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Recent research has shown that even non-salient stimuli (colored circles) can gain attentional weight, when they have been loaded with some value through previous reward learning. The present study examined such value-based attentional weighting with intrinsically rewarding food stimuli. Different snacks were assumed to have different values for people due to individual food preferences. Participants indicated their preferences toward various snacks and then performed a flanker task with these snacks: they had to categorize a target snack as either sweet or salty; irrelevant flanker snacks were either compatible or incompatible with the target category. Results of a linear mixed-effects model show that the effect of flanker compatibility on participants' performance (response times) increased with the participants' preference toward the flanking snacks. This shows, for the first time, that attentional weightings in a flanker task with naturalistic stimuli (snacks) are modulated by participants' preferences toward the flankers.

It is well known that the Simon effect usually decreases with an increasing response time. According to a prominent account this is due to a gradually increasing suppression of irrelevant location-induced activation. What is open, however, and what was investigated in the present study, is to what extent this selective suppression can be adjusted strategically. We hypothesized that strategic suppression should depend on the availability of information about the inhibitory demands. Therefore, in two experiments the demand was modulated by varying the delay between a spatial cue and the target. In the first experiment, where target delay was randomized, there was a negative Simon effect for the longer delays. In a second experiment, where delay was blocked, the Simon effect remained positive. However, the overall Simon effect was larger than in Experiment 1. Together, our results show that the strength of selective suppression can be adjusted strategically, but that this does not necessarily lead to a smaller Simon effect., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Deadlines (DLs) and response signals (RSs) are two well-established techniques for investigating speed-accuracy trade-offs (SATs). Methodological differences imply, however, that corresponding data do not necessarily reflect equivalent processes. Specifically, the DL procedure grants knowledge about trial-specific time demands and requires responses before a prespecified period has elapsed. In contrast, RS intervals often vary unpredictably between trials, and responses must be given after an explicit signal. Here, we investigated the effects of these differences in a flanker task. While all conditions yielded robust SAT functions, a right-shift of the curves pointed to reduced performance in RS conditions (Experiment 1, blocked; Experiments 2 and 3, randomized), as compared with DL conditions (Experiments 1-3, blocked), indicating that the detection of the RS imposes additional task demands. Moreover, the flanker effect vanished at long intervals in RS settings, suggesting that stimulus-related effects are absorbed in a slack when decisions are completed prior to the signal. In turn, effects of a flat (Experiment 2) versus a performance-contingent payment (Experiment 3) indicated that susceptibility to response strategies is higher in the DL than in the RS method. Finally, the RS procedure led to a broad range of slow responses and high accuracies, whereas DL conditions resulted in smaller variations in the upper data range (Experiments 1 and 2); with performance-contingent payment (Experiment 3), though, data ranges became similar. Together, the results uncover characteristic procedure-related effects and should help in selection of the appropriate technique.

A common finding is that there are response-repetition (RR) costs under task switching. Moreover, when the stimulus on the previous trial was congruent then RR costs are usually larger than when it was incongruent. This effect of the previous trial has been explained by assuming that a response category is generally inhibited after the execution of its corresponding response on the previous trial and that the amount of inhibition depends on the activation of the response category. However, up to now it was open which property of the response-category activation on the previous trial is crucial: the absolute activation of the correct response category or the activation difference between the alternative response categories. To differentiate between these two possibilities we compared RR costs after congruent, neutral, and incongruent trials. In two experiments we found similar RR costs after congruent and neutral trials, whereas the RR costs were smaller after incongruent trials. These results support the hypothesis that the amount of response inhibition is determined by the activation differences between the alternative response categories on the previous trial., (Copyright © 2011 Elsevier B.V. All rights reserved.)

It has been suggested that performance in the Stroop task is influenced by response conflict as well as task conflict. The present study investigated the idea that both conflict types can be isolated by applying ex-Gaussian distribution analysis which decomposes response time into a Gaussian and an exponential component. Two experiments were conducted in which manual versions of a standard Stroop task (Experiment 1) and a separated Stroop task (Experiment 2) were performed under task-switching conditions. Effects of response congruency and stimulus bivalency were used to measure response conflict and task conflict, respectively. Ex-Gaussian analysis revealed that response conflict was mainly observed in the Gaussian component, whereas task conflict was stronger in the exponential component. Moreover, task conflict in the exponential component was selectively enhanced under task-switching conditions. The results suggest that ex-Gaussian analysis can be used as a tool to isolate different conflict types in the Stroop task., (PsycINFO Database Record (c) 2009 APA, all rights reserved.)

The goal of the present study was to investigate the costs and benefits of different degrees of strategic parallel processing between two tasks. In a series of experiments with the dual-task flanker paradigm, participants were either instructed to process the tasks serially or in parallel, or--in a control condition--they received no specific instruction. Results showed that the participants were able to adjust the degree of parallel processing as instructed in a flexible manner. Parallel processing of the two tasks repeatedly led to large costs in performance and to high crosstalk effects compared to more serial processing. In spite of the costs, a moderate degree of parallel processing was preferred in the condition with no specific instruction. This pattern of results was observed if the same task set was used for the two tasks, but also if different ones were applied. Furthermore, a modified version of the central capacity sharing (CCS) model (Tombu and Jolicoeur in J Exp Psychol Hum Percept Perform 29:3-18, 2003) was proposed that accounts also for crosstalk effects in dual tasks. The modified CCS model was then evaluated by fitting it successfully to the present data.

When rapidly switching between two tasks, bivalent stimuli can accidentally trigger the previously executed and therefore still activated response. Recently, it has been suggested that behavioral response-repetition effects reflect response inhibition that reduces the risk of such erroneous response repetitions. The present study investigated neural correlates of this inhibition process using lateralized readiness potentials (LRP). In three experiments, we demonstrate a response-switch bias emerging during the preparatory interval which is independent of task sequence (Experiment 1), which is linked to task preparation (Experiment 2), and which is present only under task-switching conditions (Experiment 3). These results suggest that the bias reflects a control process that adaptively regulates response preparedness.

Under task switch conditions, response repetitions usually produce benefits if the task also repeats, but costs if the task switches. So far, it is largely undecided how to account for these effects. In the present study, we provide additional evidence in favor of the account that each response is inhibited in order to prevent its accidental re-execution. To test this hypothesis, the risk of an accidental re-execution of a given response was manipulated by modulating the activation of the response in the previous task. In Experiment 1, this was done by means of congruent and incongruent stimuli. As expected, on task switch trials, the repetition costs were larger if a congruent rather than an incongruent stimulus occurred in the previous task. In Experiment 2, the same effect occurred for stimulus-response compatible versus incompatible stimuli in the previous task. In Experiment 3, both manipulations were applied together, which produced almost additive effects. Altogether, the results support the inhibition account for the response repetition effects under task switch conditions.

The present study investigated the mechanisms underlying error detection in the error signaling response. The authors tested between a response monitoring account and a conflict monitoring account. By implementing each account within the neural network model of N. Yeung, M. M. Botvinick, and J. D. Cohen (2004), they demonstrated that both accounts make different predictions as to how error signaling performance is influenced by varying the participants' response criterion. These predictions were tested in an experiment using the Eriksen-flanker task. The qualitative pattern as well as a model fit favored the response monitoring account, which states that error detection is mediated by detecting internal error corrections.

One of the proposed mechanisms for sequential control in task-shift conditions is backward inhibition (BI), which is usually measured in terms of lag-2 task repetition costs in A-B-A task sequences relative to C-B-A task sequences. By considering the so far existing experiments it seems that these lag-2 repetition costsoccur only with temporally overlapping cues and targets. In the present study this issue was further examined in two experiments, in which temporal cue-target overlap was varied blockwise (Experiment 1) and from trial-to-trial (Experiment 2). Experiment 1 shows that lag-2 repetition effects can only be observed with temporally overlapping cues and targets, indicating that there was no BI with temporally separated cues and targets. However, the results of Experiment 2 suggest that both irrelevant task sets are inhibited in this case, and that with temporally overlapping cues and targets only the previously relevant task set is inhibited.

Although it is often assumed that the left and right cerebral hemispheres are specialized for local and global processing, respectively, recent studies show that this difference mainly occurs if the responses to the two levels of a stimulus are conflicting. In the present study we examined whether the favorable effect of response conflicts is caused by the increased task difficulty in this situation. To this end, the response selection for nonconflicting stimuli was complicated by frequently changing the stimulus-response mappings. As a result, the reactions to nonconflicting stimuli were as slow as those to conflicting ones. Nevertheless, hemispheric differences were again restricted to the latter situation. This shows that increased task difficulty can not explain the modulating effect of response conflicts. The results support the alternative hypothesis that different representations are needed for the response selection for nonconflicting and conflicting stimuli, and that the hemispheres differ only with respect to the latter.

The hypothesis is introduced that 1 source of shift costs is the strengthening of task-related associations occurring whenever an overt response is produced. The authors tested this account by examining shift effects following errors and error compensation processes. The authors predicted that following a specific type of error, called task confusion, shift benefits instead of shift costs should result. A series of 3 experiments confirmed this prediction showing that task confusions produce shift benefits in subsequent trials (Experiment 1), even when the error is detected (Experiment 2). Moreover, only posterror processes that imply an error correction response produce shift costs (Experiment 3). These results additionally suggest that error detection cannot prevent errors from affecting subsequent performance., (Copyright 2006 APA)

We investigated the hypothesis that mixing costs intask shifting reflect th e sequential selection of task components (e.g., stimulus categories) during task execution. This proposition was supported by Hübner, Futterer, and Steinhauser (2001), who showed that the amount of mixing costsdepends on the number of mixed task components (e.g., stimulus level and judgment). However, their results could also be explained by a task set selection account, because task components and task sets were confounded. In Experiments 1 and 2, we compared conditions in which either the number of task sets varied and the number of mixed task components was constant or vice versa. Only the number of mixed task components was predictive for the mixing costs. In Experiment 3, we replicated the additivity of mixing costs from level a ndjudgment mixing. Our results suggest thatthe mixingcosts reflect a selection strategy in which interference is reduced in a stepwise manner.

It is widely accepted that the left and right hemispheres differ with respect to the processing of global and local aspects of visual stimuli. Recently, behavioural experiments have shown that this processing asymmetry strongly depends on the response competition between the global and local levels of a stimulus. Here we report electrophysiological data that underline this observation. Hemispheric differences for global/local processing were mainly observed for response-incompatible stimuli and were most prominent between 320 and 400 ms after stimulus onset. These results underpin the idea that hemispheric differences are more likely to show up when a more elaborated stimulus representation is needed for triggering the response, that is, when a response conflict has to be resolved.

Guided Search 2 (GS2) is currently one of the most detailed models of visual search and has been used to predict search times for different stimulus conditions by means of detailed computer simulations. The present article goes a step further and presents formulas that allow for the calculation of the search times and their variances. Moreover, these formulas can be applied to fit GS2 to data. An example is provided in which GS2 is fitted to search functions representing search asymmetries.

In a series of four experiments, we investigated the conditions under which target-absent responses are faster than target-present responses in visual search. Previous experiments have shown that such an absent-advantage occurs mainly for homogeneous distractors arranged in a regular pattern. From these results, it has been concluded that the absent-advantage is due to perceptual processes, such as grouping by similarity. Our data show that such processes are not sufficient. Rather, the absent-advantage is the result of interactions between perceptual and decisional processes. Certain perceptual conditions, such as randomizing stimulus patterns, lead to specific criteria settings that produce an absent-advantage. That such an account can explain our main results is demonstrated by modeling our data with a modified version of the Guided Search 2 model.