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     

任务转换条件下对特征的并行搜索

采用双任务范式,以两个实验探讨了任务设置与刺激特征的匹配程度对特征搜索方式的影响。要求被试首先辨认数字序列中包含的字母,随后完成特征搜索任务。在实验一中特征搜索任务是检测同时呈现的多个灰色圆点(干扰子）中是否有红色圆点(目标）出现。在实验二中,以多种不同颜色的圆点代替实验一中的灰色干扰子。结果发现：在特征搜索主要由自下而上的信息或自上而下的信息引导的两种条件下,任务设置与刺激特征的匹配程度均不影响特征搜索方式,特征搜索仍以并行方式进行。据上述结果笔者推测,在任务设置与刺激特征不匹配的条件下,视觉加工系统首先调整任务设置使二者相匹配,随后进行高效率的并行搜索,而非在二者不匹配的条件下进行低效率的系列搜索。     

任务维度和任务无关维度干扰信息的同质性影响视觉搜索的神经机制

在三个实验中, 我们利用功能性磁共振成像(functional magnetic resonance imaging, fMRI)技术考察了在简单特征搜索任务和客体内联合搜索任务中任务维度干扰项的同质性(或称一致性, homogeneity)和任务无关维度干扰信息的同质性对视觉搜索行为的影响及其神经机制。主要探讨了三个问题：(1) 任务维度干扰信息的同质性与目标存在性之间交互作用的神经机制; (2) 任务维度干扰信息的同质性与任务无关维度干扰信息的同质性之间的交互作用及其神经机制; (3) 上述神经机制在不同类型的视觉搜索(特征搜索和联合搜索)中的异同。     

情绪调节策略对表情视觉搜索的影响

表情视觉搜索任务是让作为目标的情绪面孔在其他干扰面孔中呈现,并要求被试快速搜索目标以做出反应.本研究采用实验的方法,以表情面孔图片作为实验材料,比较了情绪诱发状态下,情绪调节策略使用与否以及两种不同的情绪调节策略对搜索绩效的影响,同时探讨了目标情绪面孔特征和搜索者即时情绪状态对搜索绩效的作用.结果发现:(1)对微笑面孔的搜索快于生气面孔,且存在显著差异,说明人们对积极的信息有觉察优势;(2)中性情绪状态优于正性和负性情绪状态,且存在显著差异,说明情绪唤起会干扰搜索过程;(3)认知重评和表达抑制策略均优于无情绪调节策略,且存在显著差异.因此,表情搜索绩效与是否使用调节策略、搜索目标特征及搜索者情绪状态有关.     

奖赏预期调节局部注意干扰效应

局部注意干扰效应(Localized attentional interference, LAI)是指在视觉搜索任务中同时搜索在空间上分离的两个目标时, 或者目标周围存在一个无关奇异项时, 这两个关键刺激相距较近时产生的干扰现象。本实验采用视觉搜索范式, 探讨了奖赏预期对局部注意干扰效应的影响。实验1采用双目标搜索任务, 要求被试判断搜索画面中两个奇异项刺激的形状是否相同。结果显示奖赏条件和无奖赏条件都表现出显著的距离主效应, 随着目标间距离增大, 被试的正确率提高, 反应时下降。同时, 在远距离时, 奖赏条件下的正确率高于无奖赏条件, 而在近距离时, 奖赏条件下的正确率反而低于无奖赏条件, 即, 奖赏条件下局部注意干扰效应反而增大。高动机状态增强了两个目标的表征, 反而不利于解决局部注意干扰效应。实验2采用单目标搜索任务, 要求被试判断特定目标的方位并忽略另一无关奇异项刺激。与实验1不同的是, 实验2仅在无奖赏条件下观察到显著的距离主效应, 即被试行为表现在远距离时更好; 而在奖赏条件下, 被试在近距离和远距离的表现一样好, 即没有局部注意干扰效应。这说明在奖赏预期条件, 个体可以有效抑制分心物刺激的干扰, 将注意集中于目标刺激的加工, 从而对局部注意干扰效应产生调节。整个研究表明, 奖赏整体上能够提高对任务相关刺激的表征, 并抑制任务无关刺激, 虽然这并不总是能够提高任务表现。     

视觉负后像对视觉搜索效率的干扰效应

为了探究视觉负后像对视觉搜索效率是否会通过颜色这一特征产生干扰,结合Van Lier后像和视觉搜索范式,通过两个实验考察了负后像对视觉搜索效率的干扰效应,并对负后像填充区域和原始发生区域进行了对比。实验结果表明,在有负后像的情况下,视觉搜索效率明显降低,但是不同颜色之间的差异并不显著;而负后像填充区域的干扰效应要弱于原始发生区域。研究结论对于进一步提高视觉搜索效率的颜色设计以及视觉负后像的新研究方法具有重要的参考意义。     

目标或背景:联合搜索知觉学习的内容

采用颜色-形状联合搜索任务探讨短期特征联结知觉学习的效果和机制。训练被试在由不同颜色和形状组合的字母干扰子中搜索具有特定颜色和形状的目标字母,训练时间约为40分钟。通过训练,被试搜索特定的颜色-形状联结的目标字母的能力有所提升,并且学习效应能够迁移至背景改变目标不变的条件中,但是不能迁移至背景不变目标改变的条件中。这一结果提示,被试在进行短期联合搜索知觉学习时,学习到的是目标,而并非背景或目标与背景的联系。     

基于N2pc成分的视觉空间注意功能老化机制

视觉空间注意是人的一种基本认知功能,对老年人的生活有重要影响。N2pc作为一种与注意选择相关的ERP成分,可以反映注意资源在空间上的分配,是研究视觉空间注意的一个良好指标。本文对此前基于N2pc成分的注意功能老化研究进行了综述。前人研究主要采用视觉搜索范式与空间线索范式。采用视觉搜索范式的研究发现,当目标周围有干扰子时,目标诱发的N2pc在老年人中振幅减小,潜伏期延迟,同时在行为上老年人与年轻人相比,正确率更低,反应时更长; 当目标周围无干扰子时,目标诱发的N2pc振幅老年人与年轻人相当或比年轻人更大,老年人的正确率与年轻人无显著差异。采用空间线索范式的研究发现,与目标无相同特征的线索奇异子(singleton cue)不会诱发N2pc,与目标有相同特征的线索奇异子诱发的N2pc未表现出年龄差异,差异体现在一种反映抑制的ERP成分—Pd上(年轻人有Pd而老年人没有),此时老年人在行为上表现出比年轻人更强的空间线索效应。这些研究共同说明,视觉空间注意功能的老化是一个复杂的过程,涉及到搜索目标时注意分配速度的减慢,对干扰子抑制能力的下降以及基于特征的注意捕获能力的良好保持。     

13~15岁儿童对愤怒表情觉察的特点

本研究以13~15岁的青少年为被试,使用视觉搜索任务,要求被试对呈现在愤怒、愉快和中性图示面孔表情图片中的表情相同和表情不同的图片进行判断,从而检验青少年对愤怒表情、愉快表情和中性表情觉察效果的差异.结果表明:(1)当呈现相同的表情时,青少年对愤怒表情的图片的觉察比对愉快表情的图片的觉察要慢.(2)当呈现的表情中有不同的表情时,青少年对愤怒表情的觉察要快于对愉快表情的觉察.(3)青少年对愤怒表情的搜索斜率低于对愉快表情的搜索斜率.对愤怒表情的搜索和对愉快表情的搜索都为系列搜索.     

颜色对基于时间的视觉选择的影响

旨在探讨颜色属性对基于时间的图形预览搜索的影响及其机制。实验采用视觉标记实验范式的变式考察三种颜色的图形刺激的预览收益。结果发现:搜索与旧干扰物相同颜色的靶子和搜索新异颜色刺激并未出现反应时的差异,而且,两者都快于搜索与新干扰物颜色相同的靶子。这说明,在图形刺激的预览搜索中,观察者没有主动抑制旧干扰物的颜色,而是主动加工新出现的刺激。还探讨了基于颜色标记的抑制机制和主动非抑制机制。     

The effect of novel distractors on performance in focused attention tasks: A cognitive-psychophysiological approach

In the present study, we examined whether or not novel stimuli affect performance in a focused attention task. Participants responded to a central target while an irrelevant distractor in the visual display was occasionally changed. In Experiment 1, both target and distractor were presented centrally within the focus of attention. In Experiment 2, a central target was presented along with an irrelevant distractor at a peripheral location, outside the focus of attention. Novel distractors were associated with longer latencies and enhanced orienting responses (as measured by skin conductance responses) only when presented at an attended location. In contrast, as is demonstrated in Experiment 3, the same peripheral novel distractors interfered with task performance when they possessed task-relevant information. These results indicate that there is a fundamental difference between novel stimuli and task-relevant stimuli. Whereas the former exert influence only within the focus of attention, the latter affect performance even when positioned in an unattended location. Our findings have important implications for the operation of visual attention.     

Priming and intrusion errors in RSVP streams with two response dimensions

Loach and Marí-Beffa (Vis Cogn, 10:513-526, 2003) observed that a distractor stimulus, presented immediately after a behaviorally relevant target stimulus, negatively primed a related probe stimulus indicating that the distractor had been inhibited. They argued that "post-target inhibition" may be a mechanism for preventing interference from temporally proximal stimuli; interference that could potentially result in a binding/intrusion error. In order to test this hypothesis, the authors carried out two rapid serial visual presentation (RSVP) experiments in which participants had to report either the identity (Experiment 1) or color (Experiment 2) of a target letter surrounded by distractor letters. In Experiment 1, a close relationship between priming and errors was observed. When a distractor stimulus showed evidence of being inhibited the participant was less likely to commit a binding error. The opposite was true when a distractor stimulus showed evidence of being facilitated. The results of Experiment 2 showed limited evidence of the same relationship.     

Conflict-induced perceptual filtering

In a variety of conflict paradigms, target and distractor stimuli are defined in terms of perceptual features. Interference evoked by distractor stimuli tends to be reduced when the ratio of congruent to incongruent trials is decreased, suggesting conflict-induced perceptual filtering (i.e., adjusting the processing weights assigned to stimuli associated with the target and with the distractor features). In search of evidence for such a mechanism, we administered a flanker task, in which targets and distractors were defined in terms of stimulus location (Experiment 1) or color (Experiment 2). The efficiency of processing stimuli associated with target and distractor features was assessed in intermixed trials of a visual search task, in which a target had to be detected irrespective of these features. In both experiments search times were shorter for stimuli associated with the target feature than with the distractor feature of the flanker task. This effect was increased under conditions of a reduced congruent/incongruent ratio, thereby providing evidence for conflict-dependent perceptual filtering.     

预期对注意的影响受制于被预期主体是目标还是分心物

以往研究表明, 预期机制和注意机制都能促进感知行为, 但两者以何种方式共同作用于感知行为仍然存在争议, 特别是, 对于预期主体在其中的作用尚不清楚。本研究采用空间提示以及视觉搜索相结合的范式, 通过4个实验, 考察了当被试对目标进行预期以及对分心物进行预期时, 空间预期对空间注意效应的不同影响。结果显示：(1)当目标为预期主体时, 预期对注意效应具有调节作用; (2)当分心物为预期主体时, 预期与注意的作用独立; (3)当目标为预期主体时, 通过刺激数增加而导致的任务难度变化不影响预期和注意之间的关系。这表明, 空间预期是否影响空间注意效应受制于预期主体——当预期主体为目标时, 预期和注意两者交互式地影响感知行为; 当预期主体为分心物时, 预期和注意独立地影响感知行为; 而且, 预期和注意之间的关系不受任务难度影响。     

From reorienting of attention to biased competition: Evidence from hemifield effects

When a distractor was presented simultaneously with or directly following a target, it produced more interference when it was presented in the same visual hemifield as the target than when it was presented in the opposite visual field. This result is interpreted in terms of biased competition; there is more competition between stimuli when they are presented in the same visual field, rather than in opposite visual fields. However, when the distractor was presented 125 msec or more prior to the target, this pattern was reversed. In those cases, there was more distractor interference when target and distractor were presented in opposite visual fields. This can be explained by assuming that attention was captured by the distractor, and that there was an additional cost of reorienting to a location in the opposite visual field.     

Taking a bright view of negative priming in the light of dim stimuli: further evidence for memory confusion during episodic retrieval.

A same-different letter-matching task was used to examine the effects of stimulus intensity on negative priming, which is poorer performance when target letters have been presented as distractor letters on the immediately preceding trial. In Experiment 1, stimulus intensity was manipulated between-participants, whereas in Experiment 2, it varied randomly from trial-to-trial within-participants. In Experiment 1, negative priming was equivalent for both stimulus intensities. In Experiment 2, negative priming effects were larger for repeated intensity stimuli than for nonrepeated intensity stimuli, when stimulus intensity was dim. Furthermore, for repeated intensity stimuli, negative priming effects were enhanced when the overt response required to the stimulus was repeated from prime to probe trial. These results are consistent with the hypothesis that negative priming may be due to memory confusion, rather than to inhibition of the distractor stimuli.     

On the fate of distractor representations

Research on the topic of distractor inhibition has used different empirical approaches to study how the human mind selects relevant information from the environment, and the results are controversially discussed. One key question that typically arises is how selection deals with the irrelevant information. We used a new selection task, in which participants sometimes had to respond to the distractors instead of the target. Importantly, we varied the time interval between stimuli onset and the cue that signaled participants to respond to the distractors. We analyzed RTs and error rates from responses to distractors as a function of how long the target had been processed (and the distractor ignored) before the cue required a response to the distractor (i.e., stimulus-cue SOA). The data are compatible with selection models assuming that distractor stimuli are initially activated and then deactivated. Thus, we argue for selection models assuming top down deactivation of distractor representations that work in parallel with top down activation of target representations.     

Asynchronous stimulus presentation in visual extinction: A psychophysical study

Patients showing visual extinction as a consequence of a unilateral brain lesion can correctly detect a single stimulus in either hemifield but fail to detect the contralesional stimulus (or at least process the stimulus less efficiently) when it is presented simultaneously with an ipsilesional stimulus. In an attempt to uncover the nature of the underlying deficit, some studies have manipulated the temporal characteristics of stimulus presentation. Contra- and ipsilesional stimuli with different stimulus onset asynchronies are typically used. In the present study, visual extinction was investigated in a group of left neglect patients (N=10) using a psychophysical paradigm with different stimulus onset asynchronies of target and distractor stimuli presented in different hemifields. Contrast thresholds for a target grating were determined with the target either in isolation or in the presence of an irrelevant distractor grating. When target and distractor gratings were presented simultaneously, neglect patients showed a significant extinction effect, i.e., a significant interference from the right hemifield distractor with left hemifield contrast sensitivity. When the right hemifield distractor preceded the left hemifield target stimulus by 250 ms, two different patterns of results were observed in the neglect patients. Five patients showed a significant improvement compared to the simultaneous presentation condition, five other patients showed a significant increase of the extinction effect. The results suggest that different underlying mechanisms, maybe due to different lesion locations, can cause extinction in neglect patients.     

The linear separability effect in color visual search: Ruling out the additive color hypothesis

Bauer, Jolicoeur, and Cowan (1996b, 1996c) demonstrated difficult visual search for color targets that were not linearly separable (in color space) from two distractor colors and easier search for linearly separable targets. This suggested that search is mediated by a chromatically linear discrimination mechanism (see D’Zmura, 1991). However, in those experiments, the targets that were not linearly separable fell midway between the distractor colors and thus corresponded to the admix of the distractor colors. An alternate interpretation of the results of Bauer et al. is that search was more difficult when the target corresponded to the distractor admix than when it did not. We tested this hypothesis in three experiments by contrasting conditions in which a target that was not linearly separable did or did not correspond to the admix of the distractor colors. In all cases, a target that was not linearly separable produced difficult search, demonstrating that linear separability determines search performance.     

Divided attention enhances the recognition of emotional stimuli: evidence from the attentional boost effect

The present study examined predictions of the early-phase-elevated-attention hypothesis of the attentional boost effect (ABE), which suggests that transient increases in attention at encoding, as instantiated in the ABE paradigm, should enhance the recognition of neutral and positive items (whose encoding is mostly based on controlled processes), while having small or null effects on the recognition of negative items (whose encoding is primarily based on automatic processes). Participants were presented a sequence of negative, neutral and positive stimuli (pictures in Experiment 1, words in Experiment 2) associated to target (red) squares, distractor (green) squares or no squares (baseline condition). They were told to attend to the pictures/words and simultaneously press the spacebar of the computer when a red square appeared. In a later recognition task, stimuli associated to target squares were recognised better than stimuli associated to distractor squares, replicating the standard ABE. More importantly, we also found that: (a) the memory enhancement following target detection occurred with all types of stimuli (neutral, negative and positive) and (b) the advantage of negative stimuli over neutral stimuli was intact in the DA condition. These findings suggest that the encoding of negative stimuli depends on both controlled (attention-dependent) and automatic (attention-independent) processes.