Academic journal article Memory & Cognition

On the Representation of Task Information in Task Switching: Evidence from Task and Dimension Switching

Academic journal article Memory & Cognition

On the Representation of Task Information in Task Switching: Evidence from Task and Dimension Switching

Article excerpt

Task switching research has revealed that task changes lead to a performance switch cost. The present study focuses on the organization of task components in the task set. Three different views of task set organization have been distinguished and evidence in favor of each of these has been reported in the literature. In four experiments, we orthogonally varied the categorization task (magnitude and parity) and the stimulus dimension on which the categorization was to be made. Experiments 1, 2, and 4 used Stroop-like number stimuli, whereas Experiment 3 used global-local stimuli to define the stimulus dimension. In Experiments 2-4, the cue-stimulus interval was also varied. The findings showed that a change of any component resulted in a cost, without any reliable difference in the size of these costs. These results are consistent with the flat view on task-set organization, which assumes that the task set binds all elements in an unstructured representation, which is completely reconfigured each time a change to the task set is required. The implications of these findings are discussed in relation to other findings and the different views on task-set organization.

Flexible behavior is an important characteristic of daily cognitive activities and is therefore crucial for our understanding of human cognition. The task-switching paradigm has proven to be a useful tool to investigate the processes and factors related to this matter. In general, people switch rather easily from one task to another. Yet research has shown that task switching is accompanied by a cost: After a task switch, compared with situations in which the task does not change, performance latency increases and errors become more likely (e.g., Allport, Styles, & Hsieh, 1994; Jersild, 1927; Logan & Bundesen, 2003; Meiran, 1996; Rogers & Monsell, 1995; Spector & Biederman, 1976). According to some authors, reconfiguration of the task settings is at the basis of the switch cost (e.g., Mayr & Kliegl, 2000, 2003; Meiran, 1996, 2000; Monsell & Mizon, 2006), whereas other authors have proposed that interference from a previous task execution is responsible for the switch cost (e.g., Allport et al., 1994; Waszak, Hommel, & Allport, 2003, 2004, 2005). Common to these views is that a representation of the task goal and a representation of task parameters or constraints is needed to correctly execute a task; in other words, a representation of the task settings must be made active. This is called the task set. According to the reconfiguration view, a new task set must be configured on switch trials, whereas the same task set can be used again on repetition trials; this difference in time and effort results in the switch cost. For the interference view, in contrast, the switch cost is not due to preparation or configuration of a task set, but to the need to resolve interference due to a previous task execution.

Although the task-set notion plays a central role in accounts of task switching, its definition has remained open-ended. Apart from the agreement that a task set is a temporary active representation and that it contains information relevant to task execution, it is not clear which information is and is not included, and there is some debate about whether and how the information is structured. Because an approved definition of task set has not been formulated thus far, in the present article we assume that the temporary representation contains the parameters needed for the correct execution of the task, such as the relevant stimulus dimension, the stimulus-response mapping, and the response modality. This idea is similar to the definition of executive control in the ECTVA model (Logan & Gordon, 2001). On the basis of this definition, the present study addresses how the elements of the task set are structured.

Three different ways of structuring task-set elements can be distinguished: the hierarchical structure, the componential structure, and the flat organization. …

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