How strategic is the central bottleneck: can it be overcome by trying harder?
ABSTRACT Recent dual-task studies suggest that a bottleneck prevents central mental operations from working on more than one task at a time, especially at relatively low practice levels. It remains highly controversial, however, whether this bottleneck is structural (inherent to human cognitive architecture) or merely a strategic choice. If the strategic hypothesis is testable, it ought to predict that, under sufficiently strong incentives, people could choose to bypass the bottleneck and perform both tasks in parallel. Because the incentives for parallel processing in previous studies have been modest, the authors introduced a novel dual-task paradigm with much greater incentives, induced by strict time deadlines for each task. With this paradigm, bottleneck delays would cause participants to frequently miss the time deadline or make errors, triggering immediate negative consequences (failure feedback). Nevertheless, participants had little success performing central operations in parallel; severe dual-task performance costs were observed, even with relatively easy tasks. These results greatly strengthen the case that the central bottleneck reflects a structural limitation that, at least at modest practice levels, cannot be avoided merely by trying harder.
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ABSTRACT: Although it is generally recognized that the concurrent performance of two tasks incurs costs, the sources of these dual-task costs remain controversial. The serial bottleneck model suggests that serial postponement of task performance in dual-task conditions results from a central stage of response selection that can only process one task at a time. Cognitive-control models, by contrast, propose that multiple response selections can proceed in parallel, but that serial processing of task performance is predominantly adopted because its processing efficiency is higher than that of parallel processing. In the present study, we empirically tested this proposition by examining whether parallel processing would occur when it was more efficient and financially rewarded. The results indicated that even when parallel processing was more efficient and was incentivized by financial reward, participants still failed to process tasks in parallel. We conclude that central information processing is limited by a serial bottleneck.Attention Perception & Psychophysics 07/2013; · 1.97 Impact Factor
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ABSTRACT: The present study was designed to investigate the mechanism associated with dual-task interference in a psychological refractory period (PRP) paradigm. We used a simple reaction time paradigm consisting of a vocal response (R1) and key-lift task (R2) with a stimulus onset asynchrony (SOA) between 100ms and 1500ms. On selected trials we implemented a startling acoustic stimulus concurrent with the second stimulus to determine if we could involuntarily trigger the second response. Our results indicated that the PRP delay in the second response was present for both control and startle trials at short SOAs, suggesting the second response was not prepared in advance. These results support a response preparation bottleneck and can be explained via a neural activation model of preparation. In addition, we found that the reflexive startle activation was reduced in the dual-task condition for all SOAs, a result we attribute to prepulse inhibition associated with dual-task processing.Acta psychologica 09/2013; 144(3):481-487. · 2.19 Impact Factor
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ABSTRACT: Insight into the neural architecture of multitasking is crucial when investigating the pathophysiology of multitasking deficits in clinical populations. Presently, little is known about how the brain combines dual-tasking with a concurrent short-term memory task, despite the relevance of this mental operation in daily life and the frequency of complaints related to this process, in disease. In this study we aimed to examine how the brain responds when a memory task is added to dual-tasking. Thirty-three right-handed healthy volunteers (20 females, mean age 39.9±5.8) were examined with functional brain imaging (fMRI). The paradigm consisted of two cross-modal single tasks (a visual and auditory temporal same-different task with short delay), a dual-task combining both single tasks simultaneously and a multi-task condition, combining the dual-task with an additional short-term memory task (temporal same-different visual task with long delay). Dual-tasking compared to both individual visual and auditory single tasks activated a predominantly right-sided fronto-parietal network and the cerebellum. When adding the additional short-term memory task, a larger and more bilateral frontoparietal network was recruited. We found enhanced activity during multitasking in components of the network that were already involved in dual-tasking, suggesting increased working memory demands, as well as recruitment of multitask-specific components including areas that are likely to be involved in online holding of visual stimuli in short-term memory such as occipito-temporal cortex. These results confirm concurrent neural processing of a visual short-term memory task during dual- tasking and provide evidence for an effective fMRI multitasking paradigm.Neuropsychologia 08/2013; · 3.48 Impact Factor