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Abstract:
The Psychological Refractory Period (PRP) has been
interpreted as revealing a fundamental limitation in the
parallel-processing capabilities of the human brain. However,
contrary to this interpretation, we provide the first demonstration
that the PRP effect can be eliminated even when concurrent
choice-RT tasks involve the same perceptual and response
modalities. In our first experiment, two visual-manual tasks were
performed on each trial, with successive task stimuli separated by
a variable stimulus-onset asynchrony (SOA). Under a canonical PRP
condition, subjects were required to respond to the first stimulus
before responding to the second stimulus. Also, there was a
condition under which subjects always responded to the second
stimulus before responding to the first stimulus, and another
condition under which subjects were permitted to execute their two
responses simultaneously or in either order. After moderate
practice, PRP effects were extremely small or absent, even under
the canonical PRP condition. Results from a second experiment
further clarify the roles of variable-order training, ample
incentive for good performance, and extensive performance feedback
in eliminating the PRP effect. Our research suggests that large PRP
effects found in previous studies of dual-task performance may have
stemmed from executive task-scheduling strategies that, in accord
with designated task priorities, mask otherwise highly parallel
neurocognitive information processing.
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