Now showing 1 - 10 of 11
  • Publication
    Open Access
    No evidence for the reduction of task competition and attentional adjustment during task-switching practice
    (Elsevier, 2020-03)
    Strobach, Tilo
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    Wendt, Mike
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    ; ;
    Performance in task switching experiments is worse when the current stimulus is associated with different responses in the two tasks (i.e., incongruent condition) than when it is associated with the same response (i.e., congruent condition). This congruency effect reflects some sort of application of the irrelevant task's stimulus-response translation rules. Manipulating the recency and the proportion of congruent and incongruent trials results in a modulation of the congruency effect (i.e., Congruency Sequence Effect, CSE, and Proportion Congruency Effect, PCE, respectively), suggesting attentional adjustment of processing weights. Here, we investigated the impact of task switching practice on the congruency effect and the modulation thereof by (a) re-analyzing the data of a task switching experiment involving six consecutive sessions and (b) conducting a novel four-session experiment in which the proportions of congruent and incongruent trials were manipulated. Although practice appeared to reduce the reaction times overall and the task switch costs (i.e., slower reaction times after task switches than after task repetitions) to an asymptotic level, the congruency effect as well as its modulations remained remarkably constant. These findings thus do not provide evidence that conflict effects between tasks and attentional adjustment are affected by task switching practice.
  • Publication
    Metadata only
    The time course of distractor-based response activation with predictable and unpredictable target onset
    (Springer, 2019)
    Jost, Kerstin
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    Wendt, Mike
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    ; ;
    Electrophysiological recording in a temporal flanker task (i.e., distractors preceding the targets) has demonstrated that distractor processing is adjusted to the overall utility of the distractors. Under high utility, that is, distractors are predictive of the target/response, distractors immediately activate the corresponding response (as indicated by the lateralized readiness potential, LRP). This activation has been shown to be markedly postponed when the target predictably occurs delayed. To investigate the occurrence and time course of distractor-related response activation under conditions of unpredictable target onset, we randomly varied the stimulus-onset asynchrony (SOA) between distractors and targets and recorded the distractor-evoked LRP. When the distractor utility was high, an LRP occurred shortly after distractor presentation. In case of a long SOA the time course of this LRP was characterized by a drop back to baseline and a subsequent re-activation that reached a substantial level before target onset. These results suggest that distractor processing is characterized by sophisticated adjustments to experienced utility and temporal constraints of the task as well as by further control processes that regulate premature response activation. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
  • Publication
    Metadata only
    Selective impairment of attentional set shifting in adults with ADHD
    (Springer Nature, 2018) ;
    Wendt, Mike
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    Gawrilow, Caterina
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    BACKGROUND: Task switch protocols are frequently used in the assessment of cognitive control, both in clinical and non-clinical populations. These protocols frequently confound task switch and attentional set shift. The current study investigated the ability of adult ADHD patients to shift attentional set in the context of switching tasks. METHOD: We tested 38 adults with ADHD and 39 control adults with an extensive diagnostic battery and a task switch protocol without proactive interference. The experiment combined orthogonally task-switch vs. repetition, and attentional set shift vs. no shift. Each experimental stimulus had global and local features (Hierarchical/"Navon" stimuli), associated with corresponding attentional sets. RESULTS: ADHD patients were slower than controls in task switch trials with a simultaneous shift of attention between global/local attentional sets. This also correlated significantly with diagnostic scales for ADHD symptoms. The patients had more variable reaction times, but when the attentional set was kept constant neither were they significantly slower nor showed higher task switch costs. CONCLUSION: ADHD is associated with a deficit in flexible deployment of attention to varying sources of stimulus information.
  • Publication
    Metadata only
    Shifting the set of stimulus selection when switching between tasks
    (Springer Nature, 2018)
    Wendt, Mike
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    ;
    Switching between tasks associated with different requirements of stimulus selection may suffer interference from persisting attentional settings or processes of reconfiguration, possibly constituting a source of task switch costs (i.e., impaired performance in task switch trials compared to task repetition trials). To explore the processes involved in task switching with and without a switch in stimulus selection requirements, we administered a task-switching paradigm that involved task-unique sets of hierarchical (Navon) stimuli, preventing stimulus-related proactive interference (i.e., impaired responding to a stimulus that was previously processed in the context of a different task), and varied, between groups of participants, whether the target stimulus level (i.e., global vs. local) was held constant or varied between the tasks. Mixing target levels impaired performance overall and increased the task switch costs. Moreover, (within-task) global–local congruency effects were larger when target levels were mixed, particularly in task switch trials, suggesting relatively stronger stimulus processing according to the attentional set of the other task. In a second phase of the experimental session, the target level was changed persistently for either one or for both tasks, presumably evoking stimulus-related proactive interference. This change yielded large task switch costs and global–local congruency effects when it resulted in mixed target levels, but not when it resulted in a constant target level. These results are consistent with the notion that stimulus-related proactive interference is reduced by constant withdrawal of attention from the perceptual dimension of the interference-eliciting stimuli. © 2017, Springer-Verlag GmbH Germany.
  • Publication
    Metadata only
    Target–distractor congruency: sequential effects in a temporal flanker task
    The Congruency Sequence Effect (CSE) denotes the common finding that distractor–target Congruency Effects are reduced after incongruent compared to after congruent trials. Although the CSE is widely attributed to attentional adjustment (i.e., increasing or decreasing the bias in attentional weights regarding processing the target or distractor), unequivocal evidence for this assumption is missing. To investigate the CSE and attentional adjustment we used a temporal flanker task and intermixed a “temporal search task”, in which a target stimulus occurred randomly at one of two temporal positions, corresponding to the temporal positions of the target and the distractor occurrence in the temporal flanker task. We observed a CSE that could not be explained in terms of feature sequences, distractor-related contingencies, or a strategy of reversed distractor–response priming after incongruent trials. Furthermore, following a temporal search task trial, the Congruency Effect was larger when the search target occurred on the first than on the second temporal position, demonstrating that a reduced attentional bias towards the second temporal position increased interference from a distractor presented on the first temporal position. This supports a crucial assumption of the attentional adjustment account of the CSE. Performance in the temporal search task, however, provided no evidence for attentional adjustment. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
  • Publication
    Metadata only
    Adoption of task-specific sets of visual attention
    Evidence from behavioral and physiological studies suggests attentional weighting of stimulus information from different sources, according to task demands. We investigated the adoption of task-specific attentional sets by administering a flanker task, which required responding to a centrally presented letter while ignoring two adjacent letters, and a same-different judgment task, which required a homogenous/heterogeneous classification concerning the complete three-letter string. To assess the distribution of attentional weights across the letter locations we intermixed trials of a visual search task, in which a target stimulus occurred randomly in any of these locations. Search task reaction times displayed a stronger center-to periphery gradient, indicating focusing of visual attention on the central location, when the search task was intermixed into blocks of trials of the flanker task than into blocks of trials of the same-different task (Experiment 1) and when a cue indicated the likely occurrence of the flanker task as compared to the likely occurrence the same-different task (Experiment 2). These findings demonstrate flexible adoption of task-specific sets of visual attention that can be implemented during preparation. In addition, responses in the intermixed search task trials were faster and (marginally significantly) more error-prone after preparation for a (letter) task repetition than for a task switch, suggesting that response caution is reduced during preparation for a task repetition.
  • Publication
    Metadata only
    Strategic control over extent and timing of distractor-based response activation
    (2017)
    Jost, Kerstin
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    Wendt, Mike
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    ; ;
    In choice reaction time (RT) tasks, performance is often influenced by the presence of nominally irrelevant stimuli, referred to as distractors. Recent research provided evidence that distractor processing can be adjusted to the utility of the distractors: Distractors predictive of the upcoming target/response were more attended to and also elicited stronger motor responses. In an event-related potential (ERP) study, we investigated whether not only the extent of distractor processing (as suggested by these previous results), but also the timing of distractor-based response activation is subject to strategic control. In a temporal flanker task, in which a distractor stimulus preceded the target, we manipulated distractor utility (i.e., by varying the proportion of congruent distractor-target combinations, 75% vs. 25%) as well as the stimulus onset asynchrony (SOA) between distractors and targets (350 ms vs. 1,000 ms) in different blocks of trials. The distractor-locked lateralized readiness potential (LRP) was overall larger in blocks with a high proportion of congruent trials indicating stronger distractor-based response activation when distractor utility was high. Of importance, the LRPs occurred overall later when the SOA was long. This suggests that distractor-based response activation can be postponed and thus adjusted to the temporal factors of the context. Modulations of early visual potentials (P1 and N1) indicate that this postponement of motor activation is related to both sensory-perceptual downgrading of distractor stimuli and reduced activation of task-relevant stimulus-response transformation processes at the time of distractor perception.