Academic journal article Perception and Psychophysics

Probe-Specific Proportion Task Repetition Effects on Switching Costs

Academic journal article Perception and Psychophysics

Probe-Specific Proportion Task Repetition Effects on Switching Costs

Article excerpt

In two experiments, participants were presented with successive presentations of animal names (e.g., GORILLA, WHALE)-a prime display followed by a probe display. In response to each display, participants judged either the typical habitat or the relative size of those animals, repeating the same task in response to both displays on half of the experimental trials and switching from one task to the other on the other half of trials. Our results demonstrate that switch costs can be reduced when either the probe's identity or its location is predictive of a change in task. This result establishes that the presentation of a stimulus can serve as a rapid cue for facilitating a switch in task, independent of processes occurring both at the time of the prime task and during the intervening period between the prime and probe tasks. We discuss the implications of these results for prevailing explanations of task switching costs.

People typically perform a task more slowly following the completion of some other task than after performing the same task (Allport, Styles, & Hsieh, 1994; Jersild, 1927; Monsell, 2003; Monsell, Yeung, & Azuma, 2000; Rogers & Monsell, 1995; Spector & Biederman, 1976). Such costs of task switching are thought to reflect two distinct components. One source of these switch costs is considered to be unconsciously and exogenously determined by the interaction of processes occurring during the performance of the task to be switched from and processes associated with subsequent performance of a different task. Alternatively, switch costs may arise from time-consuming endogenous control processes-often referred to as task-set reconfiguration processes (see Monsell, 2003, p. 135).

Observations of smaller task switching costs when participants are provided with time to prepare for a task change are typically interpreted as reflecting the contribution of time-consuming, endogenous efforts to configure a new task set. In contrast, when participants are given ample time to prepare for a task switch, a residual switching cost is often observed (De Jong, 2000; De Jong, Berendsen, & Cools, 1999; Goschke, 2000; Lien, Ruthruff, Remington, & Johnston, 2005; Meiran, 1996; Meiran & Chorev, 2005; Meiran, Chorev, & Sapir, 2000; Nieuwenhuis & Monsell, 2002; Rogers & Monsell, 1995; Schuch & Koch, 2003; but see Verbruggen, liefooghe, Vandierendonck, & Demanet, 2007). These residual switching costs are often thought to arise from additional sources of impairment that are not within the participant's conscious control.

Exogenous Sources of Task Switching Costs

One class of exogenous influences that have been proposed as contributing to task switching costs emphasizes processes occurring at the time of performing the task that participants are required to switch from (the prime task). Task switching costs occur because processes engaged by completion of the prime task interfere with efforts to perform a different task in response to a subsequent display (the probe task). For example, Allport and colleagues (Allport et al., 1994; Meuter & Allport, 1999) have proposed that such costs are the outcome of persistent inhibition and/or activation of the prime task set. A number of other researchers have since provided further evidence in support of the idea that task switching costs are at least partly a consequence of inhibition and activation of the prime task set (Mayr, 2002, 2006; Mayr & Keele, 2000; Mayr & Kliegl, 2003; Monsell et al., 2000; Yeung & Monsell, 2003). By this view, performance of a prime task increases the activation level of mental representations corresponding to that task and decreases (or inhibits) the activation level of task-set representations corresponding to the alternate task.

Other researchers have focused on the requirement for participants to rely on a task cue to select between two alternative tasks in many studies of task switching (Arlington & Logan, 2004; Logan & Bundesen, 2003, 2004; Mayr & Kliegl, 2003; Monsell & Mizon, 2006). …

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