Tuning perception: Visual working memory biases the quality of visual awareness

Studies of consciousness reveal that it is possible to manipulate subjective awareness of a visual stimulus. For example, items held in visual working memory (VWM) that match target features increase the speed with which the target reaches visual awareness. To examine the effect of VWM on perception, previous studies have mainly used coarse measures of awareness, such as present/absent or forced-choice judgments. These methods can reveal whether or not an individual has seen an item, but they do not provide information about the quality with which the item was seen. Using continuous report methods it has been shown that the fidelity of a perceived item can be affected by whether or not that item is masked. In the present study, we used an object-substitution masking task to examine whether items held in VWM would influence the quality with which a masked target reached awareness, or whether the threshold for awareness was instead affected by stimuli held in memory. We observed that targets matching the contents of VWM were recalled with greater precision compared to items that did not match the contents of VWM. Importantly, this effect occurred without affecting the likelihood of the target being perceived. These results suggest that VWM plays a greater role in modulating the fidelity of perceived representations than in lowering the overall threshold of awareness.     

Working memory can enhance unconscious visual perception

We demonstrate that unconscious processing of a stimulus property can be enhanced when there is a match between the contents of working memory and the stimulus presented in the visual field. Participants first held a cue (a colored circle) in working memory and then searched for a brief masked target shape presented simultaneously with a distractor shape. When participants reported having no awareness of the target shape at all, search performance was more accurate in the valid condition, where the target matched the cue in color, than in the neutral condition, where the target mismatched the cue. This effect cannot be attributed to bottom-up perceptual priming from the presentation of a memory cue, because unconscious perception was not enhanced when the cue was merely perceptually identified but not actively held in working memory. These findings suggest that reentrant feedback from the contents of working memory modulates unconscious visual perception.     

Looking sharp: Becoming a search template boosts precision and stability in visual working memory

Visual working memory (VWM) plays a central role in visual cognition, and current work suggests that there is a special state in VWM for items that are the goal of visual searches. However, whether the quality of memory for target templates differs from memory for other items in VWM is currently unknown. In this study, we measured the precision and stability of memory for search templates and accessory items to determine whether search templates receive representational priority in VWM. Memory for search templates exhibited increased precision and probability of recall, whereas accessory items were remembered less often. Additionally, while memory for Templates showed benefits when instances of the Template appeared in search, this benefit was not consistently observed for Accessory items when they appeared in search. Our results show that becoming a search template can substantially affect the quality of a representation in VWM.     

空间距离对视觉工作记忆巩固的影响

以往研究发现,个体对不同类型的视觉信息进行视觉工作记忆巩固的模式存在差异,如对于方向信息,一次只能有一个项目被巩固进入视觉工作记忆系统,而对于颜色信息,个体则可以一次巩固两个项目进入视觉工作记忆系统。但对于视觉信息的巩固模式是否会受其他因素的影响,目前仍然没有明确的定论。本研究将探讨视觉信息的巩固模式是否可能受到记忆项目空间距离因素的影响。研究采用变化觉察范式、序列-同时呈现操作及控制记忆项目呈现间距的方法,通过3个实验考察记忆项目之间的空间距离是否能够影响个体对颜色信息和方向信息的巩固模式。在三种空间距离水平上序列呈现或同时呈现两个记忆项目,实验结果一致发现记忆项目之间的空间距离会对视觉工作记忆巩固模式产生明显影响,个体在同时呈现条件下的正确率会随着空间距离的增大而降低。这些结果表明对同一类视觉信息进行巩固的过程中所存在的项目数量限制并不是固定的,个体可以采用序列模式或有限容量的并行模式对同一类信息进行巩固,巩固的模式可能与视觉空间注意的分配以及视觉信息所能获得的注意资源有关。     

Indirect assessment of visual working memory for simple and complex objects

Previous research has shown that visual search performance is modulated by the current contents in visual working memory (VWM), even when the contents of VWM are irrelevant to the search task. For example, visual search is faster when the target--rather than a distractor--is surrounded by a shape currently held in VWM. This study uses the modulation of visual search by VWM to investigate properties of VWM. Participants wereasked to remember the color or the shape of novel polygons whose "goodness" of figure varied according to Garner's (1962) rotation and reflection transformation principle. During the memory retention interval, participants searched for a tilted line among vertical lines embedded inside colored polygons. Search was faster when the target--rather than a distractor--was enclosed by the remembered polygons. The congruity effect diminished with increasing memory load and decreasing figure goodness. We conclude that congruity effects in visual search can indirectly assess VWM representation strength.     

注意范围分布对视觉工作记忆巩固过程的影响

以往研究发现个体能够同时巩固一定数量的项目信息进入视觉工作记忆系统。本研究将考察视觉工作记忆的巩固容量是否会受到分配到记忆项目上的注意资源量的影响。实验1在同时序列掩蔽范式的基础上, 用控制记忆项目呈现区域的大小的方法操纵被试的注意范围, 从而达到操纵分配到单个项目上的注意资源量的目的。研究结果显示, 被试的记忆成绩随着注意范围的扩大显著降低, 但在并行和序列呈现条件之间不存在显著差异; 实验2则证实实验1中对注意资源量分配的控制不会影响对项目的知觉编码效率。本研究结果表明, 分配在记忆项目上的注意资源量能够影响记忆巩固的效率, 但不会影响巩固容量。     

Strategic and automatic effects of visual working memory on attention in visual search

Previous research indicates that visual attention can be automatically captured by sensory inputs that match the contents of visual working memory. However, Woodman and Luck (2007) showed that information in working memory can be used flexibly as a template for either selection or rejection according to task demands. We report two experiments that extend their work. Participants performed a visual search task while maintaining items in visual working memory. Memory items were presented for either a short or long exposure duration immediately prior to the search task. Memory was tested by a change-detection task immediately afterwards. On a random half of trials items in memory matched either one distractor in the search task (Experiment 1) or three (Experiment 2). The main result was that matching distractors speeded or slowed target detection depending on whether memory items were presented for a long or short duration. These effects were more in evidence with three matching distractors than one. We conclude that the influence of visual working memory on visual search is indeed flexible but is not solely a function of task demands. Our results suggest that attentional capture by perceptual inputs matching information in visual working memory involves a fast automatic process that can be overridden by a slower top-down process of attentional avoidance.     

Orienting attention in visual working memory reduces interference from memory probes

Given a changing visual environment, and the limited capacity of visual working memory (VWM), the contents of VWM must be in constant flux. Using a change detection task, the authors show that VWM is subject to obligatory updating in the face of new information. Change detection performance is enhanced when the item that may change is retrospectively cued 1 s after memory encoding and 0.5 s before testing. The retro-cue benefit cannot be explained by memory decay or by a reduction in interference from other items held in VWM. Rather, orienting attention to a single memory item makes VWM more resistant to interference from the test probe. The authors conclude that the content of VWM is volatile unless it receives focused attention, and that the standard change detection task underestimates VWM capacity.     

Searching while loaded: Visual working memory does not interfere with hybrid search efficiency but hybrid search uses working memory capacity

In “hybrid search” tasks, such as finding items on a grocery list, one must search the scene for targets while also searching the list in memory. How is the representation of a visual item compared with the representations of items in the memory set? Predominant theories would propose a role for visual working memory (VWM) either as the site of the comparison or as a conduit between visual and memory systems. In seven experiments, we loaded VWM in different ways and found little or no effect on hybrid search performance. However, the presence of a hybrid search task did reduce the measured capacity of VWM by a constant amount regardless of the size of the memory or visual sets. These data are broadly consistent with an account in which VWM must dedicate a fixed amount of its capacity to passing visual representations to long-term memory for comparison to the items in the memory set. The data cast doubt on models in which the search template resides in VWM or where memory set item representations are moved from LTM through VWM to earlier areas for comparison to visual items.     

Working memory biasing of visual perception without awareness

Previous research has demonstrated that the contents of visual working memory can bias visual processing in favor of matching stimuli in the scene. However, the extent to which such top-down, memory-driven biasing of visual perception is contingent on conscious awareness remains unknown. Here we showed that conscious awareness of critical visual cues is dispensable for working memory to bias perceptual selection mechanisms. Using the procedure of continuous flash suppression, we demonstrated that “unseen” visual stimuli during interocular suppression can gain preferential access to awareness if they match the contents of visual working memory. Strikingly, the very same effect occurred even when the visual cue to be held in memory was rendered nonconscious by masking. Control experiments ruled out the alternative accounts of repetition priming and different detection criteria. We conclude that working memory biases of visual perception can operate in the absence of conscious awareness.     

视觉工作记忆对前注意阶段注意定向的调节

在注意阶段,视觉工作记忆与注意共享某些特征时,视觉工作记忆内容会引导注意定向。在前注意阶段的影响又是如何？对此问题的研究却很少见,本研究采用工作记忆与基于特征的视觉搜索相结合的任务深入探讨了此问题。研究结果发现：即使在前注意阶段,注意定向也会受到视觉工作记忆自上而下的调节。然而与注意阶段不同的是：当视觉工作记忆内容与随后视觉搜索任务的目标相关时,与记忆内容匹配的搜索项目会引导注意定向到该项目所在的位置,但只有此项目作为分心物时,才会明显地延迟对靶子的加工,而此项目作为靶子时,这种影响并不明显;当视觉工作记忆中保持的项目与随后视觉搜索任务的目标无关时,注意会忽略视觉工作记忆中保持的项目,有效地检测靶子     

The cost of facing fear: Visual working memory is impaired for faces expressing fear

Previous research has identified numerous factors affecting the capacity and accuracy of visual working memory (VWM). One potentially important factor is the emotionality of the stimuli to be encoded and held in VWM. We often must hold in VWM information that is emotionally charged, but much is still unknown about how the emotionality of stimuli impacts VWM performance. In the current research, we performed four studies examining the impact of fearful facial expressions on VWM for faces. Fearful expressions were found to produce a consistent cost to VWM performance. This cost was modulated by encoding time, but not set size. This cost was only present for faces in an upright orientation consistent with this cost being a product of the emotionality of the faces rather than lower‐level perceptual differences between neutral and fearful faces. These findings are discussed in the context of existing theoretical accounts of the impact of emotion on information processing. We suggest that a number of competing effects drive both costs and benefits and are at play when emotional information must be stored in VWM, with the task context determining the balance between them.     

Action relevance induces an attentional weighting of representations in visual working memory

Information maintained in visual working memory (VWM) can be strategically weighted according to its task-relevance. This is typically studied by presenting cues during the maintenance interval, but under natural conditions, the importance of certain aspects of our visual environment is mostly determined by intended actions. We investigated whether representations in VWM are also weighted with respect to their potential action relevance. In a combined memory and movement task, participants memorized a number of items and performed a pointing movement during the maintenance interval. The test item in the memory task was subsequently presented either at the movement goal or at another location. We found that performance was better for test items presented at a location that corresponded to the movement goal than for test items presented at action-irrelevant locations. This effect was sensitive to the number of maintained items, suggesting that preferential maintenance of action relevant information becomes particularly important when the demand on VWM is high. We argue that weighting according to action relevance is mediated by the deployment of spatial attention to action goals, with representations spatially corresponding to the action goal benefitting from this attentional engagement. Performance was also better at locations next to the action goal than at locations farther away, indicating an attentional gradient spreading out from the action goal. We conclude that our actions continue to influence visual processing at the mnemonic level, ensuring preferential maintenance of information that is relevant for current behavioral goals.     

Spatiotemporal competition and task-relevance shape the spatial distribution of emotional interference during rapid visual processing: Evidence from gaze-contingent eye-tracking

People’s ability to perceive rapidly presented targets can be disrupted both by voluntary encoding of a preceding target and by spontaneous attention to salient distractors. Distinctions between these sources of interference can be found when people search for a target in multiple rapid streams instead of a single stream: voluntary encoding of a preceding target often elicits subsequent perceptual lapses across the visual field, whereas spontaneous attention to emotionally salient distractors appears to elicit a spatially localized lapse, giving rise to a theoretical account suggesting that emotional distractors and subsequent targets compete spatiotemporally during rapid serial visual processing. We used gaze-contingent eye-tracking to probe the roles of spatiotemporal competition and memory encoding on the spatial distribution of interference caused by emotional distractors, while also ruling out the role of eye-gaze in driving differences in spatial distribution. Spontaneous target perception impairments caused by emotional distractors were localized to the distractor location regardless of where participants fixated. But when emotional distractors were task-relevant, perceptual lapses occurred across both streams while remaining strongest at the distractor location. These results suggest that spatiotemporal competition and memory encoding reflect a dual-route impact of emotional stimuli on target perception during rapid visual processing.     

视觉工作记忆负载类型对注意选择的影响

通过操纵Flanker任务相对于视觉工作记忆任务的呈现位置, 探讨在视觉工作记忆编码和保持阶段, 精度负载和容量负载对注意选择的影响。行为结果发现, Flanker任务呈现位置和视觉工作记忆负载类型影响注意选择; ERP结果发现, 在保持阶段, 当搜索目标和干扰项不一致时, 负载类型影响N2成分。研究表明, 在编码阶段, 视觉工作记忆负载主要通过占用更多知觉资源降低干扰效应, 支持知觉负载理论; 而在保持阶段, 当Flanker任务位于记忆项内部时, 两类负载在工作记忆表征过程中不同的神经活动导致投入到注意选择的认知控制资源不同, 可能是两类负载影响保持阶段注意选择的机制。     

Words,shape, visual search and visual working memory in 3‐year‐old children

Do words cue children's visual attention, and if so, what are the relevant mechanisms? Across four experiments, 3‐year‐old children (N = 163) were tested in visual search tasks in which targets were cued with only a visual preview versus a visual preview and a spoken name. The experiments were designed to determine whether labels facilitated search times and to examine one route through which labels could have their effect: By influencing the visual working memory representation of the target. The targets and distractors were pictures of instances of basic‐level known categories and the labels were the common name for the target category. We predicted that the label would enhance the visual working memory representation of the target object, guiding attention to objects that better matched the target representation. Experiments 1 and 2 used conjunctive search tasks, and Experiment 3 varied shape discriminability between targets and distractors. Experiment 4 compared the effects of labels to repeated presentations of the visual target, which should also influence the working memory representation of the target. The overall pattern fits contemporary theories of how the contents of visual working memory interact with visual search and attention, and shows that even in very young children heard words affect the processing of visual information.     

Working memory and target-related distractor effects on visual search

We examined two forms of top-down effects on visual selection: (1) information held in working memory (WM) and (2) the semantic relations between targets and distractors. We found that items held in WM affected search for a different target. This WM-based interference effect generalized across different exemplars, even though participants could remember the specific exemplar on the trial. This argues against a memory top-up account of performance. In addition, there was interference from distractors that were not held in WM but were semantically related to the target. The effects of WM capture and the effects of capture by a distractor related to the target combined additively. The data suggest that task-irrelevant information in WM and task-relevant templates for targets compete separately for selection. The implications for understanding top-down processes in search are discussed.     

Concurrent guidance of attention by multiple working memory items: Behavioral and computational evidence

During visual search, task-relevant representations in visual working memory (VWM), known as attentional templates, are assumed to guide attention. A current debate concerns whether only one (Single-Item-Template hypothesis; SIT) or multiple (Multiple-Item-Template hypothesis; MIT) items can serve as attentional templates simultaneously. The current study was designed to test these two hypotheses. Participants memorized two colors, prior to a visual-search task in which the target and the distractor could match or not match the colors held in VWM. Robust attentional guidance was observed when one of the memory colors was presented as the target (reduced response times (RTs) on target-match trials) or the distractor (increased RTs on distractor-match trials). We constructed two drift-diffusion models that implemented the MIT and SIT hypotheses, which are similar in their predictions about overall RTs, but differ in their predictions about RTs on individual trials. Critically, simulated RT distributions and error rates revealed a better match of the MIT hypothesis to the observed data than the SIT hypothesis. Taken together, our findings provide behavioral and computational evidence for the concurrent guidance of attention by multiple items in VWM.

     

The Gestalt principle of similarity benefits visual working memory

Visual working memory (VWM) is essential for many cognitive processes, yet it is notably limited in capacity. Visual perception processing is facilitated by Gestalt principles of grouping, such as connectedness, similarity, and proximity. This introduces the question, do these perceptual benefits extend to VWM? If so, can this be an approach to enhance VWM function by optimizing the processing of information? Previous findings have demonstrated that several Gestalt principles (connectedness, common region, and spatial proximity) do facilitate VWM performance in change detection tasks (Jiang, Olson, & Chun, 2000; Woodman, Vecera, & Luck, 2003; Xu, 2002, 2006; Xu & Chun, 2007). However, one prevalent Gestalt principle, similarity, has not been examined with regard to facilitating VWM. Here, we investigated whether grouping by similarity benefits VWM. Experiment 1 established the basic finding that VWM performance could benefit from grouping. Experiment 2 replicated and extended this finding by showing that similarity was only effective when the similar stimuli were proximal. In short, the VWM performance benefit derived from similarity was constrained by spatial proximity, such that similar items need to be near each other. Thus, the Gestalt principle of similarity benefits visual perception, but it can provide benefits to VWM as well.     

Understanding age-related reductions in visual working memory capacity: Examining the stages of change detection

Visual working memory (VWM) capacity is reduced in older adults. Research has shown age-related impairments to VWM encoding, but aging is likely to affect multiple stages of VWM. In the present study, we recorded the event-related potentials (ERPs) of younger and older adults during VWM maintenance and retrieval. We measured encoding-stage processing with the P1 component, maintenance-stage processing with the contralateral delay activity (CDA), and retrieval-stage processing by comparing the activity for old and new items (old–new effect). Older adults showed lower behavioral capacity estimates (K) than did younger adults, but surprisingly, their P1 components and CDAs were comparable to those of younger adults. This remarkable dissociation between neural activity and behavior in the older adults indicated that the P1 and CDA did not accurately assess their VWM capacity. However, the neural activity evoked during VWM retrieval yielded results that helped clarify the age-related differences. During retrieval, younger adults showed early old–new effects in frontal and occipital areas and a late central–parietal old–new effect, whereas older adults showed a late right-lateralized parietal old–new effect. The younger adults’ early old–new effects strongly resembled an index of perceptual fluency, suggesting that perceptual implicit memory was activated. The activation of implicit memory could have facilitated the younger adults’ behavior, and the lack of these early effects in older adults may suggest that they have much lower-resolution memory than do younger adults. From these data, we speculated that younger and older adults store the same number of items in VWM, but that younger adults store a higher-resolution representation than do older adults.