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

Abstract

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...

Proactive inhibitory control: A general biasing account

“…A robust finding in the task-switching literature is that switching between tasks is associated with a cost, which is typically substantially reduced by providing an opportunity to prepare for the switch (for reviews, see Kiesel et al, 2010 , Monsell, 2003 , Vandierendonck et al, 2010 ). When changing task involves shifts of attention among locations or stimulus dimensions, a substantial part of the switch cost has been attributed to (re)setting of attentional selection parameters ( Elchlepp et al, 2015 , Longman et al, 2013 , Longman et al, 2014 , Mayr et al, 2013 ). Similarly, when changing task involves updating the stimulus–response mappings, a substantial part of the switch cost has been attributed to (re)setting the response parameters ( Kieffaber et al, 2013 , Meiran et al, 2000 , Rushworth et al, 2002 , Yeung and Monsell, 2003 ).…”

Shifting Attention Between Visual Dimensions as a Source of Switch Costs

“…Others attribute it to intrinsic limitations of preparation, either because some components of "task-set reconfiguration" cannot occur in advance of the stimulus (e.g., Rogers & Monsell, 1995;Meiran, 2000) or because proactive task-set reconfiguration sometimes "fails to engage" (DeJong, 2000). But these accounts have generally shared an assumption: that the residual switch cost arises at a relatively late stageduring the response selection processas a result of competition from the alternative task's stimulusresponse (S-R) rules (see Elchlepp, Lavric & Monsell, 2015, for a review). For example, suppose the participant sees on each trial one of several letters presented in one of several colors, and is asked to classify either the letter (as vowel vs. consonant) or its color (as "warm" vs. "cold", see Figure 1).…”

“…To determine whether having just switched from the letter task delayed processing of color, we could then compare the latencies of the color frequency EEG markers on switch versus repeat trials. We adopted a similar approach in a recent study (Elchlepp et al, 2015). A string of red and blue letters was classified either by its linguistic properties (word versus non-word in one experiment, semantic category in another), or by a perceptual property (symmetry versus asymmetry of the color pattern across the string).…”

The coupling between spatial attention and other components of task-set: A task-switching investigation

“…The delay in appropriate orientation was also predictive, across and within individuals, of the success of task-set preparation as reflected in RT switch costs. Task-switch-induced delays were also recently documented in the allocation of (non-spatial) attention to the relevant perceptual dimension, using both eye-tracking (Mayr, Kuhns, & Rieter, 2013) and brain potentials (Elchlepp, Lavric, & Monsell, 2015).…”