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Abstract:
When a subject alternates between two different tasks, the
reaction time for each task is greater then the reaction time for
the particular tasks when executed independently in repetitive,
non-alternating paradigms. The decline in performance for the
alternating paradigm is referred to as the task-switching cost
(TSC). Task-switching cost has been explained in terms of two
distinct processes: a) voluntary reconfiguration to process and
execute the new task and b) involuntary "task-set inertia" from the
preceding task. To investigate the relationship between TSC and
task difficulty, 4x4 matrix task was used in which a subject
identified a target letter or position from a set of two stimuli
(easy task) or four stimuli (difficult task). Ten subjects
performed all matrix tasks in pure single-task blocks and in mixed,
alternating-task blocks. Results confirmed task difficulty;
subjects averaged ~ 122 msec greater reaction time and 11 % lower
accuracy for the difficult task when compared to the easy task. We
found, surprisingly, that as task difficulty increased, the TSC
remained constant. For both "easy" and "difficult" task sets, the
elevation of reaction time due to task-switching was ~ 120ms.
Similar TSCs across two levels of task difficulty indicates that
task-switching reconfiguration and/or task-set inertia are
independent of task difficulty. This finding has implications for
the neural basis of task-switching.
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