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 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.     

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.     

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).     

An orienting response is not enough: Bivalency not infrequency causes the bivalency effect

When switching tasks, occasionally responding to bivalent stimuli (i.e., stimuli with relevant features for two different tasks) slows performance on subsequent univalent stimuli, even when they do not share relevant features with bivalent stimuli. This performance slowing is labelled the bivalency effect. Here, we investigated whether the bivalency effect results from an orienting response to the infrequent stimuli (i.e., the bivalent stimuli). To this end, we compared the impact of responding to infrequent univalent stimuli to the impact of responding to infrequent bivalent stimuli. For the latter, the results showed a performance slowing for all trials following bivalent stimuli. This indicates a long-lasting bivalency effect, replicating previous findings. For infrequent univalent stimuli, however, the results showed a smaller and shorter-lived performance slowing. These results demonstrate that the bivalency effect does not simply reflect an orienting response to infrequent stimuli. Rather it results from the conflict induced by bivalent stimuli, probably by episodic binding with the more demanding context created by them.     

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。     

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.     

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.     

冲突适应效应是领域特定的

本研究采用整合的交叉任务范式,通过任务类型的操纵,对冲突适应效应是领域一般的还是领域特定的问题进行了探讨。结果发现当时,在刺激-反应集为4的字母flanker+Simon的整合交叉任务中和刺激-反应集为4的Stroop+Simon的整合交叉任务中,冲突适应效应都是仅存在于任务内,不存在于任务间。说明在控制了重复启动效应且排除了任务之间维度重叠的影响后,两种类型的整合交叉任务都只在任务内观察到冲突适应效应。这表明在控制特征整合的影响后,冲突适应效应是领域特定的,同时说明冲突监测系统不仅是对冲突进行监测,也对冲突的来源进行识别。     

Attentional control adjustments in Eriksen and Stroop task performance can be independent of response conflict

In the Eriksen flanker and colour-word Stroop tasks, the response time (RT) difference between incongruent and congruent trials is smaller following incongruent trials than following congruent trials: the "Gratton effect" (Gratton, Coles, & Donchin, 1992). According to the prevailing conflict-monitoring theory (Botvinick, Braver, Barch, Carter, & Cohen, 2001), the Gratton effect reflects attentional control adjustment following response conflict on incongruent trials. However, because previous studies compared incongruent and congruent trials, it remains unclear to what extent the Gratton effect is driven by incongruent rather than congruent trials. To resolve this issue, we included neutral trials in addition to incongruent and congruent trials in the Eriksen (Experiment 1) and Stroop (Experiment 2) tasks. Participants responded manually and vocally in both tasks. Moreover, we assessed responding to Stroop stimuli that were preceded by neutral cues or by incongruent- or congruent-predicting cues (Experiment 3). In all three experiments, the RT difference between incongruent and congruent trials was larger for postcongruent trials than for postincongruent and postneutral trials. These findings suggest that control adjustments can be independent of response conflict, challenging conflict-monitoring theory.     

Task-switching and long-term priming: role of episodic stimulus-task bindings in task-shift costs

When subjects switch between two tasks, performance is slower after a task switch than after a task repetition. We report five experiments showing that a large part of these "task-shift-costs" cannot be attributed to a control operation, needed to configure the cognitive system for the upcoming task (e.g., ). In all experiments subjects switched between picture-naming and word-reading. We presented different stimuli either in just one of the two tasks, or in both of them. Shift-costs were larger for stimuli presented in both tasks than for those presented in only one task, even after more than 100 intervening trials between prime and probe events. We suggest (as proposed by ) that stimuli acquire associations with the tasks in which they occur. When the current task activation is weak, as on a switch of tasks, stimuli can trigger retrieval of the associated, competing task, provoking larger time costs.     

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。     

Attentional control adjustments in Eriksen and Stroop task performance can be independent of response conflict

In the Eriksen flanker and colour-word Stroop tasks, the response time (RT) difference between incongruent and congruent trials is smaller following incongruent trials than following congruent trials: the “Gratton effect” (Gratton, Coles, & Donchin, 1992). According to the prevailing conflict-monitoring theory (Botvinick, Braver, Barch, Carter, & Cohen, 2001), the Gratton effect reflects attentional control adjustment following response conflict on incongruent trials. However, because previous studies compared incongruent and congruent trials, it remains unclear to what extent the Gratton effect is driven by incongruent rather than congruent trials. To resolve this issue, we included neutral trials in addition to incongruent and congruent trials in the Eriksen (Experiment 1) and Stroop (Experiment 2) tasks. Participants responded manually and vocally in both tasks. Moreover, we assessed responding to Stroop stimuli that were preceded by neutral cues or by incongruent- or congruent-predicting cues (Experiment 3). In all three experiments, the RT difference between incongruent and congruent trials was larger for postcongruent trials than for postincongruent and postneutral trials. These findings suggest that control adjustments can be independent of response conflict, challenging conflict-monitoring theory.     

Accounting for sequential trial effects in the flanker task: Conflict adaptation or associative priming?

The conflict-control loop theory proposes that the detection of conflict in information processing triggers an increase in cognitive control, resulting in improved performance on the subsequent trial. This theory seems consistent with the robust finding that conflict susceptibility is reduced following correct trials associated with high conflict: the conflict adaptation effect. However, despite providing favorable conditions for eliciting and detecting conflict-triggered performance adjustments, none of the five experiments reported here provide unequivocal evidence of such adjustments. Instead, the results corroborate and extend earlier findings by demonstrating that the conflict adaptation effect, at least in the flanker task, is only present for a specific subset of trial sequences that is characterized by a response repetition. This pattern of results provides strong evidence that the conflict adaptation effect reflects associative stimulus-response priming instead of conflict-driven adaptations in cognitive control.     

Individual differences in conflict-monitoring: testing means and covariance hypothesis about the Simon and the Eriksen Flanker task

Conflict and context slow-down have been proposed as indicators of a conflict-monitoring system that initiates cognitive control to resolve conflicts in information processing. We investigated individual differences in conflict-monitoring and their associations with working memory (WM) and impulsivity. A total of 150 adults completed a Simon and an Eriksen flanker task, together with measures of WM and impulsivity. On both tasks, responses were slower and less accurate on incompatible than on compatible trials (conflict effect), and the conflict effect was larger when the preceding trial was compatible than when it was incompatible (context effect). Stimulus repetition did not explain the context effect. Individual differences could be attributed to three separable factors for each task: general speeded performance, conflict effect, and context effect. Evidence for across-task generality of these factors was sparse. Associations of these factors with impulsivity were weak at best. WM was correlated with general speed, and also with some but not all factors reflecting conflict-related processes.     

工作记忆中转换加工的内源性准备 和外源性调节

考察工作记忆中转换加工的控制过程。采用“任务转换”范式,探究预知条件（实验一）和未预知条件（实验二）下的转换加工。结果发现：（1）任务重复与任务转换是两个不同的过程;无论是在预知条件还是未预知条件下都出现任务重复效应显著大于任务转换效应;（2）验证了转换加工包括内源性准备和外源性调节两个不同的加工过程, 内源性准备只是任务设置重建的一部分;（3）对先后呈现的两个任务（任务1—任务2 ：任务重复或任务转换）在预知重复、预知转换和未预知条件下,任务2对任务1的影响不同,存在前瞻性记忆效应。由此推断转换加工的心理过程是：在预知情况下,任务1呈现后即启动内源性准备,直到任务2呈现时,通过外源性调节最终完成任务转换;而在未预知情况下,只能依赖外源性调节来实现     

Cognitive control: dynamic, sustained, and voluntary influences

The cost of incongruent stimuli is reduced when conflict is expected. This series of experiments tested whether this improved performance is due to repetition priming or to enhanced cognitive control. Using a paradigm in which Word and Number Stroop alternated every trial, Experiment 1 assessed dynamic trial-to-trial changes. Incongruent trials led to task-specific reduction of conflict (trial n + 2) without cross-task modulation (trial n + 1), but this was fully explained by repetition priming. In contrast, an increased ratio of incongruent words did lead to sustained task-specific enhancement, above and beyond repetition priming (Experiment 2). Experiments 3 and 4 assessed the voluntary modulation of cognitive control: A cue predicted the congruency of the incoming trial, allowing participants to establish the correct mindset (Word Stroop in Experiment 3, Flanker task in Experiment 4). Preparing oneself to process an incongruent word (or flanker) enhanced conflict resolution in the subsequent Number Stroop, an example of cross-task modulation. Taken together, these experiments reveal the multifaceted aspects of conflict resolution: Trial-to-trial changes are often due to repetition priming; sustained modulations brought about by task demands are task specific; and voluntary modulations are task general.     

预知任务转换的内源性准备和外源性调节

采用ERP探究在预知条件下任务转换的神经机制。使用“任务转换”实验范式,以汉字（名词/动词）或数字（奇数/偶数）的归类为任务。被试执行任务重复（AA,BB,…）或在两个任务间转换（AB,BA,…）,每个任务序列为连续的两个任务（任务1,任务2）。结果发现,任务1中,在刺激呈现后300ms左右,数、词的转换序列与重复序列出现显著差异;在中央区,320ms左右,任务1中转换序列比重复序列、任务2中转换任务比重复任务都产生一个更为负走向的波。这些结果表明,在预知条件下,简单任务转换的内源性准备可能开始于任务1呈现后300ms左右;内源性准备和外源性调节可能都反映了认知冲突过程,此认知冲突可能是转换代价的主要来源     

The N2 in go/no-go tasks reflects conflict monitoring not response inhibition

The functional significance of the N2 in go/no-go tasks was investigated by comparing electrophysiological data obtained from two tasks: a go/no-go task involving both response inhibition as well as response conflict monitoring, and a go/GO task associated with conflict monitoring only. No response was required to no-go stimuli, and a response with maximal force to GO stimuli. The relative frequency of the go stimuli (80% vs. 50%) was varied. The N2 peaked on both no-go and GO trials, with larger amplitudes for both signals when presented in a context of frequent (80%) go signals. These results support the idea that the N2 reflects conflict monitoring not response inhibition.