Academic journal article Psychonomic Bulletin & Review

Task-Set Inhibition in Chunked Task Sequences

Academic journal article Psychonomic Bulletin & Review

Task-Set Inhibition in Chunked Task Sequences

Article excerpt

Exploring the hierarchical control relationship between different levels of representation and processing is important for understanding how the mind controls itself. In the present study, the relationship between chunking (a sequence-level process) and task-set inhibition (a task-level process) in the performance of task sequences was investigated to evaluate the hypothesis that within-chunk facilitation reduces the n-2 repetition cost (slower performance for n-2 task repetitions than for n-2 task switches) attributed to task-set inhibition. An experiment is reported in which subjects were induced to chunk sequences such that n-2 repetitions occurred within or between chunks. Direct evidence of chunking was obtained, and n-2 repetition cost was smaller when n-2 repetitions occurred within chunks than between chunks. These findings are consistent with an elaborated hypothesis that attributes the reduction in n-2 repetition cost to priming of task goals rather than direct modulation of task-set inhibition.

Understanding how the mind controls itself is a fundamental aim of cognitive psychology. Recent studies of executive control have been centered around task-switching situations in which people repeat or switch tasks in rapid succession. People are slower and more error prone at switching than repeating tasks, and this switch cost is often thought to reflect the functioning of myriad executive control processes, such as attention shifting, goal retrieval, response-set adjustment, and inhibition of prior task sets (Monsell, 2003). This last process-task-set inhibition-is considered to be a basic executive control process (Mayr & Keele, 2000) that functions at the task level to enable the performance of different task sequences.

An important issue that has received limited attention is how task-level processing-such as task-set inhibition-is affected by sequence-level processing that is associated with instantiating and maintaining a task sequence in memory. Recent research has provided evidence of a hierarchical control relationship between the sequence and task levels, such that what happens at one level is affected by what happens at the other level (Schneider & Logan, 2006). The purpose of the present study was to explore this hierarchical control relationship by investigating how a task-level process (task-set inhibition) is affected by a sequence-level process (chunking) when switching tasks in sequences.

From the Task Level to the Sequence Level

When switching between three tasks (denoted A, B, and C), people are slower at n-1 task repetitions (ABA) than n-1 task switches (CBA). The dominant interpretation of this n-1 repetition cost is task-set inhibition (Mayr & Keele, 2000): When performing an ABA sequence, switching from task A to task B is thought to involve inhibition of the task set for task A; switching from task B back to task A requires time to overcome this inhibition, resulting in a performance cost. When performing a CBA sequence, prior inhibition of the task set for task A has occurred less recently, so there is less inhibition to overcome, resulting in relatively faster performance. Taskset inhibition is a robust phenomenon in task switching (Arbuthnott & Frank, 2000; Hübner, Dreisbach, Haider, & Kluwe, 2003; Mayr & Keele, 2000; Schuch & Koch, 2003) and is considered to be an executive control process that is distinct from negative priming (Mayr & Keele, 2000), occurs for both perceptual (Mayr & Keele, 2000) and semantic (Arbuthnott & Frank, 2000) tasks, and may function to reduce task-set competition (Hiibner et al., 2003), possibly by inhibiting category-response rules associated with irrelevant tasks (Schuch & Koch, 2003).

Task-set inhibition is assumed to act on individual task sets, but the primary evidence for its existence comes from a sequential effect that is based on a contrast between different task sequences (ABA vs. …

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