Effects of visual and auditory noise on visual choice reaction time in a continuous-flow paradigm

Behavioral and neural measures of semantic conflict monitoring: Findings from a novel picture-word interference task

Conflict monitoring has been studied extensively using experimental paradigms that manipulate perceptual dimensions of stimuli and responses. The picture-word interference (PWI) task has historically been used to examine semantic conflict, but primarily for the purpose of examining lexical retrieval. In this study, we utilized two novel PWI tasks to assess conflict monitoring in the context of semantic conflict. Participants included nineteen young adults (14F, age = 20.79 ± 3.14) who completed two tasks: Animals and Objects. Task and conflict effects were assessed by examining behavioral (reaction time and accuracy) and neurophysiological (oscillations in theta, alpha, and beta band) measures. Results revealed conflict effects within both tasks, but the pattern of findings differed across the two semantic categories. Participants were slower to respond to unmatched versus matched trials on the Objects task only and were less accurate responding to matched versus unmatched trials in the Animals task only. We also observed task differences, with participants responding more accurately on conflict trials for Animals compared to Objects. Differences in neural oscillations were observed, including between-task differences in low beta oscillations and within-task differences in theta, alpha, and low beta. We also observed significant correlations between task performance and standard measures of cognitive control. This work provides new insights into conflict monitoring, highlighting the importance of examining conflict across different semantic categories, especially in the context of animacy. The findings serve as a benchmark to assess conflict monitoring using PWI tasks across populations of varying cognitive ability.

The neutral condition in conflict tasks: On the violation of the midpoint assumption in reaction time trends

Although the relation between congruent and incongruent conditions in conflict tasks has been the primary focus of cognitive control studies, the neutral condition is often set as a baseline directly between the two conditions. However, empirical evidence suggests that the average neutral reaction time (RT) is not placed evenly between the two opposing conditions. This article set out to establish two things: First, to reinforce the informative nature of the neutral condition and second, to highlight how it can be useful for modelling. We explored how RT in the neutral condition of conflict tasks (Stroop, Flanker, and Simon Tasks) deviated from the predictions of current diffusion models. Current diffusion models of conflict tasks predict a neutral RT that is the average of the congruent and incongruent RT, called the midpoint assumption. To investigate this, we first conducted a cursory limited search that recorded the average RT's of conflict tasks with neutral conditions. Upon finding evidence of a midpoint assumption violation which showed a larger disparity between average neutral and incongruent RT, we tested the previously mentioned conflict tasks with two different sets of stimuli to establish the robustness of the effect. The midpoint assumption violation is sometimes inconsistent with the prediction of diffusion models of conflict processing (e.g., the Diffusion Model of Conflict), suggesting possible elaborations of such models.

GABA, glutamatergic dynamics and BOLD contrast assessed concurrently using functional MRS during a cognitive task

A recurring issue in functional neuroimaging is how to link task-driven haemodynamic blood oxygen level dependent functional MRI (BOLD-fMRI) responses to underlying neurochemistry at the synaptic level. Glutamate and γ-aminobutyric acid (GABA), the major excitatory and inhibitory neurotransmitters respectively, are typically measured with MRS sequences separately from fMRI, in the absence of a task. The present study aims to resolve this disconnect, developing acquisition and processing techniques to simultaneously assess GABA, glutamate and glutamine (Glx) and BOLD in relation to a cognitive task, at 3 T. Healthy subjects (N = 81) performed a cognitive task (Eriksen flanker), which was presented visually in a task-OFF, task-ON block design, with individual event onset timing jittered with respect to the MRS readout. fMRS data were acquired from the medial anterior cingulate cortex during task performance, using an adapted MEGA-PRESS implementation incorporating unsuppressed water-reference signals at a regular interval. These allowed for continuous assessment of BOLD activation, through T2 *-related changes in water linewidth. BOLD-fMRI data were additionally acquired. A novel linear model was used to extract modelled metabolite spectra associated with discrete functional stimuli, building on well established processing and quantification tools. Behavioural outcomes from the flanker task, and activation patterns from the BOLD-fMRI sequence, were as expected from the literature. BOLD response assessed through fMRS showed a significant correlation with fMRI, specific to the fMRS-targeted region of interest; fMRS-assessed BOLD additionally correlated with lengthening of response time in the incongruent flanker condition. While no significant task-related changes were observed for GABA+, a significant increase in measured Glx levels (~8.8%) was found between task-OFF and task-ON periods. These findings verify the efficacy of our protocol and analysis pipelines for the simultaneous assessment of metabolite dynamics and BOLD. As well as establishing a robust basis for further work using these techniques, we also identify a number of clear directions for further refinement in future studies.

Ovarian hormones reduce the negative association between worry and cognitive control: A combined neural and behavioral investigation

BACKGROUND

Increased reactivity to response conflict and errors, processes governed by the dorsal anterior cingulate cortex (dACC), have both been implicated in anxiety. Anxiety is also more common in females than males. Importantly, natural changes in ovarian hormones levels are related to fluctuations in anxiety symptoms in healthy and clinical populations, and ovarian hormones likely modulate prefrontal cortex structure and function. No studies, however, have examined the role of fluctuating ovarian hormones in the association between anxiety and cognitive control across the menstrual cycle.

METHODS

In this multimodal proof-of-concept study, naturally cycling females (N = 30 twins from 14 complete twin pairs and 2 participants whose co-twin was not in the final sample; age 18-29) provided saliva samples to assay for estradiol and progesterone and completed the Penn State Worry Questionnaire for 35 consecutive days. At two time points, during projected pre-ovulatory and post-ovulatory phases, they also completed the Flanker task while undergoing functional magnetic resonance imaging to probe cognitive control-related dACC activity. Multilevel modeling was used to examine within- and between-person effects of hormones and worry on cognitive-control indices.

RESULTS

On days when estradiol and progesterone were low relative to a female's own average (i.e., within-subjects effect), worry was associated with greater flanker interference. In females with higher estradiol and progesterone levels compared to other females (i.e., between-subject effects), worry was associated with less error-related dACC activity, irrespective of the day that dACC activity was assessed.

CONCLUSION

Findings suggest a protective effect of ovarian hormones on the link between worry and cognitive control. Associations between worry and conflict-monitoring were sensitive to daily hormonal fluctuations (within-person states), whereas associations between worry and error-monitoring were sensitive to mean hormone levels (between-person traits), suggesting that ovarian hormones are critical to consider in studies examining associations between anxiety and cognitive control in females.

Replication and extension of the toolbox approach to measuring attention control

There is an increasing consensus among researchers that traditional attention tasks do not validly index the attentional mechanisms that they are often used to assess. We recently tested and validated several existing, modified, and new tasks and found that accuracy-based and adaptive tasks were more reliable and valid measures of attention control than traditional ones, which typically rely on speeded responding and/or contrast comparisons in the form of difference scores (Draheim et al. Journal of Experimental Psychology: General, 150(2), 242-275, 2021). With these improved measures, we found that attention control fully mediated the working memory capacity-fluid intelligence relationship, a novel finding that we argued has significant theoretical implications. The present study was both a follow-up and extension to this "toolbox approach" to measuring attention control. Here, we tested updated versions of several attention control tasks in a new dataset (N = 301) and found, with one exception, that these tasks remain strong indicators of attention control. The present study also replicated two important findings: (1) that attention control accounted for nearly all the variance in the relationship between working memory capacity and fluid intelligence, and (2) that the strong association found between attention control and other cognitive measures is not because the attention control tasks place strong demands on processing speed. These findings show that attention control can be measured as a reliable and valid individual differences construct, and that attention control shares substantial variance with other executive functions.

Spatiotemporal evidence uncovers differential neural activity patterns in cognitive and affective conflict control

Studies have shown that there are overlapping neural bases for cognitive and affective conflict control, but whether the neural activity patterns caused by the two types of conflict are similar remains to be explored. The present study utilizes electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) to temporally and spatially analyze the differences between cognitive and affective conflict control. We employ a semantic conflict task which includes blocks of cognitive and affective judgements primed by conflicting and non-conflicting contexts. The results showed a typical neural conflict effect in the cognitive judgment blocks as reflected by greater amplitudes of P2, N400, and the late positive potential (LPP), as well as greater activation of the left pre-supplementary motor area (pre-SMA) and the right inferior frontal gyrus (IFG) in the conflict condition relative to the non-conflict condition. These patterns did not emerge in the affective judgments, but instead, showed reversed effects of the LPP and in the left SMA. Taken together, these findings suggest that cognitive and affective conflict control result in different neural activity patterns.

Testing locus coeruleus-norepinephrine accounts of working memory, attention control, and fluid intelligence

The current set of studies examined the relationship among working memory capacity, attention control, fluid intelligence, and pupillary correlates of tonic arousal regulation and phasic responsiveness in a combined sample of more than 1,000 participants in two different age ranges (young adults and adolescents). Each study was designed to test predictions made by two recent theories regarding the role of the locus coeruleus-norepinephrine (LC-NE) system in determining individual differences in cognitive ability. The first theory, proposed by Unsworth and Robison (2017a), posits two important individual differences: the moment-to-moment regulation of tonic arousal, and the phasic responsiveness of the system to goal-relevant stimuli. The second theory, proposed by Tsukahara and Engle (2021a), argues that people with higher cognitive abilities have greater functional connectivity between the LC-NE system and cortical networks at rest. These two theories are not mutually exclusive, but they make different predictions. Overall, we found no evidence consistent with a resting-state theory. However, phasic responsiveness was consistently correlated with working memory capacity, attention control, and fluid intelligence, supporting a prediction made by Unsworth and Robison (2017a). Tonic arousal regulation was not correlated with working memory or fluid intelligence and was inconsistently correlated with attention control, which offers only partial support for Unsworth and Robison's (2017a) second prediction.

Transfer of learned cognitive control settings within and between tasks

Cognitive control is modulated based on learned associations between conflict probability and stimulus features such as color. We investigated whether such learning-guided control transfers to novel stimuli and/or a novel task. In Experiments 1 and 2, participants experienced an item-specific proportion congruence (ISPC) manipulation in a Stroop (Experiment 1) or Flanker (Experiment 2) task with mostly congruent (MC) and mostly incongruent (MI) colors in training blocks. During a transfer block, participants performed the same task and encountered novel transfer stimuli paired with MC or MI colors. Evidencing within-task transfer, in both experiments, responses were faster to incongruent transfer stimuli comprising an MI color compared with an MC color. In Experiment 3, we investigated between-task transfer from Stroop to Flanker. After training with an ISPC manipulation in the Stroop task, a Flanker task was completed with the same colors but without an ISPC manipulation (i.e., 50% congruent). Responses were faster to incongruent transfer stimuli paired with the previously-MI colors compared with the previously-MC colors. Additionally, transfer was evident in the first half of the Flanker task but not the second half. The evidence for within-task transfer, in combination with the novel evidence for between-task transfer, suggests learned control settings are flexibly retrieved and executed when predictive cues signaling these control settings are encountered in novel stimuli or a novel task. Theoretical implications are discussed alongside potential neural mechanisms mediating transfer of learning-guided control.

Assessing Inhibitory Control in the Real World Is Virtually Possible: A Virtual Reality Demonstration

Executive functions are the key ingredient for behaviour regulation. Among them, inhibitory control is one of the main exponents of executive functions, and in the last decades, it has received a good amount of attention thanks to the development of chronometric tasks associated with paradigms that allow exploring human behaviour when the inhibitory component is needed. Among the different paradigms typically used, the Simon and flanker tasks are probably the most popular ones. These have been subjected to modifications in order to assess inhibitory control from different perspectives (e.g., in different samples or in combination with different research techniques). However, its use has been relegated to classical presentation modalities within laboratory settings. The accessibility of virtual reality (VR) technology has opened new research avenues to investigate inhibition control with a high ecological validity while retaining tightly controlled lab conditions and good measurement accuracy. We present two cutting-edge modifications of the standard Simon and flanker tasks that have been adapted to real-world settings using VR and human-like avatars as target stimuli. Our findings show that virtual reality is a credible tool for testing inhibitory control with a high degree of transferability and generalizability to the real world.

Neural Underpinnings of Proactive and Preemptive Adjustments of Action Control

This study aimed to trace the neural basis of proactive and preemptive adjustments of executive control and their effects on online processing of response conflict. In two EEG experiments, participants performed the flanker task with predictive cueing of conflict. The following questions were addressed: "Does conflict cueing improve performance?" We observed improved behavioral performance in the predictive condition, suggesting that participants proactively utilized the cues to prepare for the upcoming demands. "How is conflict processing affected by predictive cueing?" Conflict-related modulations of midfrontal N2 and theta power were smaller in the predictive than in the neutral condition. This suggests that proactive control suppressed the impact of incongruent flankers so that the conflict was reduced, and so was the involvement of online control. "Is proactive control implemented through preactivation of online control?" Conflict cueing increased midfrontal theta power also before target onset, suggesting preactivation of the control processes beforehand. "Do proactive and reactive control depend on common or unique processes?" Unlike the online control, the proactive control triggered a burst of theta power in the right hemisphere's dorsal and ventral lateral prefrontal cortices, connected with the midfrontal area via theta phase coherence. This indicates that the two control modes involve partially unique but coordinated neural processes. "Is preemptive control implemented through modulations of visual processing?" Predictive cueing modulated both the pretarget preparatory alpha desynchronization and the target selection-related posterior contralateral negativity (N2pc and sustained posterior contralateral negativity), in line with the hypothesis of preemptive tuning of sensory selection aimed at reducing the impact of conflicting stimuli.

Inconsistent flanker congruency effects across stimulus types and age groups: A cautionary tale

The flanker task is a common measure of selective attention and response competition across populations, age groups, and experiential contexts. Adapting it for different uses often involves changing methodological features that are rarely empirically compared with the previous design. This paper presents an example of how typical methodological changes can differentially elicit congruency effects across age groups. We compared two flanker tasks, using direction stimuli on a laptop versus color stimuli on a tablet, in young children (2-7 years; Experiment 1), older children (6-10 years; Experiment 2a), and adults (19-23 years; Experiment 2b). Young children showed the expected congruency effects in the direction task, and one year later a subset of the sample completed the color task, also showing congruency effects. Longitudinal comparisons showed no difference in the congruency effect across tasks, but nearly half of the sample was excluded due to high error rates. To avoid excluding children with few correct trials, we modified a new measure, signed residual time, to incorporate correctness and reaction time per trial. With the larger sample, this measure showed no difference in congruency effects across tasks. To compare these tasks when completed within the same session, we tested older children and young adults in both tasks and found congruency effects in the direction task but not the color task. These results raise concern that tasks adapted for young children may not perform comparably in other samples, and we caution researchers to anticipate this possibility when modifying cognitive tasks.

Is the alerting-congruency interaction that is seen in experiments with stimulus-response motor associations moderated by a concurrent working-memory load?

The mechanisms underlying attention, distraction, and cognitive control have been widely studied, and results consistently show that reaction times are affected by alerting cues as well as by concurrent distraction. In addition, when distractors have pre-existing directional motor associations, alerting and distractor congruency interact in a manner where distractors have a larger effect when people are alerted to an upcoming target relative to when people are not alerted to the target's presentation. However, does a concurrent working memory load moderate this interaction in multitasking experiments, and if so, does it magnify or suppress this effect? The current study (N = 40) finds that although a memory-load significantly slows reaction times it does not moderate the alerting-congruency interaction. Discussion focuses on theoretical and applied implications of this empirical result.

Assessing the validity and reliability and establishing norm values for a selective attention test in a Turkish sample of 6–14-year-old participants

Selective attention is a cognitive skill that allows an individual to focus on a particular input for further processing while simultaneously suppressing irrelevant or distracting information. In this study, we have developed a new test to assess selective attention-the Cognitive Skills Assessment of Minerva (CSM) Selective Attention Test-and have established selective attention norm values for Turkish individuals aged 6-14 years. This new online selective attention assessment test includes the flanker task. We employed split-half reliability to prove the reliability of the test. Based on the analysis, there was no significant difference between the groups, indicating that the test is reliable. We used criterion-related validity (congruent validity) analysis to evaluate the CSM Selective Attention Test. The correlation between the results of the new test and the Eriksen Flanker Test showed that the new test is valid. Finally, we conducted a comprehensive norm study with 2,297 participants aged 6-14 years from 12 different regions and schools in Turkey. According to the analysis of variance, age but not gender is a distinguishing factor for selective attention. We subsequently established norm values for each age group. The findings also show that the CSM Selective Attention Test provides reliable results across all samples and populations aged 6-14.

Investigating the Link Between Linguistic and Non-Linguistic Cognitive Control in Bilinguals Using Laplacian-Transformed Event Related Potentials

Bilinguals' need to suppress the activation of their other language while speaking has been proposed to result in enhanced cognitive control abilities outside of language. Several studies therefore suggest shared cognitive control processes across linguistic and non-linguistic tasks. Here we investigate this potential overlap using scalp electroencephalographic recordings and the Laplacian transformation, providing an estimation of the current source density and enabling the separation of EEG components in space. Fourteen Spanish-English bilinguals performed a picture-word matching task contrasting incongruent trials using cross-linguistic false cognates (e.g., a picture - foot, overlaid with distractor text: the English word PIE, i.e., the false cognate for the Spanish pie meaning "foot") with congruent trials (matching English picture names and words, i.e., a picture - foot, with overlaid text: the English word FOOT), and an unrelated control condition. In addition, participants performed an arrow-version of the Eriksen flanker task. Worse behavioral performance was observed in incongruent compared to congruent trials in both tasks. In the non-linguistic task, we replicated the previously observed congruency effect on a medial-frontal event-related potential (ERP) peaking around 50 ms before electromyography (EMG) onset. A similar ERP was present in the linguistic task, was sensitive to congruency, and peaked earlier, around 150 ms before EMG onset. In addition, another component was found in the linguistic task at a left lateralized anterior frontal site peaking around 200 ms before EMG onset, but was absent in the non-linguistic task. Our results suggest a partial overlap between linguistic and non-linguistic cognitive control processes and that linguistic conflict resolution may engage additional left anterior frontal control processes.

Performance differences between instructions on paper vs digital glasses for a simple assembly task

OBJECTIVE

Providing instruction for assembly tasks is essential in modern manufacturing industry, as well as in households for customers that buy products to be assembled at home. Recent technological developments might be able to assist in completing an assembly task faster and more accurately. The aim of this study was to evaluate whether performance and usability differs when instructions for an assembly task are presented on digital glasses versus paper.

METHODS

Participants (n = 63) completed one of three versions of an assembly task (between-subject-design) with LEGO® bricks: (1) with paper instruction (P), (2) with text instructions presented stepwise via digital glasses (GT), (3) with stepwise text and auditory instruction (in parallel) on digital glasses (GA). Outcome measures on performance were completion time and errors. Furthermore, usability was measured by the User Experience Questionnaire, the Standardized Usability Questionnaire, the Post-Study Usability Questionnaire, and cognitive processing skills were assessed by the Trail Making Test and different versions of the Eriksen Flanker Task. Analyses were adjusted for the confounding factors age, gender, experience with glasses and LEGO, and problems with instruction.

RESULTS

Findings indicate that task completion was faster with the paper instructions compared to both versions of instruction via digital glasses (GT, GA). We observed no difference in accuracy and usability between the instructions. "Novelty" was rated higher for instructions for both GT and GA, compared to P.

DISCUSSION

Results show that instructions on digital glasses may not always be more effective for assembly than the traditional paper-based instructions. Further studies are necessary to investigate whether effectiveness may depend on task complexity, target group, experience of the user with task and device, and how the information is presented.

Multiplicative priming of the correct response can explain the interaction between Simon and flanker congruency

In the Simon task, participants perform a decision on non-spatial features (e.g., stimulus color) by responding with a left or right key-press to a stimulus presented on the left or right side of the screen. In the flanker task, they classify the central character while ignoring the flanking characters. In each task, there is a conflict between the response-relevant features and the response-irrelevant features (i.e., the location on the screen for the Simon task, and the flankers for the flanker task). Thus, in both tasks, resolving conflict requires to inhibit irrelevant features and to focus on relevant features. When both tasks were combined within the same trial (e.g., when the row of characters was presented on the left or right side of the screen), most previous research has shown an interaction. In the present study, we investigated whether this interaction is affected by a multiplicative priming of the correct response occurring when both Simon and flanker irrelevant features co-activate the correct response (Exp. 1), a spatial overlap between Simon and flanker features (Exp. 2), and the learning of stimulus-response pairings (Exp. 3). The results only show an impact of multiplicative priming.

The arrow of time: Advancing insights into action control from the arrow version of the Eriksen flanker task

Since its introduction by B. A. Eriksen and C. W. Eriksen (Perception & Psychophysics, 16, 143-49, 1974), the flanker task has emerged as one of the most important experimental tasks in the history of cognitive psychology. The impact of a seemingly simple task design involving a target stimulus flanked on each side by a few task-irrelevant stimuli is astounding. It has inspired research across the fields of cognitive neuroscience, psychophysiology, neurology, psychiatry, and sports science. In our tribute to Charles W. ("Erik") Eriksen, we (1) review the seminal papers originating from his lab in the 1970s that launched the paradigmatic task and laid the foundation for studies of action control, (2) describe the inception of the arrow version of the Eriksen flanker task, (3) articulate the conceptual and neural models of action control that emerged from studies of the arrows flanker task, and (4) illustrate the influential role of the arrows flanker task in disclosing developmental trends in action control, fundamental deficits in action control due to neuropsychiatric disorders, and enhanced action control among elite athletes.

Behavioral Measures of Listening Effort in School-Age Children: Examining the Effects of Signal-to-Noise Ratio, Hearing Loss, and Amplification

OBJECTIVES

Increased listening effort in school-age children with hearing loss (CHL) could compromise learning and academic achievement. Identifying a sensitive behavioral measure of listening effort for this group could have both clinical and research value. This study examined the effects of signal-to-noise ratio (SNR), hearing loss, and personal amplification on 2 commonly used behavioral measures of listening effort: dual-task visual response times (visual RTs) and verbal response times (verbal RTs).

DESIGN

A total of 82 children (aged 6-13 years) took part in this study; 37 children with normal hearing (CNH) and 45 CHL. All children performed a dual-task paradigm from which both measures of listening effort (dual-task visual RT and verbal RT) were derived. The primary task was word recognition in multi-talker babble in three individually selected SNR conditions: Easy, Moderate, and Hard. The secondary task was a visual monitoring task. Listening effort during the dual-task was quantified as the change in secondary task RT from baseline (single-task visual RT) to the dual-task condition. Listening effort based on verbal RT was quantified as the time elapsed from the onset of the auditory stimulus to the onset of the verbal response when performing the primary (word recognition) task in isolation. CHL completed the task aided and/or unaided to examine the effect of amplification on listening effort.

RESULTS

Verbal RTs were generally slower in the more challenging SNR conditions. However, there was no effect of SNR on dual-task visual RT. Overall, verbal RTs were significantly slower in CHL versus CNH. No group difference in dual-task visual RTs was found between CNH and CHL. No effect of amplification was found on either dual-task visual RTs or verbal RTs.

CONCLUSIONS

This study compared dual-task visual RT and verbal RT measures of listening effort in the child population. Overall, verbal RTs appear more sensitive than dual-task visual RTs to the negative effects of SNR and hearing loss. The current findings extend the literature on listening effort in the pediatric population by demonstrating that, even for speech that is accurately recognized, school-age CHL show a greater processing speed decrement than their normal-hearing counterparts, a decrement that could have a negative impact on learning and academic achievement in the classroom.

Comparing Stroop-like and Simon Effects on Perceptual Features

Stroop-like and Simon tasks produce two sources of interference in human information processing. Despite being logically similar, it is still debated whether the conflicts ensuing from the two tasks are resolved by the same or different mechanisms. In the present study, we compare two accounts of the Stroop-like effect. According to the Perceptual Account, the Stroop-like effect is due to Stimulus-Stimulus congruence. According to the Decisional Account, the Stroop-like effect results from the same mechanisms that produce the Simon effect, that is, Stimulus-Response compatibility. In two experiments we produced Stroop-like and Simon effects by presenting left/right-located stimuli consisting of a colored square surrounded by a frame of the same color as the square or of a different color. Results showed that discriminating either the color of the square (Experiment 1) or that of the frame (Experiment 2) yielded additive Stroop-like and Simon effects. In addition, the patterns of temporal distributions of the two effects were different. These results support the Perceptual Account of the Stroop-like effect and the notion that the Stroop-like effect and the Simon effect occur at different processing stages and are attributable to different mechanisms.

Interacting sources of interference during sensorimotor integration processes

Every day, a multitude of interfering sensory inputs needs to be integrated and adequately processed using response selection processes. Interference effects are typically investigated using classical paradigms like the Flanker and Simon task. The sources of interference for Flanker and Simon effect are known to be different and according to dual process accounts, two distinct functional pathways are involved in resolving these types of interference. It is an open question how far these sources of interference are related to each other and interact. We investigated this question in a system neurophysiological study utilizing a hybrid paradigm combining both Flanker effect-like and Simon effect-like features. We focus on event-related theta oscillations and use beamforming methods to examine functional neuroanatomical networks. The results show that Simon and Flanker interference interacted in a non-additive fashion by modulating theta band activity, probably reflecting the recruitment of cognitive control processes. Beamforming source reconstruction revealed that theta band activity was related to a broad neuronal network comprising prefrontal and cerebellar regions, including the MFG, SFG, IFG, and SMA. These regions were connected to interference processing and conflict resolution, but differed in the amount of specificity for different sources of interference.

Flanker and Simon effects interact at the response selection stage

The present study aimed at investigating the processing stage underlying stimulus-stimulus (S-S) congruency effects by examining the relation of a particular type of congruency effect (i.e., the flanker effect) with a stimulus-response (S-R) spatial correspondence effect (i.e., the Simon effect). Experiment 1 used a unilateral flanker task in which the flanker also acted as a Simon-like accessory stimulus. Results showed a significant S-S Congruency x S-R Correspondence interaction: An advantage for flanker-response spatially corresponding trials was observed in target-flanker congruent conditions, whereas, in incongruent conditions, there was a noncorresponding trials' advantage. The analysis of the temporal trend of the correspondence effects ruled out a temporal-overlap account for the observed interaction. Moreover, results of Experiment 2, in which the flanker did not belong to the target set, demonstrated that this interaction cannot be attributed to perceptual grouping of the target-flanker pairs and referential coding of the target with respect to the flanker in the congruent and incongruent conditions, respectively. Taken together, these findings are consistent with a response selection account of congruency effects: Both the position and the task-related attribute of the flanker would activate the associated responses. In noncorresponding-congruent trials and corresponding-incongruent trials, this would cause a conflict at the response selection stage.

Temporal and spectral profiles of stimulus-stimulus and stimulus-response conflict processing

The ability to detect and resolve conflict is an essential function of cognitive control. Laboratory studies often use stimulus-response-compatibility (SRC) tasks to examine conflict processing in order to elucidate the mechanism and modular organization of cognitive control. Inspired by two influential theories regarding cognitive control, the conflict monitoring theory (Botvinick, Braver, Barch, Carter, & Cohen, 2001) and dimensional overlap taxonomy (Kornblum, Hasbroucq, & Osman, 1990), we explored the temporal and spectral similarities and differences between processing of stimulus-stimulus (S-S) and stimulus-response (S-R) conflicts with event related potential (ERP) and time-frequency measures. We predicted that processing of S-S conflict starts earlier than that of S-R conflict and that the two types of conflict may involve different frequency bands. Participants were asked to perform two parallel SRC tasks, both combining the Stroop task (involving S-S conflict) and Simon task (involving S-R conflict). ERP results showed pronounced SRC effects (incongruent vs. congruent) on N2 and P3 components for both S-S and S-R conflicts. In both tasks, SRC effects of S-S conflict took place earlier than those of S-R conflict. Time-frequency analysis revealed that both types of SRC effects modulated theta and alpha bands, while S-R conflict effects additionally modulated power in the beta band. These results indicated that although S-S and S-R conflict processing shared considerable ERP and time-frequency properties, they differed in temporal and spectral dynamics. We suggest that the modular organization of cognitive control should take both commonality and distinction of S-S and S-R conflict processing into consideration.

Temporal dynamics of interference in Simon and Eriksen tasks considered within the context of a dual-process model

Behavioral and brain potential measures were employed to compare interference in Eriksen and Simon tasks. Assuming a dual-process model of interference elicited in speeded response tasks, we hypothesized that only lateralized stimuli in the Simon task induce fast S-R priming via direct unconditional processes, while Eriksen interference effects are induced later via indirect conditional processes. Delays to responses for incongruent trials were indeed larger in the Eriksen than in the Simon task. Only lateralized stimuli in the Simon task elicited early S-R priming, maximal at parietal areas. Incongruent flankers in the Eriksen task elicited interference later, visible as a lateralized N2. Eriksen interference also elicited an additional component (N350), which accounted for the larger behavioral interference effects in the Eriksen task. The findings suggest that interference and its resolution involve different processes for Simon and Eriksen tasks.

Dissociation between awareness and spatial coding: evidence from unilateral neglect

Prevalent theories about consciousness propose a causal relation between lack of spatial coding and absence of conscious experience: The failure to code the position of an object is assumed to prevent this object from entering consciousness. This is consistent with influential theories of unilateral neglect following brain damage, according to which spatial coding of neglected stimuli is defective, and this would keep their processing at the nonconscious level. Contrary to this view, we report evidence showing that spatial coding and consciousness can dissociate. A patient with left neglect, who was not aware of contralesional stimuli, was able to process their color and position. However, in contrast to (ipsilesional) consciously perceived stimuli, color and position of neglected stimuli were processed separately. We propose that individual object features, including position, can be processed without attention and consciousness and that conscious perception of an object depends on the binding of its features into an integrated percept.

Exploring trial-by-trial modulations of the Simon effect

The present study investigates sequential modulations of the Simon effect. The Simon effect involves faster responses to spatially corresponding than to noncorresponding stimuli, even when stimulus position is irrelevant. Recently, the Simon effect has been shown to decrease or to disappear after noncorresponding predecessor trials. Possible explanations for these sequential modulations include (a) the gating of position-based response activation (conflict monitoring), (b) repetition or alternation effects, and (c) the interaction between feature integration (binding) processes and stimulus-response (S-R) correspondence. Three experiments tested different predictions of these models by comparing Simon effects after neutral trials with those after corresponding and noncorresponding trials, respectively, and by varying the stimulus-onset asynchrony (SOA) between and within experiments. Experiments 1 and 2 revealed large Simon effects after corresponding trials, intermediate Simon effects after neutral trials, and small (or no) Simon effects after noncorresponding trials. Moreover, some systematic effects of S-R repetitions and S-R alternations were observed. Finally, the sequential modulations were maximal at short SOAs and decreased with increasing SOA, but still occurred at an SOA of 6 seconds. The results seem to exclude repetition or alternation effects as the main cause of sequential modulations of the Simon effect, but both conflict monitoring and binding may contribute to these effects.

The Eriksen flanker effect revisited

Four studies are reported on the potential role of perceptual interference in a standard Eriksen flanker task. In the first study, incongruent flanker letters showed the usual effect on choice reaction time (CRT) to the target letter but had no effect on the visual fixation time (VFT) needed to distinguish target and flankers. In the second experiment, the effect of incongruent flankers was studied in the context of a same-different response in regard to the target letter and a subsequently presented single letter. The effect of incongruent flankers vanished at an interstimulus interval of 200 ms. In Experiment 3, the same-different task was used in the paradigm of the functional visual field with a target-flankers combination as stimulus on the left (SL) and a single letter as stimulus on the right side (SR) of the visual field. Flankers did neither affect VFT nor the same-different CRT suggesting that target selection may proceed during the saccade from SL to SR. In Experiment 4 effects were studied of flanker-to-target and target-to-single-letter similarity. Flanker-to-target similarity did neither affect VFT nor same-different CRT but target-to-single-letter similarity prolonged same-different CRT. Together, the results suggest parallel perceptual processing of target and flankers, followed by competition of responses to the target and to the incongruent flankers. In line with earlier research, processes of response selection and response competition appear not to be tied to VFT but to proceed in parallel with the saccade from SL to SR.

A parallel distributed processing model of stimulus-stimulus and stimulus-response compatibility

A parallel distributed processing (PDP) model is proposed to account for choice reaction time (RT) performance in diverse cognitive and perceptual tasks such as the Stroop task, the Simon task, the Eriksen flanker task, and the stimulus-response compatibility task that are interrelated in terms of stimulus-stimulus and stimulus-response overlap (Kornblum, 1992). In multilayered (input-intermediate-output) networks, neuron-like nodes that represent stimulus and response features are grouped into mutually inhibitory modules that represent stimulus and response dimensions. The stimulus-stimulus overlap is implemented by a convergence of two input modules onto a common intermediate module, and the stimulus-response overlap by direct pathways representing automatic priming of outputs. Mean RTs are simulated in various simple tasks and, furthermore, predictions are generated for complex tasks based on performance in simpler tasks. The match between simulated and experimental results lends strong support for our PDP model of compatibility.

Spatial S-R compatibility with centrally presented stimuli. An event-related asymmetry study on dimensional overlap

Lateral presentation of relevant information facilitates manual responses if the side of relevant information corresponds to the side of the response. Recently, temporally overlapping EEG asymmetries over the central motor cortex and posterior sites were reported as a possible correlate of the sensory-motor integration of spatial information. The present study investigated whether sensory-motor integration of spatial information can occur with symbolic spatial information the same way as with laterally presented stimuli. The task required participants to respond to arrows (target stimuli), which were "flanked" (from above and below) by neutral stimuli or by other arrows (compatible or not). In Experiment 1, this task was compared to the same task with letters as stimuli and to an incompatible task where participants had to respond "against" the arrow direction. The effect of the flankers on response times was largest if subjects had to respond to the arrows in the common way. This was also the only task of Experiment 1 for which marked EEG asymmetries related to the direction of the flankers were observed. In Experiment 2, the onsets of target stimulus and flankers differed in time. Event-related lateralizations of the EEG over sensory and primary motor areas--as a lateralized readiness potential--were always, apparently automatically, evoked by flanking arrows, indicating automatic response activation evoked by symbolic spatial information. In accordance to recent theories of temporally decaying response activation, manual responses were affected only if the target was either shortly preceded by or appeared simultaneously with the flankers. The temporal overlap of EEG asymmetries related to direction encoding, automatic response activation, and to response preparation indicated that a widespread cortical network is activated by a salient directional information that enables subjects to respond quickly if the directional code of the stimulus overlaps with the directional code of the response.

The dimensionality of the flanker compatibility effect: a psychophysiological analysis

The psychophysiological approach was used to evaluate the effects of feature similarity and "intrinsic response mapping" on the flanker compatibility effect. Symbol (e.g., < > < and </<) and letter arrays (e.g., HCH and SCS) were used. Results showed that delays in stimulus evaluation and both peripheral and central response competition contributed to the compatibility effect, with the contribution of these processes depending on feature similarity and the intrinsic response mapping of the stimuli. For letter stimuli, the difference in the size of the compatibility effect for similar and dissimilar arrays could be accounted for in terms of stimulus evaluation. For symbol arrays, differences in size of the compatibility effect could be accounted for by response competition. Thus, symbol and letter arrays do not appear to be processed differently; what is different is the degree to which stimulus and response-related processes are affected by incompatibility.

A computational model of the Simon effect

Even though stimulus location is task irrelevant, reaction times are faster when the location of the stimulus corresponds with the location of the response than when it does not. This phenomenon is called the Simon effect. Most accounts of the Simon effect are based on the assumption that it arises from a conflict between the spatial code of the stimulus and that of the response. In this paper a computational model of this hypothesis is presented. It provides a computationally explicit mechanism of the Simon effect. Consistent with human performance, the model provides reaction times that indicate both an advantage for the ipsilateral, corresponding response (i.e., facilitation) and a disadvantage of the contralateral, noncorresponding response (i.e., inhibition). In addition, the model accounts for the fact that the size for the effect depends on task difficulty.

Selective response activation can begin before stimulus recognition is complete: a psychophysiological and error analysis of continuous flow

In discussions of process models of human information processing, the continuous flow conception (Eriksen and Schultz 1979) plays a prominent role. A central prediction of this conception is that any information in a display associated with a response activates that response as soon as it becomes available in the perceptual system. If it concerns the correct response channel, then response facilitation occurs. If it concerns the incorrect response channel, then response competition occurs. To assess these mechanisms more directly, we used psychophysiological measures as well as reaction time (RT). We used the latency of the P3 component of the event related brain potential (ERP) as an index of stimulus evaluation duration, the onset of lateralized motor activity derived from the ERP as an index of selective central motor activation, and the onset of electromyographic activity as an index of the start of peripheral motor activation. Subjects were required to respond to target letters that were either flanked by letters that signalled the opposite response (incompatible arrays), by the target itself (compatible arrays), by letters not associated with a response (neutral arrays), or by no other letters (targets alone). Our results replicated the basic findings obtained in this paradigm. RTs to targets alone did not differ from RTs to compatible arrays. The latter were faster than RTs to neutral arrays, which were faster than RTs to incompatible arrays. P3 latencies were longer on incompatible than on neutral trials, and longer on compatible than on target alone trials. Incorrect central response activation on incompatible trials and correct central response activation on compatible trials, both began earlier than on target alone trials. Peripheral responding on both trial types, however, began later than on target alone trials. More incompatible but less compatible trials than neutral ones exhibited incorrect peripheral response activation. Peripheral response execution was faster and more accurate on compatible than on target alone trials, while it was slower and less accurate on incompatible than on neutral trials. These results indicate, that the flankers activated their associated response channel while display evaluation was still going on, and that response facilitation and competition occurred. After applying criteria proposed by Miller (1988), it was concluded that the set of stimulus recognition processes and the set of response activation processes cannot be regarded as independent stages of processing.

An additive factors analysis of the effect(s) of location cues associated with auditory stimuli on stages of information processing

The additive factors method (AFM) was used as a tool for assessing the locus (or loci) of the detrimental effect of auditory location cues in the chain of (visual) information processing. In the first experiment the location variable was factorially combined with response specificity, which is assumed to affect the response adjustment stage. A second experiment was performed in which movement amplitude, assumed to affect the response programming stage, was manipulated in addition to the location variable and a different variety of response specificity. Finally, the location variable was combined with relative S-R frequency, which is also assumed to affect the response programming stage, in a third experiment. The results of these experiments showed additive effects of the location variable with motor variables. The remaining two experiments were designed to assess the effects of location cues on response selection. In these experiments the location variable was combined with the number of response alternatives. Response speed decreased with an increase in the number of response alternatives. However, the effects of the location variable and number of response alternatives were additive. According to the additive factor logic, then, the results of experiments 1, 2 and 3 seem to indicate that the locus of interference of the location cues is not in the later response stages of the reaction process. The results of the last two experiments were interpreted to suggest that the effects of location cues and the number of response alternatives affect either different processes within the response selection stage or affect different process stages. It was concluded that the latter alternative explains most of the data currently available and that the stimulus identification stage is the most likely candidate for the locus of the location effect.