Motor sources of dual-task interference: Evidence for effector-based prioritization in dual-task control.

Dual tasking is known to yield performance costs. Corresponding research has often focused on early or central task processing stages, that is, on features related to stimulus processing or response selection. Here, we demonstrate the important role of the final (late) stage of task processing by studying effects of effector system combinations. We used pairwise combinations of tasks requiring oculomotor, manual, vocal, and pedal responses, triggered by visual/auditory stimuli. Across task combinations, we compared dual-task costs among effector systems (e.g., oculomotor, vocal, and pedal) under controlled conditions, that is, when combined with the same "context effector" (e.g., manual) in the other task. The dual-task cost pattern was strongly determined by the particular combination of effector systems in line with the assumption of an ordinal effector-based prioritization pattern (oculomotor > pedal > vocal > manual), and could not be explained by classic "first-come, first-served" accounts of central processing. Stimulus modality and its mapping to effector systems affected reaction times (RTs), but the impact on the general prioritization scheme was negligible, suggesting a more substantial influence of output (compared with input) system characteristics on dual-task capacity scheduling. The results call for a distinct effector system weighting mechanism in models of dual-task control. (PsycINFO Database Record (c) 2019 APA, all rights reserved).