The effects of recent practice on task switching

Four experiments investigated the effect of recent selective practice on the cost of switching between 2 tasks afforded by letter-digit pairs: alphabet arithmetic and shape comparison. Experiments 1 and 2 found a greater cost associated with switching to the more recently practiced task: evidence that task-set inertia contributes to switching costs. Experiment 3 found this effect to be limited to trials on which a recently trained stimulus followed another such stimulus: a result problematic for all current theories of task-set priming. Experiment 4 showed that the effect of recent practice was eliminated by active preparation for a task switch: It appears that endogenous task-set preparation reduces the effects of task-set inertia. ((c) 2003 APA, all rights reserved)     

任务切换中切换代价产生的机制

关于任务切换中切换代价的来源和本质,目前主要有三种观点:任务设置惯性、任务设置重构和联结竞争。为揭示三者的关系,研究了在不同延迟时间条件下,预先信息与刺激类型对切换代价的影响机制。结果发现:延迟时间、预先信息和刺激类型对切换代价均有显著的作用,但是,三者之间的二次和三次交互作用均不显著。这表明,切换代价反映了任务设置惯性、任务设置重构和联结竞争三种成分,并且三者的关系是具有可加性的序列认知加工。     

Contextual control over task-set retrieval

Contextual cues signaling task likelihood or the likelihood of task repetition are known to modulate the size of switch costs. We follow up on the finding by Leboe, Wong, Crump, and Stobbe (2008) that location cues predictive of the proportion of switch or repeat trials modulate switch costs. Their design employed one cue per task, whereas our experiment employed two cues per task, which allowed separate assessment of modulations to the cue-repetition benefit, a measure of lower level cue-encoding processes, and to the task-alternation cost, a measure of higher level processes representing task-set information. We demonstrate that location information predictive of switch proportion modulates performance at the level of task-set representations. Furthermore, we demonstrate that contextual control occurs even when subjects are unaware of the associations between context and switch likelihood. We discuss the notion that contextual information provides rapid, unconscious control over the extent to which prior task-set representations are retrieved in the service of guiding online performance.     

预先信息的不确定性与准备时间对任务切换的影响

为揭示任务切换中切换代价的本质, 考察了预先信息与准备时间对任务切换的影响, 结果发现: (1) 预先信息对任务切换有显著的影响效应, 全部信息的反应时和切换代价显著低于无信息和部分信息的反应时和切换代价, 而后二者之间无显著差异; (2) 预先信息的影响效应受到准备时间的调节作用, 在准备时间为100ms时, 预先信息无显著的影响效应, 而在准备时间达到600ms以后, 预先信息的准备效应显著。这说明, 预先信息影响的认知加工是任务设置重构, 并且这种影响效应受到准备时间的调节作用。     

Probing attentional modulation of contextual cueing

The repetition of spatial layout implicitly facilitates visual search (contextual cueing effect; Chun & Jiang, 1998). Although a substantial number of studies have explored the mechanism underlying the contextual cueing effect, the manner in which contextual information guides spatial attention to a target location during a visual search remains unclear. We investigated the nature of attentional modulation by contextual cueing, using a hybrid paradigm of a visual search task and a probe dot detection task. In the case of a repeated spatial layout, detection of a probe dot was facilitated at a search target location and was inhibited at distractor locations relative to nonrepeated spatial layouts. Furthermore, these facilitatory and inhibitory effects possessed different learning properties across epochs (Experiment 1) and different time courses within a trial (Experiment 2). These results suggest that contextual cueing modulates attentional processing via both facilitation to the location of “to-be-attended” stimuli and inhibition to the locations of “to-be-ignored” stimuli.     

Transient spatial attention and the perceived duration of brief visual events

This study was designed to explore the effects of transient attention—the stimulus-driven component of spatial attention—on the perceived duration of a brief visual event. Observers had to compare the duration of two disks presented successively within a single trial. The disks’ location and duration varied independently. One of these disks, the “attended disk”, was preceded by an attentional cue indicating the disk's location, attracting transient attention in advanced to the disk location. This attentional cue was either a typical onset cue (Experiments 1, 2, and 4) or a singleton cue (Experiment 3) that minimized the differences between the cues. The other disk, the “neutral disk”, was cued with a neutral cue that did not convey information regarding the disk location. We found that the attraction of transient attention to the location of the attended disk prolonged its perceived duration, but only when compared to brief nonattend stimuli.     

Individual differences in emotional reactivity moderate the strength of the relationship between attentional and implicit-memory biases towards threat-related stimuli

The study investigated whether the strength of the relationship between attentional and implicit-memory biases for threat-related material can be moderated by individual differences in temperament and personality. A spatial cueing task, where task-irrelevant angry, happy, and neutral faces acted as spatial cues preceding a target, was immediately followed by an unexpected “old/new” task involving previously presented faces. Temperament-based emotional reactivity (ER; one's typical response strength to emotional stimuli) predicted improved memory performance for angry faces in the “old/new” task. Critically, the relationship between the attentional bias towards threat (indexed by a cue validity index, i.e., a difference in response times on trials where cues with angry expression were presented in the same versus different location to the subsequent target) and enhanced implicit-memory for previously presented task-irrelevant threat-related information was found to be moderated by ER. The current findings provide the first evidence that temperament traits can offer novel insights into the mechanisms enhancing cognitive biases towards threat in the typical population.     

意义关联的注意定向效应：基于空间位置的抑制和捕获

采用线索化范式, 通过3个实验建立线索和靶子的意义关联, 考察了意义性线索在不同空间位置的注意定向效应。结果表明, 在下视野出现抑制效应, 且位置越下抑制效应越显著; 在上视野出现捕获效应, 且位置越上捕获效应越显著; 同时注意定向效应的程度受引导线索性质的影响。这些结果说明：(1)客体间的意义关联能够引导视觉空间注意, 表现出不同空间位置的注意定向效应; (2)客体性质能够影响意义关联的注意定向, 表现为客体的生动性越高, 调节能力越强, 抽象性越高, 调节能力越弱; (3)意义关联的注意定向具有规律性变化, 表现为基于空间位置的抑制和捕获效应。     

任务切换理论争议新证据

任务切换是研究认知控制的主要范式之一。大量研究发现切换试次比重复试次的反应时更长,错误率更高,这种差异称为切换代价。任务切换时所产生切换代价的理论解释主要有惯性论、重构论和联结论。近十年来,这些理论均获得新的实验支持和发展,但其争议依旧,没有哪一理论能成功解释任务切换的所有效应。未来研究可以建立整合模型,以准确描述切换代价产生的认知机制。     

Transient attention degrades perceived apparent motion

Transient spatial attention refers to the automatic selection of a location that is driven by the stimulus rather than a voluntary decision. Apparent motion is an illusory motion created by stationary stimuli that are presented successively at different locations. In this study we explored the effects of transient attention on apparent motion. The motion target presentation was preceded by either valid attentional cues that attract attention to the target location in advance (experiments 1-4), neutral cues that do not indicate a location (experiments 1, 3, and 4), or invalid cues that direct attention to a non-target location (experiment 2). Valid attentional cues usually improve performance in various tasks. Here, however, an attentional impairment was found. Observers' ability to discriminate the direction of motion diminished at the cued location. Analogous results were obtained regardless of cue type: singleton cue (experiment 1), central non-informative cue (experiment 2), or abrupt onset cue (experiment 3). Experiment 4 further demonstrated that reversed apparent motion is less likely with attention. This seemingly counterintuitive attentional degradation of perceived apparent motion is consistent with several recent findings, and together they suggest that transient attention facilitates spatial segregation and temporal integration but impairs spatial integration and temporal segregation.     

Spatial cuing in a stereoscopic display: Evidence for a “depth-aware” attentional focus

Two experiments were conducted to explore whether attentional selection occurs in depth, or whether attentional focus is “depth blind,” as suggested by Ghiradelli and Folk (1996). In Experiment 1, observers viewed stereoscopic displays in which one of four spatial locations was cued. Two of the locations were at a near-depth location and two were at a far-depth location, and a single target was presented along with three distractors. The results indicated a larger cost in reaction time for switching attention inx,y and depth than inx,y alone, supporting a “depth-aware” attentional spotlight. In Experiment 2, no distractors were present, similar to the displays used by Ghiradelli and Folk. In this experiment, no effect for switching attention in depth was found, indicating that the selectivity of attention in depth depends on the perceptual load imposed on observers by the tasks and displays.     

Do locally defined feature discontinuities capture attention?

Results from previous visual search studies have suggested that abrupt onsets produce involuntary shifts of attention (i.e., attentional capture), but discontinuities in simple features such as color and brightness do not (Jonides & Yantis, 1988). In the present study we tested whether feature discontinuities (i.e., “singletons”) can produce attentional capture in a visual search task if defined “locally” or over a small spatial range. On each trial, a variable number of letters appeared, one of which differed from the others in color or intensity. The location of this singleton was uncorrelated with target location. Local discontinuities were created by embedding the letters in a dot texture. In Experiment 1, display size effects for singleton targets were not reduced with the addition of a background dot texture. Similar results were obtained in Experiment 2, regardless of variations in texture density. Experiment 3 confirmed that when targets are defined by a color or intensity singleton, they are detected preattentively, and that increasing texture density yields faster detection. We conclude that the spatial range over which feature discontinuities are defined may influence the guidance of spatial attention, but it has no influence on their ability to capture attention.     

Differential effects of cue changes and task changes on task-set selection costs

A task-switching paradigm with a 2:1 mapping between cues and tasks was used to separate cue-switching processes (indexed through pure cue-switch costs) from actual task-switching processes (indexed through additional costs in case of cue and task changes). A large portion of total switch costs was due to cue changes (Experiments 1 and 2), and cue-switch costs but not task-switch costs were sensitive to effects of practice (Experiment 1) and preparation (Experiment 2). In contrast, task-switch costs were particularly sensitive to response-priming effects (Experiments 1 and 2) and task-set inhibition (Experiment 3). Results suggest two processing stages relevant during task-set selection: cue-driven retrieval of task rules from long-term memory and the automatic application of rules to a particular stimulus situation.     

Is “Inhibition of Return” due to the inhibition of the return of attention?

Inhibition of Return (IOR) is usually explained in terms of orienting–reorienting of attention, emphasizing an underlying mechanism that inhibits the return of attention to previously selected locations. Recent data challenge this explanation to the extent that the IOR effect is observed at the location where attention is oriented to, where no reorienting of attention is needed. To date, these studies have involved endogenous attentional selection of attention and thus indicate a dissociation between the voluntary attention of spatial attention and the IOR effect. The present work demonstrates a dissociation between the involuntary orienting of spatial attention and the IOR effect. We combined nonpredictive peripheral cues with nonpredictive central orienting cues (either arrows or gaze). The IOR effect was observed to operate independent of involuntary spatial orienting. These data speak against the “reorienting hypothesis” of IOR. We suggest an alternative explanation whereby the IOR effect reflects a cost in detecting a new event (the target) at the location where another event (a cue) was coded before.     

任务切换机制研究的理论争议与整合

任务切换是执行控制的一种重要功能。切换代价是量化执行控制持续时间的指标。并广泛应用于各个研究领域。但是切换代价在多大程度上体现了执行控制的作用,仍然还存在争论．当前主要存在任务设置重构、任务设置惯性和联结竞争三种理论。本文首先介绍了三种理论的基本观点和实验证据,以及对任务切换加工机制的分析;其次阐明了对三种理论进行整合的相关研究;最后分析了进一步研究的方向。     

Preserved and impaired task-switching abilities in non-demented patients with Parkinson's disease

Existing studies on task switching in Parkinson's disease (PD) patients have led to somewhat different results. In particular, it is unclear whether PD patients have a deficit in attentional control. In this study, we assessed task-switching abilities in samples of non-demented PD patients and elderly controls. We used a paradigm in which there was a random task sequence and the task was cued in every trial. This allowed the investigation of both task-set reconfiguration and task-set dissipation. In terms of the proportion of errors made, the patients showed increased switch cost and congruency effects. For reaction times, PD patients showed enlarged congruency effects on switch trials, specifically in the condition in which we used a short constant response-cue interval (RCI). Nevertheless, in a similar fashion to older controls, the patients showed reductions in reaction time switch cost from a short to a long cue-target interval (CTI) and from a short to a long RCI. While these latter findings, respectively, suggest unimpaired task preparation and task dissipation on correct trials in the PD patients, the overall results show that they have a deficit in biasing and selecting currently relevant task sets and more generally argue in favour of a failure of attentional control in PD.     

The influence of cue-task association and location on switch cost and alternating-switch cost.

Task-switching performance is strongly influenced by whether the imperative stimulus uniquely specifies which task to perform: Switch cost is substantial with bivalent stimuli but is greatly reduced with univalent stimuli, suggesting that available contextual information influences processing in task-switching situations. The present study examined whether task-relevant information provided by task cues influences the magnitude of switch cost in a parallel manner. Cues presented 500 ms prior to a trivalent stimulus indicated which of three tasks to perform. These cues either had a preexisting association with the to-be-performed task (verbal cues), or a recently learned association with the task (spatial and shape cues). The results paralleled the effects of stimulus bivalence: substantial switch cost with recently learned cue-task associations and greatly reduced switch cost with preexisting cue-task associations. This suggests that both stimulus-based and cue-based information can activate the relevant task set, possibly providing external support to endogenous control processes. Alternating-switch cost, a greater cost for switching back to a recently abandoned task, was also observed with both preexisting and recently learned cue-task associations, but only when all tasks were presented in a consistent spatial location. When spatial location was used to cue the to-be-performed tasks, no alternating-switch cost was observed, suggesting that different processes may be involved when tasks are uniquely located in space. Specification of the nature of these processes may prove to be complex, as post-hoc inspection of the data suggested that for the spatial cue condition, the alternating-switch cost may oscillate between cost and benefit, depending on the relevant task.     

注意控制定势和线索类型在注意捕获中的作用

采用前线索范式, 通过3个实验考察了注意控制定势和线索类型在注意捕获中的作用。实验1要求被试搜索颜色奇异项目标或突现目标, 涉及较弱的注意控制定势, 结果表明, 突现线索在作为匹配线索和不匹配线索时都能捕获注意, 而颜色奇异项线索只有在作为匹配线索时才能捕获注意。实验2要求被试搜索具体特征的红色或白色目标, 使被试建立较强的特征搜索定势, 结果表明, 颜色奇异项线索和突现线索在作为匹配线索时都能捕获注意, 但是在不匹配条件下, 颜色奇异项线索被抑制了, 而突现线索不能捕获注意; 实验3采取go/no-go范式, 要求被试对红色目标进行反应, 对白色目标进行抑制, 并通过设置不同的线索-目标时间间隔来进一步考察注意捕获的机制, 结果表明, 在600 ms间隔下, no-go突现线索被抑制, 而对于go颜色奇异项线索来说, 随着时间间隔的增加, 注意捕获效应减少。结果与相倚捕获假说和抑制独立捕获假说不符, 支持注意转移假说：自上而下的注意控制定势通过把注意从和目标不匹配的特征位置转移发挥作用; 颜色奇异项线索和突现线索的注意捕获机制相同, 但是突现线索相对于颜色奇异项线索来说, 在与目标不匹配的条件下, 更容易捕获注意, 更难被抑制。     

Carry-over of attentional settings between distinct tasks: A transient effect independent of top-down contextual biases

Top-down attentional settings can persist between two unrelated tasks, influencing visual attention and performance. This study investigated whether top-down contextual information in a second task could moderate this “attentional inertia” effect. Forty participants searched through letter strings arranged horizontally, vertically, or randomly and then made a judgement about road, nature, or fractal images. Eye movements were recorded to the picture search and findings showed greater horizontal search in the pictures following horizontal letter strings and narrower horizontal search following vertical letter strings, but only in the first 1000 ms. This shows a brief persistence of attentional settings, consistent with past findings. Crucially, attentional inertia did not vary according to image type. This indicates that top-down contextual biases within a scene have limited impact on the persistence of previously relevant, but now irrelevant, attentional settings.     

Investigating the role of exogenous cueing on selection history formation

An abundance of recent empirical data suggest that repeatedly allocating visual attention to task-relevant and/or reward-predicting features in the visual world engenders an attentional bias for these frequently attended stimuli, even when they become task irrelevant and no longer predict reward. In short, attentional selection in the past hinders voluntary control of attention in the present. But do such enduring attentional biases rely on a history of voluntary, goal-directed attentional selection, or can they be generated through involuntary, effortless attentional allocation? An abrupt visual onset triggers such a reflexive allocation of covert spatial attention to its location in the visual field, automatically modulating numerous aspects of visual perception. In this Registered Report, we asked whether a selection history that has been reflexively and involuntarily derived (i.e., through abrupt-onset cueing) also interferes with goal-directed attentional control, even in the complete absence of exogenous cues. To build spatially distinct histories of exogenous selection, we presented abrupt-onset cues twice as often at one of two task locations, and as expected, these cues reflexively modulated visual processing: task accuracy increased, and response times (RTs) decreased, when the cue appeared near the target’s location, relative to that of the distractor. Upon removal of these cues, however, we found no evidence that exogenous selection history modulated task performance: task accuracy and RTs at the previously most-cued and previously least-cued sides were statistically indistinguishable. Thus, unlike voluntarily directed attention, involuntary attentional allocation may not be sufficient to engender historically contingent selection biases.