Proportion Congruent Effect Research Articles

Event-related potentials as brain correlates of item specific proportion congruent effects

The item-specific proportion congruency (ISPC) effect is consistent with the idea that control processes can be applied rapidly in accord with previously experienced conflict for a particular category. An alternative account of this effect is that it reflects item-specific learning processes unrelated to control at the level of the category. The accounts predict the same behaviour but differ in terms of electrophysiological predictions. Two experiments examined the ISPC effect with a particular focus on neural correlates that might reveal whether, and how early in processing, high and low proportion congruent items are treated as distinct classes of stimuli. For both tasks, the proportion congruency category was distinguished prior to the congruence of the specific stimulus, as early as 100 ms post-stimulus onset for the global/local identification task (Experiment 1) and 150 ms for the Stroop task (Experiment 2). The results support an on-line control account of ISPC effects.

Working memory capacity and Stroop interference: Global versus local indices of executive control.

Two experiments examined the relations among working memory capacity (WMC), congruency-sequence effects, proportion-congruency effects, and the color-word Stroop effect to test whether congruency-sequence effects might inform theoretical claims regarding WMC's prediction of Stroop interference. In Experiment 1, subjects completed either a high-congruency or low-congruency Stroop task that restricted trial-to-trial repetitions of stimulus dimensions to examine WMC's relation to congruency-sequence effects while minimizing bottom-up, stimulus-driven contributions. Congruency-sequence effects and congruency-proportion effects were significant but did not interact. WMC predicted global Stroop interference under low-congruency conditions but neither local congruency-sequence effects nor global Stroop interference under high-congruency conditions, contrary to previous studies (e.g., Kane & Engle, 2003). A high-congruency Stroop task in Experiment 2 removed the Experiment 1 task constraints, and, here, we obtained the typical, global association between WMC and Stroop interference but still no relation between WMC and congruency-sequence effects. We thus examined the methodological differences between Experiments 1 and 2 to determine whether any of these were locally responsible for the global WMC-related differences. They were not, suggesting that the changes between Experiments 1 and 2 created a general task context that engaged (or disengaged) the executive processes associated with WMC.

Exploration of the mechanisms underlying the ISPC effect: Evidence from behavioral and neuroimaging data

The item-specific proportion congruent (ISPC) effect in a Stroop task – the observation of reduced interference for color words mostly presented in an incongruent color – has attracted growing interest since the original study by Jacoby, Lindsay, and Hessels [(2003) Psychonomic Bulletin & Review, 10(3), 638–644]. Two mechanisms have been proposed to explain the effect: associative learning of contingencies and item-specific control through word reading modulation. Both interpretations have received empirical support from behavioral data. Therefore, the aim of this study was to investigate the responsible mechanisms of the ISPC effect with the classic two-item sets design using fMRI. Results showed that the ISPC effect is associated with increased activity in the anterior cingulate (ACC), dorsolateral prefrontal (DLPFC), and inferior and superior parietal cortex. Importantly, behavioral and fMRI analyses specifically addressing the respective contribution of associative learning and item-specific control mechanisms brought support for the contingency learning account of the ISPC effect. Results are discussed in reference to task and procedure characteristics that may influence the extent to which item-specific control and/or contingency learning contribute to the ISPC effect.

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.

Questioning conflict adaptation: proportion congruent and Gratton effects reconsidered

Conflict adaptation is one of the most popular ideas in cognitive psychology. It purports to explain a wide range of data, including both brain and behavioral data from the proportion congruent and Gratton paradigms. However, in recent years, many concerns about the viability of this account have been raised. It has been argued that contingency learning, not conflict adaptation, produces the proportion congruent effect. Similarly, the Gratton paradigm has been shown to contain several confounds-most notably, feature repetition biases. Newer work on temporal learning further calls into question the interpretability of the behavioral results of conflict adaptation studies. Brain data linking supposed conflict adaptation to the anterior cingulated cortex has also come into question, since this area seems to be responsive solely to time-on-task, rather than conflict. This review points to the possibility that conflict adaptation may simply be an illusion. However, the extant data remain ambiguous, and there are a lot of open questions that still need to be addressed in future research.

Social categories as a context for the allocation of attentional control.

Recent studies of cognitive control have highlighted the idea that context can rapidly cue the control of attention. The present study shows that faces can be quickly categorized on the basis of gender, and these gender categories can be used as a contextual cue to allocate attentional control. Furthermore, the results reported here reveal processes implicated in the development and operation of implicit social stereotypes. Three of 4 faces from 1 gender group were associated with a high proportion of congruent trials in a flanker task, while 3 of 4 faces of the other gender group were associated with a low proportion of congruent trials. A single inconsistent face within each gender group was associated with the proportion congruency of the opposite gender group. A social context-specific proportion congruent effect (PCE) was observed (i.e., larger interference for the gender category associated with a high proportion of congruent trials), even for inconsistent members of the category. This effect is consistent with the view that a new implicit stereotype was created, linking gender with a specific proportion of congruency. In Experiment 2, the task goals modulated the use of the new created stereotype. Instructions to categorize versus individuate the target faces, respectively, led participants to allocate attention either toward the category-diagnostic or the identity-diagnostic facial features. Furthermore, and in line with stereotyping research, under instructions to categorize faces this social-context-specific PCE generalized to new faces of the same gender group with whom participants did not have previous experience. These results link attention with social categorization processes.

Anticipation and the control of voluntary action

Anticipation and the control of voluntary action

Attention modulation by proportion congruency: The asymmetrical list shifting effect.

Proportion congruency effects represent hallmark phenomena in current theorizing about cognitive control. This is based on the notion that proportion congruency determines the relative levels of attention to relevant and irrelevant information in conflict tasks. However, little empirical evidence exists that uniquely supports such an attention modulation account; moreover, a rivaling account was recently proposed that attributes the effect of proportion congruency to mere contingency learning. In the present study, the influences of shifts in list-wide (Experiment 1) or item-specific (Experiment 2) proportion congruency were investigated. As predicted by attention modulation but not by contingency learning, strong asymmetries were observed in such shifting: An increase in the proportion of congruent trials had only limited impact on the size of the congruency effect when participants were initially trained with a mostly incongruent list, but the impact was substantial for an equivalent increase of incongruent trials when participants were initially trained with a mostly congruent list. This asymmetrical list shifting effect directly supports attention modulation by proportion congruency manipulations and as such provides a novel tool for exploring cognitive control. Implications of our findings for existing theories of cognitive control are discussed.

The Parallel Episodic Processing (PEP) model: Dissociating contingency and conflict adaptation in the item-specific proportion congruent paradigm

The present work introduces a computational model, the Parallel Episodic Processing (PEP) model, which demonstrates that contingency learning achieved via simple storage and retrieval of episodic memories can explain the item-specific proportion congruency effect in the colour-word Stroop paradigm. The current work also presents a new experimental procedure to more directly dissociate contingency biases from conflict adaptation (i.e., proportion congruency). This was done with three different types of incongruent words that allow a comparison of: (a) high versus low contingency while keeping proportion congruency constant, and (b) high versus low proportion congruency while keeping contingency constant. Results demonstrated a significant contingency effect, but no effect of proportion congruence. It was further shown that the proportion congruency associated with the colour does not matter, either. Thus, the results quite directly demonstrate that ISPC effects are not due to conflict adaptation, but instead to contingency learning biases.

Modulation of Brain Activity during a Stroop Inhibitory Task by the Kind of Cognitive Control Required

This study used a proportion congruency manipulation in the Stroop task in order to investigate, at the behavioral and brain substrate levels, the predictions derived from the Dual Mechanisms of Control (DMC) account of two distinct modes of cognitive control depending on the task context. Three experimental conditions were created that varied the proportion congruency: mostly incongruent (MI), mostly congruent (MC), and mostly neutral (MN) contexts. A reactive control strategy, which corresponds to transient interference resolution processes after conflict detection, was expected for the rare conflicting stimuli in the MC context, and a proactive strategy, characterized by a sustained task-relevant focus prior to the occurrence of conflict, was expected in the MI context. Results at the behavioral level supported the proactive/reactive distinction, with the replication of the classic proportion congruent effect (i.e., less interference and facilitation effects in the MI context). fMRI data only partially supported our predictions. Whereas reactive control for incongruent trials in the MC context engaged the expected fronto-parietal network including dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex, proactive control in the MI context was not associated with any sustained lateral prefrontal cortex activations, contrary to our hypothesis. Surprisingly, incongruent trials in the MI context elicited transient activation in common with incongruent trials in the MC context, especially in DLPFC, superior parietal lobe, and insula. This lack of sustained activity in MI is discussed in reference to the possible involvement of item-specific rather than list-wide mechanisms of control in the implementation of a high task-relevant focus.

In Support of a Distinction between Voluntary and Stimulus-Driven Control: A Review of the Literature on Proportion Congruent Effects.

Cognitive control is by now a large umbrella term referring collectively to multiple processes that plan and coordinate actions to meet task goals. A common feature of paradigms that engage cognitive control is the task requirement to select relevant information despite a habitual tendency (or bias) to select goal-irrelevant information. At least since the 1970s, researchers have employed proportion congruent (PC) manipulations to experimentally establish selection biases and evaluate the mechanisms used to control attention. PC manipulations vary the frequency with which irrelevant information conflicts (i.e., is incongruent) with relevant information. The purpose of this review is to summarize the growing body of literature on PC effects across selective attention paradigms, beginning first with Stroop, and then describing parallel effects in flanker and task-switching paradigms. The review chronologically tracks the expansion of the PC manipulation from its initial implementation at the list-wide level, to more recent implementations at the item-specific and context-specific levels. An important theoretical aim is demonstrating that PC effects at different levels (e.g., list-wide vs. item or context-specific) support a distinction between voluntary forms of cognitive control, which operate based on anticipatory information, and relatively automatic or reflexive forms of cognitive control, which are rapidly triggered by the processing of particular stimuli or stimulus features. A further aim is to highlight those PC manipulations that allow researchers to dissociate stimulus-driven control from other stimulus-driven processes (e.g., S-R responding; episodic retrieval). We conclude by discussing the utility of PC manipulations for exploring the distinction between voluntary control and stimulus-driven control in other relevant paradigms.

Model-Based Analysis of Context-Specific Cognitive Control

Interference resolution is improved for stimuli presented in contexts (e.g., locations) associated with frequent conflict. This phenomenon, the context-specific proportion congruent (CSPC) effect, has challenged the traditional juxtaposition of “automatic” and “controlled” processing because it suggests that contextual cues can prime top-down control settings in a bottom-up manner. We recently obtained support for this “priming of control” hypothesis with functional magnetic resonance imaging by showing that CSPC effects are mediated by contextually cued adjustments in processing selectivity. However, an equally plausible explanation is that CSPC effects reflect adjustments in response caution triggered by expectancy violations (i.e., prediction errors) when encountering rare events as compared to common ones (e.g., incongruent trials in a task context associated with infrequent conflict). Here, we applied a quantitative model of choice, the linear ballistic accumulator (LBA), to distil the reaction time and accuracy data from four independent samples that performed a modified flanker task into latent variables representing the psychological processes underlying task-related decision making. We contrasted models which differentially accounted for CSPC effects as arising either from contextually cued shifts in the rate of sensory evidence accumulation (“drift” models) or in the amount of evidence required to reach a decision (“threshold” models). For the majority of the participants, the LBA ascribed CSPC effects to increases in response threshold for contextually infrequent trial types (e.g., congruent trials in the frequent conflict context), suggesting that the phenomenon may reflect more a prediction error-triggered shift in decision criterion rather than enhanced sensory evidence accumulation under conditions of frequent conflict.

List-wide control is not entirely elusive: Evidence from picture–word Stroop

Stroop interference is attenuated in mostly incongruent lists, as compared with mostly congruent ones. This finding is referred to as the list-wide proportion congruence effect. The traditional interpretation refers to the strategic biasing of attention via list-wide control. In mostly incongruent lists, attention is biased away from the irrelevant words, whereas in mostly congruent lists, words are more fully processed. According to the item-specific account, the list-wide proportion congruence effect reflects stimulus-driven mechanisms, and not list-wide control. The unambiguous evidence available to date strongly favors the item-specific account. Using a picture-word Stroop task, we demonstrate a list-wide proportion congruence effect for 50% congruent items that are embedded in mostly incongruent and mostly congruent lists. This novel finding illustrates that the list-wide proportion congruence effect is not entirely dependent on item-specific contributions and supports the list-wide control account. We discuss factors impacting the emergence of list-wide control in Stroop tasks.

Why it is too early to lose control in accounts of item-specific proportion congruency effects.

The item-specific proportion congruency (ISPC) effect is the finding of attenuated interference for mostly incongruent as compared to mostly congruent items. A debate in the Stroop literature concerns the mechanisms underlying this effect. Noting a confound between proportion congruency and contingency, Schmidt and Besner (2008) suggested that ISPC effects are entirely contingency based. We introduce a broader theoretical analysis that points to the contribution of both contingency and item-specific control mechanisms. Our analysis highlights that proportion congruency is not confounded with contingency when the relevant dimension functions as the ISPC signal, and predicts that evidence of item-specific control should be obtained by shifting the signal from the irrelevant to the relevant dimension. We examine this prediction in a picture-word Stroop paradigm. When the relevant dimension functions as the ISPC signal (Experiments 1 and 2), evidence of control is obtained. When the irrelevant dimension functions as the ISPC signal (Experiment 3), contingencies can account for the ISPC effect. These patterns support our theoretical analysis, challenge a pure contingency account, and favor the inclusion of control in accounts of ISPC effects.

Revealing list-level control in the Stroop task by uncovering its benefits and a cost.

Interference is reduced in mostly incongruent relative to mostly congruent lists. Classic accounts of this list-wide proportion congruence effect assume that list-level control processes strategically modulate word reading. Contemporary accounts posit that reliance on the word is modulated poststimulus onset by item-specific information (e.g., proportion congruency of the word). To adjudicate between these accounts, we used novel designs featuring neutral trials. In two experiments, we showed that the list-wide proportion congruence effect is accompanied by a change in neutral trial color-naming performance. Because neutral words have no item-specific bias, this pattern can be attributed to list-level control. Additionally, we showed that list-level attenuation of word reading led to a cost to performance on a secondary prospective memory task but only when that task required processing of the irrelevant, neutral word. These findings indicate that the list-wide proportion congruence effect at least partially reflects list-level control and challenge purely item-specific accounts of this effect.

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.

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.

Multiple levels of control in the Stroop task

Multiple levels of control may be used in service of reducing Stroop interference. One is list-wide, whereby interference is reduced strategically in lists that include disproportionately more incongruent trials. A second, item-specific control is observed when proportion congruence is manipulated at the level of items. Item-specific control reduces interference for mostly incongruent relative to mostly congruent items. First, we show that item-specific control may drive both list-wide and item-specific proportion congruence effects (Experiment 1). We then show that item-specific control affects Stroop interference similarly when a single feature (a word) as opposed to a feature combination (a word+font type) signals proportion congruence (Experiment 2). Although this suggests that font type offers little advantage for controlling Stroop interference beyond the word, a novel, font-specific proportion congruence effect is observed in Experiment 3, indicating that font type can be used to control interference. These findings support the idea that multiple levels of control are used in reducing Stroop interference.

The Stroop effect: Why proportion congruent has nothing to do with congruency and everything to do with contingency.

The item-specific proportion congruent (ISPC) effect refers to the observation that the Stroop effect is larger for words that are presented mostly in congruent colors (e.g., BLUE presented 75% of the time in blue) and smaller for words that are presented mostly in a given incongruent color (e.g., YELLOW presented 75% of the time in orange). One account of the ISPC effect, the modulation hypothesis, is that participants modulate attention based on the identity of the word (i.e., participants allow the word to influence responding when it is presented mostly in its congruent color). Another account, the contingency hypothesis, is that participants use the word to predict the response that they will need to make (e.g., if the word is YELLOW, then the response is probably "orange"). Reanalyses of data from L. L. Jacoby, D. S. Lindsay, and S. Hessels (2003), along with results from new experiments, are inconsistent with the modulation hypothesis but entirely consistent with the contingency hypothesis. A response threshold mechanism that uses contingency information provides a sufficient account of the data.

Item-specific adaptation and the conflict-monitoring hypothesis: A computational model.

M. M. Botvinick, T. S. Braver, D. M. Barch, C. S. Carter, and J. D. Cohen (2001) implemented their conflict-monitoring hypothesis of cognitive control in a series of computational models. The authors of the current article first demonstrate that M. M. Botvinick et al.'s (2001) conflict-monitoring Stroop model fails to simulate L. L. Jacoby, D. S. Lindsay, and S. Hessels's (2003) report of an item-specific proportion-congruent (ISPC) effect in the Stroop task. The authors then implement a variant of M. M. Botvinick et al.'s model based on the assumption that control must be able to operate at the item level. This model successfully simulates the ISPC effect. In addition, the model provides an alternative to M. M. Botvinick et al.'s explanation of the list-level proportion-congruent effect in terms of an ISPC effect. Implications of the present modeling effort are discussed.