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.     

Domain-specific conflict adaptation without feature repetitions

An influential account of how cognitive control deals with conflicting sources of information holds that conflict is monitored by a module that automatically recruits attention to resolve the conflict. This leads to reduced effects of conflict on the subsequent trial, a phenomenon termed conflict adaptation. A prominent question is whether control processes are domain specific—that is, recruited only by the particular type of conflict they resolve. Previous studies that have examined this question used two-choice tasks in which feature repetition effects could be responsible for domain-specific adaptation effects. We report two experiments using four-choice (Experiment 1) and five-choice (Experiment 2) tasks that contain two types of irrelevant sources of potentially conflicting information: stimulus location (Simon conflict) and distractors (flanker conflict). In both experiments, we found within-type conflict adaptation for both types of conflict after eliminating trials on which stimulus features were repeated from one trial to the next. Across-type conflict adaptation, however, was not significant. Thus, conflict adaptation was due to domain-specific recruitment of cognitive control. Our results add converging evidence to the idea that multiple independent control processes are involved in reactive cognitive control, although whether control is always local remains to be determined.     

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.     

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.     

Blinking predicts enhanced cognitive control

Recent models have suggested an important role for neuromodulation in explaining trial-to-trial adaptations in cognitive control. The adaptation-by-binding model (Verguts & Notebaert, Psychological review, 115(2), 518–525, 2008), for instance, suggests that increased cognitive control in response to conflict (e.g., incongruent flanker stimulus) is the result of stronger binding of stimulus, action, and context representations, mediated by neuromodulators like dopamine (DA) and/or norepinephrine (NE). We presented a flanker task and used the Gratton effect (smaller congruency effect following incongruent trials) as an index of cognitive control. We investigated the Gratton effect in relation to eye blinks (DA related) and pupil dilation (NE related). The results for pupil dilation were not unequivocal, but eye blinks clearly modulated the Gratton effect: The Gratton effect was enhanced after a blink trial, relative to after a no-blink trial, even when controlling for correlated variables. The latter suggests an important role for DA in cognitive control on a trial-to-trial basis.     

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。     

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.     

Location-specific versus hemisphere-specific adaptation of processing selectivity

Current theories of cognitive control assume that processing selectivity is adjusted according to the utility of processing task-irrelevant stimulus features. Consistently, interference evoked by flanker stimuli is reduced when the proportion of incompatible trials—in which flankers are associated with an incorrect response—is increased. Consistent with the idea that the cerebral hemispheres select processing strategies independently of each other, Corballis and Gratton (2003) demonstrated that flanker interference for stimuli presented in either the left or right visual hemifield is affected by the ratio of compatible and incompatible target-flanker pairings presented in the same—but not in the other—hemifield. Presenting stimuli at four different locations, we demonstrated independent effects of the ratio of compatible and incompatible trials for stimulus locations in different hemifields as well as for stimulus locations within the same hemifield. Independent selectivity adjustment regarding the left and right visual hemifields thus appears to be a special case of a larger class of location-specific adaptation effects and might not be informative regarding hemisphere-specific processing.     

Stimulus- and response-conflict-induced cognitive control in the flanker task

Recently, several studies have been conducted to investigate the top-down adjustments made after incongruent trials during conflict tasks. In the present study, we investigated conflict monitoring with different types of conflict. In a modified version of the flanker task, a distinction was made between stimulus—stimulus conflict and stimulus—response conflict. Six colors were mapped to three responses in order to exclude all sequences in which a relevant or an irrelevant stimulus- or response-related feature was repeated from trialn−1 to trialn. An analysis of the effect of the congruency of the previous trial demonstrated that conflict adaptation was present. The stimulus congruency effect was reduced after both a stimulus-incongruent trial and a response-incongruent trial. The response congruency effect did not vary as a function of previous congruency. These findings are discussed in relation to the distinction between conflict detection and conflict regulation.     

Effector system-specific sequential modulations of congruency effects

Congruency effects in conflict tasks are reliably reduced after experiencing conflict, that is, following incongruent trials. Such sequential modulations (sometimes referred to as the Gratton effect) indicate the operation of conflict adaptation mechanisms. The influential conflict monitoring hypothesis suggested that after conflict the processing of relevant stimulus dimensions is increased. Alternatively, it was suggested that the influence of automatic response activation is suppressed following conflict. In two experiments, participants worked on the same cognitive task (Experiment 1: Eriksen flanker; Experiment 2: Simon) with the same kind of stimulation. A cue indicated whether they should respond with the hands or the feet. When the effector system repeated from the previous trial, a sequential modulation was reliably observed. When the effector system switched, however, the sequential modulation collapsed. These results are taken to argue for the suppression of effector system-specific response activations as a consequence of experiencing conflict. Alternative interpretations in terms of task-set and/or context switches 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.     

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.     

Age‐related change of location‐based visual selectivity depending on conflict frequency

Age‐related change in cognitive control for visual selectivity was examined using a conflict adaptation effect (CAE). The CAE reflects an increased stimulus compatibility effect for low levels of conflict frequency within blocks of trials. Younger (n = 20) and elderly (n = 20) adults received an Eriksen‐type flanker task involving compatible (e.g., “44444”) or incompatible (e.g., “44644”) arrays presented to either the left or right visual field (VF). The participants identified the central digit of an array. Relative frequency of conflict (incompatible) trials varied as a function of the VF. Also manipulated was the presentation order of more‐conflict VF and less‐conflict VF conditions over trial blocks. The results showed that a location‐based CAE appeared for both age groups in the first set of trial blocks, whereas in the final set of trial blocks the location‐based CAE appeared only for the younger adults. These results suggested that cognitive flexibility related to context‐dependent cognitive control diminishes with age.     

知觉负载影响注意选择和冲突解决的系列效应

研究考察了无关侧抑制项引起的侧抑制效应如何受到当前试次知觉负载和先前试次知觉负载与目标?侧抑制项关系的交互影响。被试在视觉搜索集中搜索目标朝向刺激(水平或竖直朝向)并作辨别反应, 非目标项在低负载条件下彼此朝向一致, 在高负载条件下彼此朝向不一致。在搜索集的左侧或右侧存在一个与当前目标一致或不一致的无关侧抑制项(flanker)。结果发现, 整体上, 在当前试次低负载条件下会产生较大的干扰效应, 而在当前试次高负载下无干扰效应。此外, 先前试次(trial n-1)为高负载条件时, 当前试次(trial n)出现了典型的知觉负载效应, 即低负载条件干扰效应较大, 高负载条件无干扰效应。但是, 先前试次为低负载条件时, 当前试次的干扰效应大小受到先前试次冲突解决状态的影响。先前试次为低负载条件且目标?无关侧抑制项不一致时, 下一试次低负载条件的侧抑制效应显著减小, 与高负载条件没有差异; 反之, 先前试次为低负载且目标?侧抑制项一致条件时, 下一试次低负载条件的侧抑制效应显著增大。先前试次为低负载条件时, 完成了知觉加工的侧抑制项或者引发了冲突效应(不一致条件), 或者促进了对目标的反应(一致条件), 造成不同的注意选择和冲突解决状态, 显著影响了下一试次的行为表现。这说明, 注意选择与冲突控制过程是动态变化的, 除了受到当前试次知觉负载的影响, 也受到先前试次注意选择和冲突解决状态的调节。     

Immediate priming and cognitive aftereffects

Three forced-choice perceptual word identification experiments tested the claim that transitions from positive to negative priming as a function of increasing prime duration are due to cognitive aftereffects. These aftereffects are similar in nature to perceptual aftereffects that produce a negative image due to overexposure and habituation to a stimulus. Each experiment tested critical predictions that come from including habituation in a dynamic neural network with multiple levels of processing. The success of this account in explaining the dynamics of repetition priming, associative-semantic priming, and forward masking effects suggests that habituation is a useful mechanism for reducing source confusion between successively presented stimuli. Implications are considered for visible persistence, repetition blindness, attention-based negative priming, attentional blink, inhibition of return, the negative compatibility effect, affect priming, and flanker preview effects.     

Masked nonword repetition effects in yes/no and go/no-go lexical decision: A test of the evidence accumulation and deadline accounts

The pattern of masked repetition priming effects for word and nonword targets differs across tasks: Maskedpriming effects in lexical decision occur for positive responses (i.e., words), but not for negative responses (nonwords), whereas masked-priming effects in the cross-case same-different task occur for positive responses (same), but not for negative responses (different)—regardless of lexical status. Here, we examined whether masked nonword priming effects are greater when the task involves an active go response to nonwords than when it involves the standard yes/no procedure in lexical decision. The obtained masked repetition priming effect for nonwords was of similar size in yes/no and go/no-go tasks. This finding is compatible with accounts of nonword priming that posit that nonword responses are produced by actively accumulating evidence for the nonword alternative in yes/no and go/no-go procedures, whereas it is inconsistent with the assumption of a deadline for no responses in the yes/no task.     

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。     

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.     

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.     

Contrasting effects of repetition across tasks: Implications for understanding the nature of refractory behavior and models of semantic memory

We describe a patient (J.M.) who showed “refractory” behavior in picture—word matching tasks—that is, his performance became poorer when items were repeated. This contrasts with the facilitatory effects of repetition usually observed in normal participants. We show for the first time that there can be facilitatory effects of repetition on some tasks, even though refractory behavior is shown on the same items in other tasks. In particular, in Experiments 1 and 2, we demonstrate that J.M. showed contrasting effects of repetition across different components of the language system: There were facilitatory effects of repetition priming on lexical decision but refractory behavior on picture—word matching. In Experiments 3 and 4, we demonstrate that J.M. showed contrasting effects of repetition within the same system (semantic memory). His performance became refractory when items were repeated in picture—word matching (Experiment 3), but it was facilitated when items were repeated in superordinate categorization (Experiment 4). These contrasting patterns of facilitation and interference from repetition priming have implications for understanding the nature of refractory behavior and for constraining theoretical accounts of semantic memory.