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Abstract:
The purpose of this experiment was to clarify the
interpretation of reaction time (RT) costs associated with
switching tasks. In our dimensional shift (DS) hypothesis, we
proposed that attentional weighting mechanisms affected
task-switching performance whenever the stimuli demanded switching
selective attention between stimulus dimensions. Results showed
that RT was slowed by (a) shifting selective attention away from
the dimension just attended to on the previous response, (b) the
avoidance of fully committing attention to the dimension to be
ignored on a future response, (c) responding to the first member of
the stimulus pair, and (d) interactions between these three
effects. Comparison of an elderly sample (N = 34) to a young sample
(N = 33) indicated that effects (a) and (b) were significantly
larger for the elderly. Conversely, comparison of a sample with
Parkinson's disease (PD; N = 34) to the age-matched elderly sample
(N = 34), showed no differences for effects (a) and (b). Effect
(c), however, was equivalent for all three groups. A separate
analysis of the traditional Stroop effect within the context of
task switching revealed group differences such that PD > elderly
> young. The implication of these findings in relation to a
dissociation of the Supervisory Attentional System (SAS) from
Contention Scheduling (CS) is discussed.
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