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Abstract:
Classical theories of human multiple-task performance
hypothesize the existence of an immutable structural processing
bottleneck in a central decision stage of task performance
(Welford, 1952; Pashler, 1994.) According to this hypothesis, when
a response for one task is being selected, decisions about
responses for other simultaneous tasks cannot be made. Several
recent studies have produced evidence consistent with the central
bottleneck hypothesis, based on the performance of callosotomy
patients in dual-task experiments (Ivry et al., 1996; Pashler et
al. 1994.) However, that an immutable structural central processing
bottleneck exists in the human brain is neurologically implausible.
Our current results suggest that there is no such bottleneck. We
had neurologically intact participants perform auditory-vocal and
visual-manual choice-RT tasks singly or simultaneously.
Participants' performance of each task was virtually identical on
dual-task and single-task trials, suggesting that each task was
processed independently of, and in parallel with, the other. Our
results are consistent with curent theories of cognitive
functioning that emphasize the modularity and parallel processing
capacities of the human brain. Previous results suggesting the
existence of a central decision or response-selection bottleneck
may have been an artifact of the dual-task procedure used in those
studies. (Supported by the Office of Naval Research).
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