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In the present study, we investigated the influence of performance-contingent reward prospects on task performance across three visual conflict tasks with manual responses (Experiments 1 & 2: Simon and Stroop tasks; Experiment 3: Simon and Eriksen flanker task) using block-wise (Experiment 1) and trial-wise (Experiments 2 & 3) manipulations to signal the possibility of reward. Across all experiments, task performance (in reaction time and/or error rates) generally improved in reward compared with no-reward conditions in each conflict task. However, there was, if any, little evidence that the reward manipulation modulated the size of the mean conflict effects, and there was also no evidence for conflict-specific effects of reward when controlling for time-varying fluctuations in conflict processing via distributional analyses (delta plots). Thus, the results provide no evidence for conflict-specific accounts and instead favor performance-general accounts, where reward anticipation leads to overall performance improvements without affecting conflict effects. We discuss possible implications for how proactive control might modulate the interplay between target- and distractor-processing in conflict tasks. [ABSTRACT FROM AUTHOR]

The visual Simon task is widely employed to explore the underlying mechanisms of sensorimotor processing in the presence of task-relevant (targets) and task-irrelevant (distracting) location information. Critically, the Simon effect is considered as an indicator of action-related interference resulting from distractor-based activation, which fades out over time. In this study, we tested whether attenuated Simon effects with slower task processing may be fully explained by the fading of distractor-based response activation. To that end, we selectively manipulated perceptual target discriminability by varying the ratio of differently colored dots within (Experiment 1) and between blocks (Experiment 2). According to pure fading activation accounts, the negative-going delta plots of the two discriminability conditions should overlap across the entire reaction time (RT) distribution. In contrast to this prediction, the negative-going DPs for the two discriminability conditions did not overlap in either experiment. Instead, the Simon effect was either consistently smaller (Experiment 1) or larger (Experiment 2) across the entire RT distribution in the easy condition compared to the hard condition. This result pattern indicates that perceptual target discriminability affected conflict resolution beyond the mere fading of distractor-based activation. Exploratory model-based analyses suggest a stronger processing of relevant perceptual information with more discriminable targets, which may counteract the influence of distracting location information. However, as the exact effects of discriminability on conflict processing seem to depend on variation mode (trialwise vs. blockwise), the importance of global strategic effects is also highlighted. Public Significance Statement: In various real-world situations, individuals face the challenge of processing goal-relevant sensory information in environments filled with distracting and potentially conflicting sources of information. Uncovering the underlying mental mechanisms enabling the successful transformation of information into appropriate motor responses is of both practical (e.g., human–machine-interaction) and theoretical (uncovering general principles of human cognition) importance. In the present study, we demonstrate that the strength of activation by relevant information directly influences action-related conflict. These findings offer new evidence, suggesting a more substantial involvement of perceptual processes in action control than previously thought. [ABSTRACT FROM AUTHOR]

Laboratory data from conflict tasks, e.g. Simon and Eriksen tasks, reveal differences in response time distributions under different experimental conditions. Only recently have evidence accumulation models successfully reproduced these results, in particular the challenging delta plots with negative slopes. They accomplish this with explicit temporal dependencies in their structure or activation functions. In this work, we introduce an alternative approach to the modeling of decision-making in conflict tasks exclusively based on inhibitory dynamics within a dual-route architecture. We consider simultaneous automatic and controlled drift diffusion processes, with the latter inhibiting the former. Our proposed Dual-Route Evidence Accumulation Model (DREAM) achieves equivalent performance to previous works in fitting experimental response time distributions despite having no time-dependent functions. The model can reproduce conditional accuracy functions and delta plots with positive and negative slopes. The implications of these results, including an interpretation of the parameters and potential links to perceptual representations, are discussed. We provide Python code to fit DREAM to experimental data. [ABSTRACT FROM AUTHOR]

Context information can guide cognitive control, but both the extent and the underlying processes are poorly understood. Previous studies often found that the congruency sequence effect (CSE) is larger when perceptual context features (e.g., modality and format) of task-related distractors and targets repeat compared to change. However, it is unclear whether control adjustments can also be contextualized by more abstract stimulus features and/or by features of task-unrelated stimuli. The present study addressed this issue using a novel context manipulation in a confound-minimized prime-probe task. In Experiment (Exp.) 1, the modality (visual and auditory) of the distractor and target either repeated or changed. Critically, in Exp. 2, the distractor and target modality always switched, but the cross-modal intensity (brightness and loudness) could either repeat (e.g., bright → loud) or change (e.g., bright → soft). A larger CSE for context repeats (vs. changes) was observed in Exps. 1 and 2, indicating that both concrete (modality) and abstract stimulus features (cross-modal intensity) can contextualize control adjustments. Exps. 3 and 4 demonstrated that the CSE was not reliably affected when the context manipulation concerned a prior signal or a simultaneous background stimulus. Thus, task-related, but not task-unrelated, concrete and abstract stimulus features contextualize control adjustments. Moreover, distributional (delta plot) analyses of present and previous data revealed that the confound-minimized CSE and its contextual modulation reflect adjustments in the strength of cognitive control rather than in its timing. Overall, the present study provides new insights into how context information interacts with cognitive control to optimize decision making under conflict. [ABSTRACT FROM AUTHOR]

The recently developed diffusion model for conflict tasks (DMC) Ulrich et al. (Cognitive Psychology, 78, 148–174, 2015) provides a good account of data from all standard conflict tasks (e.g., Stroop, Simon, and flanker tasks) within a common evidence accumulation framework. A central feature of DMC's processing dynamics is that there is an initial phase of rapid accumulation of distractor evidence that is then selectively withdrawn from the decision mechanism as processing continues. We argue that this assumption is potentially troubling because it could be viewed as implying qualitative changes in the representation of distractor information over the time course of processing. These changes suggest more than simple inhibition or suppression of distractor information, as they involve evidence produced by distractor processing "changing sign" over time. In this article, we (a) develop a revised DMC (RDMC) whose dynamics operate strictly within the limits of inhibition/suppression (i.e., evidence strength can change monotonically, but cannot change sign); (b) demonstrate that RDMC can predict the full range of delta plots observed in the literature (i.e., both positive-going and negative-going); and (c) show that the model provides excellent fits to Simon and flanker data used to benchmark the original DMC at both the individual and group level. Our model provides a novel account of processing differences across Simon and flanker tasks. Specifically, that they differ in how distractor information is processed on congruent trials, rather than incongruent trials: congruent trials in the Simon task show relatively slow attention shifting away from distractor information (i.e., location) while complete and rapid attention shifting occurs in the flanker task. Our new model highlights the importance of considering dynamic interactions between top-down goals and bottom-up stimulus effects in conflict processing. [ABSTRACT FROM AUTHOR]

The present study investigated global behavioral adaptation effects to conflict arising from different distractor modalities. Three experiments were conducted using an Eriksen flanker paradigm with constant visual targets, but randomly varying auditory or visual distractors. In Experiment 1, the proportion of congruent to incongruent trials was varied for both distractor modalities, whereas in Experiments 2A and 2B, this proportion congruency (PC) manipulation was applied to trials with one distractor modality (inducer) to test potential behavioral transfer effects to trials with the other distractor modality (diagnostic). In all experiments, mean proportion congruency effects (PCEs) were present in trials with a PC manipulation, but there was no evidence of transfer to diagnostic trials in Experiments 2A and 2B. Distributional analyses (delta plots) provided further evidence for distractor modality-specific global behavioral adaptations by showing differences in the slope of delta plots with visual but not auditory distractors when increasing the ratio of congruent trials. Thus, it is suggested that distractor modalities constrain global behavioral adaptation effects due to the learning of modality-specific memory traces (e.g., distractor–target associations) and/or the modality-specific cognitive control processes (e.g., suppression of modality-specific distractor-based activation). Moreover, additional analyses revealed partial transfer of the congruency sequence effect across trials with different distractor modalities suggesting that distractor modality may differentially affect local and global behavioral adaptations. [ABSTRACT FROM AUTHOR]

In the present study, we examined how the relevance of potentially distracting information modulates the interplay of target and distractor processing in conflict tasks. Specifically, we manipulated the degree to which distracting information is relevant for performing the overall task by varying the proportion of trials in which a response to the distractor(s) (Experiments 1a and 1b: location in a Simon task; Experiment 2: flankers in an Eriksen flanker task) instead of to the target was required. Across all experiments, the congruency effect on mean RT was larger with the increasing relevance of the distractor(s). Critically, the slopes of the delta plot were more strongly increasing when the distractors were potentially relevant (as opposed to completely irrelevant), suggesting that cognitive control affects the timing of suppressing distractor-based activation. In addition, delta plot and diffusion model analyses revealed that the strength of suppressing distractor processing and the efficiency of target processing were enhanced when the distractors were less relevant. Overall, the present study dissociated multiple and time-dependent adjustments of control processes (i.e., target processing enhancement plus timing and strength of distractor suppression) in environments that encourage either a more stable or more flexible processing mode. [ABSTRACT FROM AUTHOR]

Previous studies have shown incorrect motor activation when making perceptual decisions under conflict, but the potential involvement of motor processes in conflict resolution is still unclear. The present study tested whether the effects of distracting information may be reduced when anticipated motor processing demands increase. Specifically, across two mouse-tracking Simon experiments, we manipulated blockwise motor demands (high vs. low) by requiring participants to move a mouse cursor to either large versus small (Experiment 1) or near versus far (Experiment 2) response boxes presented on the screen. We reasoned that participants would increase action control in blocks with high versus low motor demands and that this would reduce the distracting effect of location-based activation. The results support this hypothesis: Simon effects were reduced under high versus low motor demands and this modulation held even when controlling for time-varying fluctuations in distractor-based activation via distributional analyses (i.e., delta plots). Thus, the present findings indicate that anticipation of different motor costs can influence conflict processing. We propose that the competition between distractor-based and target-based activation is biased at premotor and/or motor stages in anticipation of motor demands, but also discuss alternative implementations of action control. [ABSTRACT FROM AUTHOR]

Previous studies have suggested that performance-contingent reward can modulate cognitive control by biasing irrelevant location-response associations in the Simon task. However, the influence of reward in the case of irrelevant words (Stroop task) or irrelevant flankers (Eriksen Flanker task) remains unclear. Across two preregistered experiments, the present study investigated the influence of reward on conflict processing with different types of distractors. Conflict effects on mean reaction time (RT) were reduced in the Simon task (Experiments 1 and 2) when incongruent versus congruent trials were rewarded, and this modulating effect of reward on conflict processing was also observed in the Eriksen flanker task (Experiment 2), but not in the Stroop task (Experiment 1). We propose that cognitive control adjustments to distractor-specific reward contingencies can be generalized across distractor types producing both perceptual-related (Flanker task) and motor-related (Simon task) conflict, but, if any, to a limited degree when distractors produce additional higher-level task conflict (Stroop task). In addition, distributional RT analyses (delta plots) revealed that rewarded distractor-response associations modulate cognitive control not only via biasing the strength (Simon and Eriksen tasks) but also the time-course of suppressing distractor processing (Eriksen task). Overall, the present study dissociated distractor-general and distractor-specific effects of reward on cognitive control. [ABSTRACT FROM AUTHOR]

The cognitive processes underlying the ability of human performers to trade speed for accuracy is often conceptualized within evidence accumulation models, but it is not yet clear whether and how these models can account for decision-making in the presence of various sources of conflicting information. In the present study, we provide evidence that speed-accuracy tradeoffs (SATs) can have opposing effects on performance across two different conflict tasks. Specifically, in a single preregistered experiment, the mean reaction time (RT) congruency effect in the Simon task increased, whereas the mean RT congruency effect in the Eriksen task decreased, when the focus was put on response speed versus accuracy. Critically, distributional RT analyses revealed distinct delta plot patterns across tasks, thus indicating that the unfolding of distractor-based response activation in time is sufficient to explain the opposing pattern of congruency effects. In addition, a recent evidence accumulation model with the notion of time-varying conflicting information was successfully fitted to the experimental data. These fits revealed task-specific time-courses of distractor-based activation and suggested that time pressure substantially decreases decision boundaries in addition to reducing the duration of non-decision processes and the rate of evidence accumulation. Overall, the present results suggest that time pressure can have multiple effects in decision-making under conflict, but that strategic adjustments of decision boundaries in conjunction with different time-courses of distractor-based activation can produce counteracting effects on task performance with different types of distracting sources of information. [ABSTRACT FROM AUTHOR]

We describe a mathematically simple yet precise model of activation suppression that can explain the negative-going delta plots often observed in standard Simon tasks. The model postulates a race between the identification of the relevant stimulus attribute and the suppression of irrelevant location-based activation, with the irrelevant activation only having an effect if the irrelevant activation is still present at the moment when central processing of the relevant attribute starts. The model can be fitted by maximum likelihood to observed distributions of RTs in congruent and incongruent trials, and it provides good fits to two previously-reported data sets with plausible parameter values. R and MATLAB software for use with the model is provided. [ABSTRACT FROM AUTHOR]

We elaborated an index, the Interference Distribution Index, which allows quantifying the relation between response times and the size of the interference effect. This index is associated with an intuitive graphical representation, the Lorenz-interference plot. We show that this index has some convenient properties in terms of sensitivity to changes in the distribution of the interference effect and to aggregation of individual data. Moreover, it turns out that this index is the only one (up to an arbitrary increasing transformation) possessing these properties. The relevance of this index is illustrated through simulations of a cognitive model of interference effects and reanalysis of experimental data. [ABSTRACT FROM AUTHOR]

It is widely believed that faces are processed holistically such that their facial features or parts are represented as global wholes rather than independent entities. But how does their holistic representation evolve in time? According to the global-to-local hypothesis, the initial representation of faces is holistic and coarse at the outset but is becoming progressively detailed and analytic. The current study set to test this global-to-local hypothesis by applying fine-grained methods of response time analyses to the composite face illusion – a traditional marker of holistic face processing. The analyses included the delta plots and conditional accuracy functions. These tools move beyond the mean RT and accuracy to provide detailed analysis of the temporal dynamics of the composite face effect. The methodologies converged on the conclusion that the composite effect is minimal for fast RTs but becomes progressively larger as RT gets slower. This pattern is inconsistent with a global-to-local dynamics. The implications of these results to the study of face perception are discussed.

It is widely believed that faces are processed holistically such that their facial features or parts are represented as global wholes rather than independent entities. But how does their holistic representation evolve in time? According to the global-to-local hypothesis, the initial representation of faces is holistic and coarse at the outset but is becoming progressively detailed and analytic. The current study set to test this global-to-local hypothesis by applying fine-grained methods of response time analyses to the composite face illusion – a traditional marker of holistic face processing. The analyses included the delta plots and conditional accuracy functions. These tools move beyond the mean RT and accuracy to provide detailed analysis of the temporal dynamics of the composite face effect. The methodologies converged on the conclusion that the composite effect is minimal for fast RTs but becomes progressively larger as RT gets slower. This pattern is inconsistent with a global-to-local dynamics. The implications of these results to the study of face perception are discussed. [ABSTRACT FROM AUTHOR]

The role of response inhibition in lying is debated. By using the delta-plot method applied to the Sheffield Lie Test, Debey, Ridderinkhof, De Houwer, De Schryver, and Verschuere (2015) provided evidence supporting the role of inhibition in lying. In the study of Debey et al., inhibitory skill was measured in terms of the size of the lie effect. However, to provide convincing evidence that delta plots highlight the role of response inhibition in lying, inhibitory ability must be evaluated independently from the size of the lie effect. After replicating original findings, this article shows that a delta plot analysis does not differentiate individuals with different inhibitory abilities, when inhibitory skill is measured by means of the Stop Signal Task, instead of the size of the lie effect. This suggests that researchers should be cautious when making conclusions about cognitive mechanisms based on the sole analysis of delta plots. [ABSTRACT FROM AUTHOR]

A psychosis phenotype can be observed below the threshold of clinical detection. The study aimed to investigate whether subclinical psychotic symptoms are associated with deficits in controlling emotional interference, and whether cortical brain and cardiac correlates of these deficits can be detected using functional near-infrared spectroscopy (fNIRS). A data set derived from a community sample was obtained from the Zurich Program for Sustainable Development of Mental Health Services. 174 subjects (mean age 29.67 ± 6.41, 91 females) were assigned to four groups ranging from low to high levels of subclinical psychotic symptoms (derived from the Symptom Checklist-90-R). Emotional interference was assessed using the emotional Stroop task comprising neutral, positive, and negative conditions. Statistical distributional methods based on delta plots (behavioral response time data) and quantile analysis (fNIRS data) were applied to evaluate the emotional interference effects.Results showed that both interference effects and disorder-specific (i.e., group-specific) effects could be detected, based on behavioral response times, cortical hemodynamic signals (brain correlates), and heart rate variability (cardiac correlates). Subjects with high compared to low subclinical psychotic symptoms revealed significantly reduced amplitudes in dorsolateral prefrontal cortices (interference effect, p < 0.001) and middle temporal gyrus (disorder-specific group effect, p < 0.001), supported by behavioral and heart rate results. The present findings indicate that distributional analyses methods can support the detection of emotional interference effects in the emotional Stroop. The results suggested that subjects with high subclinical psychosis exhibit enhanced emotional interference effects. Based on these observations, subclinical psychosis may therefore prove to represent a valid extension of the clinical psychosis phenotype.

In a Stroop task, participants can be presented with a color name printed in color and need to classify the print color while ignoring the word. The Stroop effect is typically calculated as the difference in mean response time (RT) between congruent (e.g., the word RED printed in red) and incongruent (GREEN in red) trials. Delta plots compare not just mean performance, but the entire RT distributions of congruent and incongruent conditions. However, both mean RT and delta plots have some limitations. Arm-reaching trajectories allow a more continuous measure for assessing the time course of the Stroop effect. We compared arm movements to congruent and incongruent stimuli in a standard Stroop task and a control task that encourages processing of each and every word. The Stroop effect emerged over time in the control task, but not in the standard Stroop, suggesting words may be processed differently in the two tasks. [ABSTRACT FROM AUTHOR]

Lying takes more time than telling the truth. Because lying involves withholding the truth, this “lie effect” has been related to response inhibition. We investigated the response inhibition hypothesis of lying using the delta-plot method: A leveling-off of the standard increase of the lie effect with slower reaction times would be indicative of successful response inhibition. Participants performed a reaction-time task that required them to alternate between lying and truth telling in response to autobiographical questions. In two experiments, we found that the delta plot of the lie effect leveled off with longer response latencies, but only in a group of participants who had better inhibitory skills as indexed by relatively small lie effects. This finding supports the role of response inhibition in lying. We elaborate on repercussions for cognitive models of deception and the data analysis of reaction-time based lie tests. [ABSTRACT FROM AUTHOR]

An elaborated diffusion process model (a Diffusion Model for Conflict Tasks , DMC) is introduced that combines conceptual features of standard diffusion models with the notion of controlled and automatic processes. DMC can account for a variety of distributional properties of reaction time (RT) in conflict tasks (e.g., Eriksen flanker, Simon, Stroop). Specifically, DMC is compatible with all observed shapes of delta functions, including negative-going delta functions that are particularly challenging for the class of standard diffusion models. Basically, DMC assumes that the activations of controlled and automatic processes superimpose to trigger a response. Monte Carlo simulations demonstrate that the unfolding of automatic activation in time largely determines the shape of delta functions. Furthermore, the predictions of DMC are consistent with other phenomena observed in conflict tasks such as error rate patterns. In addition, DMC was successfully fitted to experimental data of the standard Eriksen flanker and the Simon task. Thus, the present paper reconciles the prominent and successful class of diffusion models with the empirical finding of negative-going delta functions. [ABSTRACT FROM AUTHOR]

It has been argued that inhibition is a mechanism of attentional control in bilingual language performance. Evidence suggests that effects of inhibition are largest in the tail of a response time (RT) distribution in non-linguistic and monolingual performance domains. We examined this for bilingual performance by conducting delta-plot analyses of naming RTs. Dutch-English bilingual speakers named pictures using English while trying to ignore superimposed neutral Xs or Dutch distractor words that were semantically related, unrelated, or translations. The mean RTs revealed semantic, translation, and lexicality effects. The delta plots leveled off with increasing RT, more so when the mean distractor effect was smaller as compared with larger. This suggests that the influence of inhibition is largest towards the distribution tail, corresponding to what is observed in other performance domains. Moreover, the delta plots suggested that more inhibition was applied by high- than low-proficiency individuals in the unrelated than the other distractor conditions. These results support the view that inhibition is a domain-general mechanism that may be optionally engaged depending on the prevailing circumstances.

Abstract: Several theoretical accounts assume that interference control deficits belong to the core symptoms of adult ADHD. However, findings of increased interference effects in adult ADHD patients compared with healthy adults may be confounded with the simultaneous finding of generally slower responses in the patient group. The current study compared the magnitude of the interference effect in the Stroop task between a group of adults with ADHD and a healthy adult control group in a procedure that accounted for differences in overall response speed by using delta plots. The amount of interference did not differ between patient and control group at comparable reaction time levels. These results challenge the conclusions of the previous studies, in that they indicate that interference control is not impaired in adult ADHD. [Copyright &y& Elsevier]

Since 1994, group reaction time (RT) distribution analyses of spatial correspondence effects have been used to evaluate the dynamics of the spatial Simon effect, a benefit of correspondence of stimulus location information with response location for tasks in which stimulus location is irrelevant. We review the history and justification for analyzing group RT distributions and clarify which conditions result in the Simon effect decreasing across the distribution and which lead to flat or increasing functions. Although the standard left-right Simon effect typically yields a function for which the effect decreases as RT increases, in most other task variations, the Simon effect remains stable or increases across the RT distribution. Studies that have used other means of evaluating the temporal dynamics of the Simon effect provide converging evidence that the changes in the Simon effect across the distribution are due mainly to temporal activation properties, an issue that has been a matter of some dispute. [ABSTRACT FROM AUTHOR]

Most models of word production converge on the assumption that selecting a specific word to name is a competitive process. Monolingual speakers experience lexical competition in their spoken language (i.e., within-language competition), but bilingual speakers who constantly juggle two sets of lexical items face within- and between-language competition. It has been argued that one of the reasons bilingual speakers perform poorly in linguistic tasks compared to monolinguals is the interference from the non-target language. However, this constant juggling of two languages has also been proposed to lead to better executive control abilities in bilinguals. The aim of this research was to determine the relationship between increased lexical competition as induced by semantic context manipulation in the blocked-cyclic picture naming paradigm, and executive control processes in bilingual and monolingual speakers. We implemented the blocked-cyclic picture naming paradigm to induce increased lexical competition and employed independent executive control tasks to understand its role in reducing increased lexical competition. We also computed delta plots – size of interference effects as a function of naming latencies – to investigate the type of inhibition involved in the blocked-cyclic picture naming paradigm. In this paradigm, objects to be named were presented in close succession, either from the same semantic categories (homogeneous: elephant, lion, deer, tiger, and cat) or different ones (heterogeneous: pear, shoes, lips, saw, and deer). Naming latencies are longer in the homogeneous context due to the heightened activation of competitors, and the difference in latencies between the homogeneous and heterogeneous contexts is referred to as semantic context effect. The participants were 25 young, healthy Bengali-English bilinguals and 25 healthy, age-, gender- and education-matched English monolinguals. All participants performed a blocked-cyclic naming task in English as well as three independent executive control tasks, tapping into their inhibitory control (Stroop task), mental-set shifting (colour-shape switch task), and working memory (backward digit span task). The key group differences were as follows: bilinguals showed less semantic context effect and more semantic facilitation on the first presentation cycle, applied more selective inhibition in both blocked-cyclic picture naming and Stroop tasks as measured by delta plots, showed better inhibitory control (Stroop task) and shifting abilities, but showed comparable working memory span. The correlation findings for both groups were as follows: slope of the slowest delta segment correlated with the magnitude of the semantic context effect in the blocked-cyclic naming task, no correlation between the slope and interference effect in the Stroop task, no correlation between slope of the two tasks, and no correlations between the semantic context effect with any of the measures derived from the independent executive control tasks. This is the first study to establish that bilinguals are less affected by semantic context manipulation and show a reduced interference effect for the longest naming latencies, compared to monolinguals. It also illustrates that even in a challenging linguistic task that heightens lexical competition, bilinguals performed better than monolinguals. This challenges the notion that bilinguals are disadvantaged compared to monolinguals in linguistic tasks, and we conclude that this study provides evidence for the advantage of bilingualism in linguistic tasks where executive control demands are higher. • The semantic context effects between bilinguals and monolinguals were explored on a blocked-cyclic picture naming task. • The type of inhibition was computed using delta plots for the blocked-cyclic picture naming task and Stroop task. • Bilinguals showed smaller semantic context effect, and larger semantic facilitation during first presentation cycle. • Bilinguals applied more selective inhibition in both blocked-cyclic picture naming and Stroop tasks. • The findings challenge the notion that bilinguals are disadvantaged compared to monolinguals in linguistic tasks. [ABSTRACT FROM AUTHOR]

• Combined chronometric approach with RT distributional analyses in the Simon task. • Observed interactive mean RT patterns of congruency and stage-specific manipulations. • Observed decreasing RT and PE delta plots for congruency effects in all conditions. • Delta plot analyses reveal influences on congruency effects not evident in mean RT. • Effects of some manipulations on delta plots not explained by fading activation. We combined analyses of reaction time (RT) distributions with experimental manipulations of different processing stages (perception, decision, motor execution) in a Simon task to investigate which changes in Simon effects could be explained entirely by fading irrelevant response activation. Consistent with fading activation accounts, the Simon effect on mean RT was usually smaller for conditions with slower responses (Expts. 1–3 but not Expt. 4), and delta plot analyses revealed that it was always smaller for the slower responses within each condition. Critically, however, these analyses also revealed that some experimental manipulations produced upward or downward shifts in the RT delta plots, thus altering the Simon effect on mean RT in ways that could not be explained by fading activation. The results demonstrate the power of combining RT distributional analyses with experimental manipulations to reveal mechanisms contributing to the Simon effect that would not be revealed using only mean RT. We consider alternatives to fading activation accounts of decreasing delta plots and discuss the contribution of different cognitive stages in modulating Simon effects. [ABSTRACT FROM AUTHOR]