Bivalency is costly: bivalent stimuli elicit cautious responding

When performing tasks in alternation, substantial slowing occurs when the stimuli have features relevant to both tasks (i.e., when stimuli are bivalent as opposed to univalent). One possible source of this slowing, herein called a bivalency cost, is that encountering bivalent stimuli leads to a more cautious response style. To investigate this, we employed a paradigm that required performing three simple tasks, with bivalent stimuli occasionally encountered on one task. The results show that regardless of the feature overlap among the stimuli used for the different tasks, the introduction of bivalent stimuli slowed responding on all tasks and it was accompanied by a decrease in response errors. Overall, it appears that bivalent stimuli recruit a more cautious approach to task-switching performance.     

The bivalency effect: adjustment of cognitive control without response set priming

The occasional occurrence of bivalent stimuli, that is, stimuli with features relevant to two tasks, slows performance on subsequent tasks with univalent stimuli, including those which have no common features with bivalent stimuli (i.e., the “bivalency effect”). We have suggested that the bivalency effect might stem from an episodic context binding arising from the occasional occurrence of bivalent stimuli. However, as the same response set is used usually for univalent and bivalent stimuli, bivalent stimulus features may be negatively primed via response features. We investigated this possibility in two experiments, in which one group of participants used the same response keys for all tasks and another group used separate response keys. The results showed a comparable bivalency effect in both groups. Thus, it rather results from episodic context binding than from response set priming.     

The bivalency effect represents an interference-triggered adjustment of cognitive control: An ERP study

When bivalent stimuli (i.e., stimuli with relevant features for two different tasks) occur occasionally among univalent stimuli, performance is slowed on subsequent univalent stimuli even if they have no overlapping stimulus features. This finding has been labeled the bivalency effect. It indexes an adjustment of cognitive control, but the underlying mechanism is not well understood yet. The purpose of the present study was to shed light on this question, using event-related potentials. We used a paradigm requiring predictable alternations between three tasks, with bivalent stimuli occasionally occurring on one task. The results revealed that the bivalency effect elicited a sustained parietal positivity and a frontal negativity, a neural signature that is typical for control processes implemented to resolve interference. We suggest that the bivalency effect reflects interference, which may be caused by episodic context binding.     

More than a surprise: The bivalency effect in task switching

When switching tasks, if stimuli are presented that contain features that cue two of the tasks in the set (i.e., bivalent stimuli), performance slowing is observed on all tasks. This generalized slowing extends to tasks in the set which have no features in common with the bivalent stimulus and is referred to as the bivalency effect. In previous work, the bivalency effect was invoked by presenting occasionally occurring bivalent stimuli; therefore, the possibility that the generalized slowing is simply due to surprise (as opposed to bivalency) has not yet been discounted. This question was addressed in two task switching experiments where the occasionally occurring stimuli were either bivalent (bivalent version) or merely surprising (surprising version). The results confirmed that the generalized slowing was much greater in the bivalent version of both experiments, demonstrating that the magnitude of this effect is greater than can be accounted for by simple surprise. This set of results confirms that slowing task execution when encountering bivalent stimuli may be fundamental for efficient task switching, as adaptive tuning of response style may serve to prepare the cognitive system for possible future high conflict trials.     

More conflict does not trigger more adjustment of cognitive control for subsequent events: A study of the bivalency effect

Encountering a conflict triggers an adjustment of cognitive control. This adjustment of cognitive control can even affect subsequent performance. The purpose of the present study was to determine whether more conflict triggers more adjustment of cognitive control for subsequent performance. To this end, we focussed on the bivalency effect, that is, the adjustment of cognitive control following the conflict induced by bivalent stimuli (i.e., stimuli with relevant features for two tasks). In two experiments, we tested whether the amount of conflict triggered by bivalent stimuli affected the bivalency effect. Bivalent stimuli were either compatible (i.e., affording one response) or incompatible (i.e., affording two different responses). Thus, compatible bivalent stimuli involved a task conflict, whereas incompatible bivalent stimuli involved a task and a response conflict. The results showed that the bivalency effect was not affected by this manipulation. This indicates that more conflict does not trigger more adjustment of cognitive control for subsequent performance. Therefore, only the occurrence of conflict – not its amount – is determinant for cognitive control.     

The bivalency effect: evidence for flexible adjustment of cognitive control

When bivalent stimuli (i.e., stimuli with features for two different tasks) appear occasionally, performance is slower on subsequent univalent stimuli. This "bivalency effect" reflects an adjustment of cognitive control arising from the more demanding context created by bivalent stimuli. So far, it has been investigated only on task switch trials, but not on task repetition trials. Here, we used a paradigm with predictable switches and repetitions on three tasks, with bivalent stimuli occasionally occurring on one task. In three experiments, we found a substantial bivalency effect for all trials with at least one source of conflict. However, this effect was reduced for the repetition trials sharing no features with bivalent stimuli, that is, for those without conflict. This confirms that the bivalency effect reflects an adjustment of cognitive control. The news is that this adjustment of cognitive control is sensitive to the presence of conflict, but neither to its amount nor to its source.     

双价效应及其认知机制

任务转换时, 如果一个刺激不仅包含当前任务的特征还包含另一任务的关联特征, 这样的刺激被称为双价刺激。双价刺激能影响个体对单价刺激的加工, 使个体对后续所有单价刺激的反应减慢, 这种现象被称为双价效应(bivalency effect)。研究者发现双价效应具有一定的普遍性和稳定性。对双价效应的理论解释主要有情境捆绑说和基于经验的预测模型。双价效应的产生与额外视觉特征的提取及自上而下的认知控制调整有关, 前者主要与颞-顶联合区的激活有关, 后者主要与背侧前扣带回以及前辅助运动区的激活相关。     

A role for recency of response conflict in producing the bivalency effect

The bivalency effect is a block-wise response slowing that is observed during task-switching when rare stimuli that cue two tasks (bivalent stimuli) are encountered. This adjustment in response style affects all trials that follow bivalent stimuli, including those trials that do not share any features with bivalent stimuli. However, the specific stimulus and response properties that trigger the bivalency effect are not well understood. In typical bivalency effect experiments, bivalent stimuli can be congruent or incongruent with respect to the response afforded by the irrelevant stimulus feature, and this distinction has never been examined. In the present study, we show that cognitive load defined by the response incongruence on bivalent trials plays a critical role in producing the subsequent response slowing observed in the bivalency effect, as well as maintaining the magnitude of the bivalency effect across practice. We propose that the bivalency effect reflects a process involved in predicting future cognitive load based on recent cognitive load experience. This is in line with a recent proposal for a role of the ACC in monitoring ongoing changes in the environment to optimize future performance (Sheth et al., in Nature 488:218–221, 2012).     

Beyond monitoring: After-effects of responding to prospective memory targets

Responding to bivalent stimuli (i.e., stimuli with features relevant for different tasks) slows subsequent performance. In prospective memory research, prospective memory targets can be considered as bivalent stimuli because they typically involve features relevant for both the prospective memory task and the ongoing task. The purpose of this study was to investigate how responding to a prospective memory target slows subsequent performance. In two experiments, we embedded the prospective memory task in a task-switching paradigm and we manipulated the degree of task-set overlap between the prospective memory task and the ongoing task. The results showed consistent after-effects of responding to prospective memory targets. The specific trajectory of the slowing depended on the amount of task-set overlap. These results demonstrate that responding to prospective memory targets results in after-effects, a so far neglected cost on ongoing task performance.     

Task switching: effects of practice on switch and mixing costs

In the task-switching paradigm, mixing costs indicate the performance costs to mix two different tasks, while switch costs indicate the performance costs to switch between two sequentially presented tasks. Applying tasks with bivalent stimuli and responses, many studies demonstrated substantial mixing and switch costs and a reduction of these costs as a result of practice. The present study investigates whether extensive practice of a task-switching situation including tasks with univalent stimuli eliminates these costs. Participants practiced switching between a visual and an auditory task. These tasks were chosen because they had shown eliminated performance costs in a comparable dual-task practice study (Schumacher et al. Psychol Sci 12:101–108, 2001). Participants either performed the tasks with univalent responses (i.e., visual-manual and auditory-verbal stimulus–response mappings) or bivalent responses (i.e., visual-manual and auditory-manual stimulus–response mappings). Both valence conditions revealed substantial mixing and switch costs at the beginning of practice, yet, mixing costs were largely eliminated after eight practice sessions while switch costs were still existent.     

A new look at “the hard problem” of bilingual lexical access: evidence for language-switch costs with univalent stimuli

Considerable work has used language-switching tasks to investigate how bilinguals manage competition between languages. Language-switching costs have been argued to reflect persisting inhibition or persisting activation of a non-target language. However, these costs might instead reflect the use of bivalent stimuli (i.e. pictures or digits that can be responded to in either language). That is, language-switching costs may simply reflect a cost of selecting the task-appropriate response for a given item and so may not be reflective of bilingual lexical access [Finkbeiner, M., Almeida, J., Janssen, N., & Carramaza, A. (2006). Lexical selection in bilingual speech production does not involve language suppression. Journal of Experimental Psychology: Learning, Memory, and Cognition, 32(5), 1075–1089]. The present study addresses this concern by having Chinese/English bilinguals switch between languages in response to inherently univalent stimuli (English words and Chinese Characters) as well as lexically univalent, but orthographically bivalent, stimuli (English words and Chinese Pinyin). Speakers showed switch costs when naming both univalent and orthographically bivalent stimuli, showing that switch costs can be found even with inherently univalent stimuli.     

The dual implication of dual affordance: stimulus-task binding and attentional focus changing during task preparation

In task switching experiments, comparing performance with bivalent stimuli (affording both tasks) to univalent stimuli (affording one task) confounds the need to change focus between dimensions and stimulus-task binding, because bivalent stimuli require focusing (and refocusing) but also appeared in the competing task before. To separate these influences, participants switched between vertical and horizontal judgments performed on bivalent (e.g., up-left) or univalent (e.g., left) actual locations or location words. In a critical condition involving bivalence without stimulus-task binding, actual locations and location words were each linked to a different task. Bivalence increased switch costs and preparation reduced switch costs only with bivalent stimuli. Stimulus-task binding affected performance in task repetitions, especially when little preparation time was afforded.     

Task conflict effect in task switching

A part of action preparation is deciding what the relevant task is. This task-decision process is conceptually separate from response selection. To show this, the authors manipulated task conflict in a spatial task-switching paradigm, using conflict stimuli that appeared during trials with univalent targets (affording 1 task). The conflict stimuli afforded task identity because they were used as task cues with bivalent targets (affording 2 tasks) that were intermixed with the univalent targets. Thus, for univalent targets, irrelevant stimuli either caused low task conflict or high task conflict. In three experiments, the authors found poorer performance in high task conflict trials than in low task conflict trials. Task conflict was introduced during target appearance (Experiment 1) or task preparation (Experiments 2 and 3). In the latter case, the task conflict effect decreased with increasing task preparation time showing that task preparation involves task decision.     

Post-conflict slowing: cognitive adaptation after conflict processing

The aftereffects of error and conflict (i.e., stimulus or response incongruency) have been extensively studied in the cognitive control literature. Each has been characterized by its own behavioral signature on the following trial. Conflict leads to a reduced congruency effect (Gratton effect), whereas an error leads to increased response time (post-error slowing). The reason for this dissociation has remained unclear. Here, we show that post-conflict slowing is not typically observed because it is masked by the processing of the irrelevant stimulus dimension. We demonstrate that post-conflict slowing does occur when tested in pure trials where helpful or detrimental impacts from irrelevant stimulus dimensions are removed (i.e., univalent stimuli).     

任务切换中的反应重复效应

在任务重复试次中反应的重复对反应有促进作用,而在任务切换试次中反应的重复对反应有阻碍作用,此现象即为反应重复效应（response repetition effects, RRE）。RRE普遍存在不同任务切换范式中,是一种抽象反应编码重复效应,受刺激效价和一致性、反应编码重复度和准备时间等因素影响。其理论解释主要有重构论、启动-抑制论、以及情境检索说。现有研究初步表明前额叶皮层是RRE的关键脑区,但RRE的认知神经机制及理论解释还有待进一步探讨。     

How long-lasting is the post-conflict slowing after incongruent trials? Evidence from the Stroop,Simon, and flanker tasks

The purpose of the present study was to determine how long-lasting the post-conflict slowing following incongruent stimuli is. In previous research, incongruent stimuli have been used to induce a conflict because they have relevant features for two different response alternatives. So far, the post-conflict slowing following incongruent stimuli has mainly been assessed up to one trial. In the first two experiments, we assessed the persistence of the post-conflict slowing across several trials. To this end, we presented a few incongruent stimuli among non-conflict stimuli. The results showed a consistent slowing for the first few trials immediately following the incongruent trials. In addition, a sporadic slowing was still found on later trials. In two subsequent experiments, we investigated to what extent the infrequency of incongruent trials — rather than their conflict — induced this slowing. To determine this, we used the same design as in the first two experiments, but we presented non-conflict stimuli as infrequent stimuli. The results showed a slowing on one subsequent trial, ruling out the possibility that the post-conflict slowing following incongruent trials was only caused by infrequency. Together, the findings of the present study indicate that the conflict induced by incongruent trials can have a longer lasting impact on subsequent trials than previously thought.     

Post-error slowing: An orienting account

It is generally assumed that slowing after errors is a cognitive control effect reflecting more careful response strategies after errors. However, clinical data are not compatible with this explanation. We therefore consider two alternative explanations, one referring to the possibility of a persisting underlying problem and one on the basis of the low frequency of errors (orienting account). This latter hypothesis argues that infrequent events orient attention away from the task. Support for the orienting account was obtained in two experiments. Using a new experimental procedure, Experiment 1 demonstrated post-error slowing after infrequent errors and post-correct slowing after infrequent correct trials. In Experiment 2, slowing was observed following infrequent irrelevant tones replacing the feedback signals.     

False external feedback modulates posterror slowing and the f-P300: implications for theories of posterror adjustment

People tend to slow down after mistakes. This posterror slowing (PES) has commonly been explained by a change to a more conservative response threshold to avoid future errors. Alternatively, the attention-orienting account posits that all infrequent, surprising events (including errors) elicit an orienting response followed by a time-consuming process of task reorientation, explaining PES without increased response caution. In the present study, we employed both behavioral and electrophysiological measures to compare the predictions of these accounts using a flanker paradigm in which accurate or false external response feedback was provided. Participants demonstrated typical posterror adjustments, responding more slowly and accurately in posterror than in postcorrect trials. This finding provides initial evidence suggesting that posterror adjustments are motivated by the avoidance of subsequent mistakes. Most importantly, PES and an event-related potential relating to the attentional processing of feedback, the feedback-related P300 (f-P300), were modulated by feedback type. More specifically, the f-P300 was larger after false than after accurate feedback, suggesting that participants oriented their attention toward (i.e., were surprised by) inaccurate feedback signals. Interestingly, false feedback differentially modulated reaction times: Participants were slower after correct responses when feedback falsely informed of an error rather than confirmed the correct response. In contrast, faster responses were made after errors when feedback falsely indicated correct rather than incorrect performance. When these patterns of results are regarded together, they are best explained by theories of cognitive control in which posterror adjustments in choice reaction time tasks are assumed to reflect control processes leading to more conservative performance after error signals.     

On the difficulty of task switching: Assessing the role of task-set inhibition

This study assessed whether or not the difficulty of task switching stems from previous inhibition of the task set. A predictable sequence of univalent stimuli (affording performance of one active task) and bivalent stimuli (affording performance of two tasks) was used in two experiments. Experiment 1 used an alternating-runs paradigm (AABB) and Experiment 2 used a strictly alternating sequence (ABAB). The critical variable was whether the incentive for task-set inhibition was strong (on bivalent trials) or weak (on univalent trials). The question was whether it would be more difficult to switch to a task that previously needed to be inhibited than to a task that did not need to be inhibited. This pattern was not observed in either experiment. Thus, the data provide no evidence that task switching is difficult because of the need to overcome recent task-set inhibition.     

Orienting to errors with and without immediate feedback

A slow-down in reaction time (RT) after committing an error is a well-known effect. Recently, Notebaert and colleagues (Notebaert et al., 2009; Núñez Castellar, Kuhn, Fias, & Notebaert, 2010) suggested that posterror slowing is a reaction to the infrequent nature of errors. After infrequent errors, posterror slowing was observed but after infrequent correct trials, postcorrect slowing was observed. These data were obtained in a paradigm with trial-by-trial feedback. In this study we tested whether posterror slowing was similar with and without immediate feedback. We manipulated the overall accuracy parametrically per condition (50%, 70%, and 90% accuracy) and predicted an increase in posterror slowing as the accuracy increased. This linear effect was observed with and without immediate feedback. The data are interpreted in terms of an orienting response towards unexpected events.