar implicit memory mechanism exists for the size of the attentional focus. By manipulating the size of the attentional focus with the repetition of search arrays with the same vs. different size, we found both facilitation for the same array size and inhibition for a different array size, as well as a progressive improvement in performance with increasing the number of repetition of search arrays with the same size. These results show that implicit memory for the size of the attentional focus can guide visual search even in the absence of feature or position priming, or distractor's contextual effects.

Short Article: Passive perceptual learning in relation to wine: Short-term recognition and verbal description

This experiment addressed the question of whether untutored experience of drinking wine improves human ability to discriminate between wines. Using a short-term recognition task a two-factor design compared more with less experienced wine drinkers (intermediates vs. novices) and a condition requiring description of the to-be-remembered wine samples with a control condition. Overall intermediates were more accurate than novices in selecting the target sample from a distractor set. The procedure was modelled on a previous study in which verbal descriptions reduced the performance of intermediates (verbal overshadowing), but here both novices and intermediates performed better in the description than in the control condition. The major result was to demonstrate that untutored experience can improve wine recognition (passive perceptual learning).

Resisting change: The influence of luminance changes on visual marking and the preview benefit

Visual search can benefit when one set of distractors is presented as a preview, prior to the appearance of the second set of distractors plus the target (Watson & Humphreys, 1997). It has been shown that changing the shape of the old, previewed stimuli when the new items appear causes the old stimuli to recompete for selection with the new ones. In contrast, changing the luminance or color of the old stimuli has no detrimental effects. Here, we present five experiments that reassessed the effect of luminance changes in preview search. We show (1) that preview search is remarkably resistant to large changes in the absolute luminance of the old stimuli, even when those changes would ordinarily be sufficient to signal the appearance of a new object and draw attention (Experiments 1 and 2), and (2) that resistance to luminance changes can be bolstered by feature-based inhibitory processes (Experiments 3-5). These findings are discussed in terms of the possible ecological properties of time-based visual selection and possible mechanisms underlying the preview benefit.

Effect of Age and Food Novelty on Food Memory

The influence of age of the consumer and food novelty on incidentally learned food memory was investigated by providing a meal containing novel and familiar target items under the pretense of a study on hunger feelings to 34 young and 36 older participants in France and to 24 young and 20 older participants in Denmark and testing them a day later on recognition of the targets among a set of distractors that were variations of the target made by adding or subtracting taste (sour or sweet) or aroma (orange or red berry flavor). Memory was also tested by asking participants to indicate whether the target and the distractors were equal to or less or more intense than the remembered target in sourness sweetness and aroma. The results showed that when novelty is defined as whether people know or not a given product, it has a strong influence on memory performance, but that age did not, the elderly performing just as well as the young. The change in the distractors was more readily detected with familiar than with novel targets where the participants were still confused by the target itself. Special attention is given to the influence of the incidental learning paradigm on the outcome and to the ways in which it differs from traditional recognition experiments.

Priming in visual search: Separating the effects of target repetition, distractor repetition and role-reversal

Recent studies have identified between-trial priming effects in visual search tasks, but often with constraints on the possible similarities or changes across successive trials, and usually with the main emphasis on effects of target repetition. Here we sought to obtain a more thorough characterization of between-trial priming effects in speeded visual search, where observers determined target presence or absence among a set of distractors. The results show that various separable priming effects have a major influence on visual search performance. Facilitation was evident when a target was repeated between-trials, but there was also strong priming due to repetition of distractor types, even between successive trials for which no target was presented on either trial. Search also proceeded faster if the same distractor types were repeated, even when the current target was different from the preceding target. We also investigated the possible impact of role-reversals for particular display items, from being a target on one trial to becoming a distractor on the next, and vice-versa. We find that such role-reversals substantially affect search performance, over and above the effects of repetition per se when those were held constant.

Repetition of distractor sets improves visual search performance in hemispatial neglect

Priming from repeated distractor sets, or search context, in conjunctive visual search was examined in four patients with hemispatial neglect. In the first experiment overall context was either changed or repeated while the target was always the same to control for any modulatory effect of target priming. Considerable priming was seen from repeated context. In the second experiment the context was either repeated on the left side, on the right side, on both sides, or the context was new. Priming from repeated context was found to arise from the left visual field, as well as the right visual field, as well as when overall context was repeated. Brief masked displays were used in experiment 3, the results again showing strong priming from repeated overall context. The results of the three experiments suggest that visual grouping, or perceptual organization, of distractor sets is relatively intact in the affected hemifield of parietal neglect patients. Furthermore, repetition of context may even temporarily ameliorate neglect symptoms in search. These findings are consistent with claims that grouping is distinct from attentional processing and that it operates at lower levels of the perceptual hierarchy.

Intensive training in adults refines A1 representations degraded in an early postnatal critical period

The spectral, temporal, and intensive selectivity of neurons in the adult primary auditory cortex (A1) is easily degraded in early postnatal life by raising rat pups in the presence of pulsed noise. The nonselective frequency tuning recorded in these rats substantially endures into adulthood. Here we demonstrate that perceptual training applied in these developmentally degraded postcritical-period rats results in the recovery of normal representational fidelity. By using a modified go/no-go training strategy, structured noise-reared rats were trained to identify target auditory stimuli of specific frequency from a set of distractors varying in frequency. Target stimuli changed daily on a random schedule. Consistent with earlier findings, structured noise exposure within the critical period resulted in disrupted tonotopicity within A1 and in degraded frequency-response selectivity for A1 neurons. Tonotopicity and frequency-response selectivity were normalized by perceptual training. Changes induced by training endured without loss for at least 2 months after training cessation. The results further demonstrate the potential utility of perceptual learning as a strategy for normalizing deteriorated auditory representations in older (postcritical-period) children and adults.

Eye movements and time-based selection: Where do the eyes go in preview search?

In visual search tasks, presenting one set of distractors (previewing them) before a second set which contains the target, improves search efficiency compared to when all items appear simultaneously. It has been proposed that this preview benefit reflects an attentional bias against old information and toward new information. Here we tested directly whether there was such a bias by measuring eye movement behavior. The main findings were that fixations were biased against, and overall dwell times were shorter on, old stimuli during search in the preview condition. In addition, the initial onset of search was delayed in the preview condition and saccades made during the preview period did not disrupt the ability to prioritize new items. The data demonstrate directly that preview search results in an attentional bias toward new items and against old items.

Age Differences in the Distractor-Ratio Effect as a Function of Contrast Level

ABSTRACT Latencies (RT) and eye movement measures were used to examine the effects of age and contrast on the distractor-ratio effect (DRE) in visual search. Younger and older adults performed a contrast × orientation conjunction search task where the ratios of white to black distractors and luminance contrast levels were varied. The distractor-ratio manipulation had similar effects for older and younger adults on both RT and the number of fixations required to find the target. Both measures were largely independent of distractor ratio on target-present trials, while both RTs and the fixation number increased with the number of items sharing the target's contrast polarity on target-absent trials. A more detailed analysis of eye movements suggested that younger adults were a bit more adept at attending to the smaller set of distractors, which presumably facilitated both overt and covert search. Generalized slowing can account for the age differences in RT, but the fixation number data speak to another mechanism, perhaps increased cautiousness on the part of the elderly when signal strength is low.

The relationship between spatial pooling and attention in saccadic and perceptual tasks

Saccades aimed at spatially extended targets land reliably at central locations determined by pooling information across the target shape [Melcher, D., & Kowler, E. (1999). Shape, surfaces and saccades. Vision Research, 39, 2929–2946; Vishwanath, D., & Kowler, E. (2003). Localization of shapes: Eye movements and perception compared. Vision Research, 43, 1637–1653]. Previous findings of saccadic errors when attempting to look at a target in the midst of distractors encouraged suggestions that pooling occurs indiscriminately, with little or no influence of a selective filter to eliminate the influence of nearby distractors. To determine the effectiveness of filtering, saccadic localization was studied for saccades made to a set of target elements (discs) interleaved with an equivalent set of distractors of a different color. With such interleaved elements, selection and spatial pooling are constrained to occur over the same spatial region. The results showed that filtering was effective and saccadic landing position was determined mainly by the target elements. Concurrent perceptual judgments made about the same stimuli (estimating the mean size of either target or distractor discs) showed better performance for the target discs than distractors, confirming that perceptual attention was allocated to the set of target elements. These results: (1) support the role of attention in setting the input to the spatial pooling process that guides saccades to spatially extended targets, and (2) show that perceptual judgments of mean value, often thought to impose modest attentional demands, are not immune to the constraints of this pre-saccadic filter.

The reconfiguration of task set has no effect on the efficiency of feature search

In this study, we investigated whether or not the reconfiguration of a set task could modulate the efficiency of feature search. In Experiment 1, target set size was manipulated. The results revealed that enumerating targets defined by color yields a much steeper slope when executed simultaneously with a discrimination task than when done singly. However, when distractor set size was manipulated, there was no significant difference in the efficiency of individualizing targets from distractors between the two task conditions, no matter whetherthe search was guided by bottom-up information (Experiment 2) or top-down information (Experiment 3). Drawing upon these results, the authors propose that (1) an additional task can impair the efficiency of enumeration, resulting in a steep slope of counting even when target set size is quite small, and (2) in feature search, the visual system first reconfigures the task set to match the input feature information and then detects the targets with an optimal efficiency, which does not support the theory proposed by Di Lollo, Kawahara, Zuvic, and Visser (2001; Di Lollo, Smilek, Kawahara, & Ghorashi, 2005).

Memory for the process of constructing an integrated mental model

We report two experiments in which people read descriptions of integrated spatial configurations, together with comparable descriptions that did not describe integrated spatial configurations. The integrated spatial descriptions, but not the comparable descriptions, thus supported the construction of a coherent mental model. In Experiment 1, each sentence of the comparable descriptions described the spatial relation between two objects that were not mentioned elsewhere in the description. In Experiment 2, the comparable descriptions were nonspatial, having been constructed by replacing the spatial relations with nonspatial relations. In both experiments, participants were given a surprise recognition test in which they had to identify each of the original descriptions--of both integrated spatial configurations and nonspatial configurations--among a set of distractors. When the sentences in the original description were reordered (and participants were instructed to ignore sentence order), recognition memory was reliably depressed, but only for the integrated spatial descriptions. Reordering descriptions does not change their propositional content, nor does it change the described situation; however, it does change the process of constructing a mental model of that situation. These findings thus suggest that memory for the descriptions retains a trace of the process of constructing an integrated mental model and that reordering the sentences disrupts this memory because the reordering reduces the similarity of the processing of the descriptions at recognition.

Visual marking: The effects of irrelevant changes on preview search

Visual search is facilitated when participants receive a preview of half of the distractors before presentation of the second distractor set (Watson & Humphreys, 1997). In seven experiments, we examined the effects of irrelevant change on this preview benefit. Experiments 1-4 showed that the benefit was not disrupted by the abrupt appearance of irrelevant distractors during the preview period unless they were the same color as the new items. However, blinking off-and-on irrelevant distractors that were present at the start of the preview period disrupted the preview benefit irrespective of their feature overlap with other items (Experiments 5-7). The data are consistent with the inhibition of old stimuli (visual marking) via a location-based template along with an anticipatory feature-based set for new stimuli.

Recognition memory and introspective remember/know judgments: Evidence for the influence of distractor plausibility on “remembering” and a caution about purportedly nonparametric measures

One popular technique in the study of human recognition memory involves the elicitation of remember and know judgments and the attribution of those judgments to qualitative states of memory retrieval. An alternative view, reviewed here, implicates quantitative, but not qualitative, differences in evidence as the basis for those two judgments. That theory makes two clear and testable predictions: that of criterion shifts in "remembering" and that of isodiscriminability across different response sets. In this experiment, the makeup of the distractor set in a recognition test is shown to influence overall recognition criterion and also rates of "remember" responses. The second portion of the article demonstrates how A' is a poor choice of a measure to test the prediction of isodiscriminability. When this measure is corrected (Equation 7) to make it more consistent with current knowledge about the receiver-operating characteristic in recognition memory, it reveals that there is no difference in discriminability between "remember" and all positive responses.

Efficient visual search without top-down or bottom-up guidance

Two types of mechanisms have dominated theoretical accounts of efficient visual search. The first are bottom-up processes related to the characteristics of retinotopic feature maps. The second are top-down mechanisms related to feature selection. To expose the potential involvement of other mechanisms, we introduce a new search paradigm whereby a target is defined only in a context-dependent manner by multiple conjunctions of feature dimensions. Because targets in a multiconjunction task cannot be distinguished from distractors either by bottom-up guidance or top-down guidance, current theories of visual search predict inefficient search. While inefficient search does occur for the multiple conjunctions of orientation with color or luminance, we find efficient search for multiple conjunctions of luminance/size, luminance/shape, and luminance/topology. We also show that repeated presentations of either targets or a set of distractors result in much faster performance and that bottom-up feature extraction and top-down selection cannot account for efficient search on their own. In light of this, we discuss the possible role of perceptual organization in visual search. Furthermore, multiconjunction search could provide a new method for investigating perceptual grouping in visual search.