Sustained vs. transient cognitive control: Evidence of a behavioral dissociation

This study assessed whether two well known effects associated with cognitive control, conflict adaptation (the Gratton effect) and conflict context (proportion congruent effects), reflect a single common or separate control systems. To test this we examined if these two effects generalized from one kind of conflict to another by using a combined-conflict paradigm (involving the Simon and Spatial Stroop tasks) and manipulating the proportion of congruent to incongruent trials for one conflict (Simon) but not the other (Spatial Stroop). We found that conflict adaptation effects did not generalize, but the effect of conflict context did. This contrasting pattern of results strongly suggests the existence of two separate attentional control systems, one transient and responsible of online regulation of performance (conflict adaptation), the other sustained and responsible for conflict context effects.     

Now you see it, now you don't: controlling for contingencies and stimulus repetitions eliminates the Gratton effect

The Gratton (or sequential congruency) effect is the finding that conflict effects (e.g., Stroop and Eriksen flanker effects) are larger following congruent trials relative to incongruent trials. The standard account given for this is that a cognitive control mechanism detects conflict when it occurs and adapts to this conflict on the following trial. Others, however, have questioned the conflict adaptation account and suggested that sequential biases might account for the Gratton effect. In two experiments, contingency biases were removed from the task and stimulus repetitions were deleted to control for stimulus bindings. This eliminated the Gratton effect in the response times in both experiments, supporting a non-conflict explanation of the Gratton effect. A Gratton effect did persist in the errors of Experiment 1; however, this effect was not produced by the type of errors (word reading errors) that a conflict adaptation account should predict. Instead, tentative support was found for a congruency switch cost hypothesis. In all, the conflict adaptation account failed to account for any of the reported data. Implications for future work on cognitive control are discussed.     

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.     

List-level transfer effects in temporal learning: Further complications for the list-level proportion congruent effect

Congruency effects are larger when most trials are congruent relative to incongruent. According to the conflict adaptation account, this proportion congruent effect is due to the decreased attention to words when most of the trials are conflicting. This paper extends on previous work arguing that list-level (contingency-unbiased) proportion congruent effects might be explainable by temporal learning biases. That is, congruency effects are larger in an easier task (i.e., mostly congruent) due to the faster pace of the task. Two non-conflict analogues of the proportion congruent effect are presented, one with a contrast manipulation and another with a contingency manipulation. Critically, both experiments control for potential item-specific temporal learning biases by intermixing biased context and unbiased transfer items. Results show a proportion congruent-like interaction for both item types, supporting the notion of task-wide temporal learning as an explanation for list-level proportion congruency effects. Distributional analyses lend further credence to the temporal learning account by showing that proportion congruent and proportion congruent-like effects are localised in the fastest and intermediate responses.     

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.     

冲突观察能诱发冲突适应

重复启动效应和一致试次所占的比例都会影响冲突适应效应。采用词-色Stroop任务, 本研究在控制了重复启动效应和一致试次的比例之后, 通过三个实验共同探讨反应执行和冲突观察对冲突适应效应的影响。实验一发现当前试次的Stroop干扰效应, 但没有得到冲突适应效应; 在实验二中, 先前试次为四选一的选择反应时任务, 当前试次为词-色Stroop任务, 得到反转的冲突适应效应; 实验三和实验一程序相似, 但在先前试次上不执行反应, 得到了稳定的冲突适应效应。这些结果证明, 冲突观察能够诱发冲突适应机制, 提升当前的操作表现。     

The conflict adaptation effect: It’s not just priming

Analyses of trial sequences in flanker tasks have revealed cognitive adaptation, reflected in a reduced interference effect following incompatible trials (Gratton, Coles, & Donchin, 1992). These effects have been explained on the basis of the response conflict monitoring model of Botvinick, Braver, Barch, Carter, and Cohen (2001), who proposed that preceding response conflict triggers stronger topdown control, leading to performance improvements on subsequent trials of similar context. A recent study (Mayr, Awh, & Laurey, 2003) has challenged this account, suggesting that the behavioral adaptations are confined to trial sequences of exact trial repetitions and can therefore be explained by repetition priming. Here, we present two experiments in which the sequential dependency effect was present even on trial sequences that did not involve stimulus repeats. We discuss the data with respect to the conflict-monitoring and repetition-priming accounts.     

Dissociating proportion congruent and conflict adaptation effects in a Simon–Stroop procedure

Proportion congruent and conflict adaptation are two well known effects associated with cognitive control. A critical open question is whether they reflect the same or separate cognitive control mechanisms. In this experiment, in a training phase we introduced a proportion congruency manipulation for one conflict type (i.e. Simon), whereas in pre-training and post-training phases two conflict types (e.g. Simon and Spatial Stroop) were displayed with the same incongruent-to-congruent ratio. The results supported the sustained nature of the proportion congruent effect, as it transferred from the training to the post-training phase. Furthermore, this transfer generalized to both conflict types. By contrast, the conflict adaptation effect was specific to conflict type, as it was only observed when the same conflict type (either Simon or Stroop) was presented on two consecutive trials (no effect was observed on conflict type alternation trials). Results are interpreted as supporting the reactive and proactive control mechanisms distinction.     

6～12岁儿童Flanker任务下的冲突适应效应

为了探讨6～12岁儿童冲突适应能力的发展,本研究使用经典的Flanker任务,考察了181名一至六年级小学生在冲突任务中的成绩。结果发现,冲突效应在各个年龄段都显著,但是冲突效应大小在不同年龄段之间没有显著差异;对于冲突适应效应,在反应时和准确率上都发现了冲突适应的证据,表现为不一致试次后的冲突效应减小和错误率降低,并且,冲突适应效应的大小在各个年龄段也没有差异。以上结果表明,对于6～12岁左右的小学生,冲突适应效应已经稳定存在,并且,不存在年龄差异。     

Hebbian learning of cognitive control: dealing with specific and nonspecific adaptation

The conflict monitoring model of M. M. Botvinick, T. S. Braver, D. M. Barch, C. S. Carter, and J. D. Cohen (2001) triggered several research programs investigating various aspects of cognitive control. One problematic aspect of the Botvinick et al. model is that there is no clear account of how the cognitive system knows where to intervene when conflict is detected. As a result, recent findings of task-specific and context-specific (e.g., item-specific) adaptation are difficult to interpret. The difficulty with item-specific adaptation was recently pointed out by C. Blais, S. Robidoux, E. F. Risko, and D. Besner (2007), who proposed an alternative model that could account for this. However, the same problem of where the cognitive system should intervene resurfaces in a different shape in this model, and it has difficulty in accounting for the Gratton effect, a hallmark item-nonspecific effect. The authors of the current article show how these problems can be solved when cognitive control is implemented as a conflict-modulated Hebbian learning rule.     

Motivational and cognitive determinants of control during conflict processing

Previous studies suggest that both reward anticipation and expected or experienced conflicts activate cognitive control. The present study investigated how these factors interact during conflict processing. In two experiments, participants performed a variant of the Stroop task, receiving performance-dependent monetary rewards in some blocks. In addition, we manipulated the level of conflict-triggered reactive and expectancy-driven proactive control: In Experiment 1, we compared the Stroop effect after previously congruent and incongruent trials to examine the conflict adaptation effect (reactive control). We found that the level of motivation did not interact with conflict adaptation. In Experiment 2, we varied the proportion of congruent and incongruent trials to manipulate conflict expectancy (proactive control). The data suggest the effects of motivation to be less pronounced under conditions of high conflict expectancy. We conclude that the interaction of motivation with cognitive determinants of control depends on whether these activate proactive or reactive control processes.     

An Integrative View of Conflict Adaptation and Active Maintenance

The conflict adaptation (CA) effect refers to the reduction in the interference effect observed in conflict tasks that follow incongruent compared to congruent trials. It has been suggested that CA is caused by the exertion of flexible cognitive control, supported by many behavioral and neuroimaging studies; however, it remains unclear how conflict‐related features of the preceding trial are conveyed to subsequent trials for following adaptation. This review aims to summarize evidence supporting the top‐down modulation of the dorsolateral prefrontal cortex and passive short‐term maintenance in the posterior brain areas as mechanisms underlying CA, respectively, and to suggest a new integrated view of CA, including active maintenance in working memory. We review empirical evidences suggesting that both dorsolateral prefrontal cortex and posterior brain regions play critical roles in CA, rather than either top‐down modulation or passive maintenance alone. Although the active maintenance view of CA appears to explain many existing findings, empirical studies are required to directly test this view.     

Congruency sequence effects and cognitive control

Congruency effects in selective attention tasks are subject to sequential modulation: They are smaller following an incongruent stimulus than following a congruent one. This congruency sequence effect has been interpreted as reflecting conflict-driven adjustments in cognitive control (conflict adaptation) or, alternatively, episodic memory effects of stimulus—response association (feature integration). The present article critically reviews support for these rival accounts in the experimental literature and discusses the implications thereof for assessing behavioral and neural signatures of cognitive control processes. It is argued that both conflict adaptation and feature integration contribute to the congruency sequence effect but that their respective contributions can be isolated experimentally. Studies that have pursued this isolation strategy have gained important insights into cognitive control processes. Finally, other factors, such as expectancies, may also contribute to the congruency sequence effect, and thus their potential role needs to be carefully examined and, if found significant, integrated into current models of cognitive control.     

Sequential dependencies in the Eriksen flanker task: A direct comparison of two competing accounts

In the conflict/control loop theory proposed by Botvinick, Braver, Barch, Carter, and Cohen (2001), conflict monitored in a trial leads to an increase in cognitive control on the subsequent trial. The critical data pattern supporting this assertion is the so-called Gratton effect—the decrease in flanker interference following incongruent trials—which was initially observed in the Eriksen flanker task. Recently, however, the validity of the idea that this pattern supports a general conflict/control mechanism has been questioned on the grounds that the Gratton effect is only observed with stimulus repetition. We present an experiment testing whether the Gratton effect reflects a stimulus-independent increase in cognitive control or stimulus-specific repetition priming. Although our results support the latter hypothesis, the priming effect is modulated by the congruency of the previous trial. We discuss a new mechanism through which monitored conflict is used to exert executive control by modulating stimulus-response associations.     

冲突控制是领域一般性的还是领域特殊性的?

本研究采用整合交叉范式整合了Stroop任务和Simon任务,在双重认知控制的框架下探讨冲突控制是领域一般性的还是领域特殊性的问题。结果发现:序列一致性效应只出现在任务内,不出现于任务间,显示对冲突的反应性控制具有领域特殊性;比例一致性效应不仅出现在同种任务中,而且扩展到不同任务中,显示对冲突的主动性控制具有领域一般性。本研究结果对于理解认知控制的本质和机制具有重要意义。     

情境特异比例一致变化对冲突效应的影响

采用Hedge和Marsh任务与比例一致性操纵相结合,分别以刺激的空间位置和形状作为比例一致操纵的情境线索,考察刺激-反应联结学习与注意调节在比例一致效应中的作用。结果发现,在情境比例一致操纵下,冲突效应的效应量受到比例一致操纵的影响产生反转。表明刺激-反应联结学习在情境特异比例一致效应中起到主要作用。     

9~10岁儿童和成人的一致性序列效应

一致性序列效应是指个体根据前一情境中的冲突信息, 灵活适应当前环境的能力。研究选取9~10岁的儿童和18~25岁的成人为被试, 采用色-词Stroop任务和Stroop与Flanker刺激混合的任务, 在控制重复启动的影响后, 考察一致性序列效应在不同任务中的年龄差异。结果发现, 在不同的任务中, 儿童和成人均表现出显著的一致性序列效应, 且一致性序列效应的大小不存在显著差异。研究结果表明, 冲突适应过程涉及更高级的加工过程, 9~10岁的儿童已具备类似成人的、更一般化的冲突适应能力。     

Conflict adaptation: It is not what you expect

In two studies, a vocal Stroop task with eight different colours was employed in order to put two core assumptions of the original interpretation of the Gratton effect to the test. We verified whether top-down control processes can elicit conflict adaptation when episodic memory effects are controlled for and to what extent proactive adjustments driven by the subjects' expectancy for congruency level repetition contribute to this effect. Therefore, we presented Stroop stimuli without feature repetitions and investigated whether the induced expectancy manipulation of raising the amount of either congruency level repetitions or alternations in a training phase transferred to an unmanipulated test phase. Over the two experiments, a sequential modulation of the Stroop effect was found in the absence of stimulus feature repetitions, strongly confirming a share for top-down control processes in bringing about the Gratton effect. In the condition where congruency level repetitions were raised, a strong Gratton effect was found. When congruency level alternations outnumbered repetitions, the Gratton effect disappeared completely. However, this difference seemed mainly due to cumulative effects of local, dynamic, trial-to-trial control adjustments rather than expectancy-induced attentional shifting. Once the transition probability changed back to 50% in the test phase of each experiment, a similar Gratton effect was found in both conditions. Taken together, these results are best explained in terms of dynamic reactive control.     

The context-specific proportion congruent Stroop effect: Location as a contextual cue

The Stroop effect has been shown to depend on the relative proportion of congruent and incongruent trials. This effect is commonly attributed to experiment-wide word-reading strategies that change as a function of proportion congruent. Recently, Jacoby, Lindsay, and Hessels (2003) reported an itemspecific proportion congruent effect that cannot be due to these strategies and instead may reflect rapid, stimulus driven control over word-reading processes. However, an item-specific proportion congruent effect may also reflect learned associations between color word identities and responses. In two experiments, we demonstrate a context-specific proportion congruent effect that cannot be explained by such word—response associations. Our results suggest that processes other than learning of word—response associations can produce contextual control over Stroop interference.     

Evidence for task conflict in the Stroop effect

C. M. MacLeod and P. A. MacDonald (2000) suggested that congruent and incongruent Stroop stimuli cause more task conflict than neutral stimuli because the anterior cingulate cortex is more activated with these stimuli. This study investigated behavioral expression for this pattern. Experiment 1 reduced task conflict control by increasing the proportion of nonword neutrals. Additionally, half the trials had conflict or neutral cues. The control reduction revealed the task conflict. For noncued trials, response time was longer for congruent stimuli than for neutral stimuli (reverse facilitation effect). In addition, response time for congruent stimuli was longer when stimuli were uncued vs. cued. Experiment 2 increased task conflict control by changing the neutral stimuli to noncolor words. Consequently, the task conflict expression disappeared.