Executive Control of Cognitive Processes in Task Switching

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167

Four experiments explored the task span procedure: Subjects received lists of 1-10 task names to remember and then lists of 1-10 stimuli on which to perform the tasks. Task span is the number of tasks performed in order perfectly. Experiment 1 compared the task span with the traditional memory span in 6 practiced subjects and found little difference. Experiment 2 compared the task span and the memory span in 64 unpracticed subjects and also found little difference. Experiment 3 compared practice with consistent and varied lists to address retrieval from long-term memory. Experiment 4 manipulated the number of task switches and found that it had little effect on task spans. The results suggest there is no trade-off between storage and task switching, which supports some theories of executive control and challenges others.Executive control is the instrument of volition. It is the process by which the mind programs itself and exercises control over the execution of its programs. Executive control is an important topic in many areas of psychology, including cognitive science, cognitive neuroscience, life span development, psychopathology, and individual differences. Executive control appears in various guises, so it is studied in various ways. Two of the most popular domains in which it is studied are working memory and task switching. This article concerns the relation between working memory and task switching and what it reveals about the nature of executive control. It introduces a new experimental paradigm called the task span procedure that was designed to reveal the interaction between working memory and task switching: Subjects are given a list of tasks to perform and then a series of stimuli to perform them on. The task span procedure requires working memory to store the list of task names and keep track of progress through the list. It requires task switching because successive tasks on the list are generally different. It also requires subordinate processes, controlled by the executive, to perform the tasks on the list. The task span procedure addresses several issues that distinguish theories of working memory, including the nature of capacity limitations, the nature of information loss, and the role of long-term memory in working-memory spans. The task span procedure also addresses issues in the task-switching literature, including what is involved in changing from one task to another. The Task Span ProcedureIn principle, the task span procedure can involve any number of tasks of any kind. In everyday life, it could involve a series of chores you hope to accomplish on a weekend or a series of meetings in your office at work. In this article, the task span procedure involves three tasks that can be performed on numbers that are presented as digits (e.g., 3) or words (e.g., nine). The three tasks are magnitude judgments (i.e., is the number greater than or less than 5?), parity judgments (i.e., is the number odd or even?), and form judgments (i.e., is the number a digit or a word?). The task names specify ...

Section: Discussionmentioning

confidence: 91%

Working Memory, Task Switching, and Executive Control in the Task Span Procedure.

Logan

2004

105

167

“…Attentional resources directly constrain retrieval times (Anderson, 1993), whereas the executive processes involved in task switching are time constrained (Rubinstein, Meyer, & Evans, 2001). Of course, the decay phenomenon is a direct function of time.…”

Section: Nature Of Working Memory Limitations and The Working Memory mentioning

confidence: 99%

Time Constraints and Resource Sharing in Adults' Working Memory Spans.

Barrouillet¹,

Bernardin²,

Camos³

2004

828

105

1,159

This article presents a new model that accounts for working memory spans in adults, the time-based resource-sharing model. The model assumes that both components (i.e., processing and maintenance) of the main working memory tasks require attention and that memory traces decay as soon as attention is switched away. Because memory retrievals are constrained by a central bottleneck and thus totally capture attention, it was predicted that the maintenance of the items to be recalled depends on both the number of memory retrievals required by the intervening treatment and the time allowed to perform them. This number of retrievals:time ratio determines the cognitive load of the processing component. The authors show in 7 experiments that working memory spans vary as a function of this cognitive load.

“…Rogers and Monsell (1995), having attributed the reduction in switch cost with preparation to a TSR process, suggested the residual cost might be due to a second stage of TSR dependent upon presentation of the stimulus. Rubinstein, Meyer and Evans (2001) speculated that the task-goal could be retrieved prior to the stimulus, but retrieval of the S-R rules can only happen after stimulus identification. Any such post-stimulus component of TSR would need to be largely completed before response selection begins, so that the S-R rules appropriate to the current task have become more active than the alternative set(s).…”

Section: Theories Of the (Residual) Task-switch Cost And Its Locusmentioning

confidence: 99%

“…Rubinstein, Meyer and Evans (2001) speculated that the task-goal could be retrieved prior to the stimulus, but retrieval of the S-R rules can only happen after stimulus identification. Any such post-stimulus component of TSR would need to be largely completed before response selection begins, so that the S-R rules appropriate to the current task have become more active than the alternative set(s).…”

mentioning

confidence: 99%

A change of task prolongs early processes: Evidence from ERPs in lexical tasks.

Elchlepp¹,

Lavric²,

Monsell³

2015

Switching tasks costs time. Allowing time to prepare reduces the cost, but usually leaves an irreducible "residual cost". Most accounts of this residual cost locate it within the responseselection stage of processing. To determine which processing stage is affected, we measured event-related potentials (ERPs) as participants performed a reading or a perceptual judgment task and examined the effect of a task-switch on early markers of lexical processing. A task cue preceding a string of blue and red letters instructed the participant either to read the letter string (for a semantic classification in Experiment 1, a lexical decision in Experiment 2), or to judge the symmetry of its color pattern. In Experiment 1, having to switch to the reading task delayed the evolution of the effect of word frequency on the reading task ERP by a substantial fraction of the effect on RT. In Experiment 2, a task switch delayed the onset of the effect of lexical status on the ERP to about the same extent that it prolonged the RT. These effects indicate an early locus of (most of) the residual switch cost: we propose that this reflects a form of task-related attentional inertia. Other findings have implications for the automaticity of lexical access: effects of frequency, lexicality and orthographic familiarity on ERPs in the symmetry task indicated involuntary but attenuated orthographic and lexical processing even when attention was focused on a non-lexical property. 3It is generally harder to switch among several cognitive tasks than to continue to perform just one. A popular way to capture at least part of this multitasking overhead in the laboratory is to conduct a reaction time (RT) experiment in which, on each of a series of trials, a stimulus is presented, and the participant must perform one of several possible tasks. On some trials the task changes, on others it does not, other things being equal. Several such "task-switching" paradigms have been developed and extensively explored over the last two decades. (For reviews see Kiesel, Steinhauser, Wendt, Falkenstein, Jost, Philipp, & Koch, 2010;Monsell, 2003;Vandierendonck, Liefooghe, & Verbruggen, 2010). The most obvious phenomenon they reveal is the substantial cost to performance of a switch of task: the average RT for a correct response is longer (and there are usually more errors) when the task changes than when it does not.The opportunity to prepare for a task before presentation of the stimulus generally reduces this switch cost, but does not eliminate it (Meiran, 1996;Rogers & Monsell, 1995). To manipulate preparation time unconfounded by the time elapsing since the previous performance of a task, task-cuing can be used (Meiran, 1996): each stimulus follows the previous response by a standard interval, and a task cue precedes the stimulus by an interval which is independently manipulated to vary preparation time. As the cue-stimulus interval (CSI) is increased from zero, the RT switch cost reduces to an asymptotic residual cost, usually reached at a CSI of bet...