On the origins of the task mixing cost in the cuing task-switching paradigm

Poorer performance in conditions involving task repetition within blocks of mixed tasks relative to task repetition within blocks of single task is called mixing cost (MC). In 2 experiments exploring 2 hypotheses regarding the origins of MC, participants either switched between cued shape and color tasks, or they performed them as single tasks. Experiment 1 supported the hypothesis that mixed-tasks trials require the resolution of task ambiguity by showing that MC existed only with ambiguous stimuli that afforded both tasks and not with unambiguous stimuli affording only 1 task. Experiment 2 failed to support the hypothesis that holding multiple task sets in working memory (WM) generates MC by showing that systematic manipulation of the number of stimulus-response rules in WM did not affect MC. The results emphasize the role of competition management between task sets during task control.     

动态非注意盲中的分心物加工机制：是否存在抑制

系统考察在控制目标与非目标颜色特征属性的条件下, 动态非注意盲中视觉系统是否存在对分心物的抑制机制。实验一为基线实验, 将目标与非目标设置为相同的白色圆形, 考察被试对不同颜色特征(白色或者黑色)新异刺激的觉察情况; 实验二和实验三通过改变目标与非目标的颜色特征, 进一步探讨视觉系统对分心物(包括非目标和新异刺激)的抑制机制。结果发现, 视觉系统对干扰目标追踪(并计数)任务的分心物均产生抑制作用, 并且不同颜色特征的分心物受到的抑制作用不同, 与目标颜色特征相同的分心物受到的抑制作用较大, 相应新异刺激的觉察率低; 与目标颜色特征区分明显的分心物受到的抑制作用较小, 相应新异刺激的觉察率较高。     

Inhibition of task set: Converging evidence from task choice in the voluntary task-switching paradigm

This study looked for evidence of task-set inhibition in a voluntary task-switching paradigm. Participants performed one of three tasks on a digit: parity (even or odd), size (less than or greater than 5), or distance (near or far from 5). On each trial, they were allowed to choose which task to perform, with encouragement to perform each task equally often overall and in a random sequence. The question was whether participants would avoid performing a task that they had recently switched away from (e.g., the task performed on trial n22), because the task set was still inhibited. Results confirmed that participants strongly avoided performing the n22 task (e.g., ABA) in favor of performing other tasks (e.g., ABC). This occurred both when participants were required to switch tasks every trial (Experiment 1) and when they were allowed to repeat tasks (Experiment 2). The results suggest that a task set is inhibited during switching to a new task, reducing the likelihood that this task will be selected in the near future.     

Task preparation based on precues versus memory: Precues lead to superior performance with two tasks but not with four tasks

There is considerable evidence that task switching proceeds more efficiently with preparation based on explicit precues than on the basis of a learned sequence of tasks. However, this evidence stems almost exclusively from experiments in which participants switched between only two tasks. In two experiments stronger preparation effects with explicit precues compared to memory-based preparation was replicated with two tasks. With four tasks, however, preparation based on memory was at least as efficient as preparation based on precues. A third experiment ruled out the possibility that this latter finding was due to increased difficulty of cue processing with two-dimensional cues. These findings question the generalisability of observations regarding preparation effects that are based on two-task situations. It is suggested that one crucial factor regarding the relative efficiency of precue-based and memory-based preparation pertains to the fact that with two tasks, the relevant task can be determined by knowing only the previous task and whether a switch is required or not. This is not possible with four tasks that require a more elaborated task representation at the outset, which in turn may be more apt to support memory-based preparation.     

The reaction-time task-rule congruency effect is not affected by working memory load: further support for the activated long-term memory hypothesis

Previous studies claimed that task representation is carried out by the activated long-term memory portion of working memory (WM; Meiran and Kessler in J Exp Psychol Human Percept Perform 34:137–157, 2008). The present study provides a more direct support for this hypothesis. We used the reaction-time task-rule congruency effect (RT-TRCE) in a task-switching setup, and tested the effects of loading WM with irrelevant task rules on RT-TRCE. Experiment 1 manipulated WM load in a between-subject design. WM participants performed a color/shape task switching, while having 0, 1 or 3 numerical task rules as WM load. Experiment 2 used a similar load manipulation (1 or 3 rules to load WM) in a within-subject design. Experiment 3 extended these results by loading WM with perceptual tasks that were more similar to the shape/color tasks. The results show that RT-TRCE was not affected by WM load supporting the activated long-term memory hypothesis.     

False recognition without intentional learning

Asked to memorize a list of semantically related words, participants often falsely recall or recognize a highly related semantic associate that has not been presented (the critical lure). Does this false memory phenomenon depend on intentional word reading and learning? In Experiment 1, participants performed a color identification task on distractor words from typical false memory lists. In Experiment 2, participants read the same words. In both experiments, the primary task was followed by a surprise recognition test for actually presented and unpresented words, including the critical lures. False alarms to critical lures were robust and quite equivalent across the two experiments. These results are consistent with an activation/monitoring account of false memory, in which processing of semantic associates can evoke false memories even when that processing is incidental.     

Change blindness and visual memory: Visual representations get rich and act poor

Change blindness is often taken as evidence that visual representations are impoverished, while successful recognition of specific objects is taken as evidence that they are richly detailed. In the current experiments, participants performed cover tasks that required each object in a display to be attended. Change detection trials were unexpectedly introduced and surprise recognition tests were given for nonchanging displays. For both change detection and recognition, participants had to distinguish objects from the same basic‐level category, making it likely that specific visual information had to be used for successful performance. Although recognition was above chance, incidental change detection usually remained at floor. These results help reconcile demonstrations of poor change detection with demonstrations of good memory because they suggest that the capability to store visual information in memory is not reflected by the visual system's tendency to utilize these representations for purposes of detecting unexpected changes.     

Declarative strategies persist under increased cognitive load

When humans simultaneously execute multiple tasks, performance on individual tasks suffers. Complementing existing theories, this article poses a novel question to investigate interactions between memory systems supporting multi-tasking performance: When a primary and dual task both recruit declarative learning and memory systems, does simultaneous performance of both tasks impair primary task performance because learning in the declarative system is reduced, or because control of the primary task is passed to slower procedural systems? To address this question, participants were trained on either a perceptual categorization task believed to rely on procedural learning or one of three different categorization tasks believed to rely on declarative learning. Task performance was examined with and without a simultaneous dual task thought to recruit working memory and executive attention. To test whether the categories were learned procedurally or declaratively, the response keys were switched after a learning criterion had been reached. Large impairments in performance after switching the response keys are taken to indicate procedural learning, and small impairments are taken to indicate declarative learning. Our results suggest that the declarative memory categorization tasks (regardless of task difficulty) were learned by declarative systems, regardless of whether they were learned under dual-task conditions.     

Two distinct patterns of interference in between-attribute Stroop matching tasks

In between-attribute Stroop matching tasks, participants compare the meaning (or the color) of a Stroop stimulus with a probe color (or meaning) while attempting to ignore the Stroop stimulus’s task-irrelevant attribute. Interference in this task has been explained by two competing theories: A semantic competition account and a response competition account. Recent results favor the response competition account, which assumes that interference is caused by a task-irrelevant comparison. However, the comparison of studies is complicated by the lack of a consensus on how trial types should be classified and analyzed. In this work, we review existing findings and theories and provide a new classification of trial types. We report two experiments that demonstrate the superiority of the response competition account in explaining the basic pattern of performance while also revealing its limitations. Two qualitatively distinct interference patterns are identified, resulting from different types of task-irrelevant comparisons. By finding the same interference pattern across task versions, we were additionally able to demonstrate the comparability of processes across two task versions frequently used in neurophysiological and cognitive studies. An integrated account of both types of interference is presented and discussed.     

The Essential Child. Susan Gelman. New York: Oxford University Press. 2003. 392 pages, $49.95 (US), cloth or paper.

To evaluate the claim that correct performance on unexpected transfer false-belief tasks specifically involves mental-state understanding, two experiments were carried out with children with autism, intellectual disabilities, and typical development. In both experiments, children were given a standard unexpected transfer false-belief task and a mental-state-free, mechanical analogue task in which participants had to predict the destination of a train based on true or false signal information. In both experiments, performance on the mechanical task was found to correlate with that on the false-belief task for all groups of children. Logistic regression showed that performance on the mechanical analogue significantly predicted performance on the false-belief task even after accounting for the effects of verbal mental age. The findings are discussed in relation to possible common mechanisms underlying correct performance on the two tasks.     

Trading off switch costs and stimulus availability benefits: An investigation of voluntary task-switching behavior in a predictable dynamic multitasking environment

In the present study, we introduce a novel, self-organized task-switching paradigm that can be used to study more directly the determinants of switching. Instead of instructing participants to randomly switch between tasks, as in the classic voluntary task-switching paradigm (Arrington & Logan, 2004), we instructed participants to optimize their task performance in a voluntary task-switching environment in which the stimulus associated with the previously selected task appeared in each trial after a delay. Importantly, the stimulus onset asynchrony (SOA) increased further with each additional repetition of this task, whereas the stimulus needed for a task switch was always immediately available. We conducted two experiments with different SOA increments (i.e., Exp. 1a = 50 ms, Exp. 1b = 33 ms) to see whether this procedure would induce switching behavior, and we explored how people trade off switch costs against the increasing availability of the stimulus needed for a task repetition. We observed that participants adapted their behavior to the different task environments (i.e., SOA increments) and that participants switched tasks when the SOA in task switches approximately matched the switch costs. Moreover, correlational analyses indicated relations between individual switch costs and individual switch rates across participants. Together, these results demonstrate that participants were sensitive to the increased availability of switch stimuli in deciding whether to switch or to repeat, which in turn demonstrates flexible adaptive task selection behavior. We suggest that performance limitations in task switching interact with the task environment to influence switching behavior.     

Across-task long-term priming: Interaction of task readiness and automatic retrieval

When humans carry out actions in response to external stimulation, they acquire associations between the stimulus and the action it triggered. When the same stimulus is used in two different tasks, the retrieval of associations compiled in the competing task hampers current performance. Previous research suggests that this across-task priming depends on the task set for the preceding task remaining active across the switch of tasks and, thus, competing with the activations needed for the new task. We present two experiments investigating this notion. Participants switched between two semantic classification tasks. In Experiment 1, participants switched between short runs of the two tasks. Across-task priming was observed on switch and repeat trials. In Experiment 2, participants switched between longer runs of the two tasks. Across-task priming was markedly reduced on repeat trials. The data suggest that whether or not across-task priming affects behaviour after the switch trial depends, amongst others, on whether the task set necessary for the previous task spills into the repeat trials. The implications of these findings for mechanisms of cognitive and mnemonic control are discussed.     

Relations between emotion,memory encoding,and time perception

This study examined duration judgments for taboo and neutral words in prospective and retrospective timing tasks. In the prospective task, participants attended to time from the beginning and generated shorter duration estimates for taboo than neutral words and for words that they subsequently recalled in a surprise free recall task. These findings suggested that memory encoding took priority over estimating durations, directing attention away from time and causing better recall but shorter perceived durations for taboo than neutral words. However, in the retrospective task, participants only judged durations in a surprise test at the end, and their duration estimates were longer for taboo than neutral words. Present findings therefore suggest that the same emotion-linked memory encoding processes can cause underestimation of durations in prospective tasks but overestimation in retrospective tasks, as if emotion enhances recall of ongoing events but causes overestimation of the durations of those events in retrospect.     

颜色特征加工任务间的注意瞬脱研究

本研究以两个实验对颜色特征加工任务间的注意瞬脱效应进行探讨。实验一要求被试对首先呈现的两个色块(记忆项)与随后呈现的两个色块(检测项)是否相同进行比较。结果发现,在记忆项与检测项的SOA为220ms的条件下,记忆项加工对认知资源的持续占用使检测项的加工绩效下降。实验二含两个需相继执行的任务(T1和T2),二者均为比较同时呈现在屏幕左右两侧的两色块颜色是否相同。结果发现,对颜色特征的觉察即可产生注意瞬脱效应,其大小及时程与经典的采用字母识别任务的研究获得的注意瞬脱效应相当。上述结果表明,特征搜索的完成需有限认知资源的参与。然而,注意瞬脱过程中,特征加工与需对知觉对象细节信息进行提取的辨别任务(如字母辨别任务)在消耗认知资源的量上并无差别。     

The influences of partner accuracy and partner memory ability on social false memories

In this study, we examined whether increasing the proportion of false information suggested by a confederate would influence the magnitude of socially introduced false memories in the social contagion paradigm Roediger, Meade, & Bergman (Psychonomic Bulletin & Review 8:365–371, 2001). One participant and one confederate collaboratively recalled items from previously studied household scenes. During collaboration, the confederate interjected 0 %, 33 %, 66 %, or 100 % false items. On subsequent individual-recall tests across three experiments, participants were just as likely to incorporate misleading suggestions from a partner who was mostly accurate (33 % incorrect) as they were from a partner who was not at all accurate (100 % incorrect). Even when participants witnessed firsthand that their partner had a very poor memory on a related memory task, they were still as likely to incorporate the confederate’s entirely misleading suggestions on subsequent recall and recognition tests (Exp. 2). Only when participants witnessed firsthand that their partner had a very poor memory on a practice test of the experimental task itself were they able to reduce false memory, and this reduction occurred selectively on a subsequent individual recognition test (Exp. 3). These data demonstrate that participants do not always consider their partners’ memory ability when working on collaborative memory tasks.     

Effects of color on perceptual and conceptual tests of implicit memory

Two experiments are reported that explore why recent investigations of implicit memory failed to find any effects of color information on test performance. In the first experiment, participants studied colored pictures as well as words printed in colored ink without any memory instructions. During the test phase, a verbal and a pictorial version of a color-choice task (a conceptual priming test) were compared to two perceptual tests (word-stem completion and picture-fragment identification). Similar and significant amounts of priming to color occurred in both color-choice tasks. The perceptual tests were found to be sensitive to changes in the stimulus-presentation mode from study to test, but stimuli remaining the same color and those changed to black-and-white did not differ in the priming scores. In the second experiment, a mild division of attention was introduced in the study phase. Once again, priming to color was observed only in the verbal version of a color-choice test and not in the word-stem completion test. Dividing attention did not decrease performance on both implicit tests, whereas an explicit test of color recall for studied pictures suffered from dividing attention at encoding. It is concluded that a perceptual attribute such as color may be represented and coded by conceptual processing. Furthermore, automatic (or not attention-demanding) encoding processes may suffice for later conceptual tests of implicit memory. Previous failures to find any effects of color information on implicit performance are attributed to the use of perceptual priming tests. Received: 30 June 1997 / Accepted: 20 April 1998     

Distracted by distractors: eye movements in a dynamic inattentional blindness task

Inattentional Blindness (IB) occurs when observers engaged in resource-consuming tasks fail to see unexpected stimuli that appear in their visual field. Eye movements were recorded in a dynamic IB task where participants tracked targets amongst distractors. During the task, an unexpected stimulus crossed the screen for several seconds. Individuals who failed to report the unexpected stimulus were deemed to be IB. Being IB was associated with making more fixations and longer gaze times on distractor stimuli, being less likely to fixate the unexpected stimulus, and having lower working memory capacity than those who were not IB. Noticing the unexpected stimulus was not contingent upon fixating it, suggesting that some individuals processed the unexpected stimulus via covert attention. The findings support earlier research on working memory and IB. In addition, IBs were less efficient attentional allocators than those who were not IB, as reflected in their eye tracking of irrelevant distractors.     

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。     

Contextual adjustments in cognitive control across tasks

Does encountering information-processing conflict recruit general mechanisms of cognitive control or change only the representations of specific cues and responses? In the present experiments, a flanker task elicited responses to symbolic information (arrow meaning), whereas Stroop-like tasks elicited responses to nonsymbolic information (color of a letter or location of a target box). Despite these differences, when participants performed the flanker and Stroop tasks intermittently in randomized orders, the extent of information-processing conflict encountered on a particular trial modulated performance on the following trial. On across-task trial pairs, increases in response time to incongruent relative to congruent stimulus arrays were smaller immediately following incongruent trials than immediately following congruent trials. The degree of cognitive control exerted on a particular task thus appears to reflect not only the quality, but also the quantity, of recent experiences of information-processing conflict.     

Local probability effects of repeating irrelevant attributes

We present two experiments in which participants classify stimuli having two potentially conflicting attributes, one of which is response-relevant whereas the other (“irrelevant”) attribute is logically and statistically independent of the response. We introduce a novel design not used with filtering tasks before in which the main factor is the local (i.e., one-step) transition probability π (= 0.25, 0.50, 0.75) that the irrelevant attribute is repeated from one trial to the next. Experiment 1 involved a visual Simon task in which the color of the stimulus is relevant and its location is irrelevant. Experiment 2 used a semantic classification task in which the parity of a digit presented is relevant and its numerical magnitude is irrelevant. The results of both experiments demonstrate that participants in the π = 0.75 group responded faster when the irrelevant attribute is in fact repeated rather than alternated; in contrast, participants in the π = 0.25 group responded faster (Experiment 1) or equally fast (Experiment 2) when the irrelevant attribute is alternated rather than repeated. These expectancy-related effects cannot be attributed to spurious design contingencies as the irrelevant attribute was independent of the relevant attribute (and thus of the response), of the congruency status, and also of their alternation/repetition. One interpretation of our findings is that information about the irrelevant attribute in the previous trial is used much as an informative central precue, so that participants can prepare early processing stages in the current trial, with the corresponding benefits and costs typical of standard cueing studies.