Dissociating Task Selection and Response Selection in Dual-Task Contexts: Evidence from a Novel Trial-by-Trial Analysis of Temporal Overlap between Tasks

Hirsch, Patricia; Koch, Iring; Bock, Otmar · 2026 · OpenAlex-citations

DOI: 10.5334/joc.485

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Summary

This study investigates the cognitive mechanisms underlying multitasking by examining the interaction between task selection and response selection. While task-switching research focuses on costs associated with selecting task sets, dual-task research typically attributes performance deficits to bottlenecks in response selection. The authors sought to determine whether these processes rely on dependent or independent cognitive mechanisms by analyzing whether task-switch costs are modulated by the temporal overlap of task processing. The researchers employed a psychological refractory period (PRP) paradigm with 44 participants. Participants performed two speeded categorization tasks (parity and letter tasks) with varying stimulus onset asynchronies (SOAs) of 50, 450, 1,000, and 2,000 ms. Trials included both task repetitions and task switches. Crucially, the study introduced a novel trial-by-trial analysis using the response-stimulus interval (RSI)—the time between the Task 1 response and Task 2 stimulus onset—as a proxy to identify whether Task 1 and Task 2 processing temporally overlapped in individual trials. This approach allowed the authors to distinguish between trials with and without overlap, overcoming the limitations of SOA-based analyses which assume constant processing times. Standard ANOVA results confirmed a robust PRP effect, with Task 2 reaction times increasing as SOA decreased, and significant switch costs, with slower responses in switch trials compared to repetition trials. However, the interaction between SOA and task sequence was non-significant, suggesting switch costs were independent of the nominal temporal overlap. The novel RSI-based linear mixed-effects models revealed that switch costs did not differ between trials classified as having temporal overlap and those without overlap. Furthermore, RSI predicted Task 2 performance more accurately than SOA, providing stronger evidence for the dissociation of processes. The findings indicate that task selection and response selection rely on independent cognitive processes. The lack of modulation of switch costs by temporal overlap suggests that the mechanisms governing task-set reconfiguration do not interfere with the response-selection bottleneck. Alternatively, the authors propose that while both processes may share central limitations, strategic or temporal factors prevent them from overlapping in time, thereby avoiding interference. This study provides persuasive evidence against the notion that task switching is deferred until response selection is complete, clarifying the distinct roles of task selection and response selection in dual-task contexts.

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Topics

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• dual task multitasking
• task switching
• dual task performance

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• Empirical Findings: behavioral performance data