Two sources of task prioritization: The interplay of effector-based and task\xa0order-based capacity allocation in the PRP paradigm

Mareike A. Hoffmann,Lynn Huestegge,Iring Koch,Aleks Pieczykolan

doi:10.3758/s13414-020-02071-6

Abstract

When processing of two tasks overlaps, performance is known to suffer. In the well-established psychological refractory period (PRP) paradigm, tasks are triggered by two stimuli with a short temporal delay (stimulus onset asynchrony; SOA), thereby allowing control of the degree of task overlap. A decrease of the SOA reliably yields longer RTs of the task associated with the second stimulus (Task 2) while performance in the other task (Task 1) remains largely unaffected. This Task 2-specific SOA effect is usually interpreted in terms of central capacity limitations. Particularly, it has been assumed that response selection in Task 2 is delayed due to the allocation of less capacity until this process has been completed in Task 1. Recently, another important factor determining task prioritization has been proposed—namely, the particular effector systems associated with tasks. Here, we study both sources of task prioritization simultaneously by systematically combining three different effector systems (pairwise combinations of oculomotor, vocal, and manual responses) in the PRP paradigm. Specifically, we asked whether task order-based task prioritization (SOA effect) is modulated as a function of Task 2 effector system. The results indicate a modulation of SOA effects when the same (oculomotor) Task 1 is combined with a vocal versus a manual Task 2. This is incompatible with the assumption that SOA effects are solely determined by Task 1 response selection duration. Instead, they support the view that dual-task processing bottlenecks are resolved by establishing a capacity allocation scheme fed by multiple input factors, including attentional weights associated with particular effector systems.

Highlights

In everyday life, we are often confronted with situations in which we have to perform more than one task at a time
We combined tasks requiring oculomotor, vocal, and manual responses in pairwise combinations initiated with a short temporal delay in order to answer the question of whether task order-based task prioritization can be modulated by Task 2 effector system
2.5% of trials included responses executed in the wrong order, and another 1.4% were excluded because an unwarranted saccade was registered in conditions that did not require saccades

Summary

Introduction

We are often confronted with situations in which we have to perform more than one task at a time. Performance (in at least one of the tasks) suffers in such situations when compared with executing only one task in isolation (see Koch, Poljac, Müller, & Kiesel, 2018; Pashler, 1994, for reviews). Several methodological approaches have been established to address cognitive mechanisms underlying dual-task control. In continuous task paradigms, participants are trained to perform two or more tasks continuously over a longer time span (e.g., Peterson, 1969; Spelke, Hirst, & Neisser, 1976; see Künstler et al, 2018). Other research paradigms aimed at maximizing control over stimulus conditions and response execution by involving clearly defined sets of stimuli and responses with discrete onsets

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