The focus of attention in working memory: evidence from a word updating task

Three experiments examined the cognitive costs of item switching within working memory with a novel word updating task, thereby extending previous research to the field of linguistic stimuli and linguistic-graphemic updating operations. In Experiments 1 and 2 costs for switching between working memory items were evident on the word level, and they increased with an increasing word set size (Experiment 2). In contrast, a surprisingly similar switch effect on the level of letters was not affected by word set size (Experiment 2). Experiment 3 showed that this effect is not simply based on the need for re-orienting visual spatial attention. To account for the overall picture of results, a recursive model of attentional foci is proposed. Moreover, individual working memory span appears to be associated with the accuracy of item switching, but not with its speed.     

Selective attention to elements in working memory

Three experiments with an arithmetic working memory task examine the object switch effect first reported by Garavan (1998), which was interpreted as evidence for a focus of attention within working memory. Experiments 1a and 1b showed object switch costs with a task that requires selective access to items in working memory, but did not involve counting, and did not require updating of working memory contents, thus ruling out two alternative explanations of Garavan's results. Experiment 2 showed object switch costs with a task that required no selective access to working memory contents, but involved updating, thus providing evidence for a second component to the overall object switch costs. Further analyses revealed that the object switch cost increased with memory set size; that there were (smaller) switch costs when the switch was to an item of the same type; that repeating an arithmetic operation does not have the same effect as repeating the object it is applied to; and that object switching is not mediated by backward inhibition of the previously focused object.     

Influence of affective valence on working memory processes

Recent research has revealed widespread effects of emotion on cognitive function and memory. However, the influence of affective valence on working or short-term memory remains largely unexplored. In two experiments, the present study examined the predictions that negative words would capture attention, that attention would be difficult to disengage from such negative words, and that the cost of attention switching would increase the time required to update information in working memory. Participants switched between two concurrent working memory tasks: word recognition and a working memory digit updating task. Experiment 1 showed substantial switching cost for negative words, relative to neutral words. Experiment 2 replicated the first experiment, using a self-report measure of anxiety to examine if switching cost is a function of an anxiety-related attention bias. Results did not support this hypothesis. In addition, Experiment 2 revealed switch costs for positive words without the effect of the attention bias from anxiety. The present study demonstrates the effect of affective valence on a specific component of working memory. Moreover, findings suggest why affective valence effects on working memory have not been found in previous research.     

Ageing and switching of the focus of attention in working memory: results from a modified N-back task.

We conducted two experiments using a modified version of the N-Back task. For younger adults, there was an abrupt increase in reaction time of about 250 ms in passing from N = 1 to N > 1, indicating a cost associated with switching of the focus of attention within working memory. Response time costs remained constant over the range N = 2 to N = 5. Accuracy declined steadily over the full range of N (Experiment 1). Focus switch costs did not interact with either working memory updating (Experiment 1), or global task switching (Experiment 2). There were no age differences in RT costs once general slowing was taken into account, but there was a larger focus-switch-related accuracy cost in older adults than in younger adults. No age sensitivity was found for either updating or global task switching. The results suggest (a) that focus switching is a cognitive primitive, distinct from task switching and updating, and (b) that focus switching shows a specific age-related deficit in the accuracy domain.     

Stimulus–response bindings contribute to item switch costs in working memory

In counter updating tasks, responses are typically faster when items repeat than when they change (item switch costs). The present study explored the contribution of stimulus–response bindings to these item switch costs. In two experiments, we orthogonally manipulated the repetition/switch of to-be-counted items and the repetition/switch of required manual responses. Item switch costs were considerably lower when item switches were accompanied by response switches than when accompanied by response repetitions. Experiment 2 showed that, although there was also a smaller contribution from stimulus–stimulus bindings (i.e., shape-location), the major part was due to stimulus-response bindings. These results show that in the widely used standard version of the counter updating task, a considerable portion of item switch costs is caused by the unbinding of stimulus–response bindings rather than by processes of switching items in working memory.     

Monitoring the capacity of working memory: Executive control and effects of listening effort

In two experiments, we used an interruption-and-recall (IAR) task to explore listeners’ ability to monitor the capacity of working memory as new information arrived in real time. In this task, listeners heard recorded word lists with instructions to interrupt the input at the maximum point that would still allow for perfect recall. Experiment 1 demonstrated that the most commonly selected segment size closely matched participants’ memory span, as measured in a baseline span test. Experiment 2 showed that reducing the sound level of presented word lists to a suprathreshold but effortful listening level disrupted the accuracy of matching selected segment sizes with participants’ memory spans. The results are discussed in terms of whether online capacity monitoring may be subsumed under other, already enumerated working memory executive functions (inhibition, set shifting, and memory updating).     

Simultaneous cognitive operations in working memory after dual-task practice

The authors tested the hypothesis that with adequate practice, people can execute 2 cognitive operations in working memory simultaneously. In Experiment 1, 6 students practiced updating 2 items in working memory through 2 sequences of operations (1 numerical, 1 spatial). In different blocks, imperative stimuli for the 2 sequences of operations were presented either simultaneously or sequentially. Initially, most participants experienced substantial dual-task costs. After 24 sessions of practice, operation latencies for simultaneous presentation were equal to the maximum of times for the 2 operations in the sequential condition, suggesting perfect timesharing. Experiment 2 showed that a reduction of dual-task costs requires practice on the combination of the 2 updating tasks, not just practice on each individual task. Hence, the reduction of dual-task costs cannot be explained by shortening or automatization of individual operations.     

长时联结表征对工作记忆的抑制效应

本研究通过两个实验探讨了长时记忆联结表征如何影响当下工作记忆任务的加工。长时记忆联结表征采用无语义联系、无视觉相似性的Emoji图片对, 提前一天让被试完成联结表征的建立, 正式工作记忆任务采用独立探测的变化觉察范式。实验1控制呈现时间(500 ms / 1000 ms)与呈现方式(联结/独立), 发现两种呈现时间均显示出联结条件的正确率与记忆容量显著低于独立条件, 说明长时记忆联结表征抑制了当前工作记忆的加工。实验2设置了记忆项目数(2/4/6项)与呈现方式(联结/独立), 采用alpha震荡作为脑电指标, 考察长时联结表征在工作记忆维持阶段的作用。结果发现在维持阶段, 独立条件的alpha震荡随着记忆项目数量的增加而增大(2项 < 4项 < 6项), 而联结条件在4项已经到达顶点(2项 < 4项 = 6项)。实验2进一步说明长时联结表征在维持阶段降低了当前工作记忆容量。本研究的两个实验结果表明, 长时记忆联结表征对当前的工作记忆任务有一定的抑制作用, 这种抑制作用产生的机制可能来自于联结表征干扰了维持阶段的注意分配。     

内隐序列学习与中央执行功能的关系

内隐序列学习与一般认知的关系一直处于争议之中。近年来,越来越多的研究显示内隐序列学习与工作记忆（尤其是中央执行功能）存在显著关联。基于此,本研究通过两个实验来探测两者的相关及机制。实验1从行为与脑电两个角度探讨经典位置序列学习与中央执行功能的相关,发现经典位置序列学习的内隐习得量与中央执行功能的抑制、刷新功能的强度呈负相关,与转换功能没有显著相关,脑电结果也支持了这一结论。实验2在内隐序列学习中加入认知冲突来增加中央执行功能的负荷。结果发现在高抑制功能负荷任务条件下,内隐习得量与抑制功能强度的相关性发生了反转,进一步证明内隐序列学习与中央执行功能的抑制子成分在脑功能上的关系：不同条件下呈现竞争、协作等不同状态。     

Effects of working memory load on long-term word priming

Three experiments assessed the role of verbal and visuo-spatial working memory in supporting long-term repetition priming for written words. In Experiment 1, two priming tasks (word stem completion and category-exemplar production) were included with three levels of load on working memory: (1) without memory load, (2) memory load that involved storing a string of six digits, and (3) memory load that involved storing a graphic shape. Experiments 2 and 3 compared the effects of a verbal (Experiment 2) or a visual (Experiment 3) working memory load at encoding on both an implicit (word stem completion) and an explicit test (cued recall). The results show no effect of memory load in any of the implicit memory tests, suggesting that priming does not rely on working memory resources. By contrast, loading working memory at encoding causes a significant disruptive effect on the explicit memory test for words when the load is verbal but not visual.     

Effects of working memory load on long‐term word priming

Three experiments assessed the role of verbal and visuo‐spatial working memory in supporting long‐term repetition priming for written words. In Experiment 1, two priming tasks (word stem completion and category‐exemplar production) were included with three levels of load on working memory: (1) without memory load, (2) memory load that involved storing a string of six digits, and (3) memory load that involved storing a graphic shape. Experiments 2 and 3 compared the effects of a verbal (Experiment 2) or a visual (Experiment 3) working memory load at encoding on both an implicit (word stem completion) and an explicit test (cued recall). The results show no effect of memory load in any of the implicit memory tests, suggesting that priming does not rely on working memory resources. By contrast, loading working memory at encoding causes a significant disruptive effect on the explicit memory test for words when the load is verbal but not visual.     

感知觉加工与概念加工对联结记忆中图片优势效应的影响

本研究采用联结再认范式考察联结记忆中感知觉水平和概念加工程度对图片优势效应的影响。实验1通过呈现清晰或模糊的词语或图片对操纵了感知觉水平,结果发现只有在清晰条件下图片优势效应才会出现;实验2则在模糊条件下通过要求被试想象两个项目之间的关系操纵了概念加工程度,结果发现在有概念加工条件下,出现了图片优势效应。研究结果表明：（1）降低的感知觉水平会导致联结记忆中的图片优势效应消失;（2）对模糊项目对进行概念加工会使联结记忆中出现图片优势效应。     

认知控制子成分与客观风险对信任行为的影响

信任是良好人际关系的基础,在维系社会稳定和谐中起着重要作用。然而,认知控制的子成分（抑制控制、认知灵活性和工作记忆刷新）与客观风险对信任行为的影响机制尚不明确。研究通过三个实验,在控制客观风险高低的同时,分别对刺激—反应一致性、任务转换和工作记忆负载进行操纵,进而考察抑制控制、认知灵活性、工作记忆刷新和客观风险对信任行为的影响。结果发现,抑制控制在反应时上表现出差异,刺激—反应一致条件下被试做出信任的反应时更快;认知灵活性和工作记忆刷新在信任率上表现出差异,不转换条件和低工作记忆负载条件下被试的信任率更高。结果表明,抑制控制主要影响反应组织过程,即为了解决反应冲突而需要更长时间做出反应;认知灵活性和工作记忆刷新则会影响个体的信任决策过程,决定了个体的信任行为表现。此外,研究中还发现客观风险高低表现出跨情景一致性,即三个实验中高风险条件下信任率均显著低于低风险条件,表明客观风险对信任行为的影响具有相对稳定性。研究探讨了认知控制三个子成分和客观风险高低对信任行为产生影响的加工机制,对现实生活中的信任行为有一定的指导意义。     

Modality, concreteness, and set-size effects in a free reconstruction of order task

Would informing subjects which items were presented on the current list remove effects of presentation modality, concreteness, and set size in a long-term free reconstruction of order task? In Experiment 1, a typical modality effect was found: memory for the final item in a list was enhanced when the item was presented auditorily rather than visually. In Experiment 2, order memory was better for concrete than for abstract items. And in Experiment 3, order memory was better when the same six items were presented on every trial than when a unique set of six items was presented. In all conditions in all experiments, the to-be-remembered items were given to the subject at test. These results suggest that contrary to a popular assumption, the reconstruction of order task does not provide a functionally pure measure of order memory     

不稳定控制感剥夺损害工作记忆刷新功能

控制感剥夺会阻碍工作记忆中的转换功能,但对工作记忆中刷新功能的影响机制尚不清楚。据此,本文通过两个实验来探究控制感剥夺对工作记忆刷新功能的影响。结果发现,相较于基线水平,无论是通过行为无助任务（实验1）还是通过信息无助任务（实验2）操纵的稳定控制感剥夺均未阻碍随后的刷新任务;但在不稳定控制感剥夺的条件下（实验2）,刷新任务的成绩显著降低。这表明,控制感剥夺对工作记忆刷新功能的影响依赖于对其操纵的稳定性。     

Single-item memory, associative memory, and the human hippocampus

We tested recognition memory for items and associations in memory-impaired patients with bilateral lesions thought to be limited to the hippocampal region. In Experiment 1 (Combined memory test), participants studied words and then took a memory test in which studied words, new words, studied word pairs, and recombined word pairs were presented in a mixed order. In Experiment 2 (Separated memory test), participants studied single words and then took a memory test involving studied word and new words. In a separate test, they studied word pairs and then took a memory test involving studied word pairs and recombined word pairs. In both experiments, patients were impaired at memory for single items as well as memory for associations, suggesting that the hippocampus is important for both of these memory functions. In Experiment 1, patients appeared to be more impaired at associative memory than item memory. In Experiment 2, patients were similarly impaired at associative memory and item memory. These different findings are considered, including the fact that in Experiment 1 the results depended on the fact that controls produced unexpectedly low false-alarm rates to recombined pairs. We discuss single-item and associative memory from the perspective that the hippocampus and adjacent cortex work cooperatively to signal recognition and that simple dichotomies do not adequately describe the division of labor within the medial temporal lobe.     

How generation affects source memory

Generation effects (better memory for self-produced items than for provided items) typically occur in item memory. Jurica and Shimamura (1999) reported a negative generation effect in source memory, but their procedure did not test participants on the items they had generated. In Experiment 1, participants answered questions and read statements made by a face on a computer screen. The target word was unscrambled, or letters were filled in. Generation effects were found for target recall and source recognition (which person did which task). Experiment 2 extended these findings to a condition in which the external sources were two different faces. Generation had a positive effect on source memory, supporting an overlap in the underlying mechanisms of item and source memory.     

Three layers of working memory: Focus-switch costs and retrieval dynamics as revealed by the N-count task

Two experiments explored the process of switching items in and out of the focus of attention using a new paradigm, the N-count task (adapted from Garavan, 1998; N varied from 1 to 4). This task yielded a focus size of one, indicated by a substantial focus-switch cost for 2-count. Additionally, the focus-switch costs in response time increased with working memory load, indicating an effortful search process occurring at a speed of about 240 ms/item. Maintaining and switching to and from a passive load did not increase the focus-switch costs or decrease memory accuracy, indicating that there is no crosstalk between passive and active items. The results support a concentric theory of working memory: a small focus at its core, a surrounding area of (at least) three readily available items referred to as the outer store, and a still wider region of passive storage, possibly more long-term memory than working memory.     

Conditions for positive and negative recencies in running memory-span recognition

A positive recency effect in a running-span recognition procedure was obtained in Experiment 1 for hits and for intratrial false alarms. In running recall procedures, recency does not fit well with an active updating hypothesis. In Experiment 2, in which the beginning of the target set was marked with a cue upon presentation, the recency effects disappeared. In Experiments 3 and 4 participants were forced to maintain 2 items in memory until the last one was presented for recognition. These three items were the target set. When the last item presentation was uncertain—because of the variable length list—an unexpected negative recency effect appeared. An explanation for this change from positive to negative recency is offered based on the sharing of attentional resources put forward by others for similar procedures.     

Effect of articulatory suppression on task-switching performance: implications for models of working memory

In a series of experiments, we examine some effects of articulatory suppression in task switching. The results from Experiments 1a and 2a showed that switch costs in the articulatory suppression condition were larger than those in the control and tapping conditions when the switching cues were not provided. On the other hand, articulatory suppression did not have any effect on switch costs in Experiments 1b and 2b, where the switching cues were provided. In Experiment 3, using a computer-assisted experimentation, this pattern of data was replicated in a two-factor design with articulatory suppression and switching cues factors. The results indicate that a specific component in working memory, the phonological loop, might contribute to the performance in task switching, at least in situations where the external task cues were not available. The data reported here suggest that the phonological loop plays an important role in one of the executive control processes, and challenge the traditional idea that the slave systems are simply governed by the central executive in the working memory.