刺激范畴的激活与抑制对预搜索的影响

考察范畴混合与预知靶子范畴对预搜索的影响。以2到9的汉字与阿拉伯数字为范畴材料,以搜索一个靶子数字（三、七、3或7）为任务,以预搜索为实验范式。在一些条件下,被试预知靶子的范畴,其它条件下则无法预知靶子的范畴。结果表明：（1）预知靶子范畴可以改进搜索;（2）当靶子与旧客体的范畴相同时,上述预期效应就会减弱;（3）当靶子与旧客体的范畴不同时,范畴预期效应又增加了。最后讨论了实验结果的理论意义     

Costs in searching for two targets: dividing search across target types could improve airport security screening

The cost of searching for two visual targets simultaneously was compared against two separate single‐target searches using exposure time and accuracy measures within a staircase procedure. Dual‐target search for all stimuli (colour, shape and orientation) exhibited a loss of accuracy for one target. For orientation and shape, this dual‐target cost in accuracy was extreme, with chance‐level performance on one target. For colour, dual‐target search exhibited an additional cost in search time, with search requiring a longer exposure than the summed time required for two single‐target searches. An additional search‐time cost was also found for orientation targets when irrelevant colour variation was added to the display. In conclusion, dual‐target search for dissimilar targets is accompanied by an accuracy cost. Furthermore, colour variation, whether task‐relevant or not, leads to an additional cost in processing speed. The results suggest that a divided‐effort strategy would improve performance in search tasks such as X‐ray baggage screening. Copyright © 2006 John Wiley & Sons, Ltd.     

Visual search for positional relationships between pattern elements

The purpose of these experiments was to illustrate how a search for positional relationships between the elements in a stimulus pattern is effortful and serial, whereas a search for pattern elements (without requiring any positional information) takes place rapidly and in parallel. In all three experiments of this study, the target and distractor patterns consisted of two vertical line segments. In the experiment concerning the search for positional relationships between pattern elements, one of the line segments in a line pair had a gap, and the observer's task was to indicate whether the positional order of the two lines was identical in all the line pairs of the display, or whether the line segments were in a mirror-image order in one line pair (the target). In the two experiments concerning the search for pattern elements (no positional information was required), the observer's task was to look for a line pair with one gap line (the target) among line pairs containing two broken lines or among line pairs with unbroken lines. In all three tasks, the reaction time for a correct target detection was measured. The results showed that the search in the first task was highly serial, and in the second and third tasks of "feature" searches, the search time was nearly independent of the number of distractor pairs. It is suggested that this dissociation may be interpreted in the context of the quality of information processing in extrafoveal vision, i. e. the elements of a stimulus pattern can be clearly visible outside the fovea, but it is not possible to perceive accurately the positional relationships between them.     

When increasing distraction helps learning: Distractor number and content interact in their effects on memory

Previous work has demonstrated that increasing the number of distractors in a search array can reduce interference from distractor content during target processing. However, it is unclear how this reduced interference influences learning of target information. Here, we investigated how varying the amount and content of distraction present in a learning environment affects visual search and subsequent memory for target items. In two experiments, we demonstrate that the number and content of competing distractors interact in their influence on target selection and memory. Specifically, while increasing the number of distractors present in a search array made target detection more effortful, it did not impair learning and memory for target content. Instead, when the distractors contained category information that conflicted with the target, increasing the number of distractors from one to three actually benefitted learning and memory. These data suggest that increasing numbers of distractors may reduce interference from conflicting conceptual information during encoding.

     

Determining subprocesses of visual feature search with reaction time models

After the classic serial/parallel dichotomy of visual search mechanisms has been increasingly doubted, we investigated what search mechanisms are used between the two poles termed "pop-out" and "strictly serial search" in an overt feature search paradigm. Since reaction time slopes do not contain sufficient information for this purpose, we developed a novel technique for analyzing reaction times. Individual reaction times are modeled as sums of the durations of successive search steps. Model parameters are task characteristics (similarity, number and arrangement of target and distractors) and processing characteristics of the participant (e.g., attention dwell and shift durations). In Experiment 1, several model variants were fitted numerically to empirical reaction times. The best fitting model suggested that more than one item can be processed in a single fixation, movement of attention is abrupt and not continuous, and even in pop out search, attention is often explicitly moved to the target. In Experiment 2, we measured the central model parameter, the so-called range of attention, more directly and thereby validated the model. The model provides an explanation for the strong variation in the slope of reaction time functions, which is not based on an explicit distinction between parallel and serial search processes.     

Visual search at different spatial scales

Treisman and Gelade's (1980) feature-integration model claims that the search for separate ("primitive") stimulus features is parallel, but that the conjunctions of those features require serial scan. Recently, evidence has accumulated that parallel processing is not limited to these "primitive" stimulus features, but that combinations of features can also produce parallel search. In the experiments reported here, the processing of feature conjunctions was studied when the stimulus features of a combination were at different spatial scales. The patterns in the search array were composed of three cross-shaped or T-shaped (local) elements, which formed an oblique bar (the global pattern) 45 deg or 135 deg in orientation. When the target and distractors differed from each other at one spatial scale only (either in the bar orientation or in the shape of the local elements), target detection was independent of the number of distractors, i.e., the search was parallel. In the conjunction task, in which the target and distractors were defined as the combinations of the bar orientation and the element shape, i.e., both spatial scales were relevant, the detection of the target required slow serial scrutiny of the search array. It is possible that the conjunction search could not be performed in parallel because switches between the two scales (or spatial frequency channels) are linked to attention and the task required the use of both scales in order to find the target.     

The development of visual search in infants and very young children.

In two experiments, 90 1- to 3-year-olds were trained in a new nonverbal task to touch a video screen that displayed a unique target resembling a popular television character. The target appeared among varying numbers of distractors that resembled another familiar television character and was either a uniquely colored shape (the feature search task) or a unique color-shape combination (the conjunction search task). Each correct response triggered a sound and produced four animated objects on the screen. Irrespective of age and experimental design (between-subjects or within-subjects), children's reaction time (RT) patterns resembled those obtained from adults in corresponding search tasks: The RT slope for feature search was flat and independent of distractor number, whereas the RT slope for conjunction search increased linearly with distractor number. These results extend visual search effects found with adults to infants and very young children and suggest that the basic perceptual processes underlying visual search are qualitatively invariant over ontogeny.     

Does partial difficult search help difficult search?

Olds, Cowan, and Jolicoeur (2000a, 2000b) showed that exposure to a display that affords pop-out search a target among distractors of only one color) can assist processing of a related display that requires difficult search. They added distractors of an additional color to the initial simple display and analyzed response time distributions to show that exposure to the initial display aided subsequent search in the difficult portion (this finding was called search assistance). To test whether search assistance depends on perceptual grouping of the initial items, we presented initial items that were more difficult to group (two colors of distractors, instead of just one). The target appeared (on 50% of the trials) among distractors of two colors, and then after a delay, more distractors of those two colors were added to the display. Exposure to the initial easier portion of the display did not assist processing of the second portion of the display when the initial display contained a large number of items; we found tentative evidence for assistance with small numbers of initial items. In the Olds et al. (2000a, 2000b) studies, it was easy to group the initial distractor items, because they were all the same color. In contrast, in the present study, it was difficult to group the heterogeneous initial distractor items. Search assistance is found only when initial item grouping is relatively easy, and thus we conclude that search assistance depends on grouping.     

The scaling of spatial attention in visual search and its modification in healthy aging

A model of visual search (Greenwood & Parasuraman, 1999) postulating that visuospatial attention is composed of two processing components--shifting and scaling of a variable-gradient attentional focus--was tested in three experiments. Whereas young participants are able to dynamically constrict or expand the focus of visuospatial attention on the basis of prior information, in healthy aging individuals visuospatial attention becomes a poorly focused beam, unable to be constricted around one array element. In the present work, we sought to examine predictions of this view in healthy young and older participants. An attentional focus constricted in response to an element-sized precue had the strongest facilitatory effect on visual search. However, this was true only when the precue correctly indicated the location of a target fixed in size. When precues incorrectly indicated target location or when target size varied, the optimal spatial scale of attention for search was larger, encompassing a number of array elements. Healthy aging altered the deployment of attentional scaling: The benefit of valid precues on search initially (in participants 65-74 years of age) was increased but later (in those 75-85 years of age) was reduced. The results also provided evidence that cue size effects are attentional, not strategic. This evidence is consistent with the proposed model of attentional scaling in visual search.     

纯小数加工的心理机制:选择通达还是平行通达?

采用数字线索提示的目标觉察范式,以60名在校大学生与研究生为被试,设计3个实验探讨纯小数(整数部分是零的小数,例如0.2)的加工及其与空间表征的联系。实验1探讨纯小数作为线索时是否能引起空间注意的空间-数字反应编码联合效应(Spatial Numerical Association of Response Codes,SNARC),结果发现,纯小数数量大小的加工可以引起空间注意的SNARC效应;实验2探讨纯小数的加工是否会同时激活小数点后对应的自然数,结果发现,对纯小数数量大小相同、小数点后对应的自然数是否有0(例如0.2和0.20,0.4和0.40)的加工能引起空间注意的转移;实验3比较纯小数的加工对纯小数本身及小数点后对应的自然数激活强度,结果发现,在纯小数数量大小判断和纯小数小数点后对应的自然数数量大小判断冲突的条件下,纯小数的加工未能引起注意的SNARC效应。该研究结果表明,在目标觉察范式中,纯小数的加工采取了平行通达的方式,引发了注意的SNARC效应,并且纯小数空间注意的转移受到纯小数本身以及对应的自然数的影响。     

比较视觉搜索任务的认知老化研究

本研究通过增加组成图片的图形数量和改变目标图形的特征,考察老年人和大学生在比较视觉搜索任务中的眼动特点和图形特征加工的优先性。结果表明与青年人相比,老年人在比较视觉搜索过程中总注视时间和注视次数增加,平均眼跳幅度减少,对目标刺激的注视时间增加。老年人和青年人在目标刺激的注视过程中都表现出图形维度数量的优先性,即表现为颜色和形状都不同的目标刺激注视时间最短,颜色不同和形状不同的目标刺激在注视时间上差异不显著。说明老年人在比较视觉搜索过程中存在认知老化,在图形特征加工的优先性上结果和青年人一致,以上结果与年龄和研究任务有关。     

Encoding numbers: Behavioral evidence for processing-specific representations

The aim of this study was to test the hypothesis of a complex encoding of numbers according to which each numerical processing requires a specific representational format for input In three experiments, adult participants were given two numbers presented successively on screen through a self-presentation procedure after being asked to add, to subtract, or to compare them. We considered the self-presentation time of the first number as reflecting the complexity of the encoding for a given planned processing. In line with Dehaene's triple-code model, self-presentation times were longer for additions and subtractions than for comparisons with two-digit numbers but longer for subtractions than for additions and comparisons with one-digit numbers. The implications of these results for different theories of number processing are discussed.     

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.     

Visual similarity is stronger than semantic similarity in guiding visual search for numbers

Using a visual search task, we explored how behavior is influenced by both visual and semantic information. We recorded participants’ eye movements as they searched for a single target number in a search array of single-digit numbers (0–9). We examined the probability of fixating the various distractors as a function of two key dimensions: the visual similarity between the target and each distractor, and the semantic similarity (i.e., the numerical distance) between the target and each distractor. Visual similarity estimates were obtained using multidimensional scaling based on the independent observer similarity ratings. A linear mixed-effects model demonstrated that both visual and semantic similarity influenced the probability that distractors would be fixated. However, the visual similarity effect was substantially larger than the semantic similarity effect. We close by discussing the potential value of using this novel methodological approach and the implications for both simple and complex visual search displays.     

Feature-based search asymmetries in pigeons and humans

Pigeon and human subjects searched for one target item amidst a number of identical distractors. Simple line forms were used. The target differed from the distractors only in terms of the presence or absence of a feature (a line or a gap); in some experimental series, the feature was present in the target; in others, the feature was in the distractors. The pigeons pecked at the target; the human subjects either reported the presence of the target or pointed to it with a light pen. The time between display onset and this response was recorded. Varied across experimental conditions were the number of distractors in the display, the nature of the stimulus forms, and certain procedural parameters; five conditions were run with pigeons and three with humans. Under all test conditions, the results from the human subjects replicated the previously reported search-asymmetry effect. That is, search speed was greater and decreased less with display size when the target bore the feature (line or gap) than when the distractors bore the feature; both yes/no and localization-response conditions yielded this effect. However, pigeons failed to show search asymmetry; neither line nor gap in a target facilitated search. The results suggest that early visual processing differs for pigeons and humans, that pigeon features differ from human features, or that search asymmetry was eliminated by the long practice given the pigeons.     

方位维度视觉搜索的影响因素

Duncan等人认为,当目标和干扰子之间差异越大且干扰子彼此之间差异越小时,则目标搜索越快。他们的结论定性地描述了目标搜索斜率（反应时间对呈现项目数的函数）的决定因素。笔者从方位维度刺激关系方面进一步定量探究该问题,并提出决定因素为g(T, D, n)（目标方位和干扰子方位间的函数关系）。实验结果证实目标搜索斜率是由g(T,D,n)值决定,目标搜索斜率随g(T, D, n)值增大而减小,相同g(T, D, n)值条件的目标搜索斜率无显著差异     

Classification without identification in visual search

Six subjects scanned displays of random consonants for a single target which was (a) another consonant; (b) a given number; or (c) any number. A second group of six subjects took part in three comparable conditions with number displays, and letters or numbers as targets. Scanning time for a number in a letter display or a letter in a number display was more rapid than scanning for a target drawn from the same set as the background. Several unpractised subjects, and all the subjects who practised the task, were able to scan as fast through letters for “any number” as for a specific number, or conversely through digits. The finding of different scanning rates for two precisely physically specified targets, depending on which class they were drawn from, runs counter to an explanation of high-speed scanning in terms of the operation of visual feature analysers. It is suggested that familiar categorization responses may be immediate and may provide the basis for the discrimination of relevant from irrelevant items in rapid visual scanning.     

Recognition time for information stored in long-term memory

Two experiments were performed to determine the effects of number of words in a target set (varying from 10 to 26) and the nature of distractor words on the latency of both positive and negative recognition responses. Before the test phase, S memorized a list of words and then was tested with a series of single words. To each presentation S made a positive or negative response to indicate whether or not the word was a member of the memorized target list. Response latency was observed to be an increasing function of memory list length. Negative response latency also was greater if distractor words were visually or semantically similar to specific target words. The results were analyzed in terms of a modified signal detection model. It is assumed that S makes a subjective judgment of the familiarity of a test item and on that basis decides either to respond immediately or to delay the response until a search of the memorized list can be executed. Several different models of the search process are considered and evaluated against latency measures and error data.     

The inability to ignore auditory distractors as a function of visual task perceptual load

Using a response competition paradigm, we investigated the ability to ignore target response-compatible, target response-incompatible, and neutral visual and auditory distractors presented during a visual search task. The perceptual load model of attention (e.g., Lavie & Tsal, 1994) states that task-relevant processing load determines irrelevant distractor processing in such a way that increasing processing load prevents distractor processing. In three experiments, participants searched sets of one (easy search) or six (hard search) similar items. In Experiment 1, visual distractors influenced reaction time (RT) and accuracy only for easy searches, following the perceptual load model. Surprisingly, auditory distractors yielded larger distractor compatibility effects (median RT for incompatible trials minus median RT for compatible trials) for hard searches than for easy searches. In Experiments 2 and 3, during hard searches, consistent RT benefits with response-compatible and RT costs with response-incompatible auditory distractors occurred only for hard searches. We suggest that auditory distractors are processed regardless of visual perceptual load but that the ability to inhibit cross-modal influence from auditory distractors is reduced under high visual load.