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.     

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.     

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.     

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.     

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.     

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。     

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.     

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).     

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.     

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.     

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.     

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.     

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.     

Age-related differences in switching between cognitive tasks: does internal control ability decline with age?

The present study tested the hypothesis that older adults establish a weaker task set than younger adults and therefore rely more on stimulus-triggered activation of task sets. This hypothesis predicts that older adults should have difficulty with task switches, especially when the stimuli-responses are associated with multiple, competing tasks. Weak task preparation, however, could actually benefit older adults when performing an unexpected task. The authors tested this prediction in Experiment 1 using a repeating AABB task sequence, with univalent and bivalent stimuli intermixed. On some univalent trials, participants received an unexpected task. Contrary to the authors' predictions, expectancy costs were not smaller for older adults. Similar findings were obtained in Experiments 2 and 3, in which the authors used a task-cueing paradigm to more strongly promote deliberate task preparation. The authors found no disproportionate age effects on switch costs but did find age effects on bivalence costs and mixing costs. The authors conclude that older adults do experience extra difficulty dealing with stimuli associated with 2 active tasks but found no evidence that the problem specifically stems from an increased reliance on bottom-up task activation rather than top-down task preparation.     

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.     

Nonconcurrently presented auditory tones reduce distraction

Recent research has demonstrated that task-irrelevant stimuli presented simultaneously with a target-distractor stimulus reduce distraction and improve selective attention. In studies examining this reduced interference effect, visual selective attention tasks and concurrently presented task-irrelevant stimuli are used. We report first evidence for a similar effect in the auditory domain and with nonconcurrent stimuli (i.e., the task-irrelevant stimuli are presented before the target). The effect of nonconcurrently presented auditory tones on an auditory Stroop task developed by Leboe and Mondor (Psychological Research, 71, 568--575, 2007) was investigated. Stroop interference was reduced when task-irrelevant tones were presented before the Stroop stimulus. We conclude that task-irrelevant stimuli can improve selective attention not only when presented concurrently, but also when presented before the selective attention task. Our results are consistent with the hypothesis that interference reduction is due to perceptual dilution caused by task-irrelevant stimuli.     

Does switching between strategies within the same task involve a cost?

In two experiments, participants had to switch regularly between two cognitive strategies of a different complexity in the context of a numerosity judgement task. Expt 1 comprised bivalent stimuli (i.e. allowing the application of the two strategies), whereas Expt 2 involved univalent stimuli (i.e. allowing the application of only one strategy). Both experiments revealed that switching between strategies entailed a cognitive cost that was reflected in longer response times on switch compared to non‐switch trials but not in reduced accuracy. The size of this switch cost did not differ as a function of strategy complexity but tended to diminish as a strategy became more appropriate for solving a particular problem. We discuss the extent to which current theories of task switching can account for these findings.     

Incidental task sequence learning: perceptual rather than conceptual?

In four experiments we investigated whether incidental task sequence learning occurs when no instructional task cues are available (i.e. with univalent stimuli). We manipulated task sequence by presenting three simple binary-choice tasks (colour, form or letter case decisions) in regular repeated or random order. Participants were required to use the same two response keys for each of the tasks. We manipulated response sequence by ordering the stimuli so as to produce either a regular or a random order of left versus right-hand key presses. When sequencing in both, or either, separate stream (i.e. task sequence and/or response sequence) was changed to random, only those participants who had processed both sequences together showed evidence of sequence learning in terms of significant response time disruption (Experiments 1-3). This effect disappeared when the sequences were uncorrelated (Experiment 4). The results indicate that only the correlated integration of task sequence and response sequence produced a reliable incidental learning effect. As this effect depends on the predictable ordering of stimulus categories, it suggests that task sequence learning is perceptual rather than conceptual in nature.     

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。