颜色凸显条件下基于工作记忆内容的视觉注意

采用记忆任务与视觉搜索任务相结合的实验范式,通过操纵背景颜色与刺激颜色,考察了工作记忆内容对视觉注意的引导是否存在强自动性。实验一通过操作背景颜色以突显记忆项目,结果发现即使工作记忆内容在匹配分心物的情况下仍然自动地捕获视觉注意。实验二通过操作背景颜色以突显目标项目,结果发现工作记忆内容对视觉注意的自动引导作用消失。说明了与工作记忆内容匹配的刺激能够自动地引导视觉注意,但是这种引导并非完全自动化,具有一定的条件性。     

客体工作记忆对注意的导向作用：抑制动机的影响

通过两个实验验证了客体工作记忆内容对注意的导向过程是灵活可控的; 与客体工作记忆内容匹配的刺激既可以捕获注意, 也可以被抑制。实验1通过操作匹配试验概率来诱发不同水平的抑制动机, 考察在客体工作记忆内容对注意的导向作用中抑制动机的影响。匹配试验中有分心物与客体工作记忆内容相同。控制试验中所有搜索项目均与客体工作记忆内容不同。实验2保持实际匹配试验概率恒定, 仅通过改变指导语来调节抑制动机水平, 以排除练习的干扰。两实验结果均表明, 当抑制动机水平较低时, 匹配分心物会捕获注意; 而当抑制动机水平足够高时, 匹配分心物会被抑制。并且, 抑制动机水平的高低还会影响认知控制的效应量和时程。     

Attention capture by contour onsets and offsets: No special role for onsets

In five experiments, we investigated the power of targets defined by the onset or offset of one of an object’s parts (contour onsets and offsets) either to guide or to capture visual attention. In Experiment 1, search for a single contour onset target was compared with search for a single contour offset target against a static background of distractors; no difference was found between the efficiency with which each could be detected. In Experiment 2, onsets and offsets were compared for automatic attention capture, when both occurred simultaneously. Unlike in previous studies, the effects of overall luminance change, new-object creation, and number of onset and offset items were controlled. It was found that contour onset and offset items captured attention equally well. However, display size effects on both target types were also apparent. Such effects may have been due to competition for selection between multiple onset and offset stimuli. In Experiments 3 and 4, single onset and offset stimuli were presented simultaneously and pitted directly against one another among a background of static distractors. In Experiment 3, we examined “guided search,” for a target that was formed either from an onset or from an offset among static items. In Experiment 4, the onsets and offsets were uncorrelated with the target location. Similar results occurred in both experiments: target onsets and offsets were detected more efficiently than static stimuli which needed serial search; there remained effects of display size on performance; but there was still no advantage for onsets. In Experiment 5, we examined automatic attention capture by single onset and offset stimuli presented individually among static distractors. Again, there was no advantage for onset over offset targets and a display size effect was also present. These results suggest that, both in isolation and in competition, onsets that do not form new objects neither guide nor gain automatic attention more efficiently than offsets. In addition, in contrast to previous studies in which onsets formed new objects, contour onsets and offsets did not reliably capture attention automatically.     

Cognitive control over working memory biases of selection

Across many studies, researchers have found that representations in working memory (WM) can guide visual attention toward items that match the features of the WM contents. While some researchers have contended that this occurs involuntarily, others have suggested that the impact of WM contents on attention can be strategically controlled. Here, we varied the probability that WM items would coincide with either targets or distractors in a visual search task to examine (1) whether participants could intentionally enhance or inhibit the influence of WM items on attention and (2) whether cognitive control over WM biases would also affect access to the memory contents in a surprise recognition test. We found visual search to be faster when the WM item coincided with the search target, and this effect was enhanced when the memory item reliably predicted the location of the target. Conversely, visual search was slowed when the memory item coincided with a search distractor, and this effect was diminished, but not abolished, when the memory item was reliably associated with distractors. This strategic dampening of the influence of WM items on attention came at a price to memory, however, as participants were slowest to perform WM recognition tests on blocks in which the WM contents were consistently invalid. These results document that attentional capture by WM contents is partly, but not fully, malleable by top-down control, which appears to adjust the state of the WM contents to optimize search behavior. These data illustrate the role of cognitive control in modulating the strength of WM biases of selection, and they support a tight coupling between WM and attention.     

工作记忆表征的激活与抑制状态对注意引导效应的影响

本研究采用双任务范式, 通过定向遗忘任务操纵工作记忆表征状态, 分别在目标无关和目标相关条件下考察工作记忆激活与抑制状态对视觉搜索早期注意引导效应的影响。实验1与实验2发现当工作记忆表征只可能与视觉搜索分心物匹配时(目标无关条件), 处于激活状态的工作记忆表征会引导视觉注意偏向到与之匹配的分心物, 表现出注意引导效应, 而处于抑制状态的工作记忆表征则没有观察到注意引导效应。实验3与实验4发现, 当工作记忆表征有可能与视觉搜索目标匹配时(目标相关条件), 处于激活状态的工作记忆表征能捕获注意, 而处于抑制状态的工作记忆表征只有与视觉搜索目标匹配时, 才表现出对该搜索目标反应的延迟。这些研究的结果表明(1)处于激活状态的工作记忆表征能有效地引导注意偏向到与之匹配的搜索目标或分心物, 并且这种注意引导效应并未受到抑制动机的影响而被消除或反转; (2)处于抑制状态的工作记忆表征能将抑制状态传递到视觉搜索阶段, 并延迟对与之匹配的搜索目标的反应。     

Novelty and saliency in attentional capture by unannounced motion singletons

The present study examined attentional capture by an unannounced motion singleton in a visual search task. The results showed that a motion singleton only captured attention on its first unannounced occurrence when the observers had not encountered moving items before in the experiment, whereas it failed to capture when observers were familiar with moving items. This indicates that motion can capture attention independently of top-down attentional control settings, but only when motion as a feature is unexpected and new. An additional experiment tested whether salient items can capture attention when all stimuli possess new and unexpected features, and novelty information cannot guide attention. The results showed that attention was shifted to the location of the salient item when all items were new and unexpected, reinforcing the view that salient items receive attentional priority. The implications of these results for current theories of attention are discussed.     

Comparing target detection errors in visual search and manually-assisted search

Subjects searched for low- or high-prevalence targets among static nonoverlapping items or items piled in heaps that could be moved using a computer mouse. We replicated the classical prevalence effect both in visual search and when unpacking items from heaps, with more target misses under low prevalence. Moreover, we replicated our previous finding that while unpacking, people often move the target item without noticing (the unpacking error) and determined that these errors also increase under low prevalence. On the basis of a comparison of item movements during the manually-assisted search and eye movements during static visual search, we suggest that low prevalence leads to broadly reduced diligence during search but that the locus of this reduced diligence depends on the nature of the task. In particular, while misses during visual search often arise from a failure to inspect all of the items, misses during manually-assisted search more often result from a failure to adequately inspect individual items. Indeed, during manually-assisted search, over 90 % of target misses occurred despite subjects having moved the target item during search.     

基于记忆的注意捕获和注意抑制效应：ERP证据

采用工作记忆与视觉搜索双任务范式, 通过操作匹配试次出现概率来诱发不同水平的认知控制动机, 考察了基于记忆的注意引导过程的时程特点。结果：记忆匹配刺激首先诱发了N2pc成分, 随后诱发了与抑制过程相关的差异正波。并且, 认知控制动机水平越高, N2pc波幅越小、潜伏期越短; 抑制性差异正波波幅越大。结论：基于记忆的注意引导过程包括早期的注意捕获和后期的注意抑制两个阶段; 其效应量和时程受到认知控制动机水平的调节。     

When is search for a static target among dynamic distractors efficient?

Intuitively, dynamic visual stimuli, such as moving objects or flashing lights, attract attention. Visual search tasks have revealed that dynamic targets among static distractors can indeed efficiently guide attention. The present study shows that the reverse case, a static target among dynamic distractors, allows for relatively efficient selection in certain but not all cases. A static target was relatively efficiently found among distractors that featured apparent motion, corroborating earlier findings. The important new finding was that static targets were equally easily found among distractors that blinked on and off continuously, even when each individual item blinked at a random rate. However, search for a static target was less efficient when distractors abruptly varied in luminance but did not completely disappear. The authors suggest that the division into the parvocellular pathway dealing with static visual information, on the one hand, and the magnocellular pathway common to motion and new object onset detection, on the other hand, allows for efficient filtering of dynamic and static information.     

工作记忆表征精度加工需求对注意引导的影响

采用注意捕获范式, 通过行为和事件相关脑电位(ERP)实验, 探讨工作记忆表征精度加工需求对注意引导的影响, 行为结果发现, 在低精度加工需求条件下, 只有一个工作记忆表征引导注意, 且处于高激活状态的工作记忆表征产生的注意捕获大于低激活状态; 而在高精度加工需求条件下, 有两个工作记忆表征引导注意, 且处于高、低激活状态的工作记忆表征产生的注意捕获没有差异。ERP结果显示, 高精度加工需求条件下诱发的NSW和LPC大于低精度加工需求条件; 在高精度加工需求条件下, 干扰项与记忆项匹配比不匹配时, 诱发更大的N2和更小的N2pc, 而在低精度加工需求条件下, 干扰项与记忆项匹配和不匹配时诱发的N2、N2pc没有差异。研究表明, 工作记忆表征精度加工需求影响注意引导的机制可能是高精度加工需求下, 工作记忆表征消耗的认知资源增加, 搜索目标获得的资源减少, 干扰项捕获的注意增加。     

The effect of items in working memory on the deployment of attention and the eyes during visual search

Paying attention to an object facilitates its storage in working memory. The authors investigate whether the opposite is also true: whether items in working memory influence the deployment of attention. Participants performed a search for a prespecified target while they held another item in working memory. In some trials this memory item was present in the search display as a distractor. Such a distractor has no effect on search time if the search target is in the display. In that case, the item in working memory is unlikely to be selected as a target for an eye movement, and if the eyes do land on it, fixation duration is short. In the absence of the target, however, there is a small but significant effect of the memory item on search time. The authors conclude that the target for visual search has a special status in working memory that allows it to guide attention. Guidance of attention by other items in working memory is much weaker and can be observed only if the search target is not present in the display.     

Serial deployment of attention during visual search

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks.     

Salience-based progression of visual attention: Time course

In a visual search task, visual attention progresses from the most to the least salient item until a target is found. The time course of such salience-based progression remains unclear although the temporal deployment seems as crucial as the spatial deployment. The present study investigated how the general hierarchical pattern takes place. Healthy volunteers were presented with a primed visual search paradigm in which the primes consisted of three items differing in salience for either 33, 50 or 100 ms. Subsequently one of them became the target and participants had to make a judgment about it. In order to progress on the basis of salience, attention seemed first to be captured by the most salient item. Secondly, the first two most salient items seemed both encompassed within the attentional spotlight. At that time, the least salient item seemed inhibited, completing the stepwise progression of attention. In summary, our data suggest that the hierarchical pattern is built up over time through orienting and expansion of the spotlight, and inhibition of the least salient signals. Furthermore, complementary analyses revealed a proximity effect influencing the selection of the next location to visit. As predicted by different computational models, items located closely to the first visited location were more prone to attract attention than distant items but interestingly enough, this effect only applied to the least salient item suggesting a balance between salience and proximity criteria. Critically also, salience and proximity effects seem to have different time courses. Results are only partially explained by current visual attention models and require further investigation.     

工作记忆表征捕获眼动中的颜色优先性

刺激属性所具有的引导效力在工作记忆表征自上而下地引导注意捕获过程中起重要作用, 已有研究表明工作记忆表征的颜色属性在引导注意时具有一定的优势。研究采用工作记忆任务与视觉搜索任务相结合的双任务范式, 结合眼动追踪技术, 通过设置具有较强引导效力的颜色属性与朝向属性进行直接竞争的实验条件, 进一步考察工作记忆表征的颜色属性是否依然具有优先性。实验1发现工作记忆表征的颜色属性与朝向属性同时竞争眼动捕获时, 颜色属性表现出较强的优势, 而朝向属性单独呈现时并未表现出任何捕获效应。实验2与3进一步证实了颜色属性捕获眼动的优先性, 即当颜色属性在面临作为靶子属性的朝向属性的竞争时, 依然能捕获更多的注视点。这些结果直接证实了工作记忆表征的颜色属性在工作记忆表征的捕获眼动的过程中具有较强的引导效力, 相对于其他刺激属性(如朝向、形状)更具有优先性。     

Coordination of voluntary and stimulus-driven attentional control in human cortex

Visual attention may be voluntarily directed to particular locations or features (voluntary control), or it may be captured by salient stimuli, such as the abrupt appearance of a new perceptual object (stimulus-driven control). Most often, however, the deployment of attention is the result of a dynamic interplay between voluntary attentional control settings (e.g., based on prior knowledge about a target's location or color) and the degree to which stimuli in the visual scene match these voluntary control settings. Consequently, nontarget items in the scene that share a defining feature with the target of visual search can capture attention, a phenomenon termed contingent attentional capture. We used functional magnetic resonance imaging to show that attentional capture by target-colored distractors is accompanied by increased cortical activity in corresponding regions of retinotopically organized visual cortex. Concurrent activation in the temporoparietal junction and ventral frontal cortex suggests that these regions coordinate voluntary and stimulus-driven attentional control settings to determine which stimuli effectively compete for attention.     

Space-based and object-based capacity limitations in visual search

Space-based accounts of visual attention assume that we select a limited spatial region independent of the number of objects it contains. In contrast, object-based accounts suggest that we select objects independent of their location. We investigated the boundary conditions on the selection modes of attention in a series of tachistoscopic visual search tasks, where the nature of capacity limitations on search was examined. Observers had to search for a horizontally oriented target ellipse among differently oriented distractor ellipses. Across four experiments, we orthogonally manipulated target-distractor (TD) similarity and distractor-distractor (DD) similarity. Each experiment consisted of a two-way design: Firstly, with a central cue, we indicated the spatial extent of the relevant search area. Secondly, we varied the number and spatial proximity of items in the display. Performance could be accounted for in terms of capacity limited object-based attention, assuming also that the spatial proximity of items enhances performance when there is high DD-similarity (and grouping). In addition, the cueing effect interacted with spatial proximity when DD-similarity was high, suggesting that grouping was influenced by attention. We propose that any capacity limits on visual search are due to object-based attention, and that the formation of perceptual objects and object groups is also subject to attentional modulation.     

Matching of visual input to only one item at any one time

When we perform a visual search we know what we are looking for and determine where it is. A representation of the object in our working memory, the ‘search-template’, is compared to the items in the scene until a match is found. So far it is unknown whether observers can search for multiple items at the same time. Here we compare the performance of subjects between a task in which they search for one of two target-items in a stream of visual objects and a task with only a single target. We find that search is effectively limited to one item at a time. This limitation occurs for simple and complex objects and even if the subjects have to look for two features from different domains. We conclude that matching has a fundamental capacity-limitation as the visual input can be matched to only one search-template at a time.     

Abrupt visual onsets and selective attention: evidence from visual search

The effect of temporal discontinuity on visual search was assessed by presenting a display in which one item had an abrupt onset, while other items were introduced by gradually removing line segments that camouflaged them. We hypothesized that an abrupt onset in a visual display would capture visual attention, giving this item a processing advantage over items lacking an abrupt leading edge. This prediction was confirmed in Experiment 1. We designed a second experiment to ensure that this finding was due to attentional factors rather than to sensory or perceptual ones. Experiment 3 replicated Experiment 1 and demonstrated that the procedure used to avoid abrupt onset--camouflage removal--did not require a gradual waveform. Implications of these findings for theories of attention are discussed.     

Attentional capture by motion onsets is modulated by perceptual load

The onset of motion captures attention during visual search even if the motion is not task relevant, which suggests that motion onsets capture attention in a stimulus-driven manner. However, we have recently shown that stimulus-driven attentional capture by abruptly appearing objects is attenuated under conditions of high perceptual load. In the present study, we examined the influence of perceptual load on attentional capture by another type of dynamic stimulus: the onset of motion. Participants searched for a target letter through briefly presented low- and high-load displays. On each trial, two irrelevant flankers also appeared, one with a motion onset and one that was static. Flankers defined by a motion onset captured attention in the low-load but not in the high-load displays. This modulation of capture in high-load displays was not the result of overall lengthening of reaction times (RTs) in this condition, since search for a single low-contrast target lengthened RTs but did not influence capture. These results, together with those of previous studies, suggest that perceptual load can modulate attentional capture by dynamic stimuli.     

Selecting from dynamic environments: attention distinguishes between blinking and moving

Pinto, Olivers, and Theeuwes (2006) showed that a static target can be efficiently found among different types of dynamically changing distractors. They hypothesized that attention employs a broad division between static and dynamic information, a hypothesis that conforms with earlier research. In the present study, we investigated whether attention can only make use of this crude division or can exploit more subtle discriminations within the dynamic domain. In Experiment 1, participants were able to efficiently find a blinking target among moving distractors and moving targets among blinking distractors, although all items changed at the same rate and produced the same change in local luminance. In Experiment 2, search for a dynamic target among dynamic distractors was aided when we gave the distractors additional dynamic cues. Experiment 3 showed that making the displays equiluminant affected search efficiency for a static target among moving distractors, but not among blinking distractors. The findings refute the broad division hypothesis and suggest that object continuity plays an important role in selection.