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.     

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。     

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.     

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。     

Context-specific control and context selection in conflict tasks

This study investigated whether participants prefer contexts with relatively little cognitive conflict and whether this preference is related to context-specific control. A conflict selection task was administered in which participants had to choose between two categories that contained different levels of conflict. One category was associated with 80% congruent Stroop trials and 20% incongruent Stroop trials, while the other category was associated with only 20% congruent Stroop trials and 80% incongruent Stroop trials. As predicted, participants selected the low-conflict category more frequently, indicating that participants avoid contexts with high-conflict likelihood. Furthermore, we predicted a correlation between this preference for the low-conflict category and the control implementation associated with the categories (i.e., context-specific proportion congruency effect, CSPC effect). Results however did not show such a correlation, thereby failing to support a relationship between context control and context selection.     

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。     

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。     

Sequential congruency effects: disentangling priming and conflict adaptation

Responding to the color of a word is slower and less accurate if the word refers to a different color (incongruent condition) than if it refers to the same color (congruent condition). This phenomenon, known as the Stroop effect, is modulated by sequential effects: it is bigger when the current trial is preceded by a congruent condition than by an incongruent one in the previous trial. Whether this phenomenon is due to priming mechanisms or to cognitive control is still debated. To disentangle the contribution of priming with respect to conflict adaptation mechanisms in determining sequential effects, two experiments were designed here with a four-alternative forced choice (4-AFC) Stroop task: in the first one only trials with complete alternations of features were used, while in the second experiment all possible types of repetitions were presented. Both response times (RTs) and errors were evaluated. Conflict adaptation effects on RTs were limited to congruent trials and were exclusively due to priming: they disappeared in the priming-free experiment and, in the second experiment, they occurred in sequences with feature repetitions but not in complete alternation sequences. Error results, instead, support the presence of conflict adaptation effects in incongruent trials. In priming-free sequences (Experiment 1 and complete alternation sequences of Experiment 2) with incongruent previous trials there was no error Stroop effect, while this effect was significant with congruent previous trials. These results indicate that cognitive control may modulate performance above and beyond priming effects.     

Working memory capacity predicts conflict-task performance

The relationship between the ability to maintain task goals and working memory capacity (WMC) is firmly established, but evidence for WMC-related differences in conflict processing is mixed. We investigated whether WMC (measured using two complex-span tasks) mediates differences in adjustments of cognitive control in response to conflict. Participants performed a Simon task in which congruent and incongruent trials were equiprobable, but in which the proportion of congruency repetitions (congruent trials followed by congruent trials or incongruent trials followed by incongruent trials) and thus the need for trial-by-trial adjustments in cognitive control varied by block. The overall Simon effect did not depend on WMC capacity. However, for the low-WMC participants the Simon effect decreased as the proportion of congruency repetitions decreased, whereas for the high- and average-WMC participants it was relatively constant across conditions. Distribution analysis of the Simon effect showed more evidence for the inhibition of stimulus location in the low- than in the high-WMC participants, especially when the proportion of congruency repetitions was low. We hypothesize that low-WMC individuals exhibit more interference from task-irrelevant information due to weaker preparatory control prior to stimulus presentation and, thus, stronger reliance on reactive recruitment of cognitive control.     

Congruency sequence effect in cross-task context: Evidence for dimension-specific modulation

The congruency sequence effect refers to a reduced congruency effect after incongruent trials relative to congruent trials. This modulation is thought to be, at least in part, due to the control mechanisms resolving conflict. The present study examined the nature of the control mechanisms by having participants perform two different tasks in an alternating way. When participants performed horizontal and vertical Simon tasks in Experiment 1A, and horizontal and vertical spatial Stroop task in Experiment 1B, no congruency sequence effect was obtained between the task congruencies. When the Simon task and spatial Stroop task were performed with different response sets in Experiment 2, no congruency sequence effect was obtained. However, in Experiment 3, in which the participants performed the horizontal Simon and spatial Stroop tasks with an identical response set, a significant congruency sequence effect was obtained between the task congruencies. In Experiment 4, no congruency sequence effect was obtained when participants performed two tasks having different task-irrelevant dimensions with the identical response set. The findings suggest inhibitory processing between the task-irrelevant dimension and response mode after conflict.     

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.     

Cognitive control outside of conscious awareness

To test whether cognitive control can operate fully unconsciously on conflicts arising between two interfering subliminal stimuli, we designed a priming paradigm in which a subliminal reverse Color-Word Stroop item (a color word written on a congruent/incongruent color rectangle) preceded a supraliminal one in each trial. We found (a) a conflict adaptation effect, with a smaller reverse Stroop effect on the visible probe items after incongruent than after congruent subliminal prime items and (b) a negative priming effect, with longer reaction-times on incongruent visible probe items when the color word corresponded to the color of the rectangle in the preceding subliminal prime item than when it was not. These effects replicate the ones classically reported in studies using visible items and suggest that cognitive control was transferred from the subliminal prime to the visible probe items. Taken together, our results demonstrate that cognitive control can operate on conflicting subliminal information.     

Cognitive control acts locally

Cognitive control adjusts information processing to momentary needs and task requirements. We investigated conflict adaptation when participants are performing two tasks, a Simon task and a SNARC task. The results indicated that one congruency effect (e.g., Simon) was reduced after conflict in the other task (e.g., SNARC), but only when both tasks used identical relevant information. On the other hand, when both tasks used different relevant information, a larger congruency effect was observed after conflict in the other task. The results are explained in terms of a local control mechanism.     

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.     

Opposing influences on conflict-driven adaptation in the Eriksen flanker task

Compatibility effects in conflict paradigms are reduced following incompatible trials, and this effect is referred to as conflict adaptation. A perplexing pattern exists, however, with conflict-driven adaptation emerging in several paradigms (e.g., Stroop, Simon) but not consistently in the Eriksen and Eriksen (1974) flanker task. The present experiments address the seemingly elusive presence of conflict adaptation in this task. Experiment 1 shows that a negative-priming-like slowing may be masking conflict adaptation in the flanker task. In Experiment 2, conflict adaptation was revealed when a larger stimulus set designed to reduce negative priming was implemented. Taken together, the findings indicate that a consideration of processes opposing conflict adaptation in the flanker task may help reconcile prior findings.     

Location-specific attentional control is also possible in the Simon task

Goal-directed behavior usually requires mental control that directs attention to task-relevant information and ignores irrelevant information. For investigating how flexible this mechanism is, researchers have varied the proportion of congruent trials depending on some context, such as stimulus location. The corresponding studies revealed that attentional control indeed adapts to location-specific demands. However, until now, this flexibility has only been demonstrated for the Eriksen flanker task and for the Stroop task but not for the Simon task. Therefore, a Simon-task experiment was conducted in the present study, where the proportion of congruent trials differed for stimuli appearing above or below fixation, respectively. As a result, a reliable interaction between congruency and stimulus location was found. This demonstrates, for the first time, that location-specific control also is possible in the Simon task.     

基于Flanker、Stroop和Simon多重冲突驱动的认知控制机制

认知控制是维持和调整多任务目标导向的加工策略,而基于多任务冲突的认知控制是一般领域上还是特定领域上,即一种冲突是否会影响另一种冲突的解决,已有研究并没有得到统一的结论。本研究运用事件相关电位（ERP）方法考察了同一任务中不同类型冲突（Stroop、Simon和Flanker冲突）驱动认知控制调节的脑机制。数据显示：各冲突都出现了一致性效应和冲突适应性效应;实验中每种冲突的上一个trial只与该类冲突的当前trial的交互效应显著,而与其他类型冲突的当前trial的交互效应不显著;几乎所有冲突都发现了P300、N450、SP成分一致性效应。结果表明：在不同类型冲突驱动条件下,人脑能够同时监控并解决不同类型的冲突;冲突驱动的认知控制系统以局部的控制方式工作;人脑是基于多冲突驱动的认知控制系统的灵活性和某类型冲突所特有的控制机制来解决冲突,且冲突解决机制是相互独立、互不干扰的。     

The interactive effects of listwide control, item-based control, and working memory capacity on Stroop performance

Hypothesized top-down and bottom-up mechanisms of control within conflict-rich environments were examined by presenting participants with a Stroop task in which specific words were usually presented in either congruent or incongruent colors. Incongruent colors were either frequently (high contingency) or infrequently (low contingency) paired with the word. These items were embedded within lists consisting of either 100% congruent or 100% incongruent filler items to create mostly congruent or mostly incongruent lists. Results indicated a significant item-specific congruency effect, which was largest for high contingency responses and within mostly congruent lists. In addition, a significant listwide congruency effect was obtained, and this interacted with working memory capacity (WMC). There were larger listwide congruency effects for low WMC individuals. Finally, the pattern of Stroop interference across lists for low WMC individuals was dependent upon the congruency of the preceding trial. These results support multiple forms of cognitive control, as well as contingency learning, as mechanisms underlying proportion congruence effects in Stroop and other conflict tasks. These findings are interpreted within Braver, Gray, and Burgess's (2007) dual mechanisms of control theory.     

Generalizing attentional control across dimensions and tasks: Evidence from transfer of proportion-congruent effects

Three experiments investigated transfer of list-wide proportion congruent (LWPC) effects from a set of congruent and incongruent items with different frequency (inducer task) to a set of congruent and incongruent items with equal frequency (diagnostic task). Experiments 1 and 2 mixed items from horizontal and vertical Simon tasks. Tasks always involved different stimuli that varied on the same dimension (colour) in Experiment 1 and on different dimensions (colour, shape) in Experiment 2. Experiment 3 mixed trials from a manual Simon task with trials from a vocal Stroop task, with colour being the relevant stimulus in both tasks. There were two major results. First, we observed transfer of LWPC effects in Experiments 1 and 3, when tasks shared the relevant dimension, but not in Experiment 2. Second, sequential modulations of congruency effects transferred in Experiment 1 only. Hence, the different transfer patterns suggest that LWPC effects and sequential modulations arise from different mechanisms. Moreover, the observation of transfer supports an account of LWPC effects in terms of list-wide cognitive control, while being at odds with accounts in terms of stimulus–response (contingency) learning and item-specific 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.