Costs of a predictible switch between simple cognitive tasks.

Abstract

In an investigation of task-set reconfiguration, participants switched between 2 tasks on every 2nd trial in 5 experiments and on every 4th trial in a final experiment. The tasks were to classify either the digit member of a pair of characters as even/odd or the letter member as consonant/vowel. As the response-stimulus interval increased up to 0.6 s, the substantial cost to performance of this predictable task-switch fell: Participants could partially reconfigure in advance of the stimulus. However, even with 1.2 s available for preparation, a large asymptotic reaction time (RT) cost remained, but only on the 1st trial of the new task. This is attributed to a component of reconfiguration triggered exogenously, i.e., only by a task-relevant stimulus. That stimuli evoke associated task-sets also explains why RT and switch costs increased when the stimulus included a character associated with the currently irrelevant task.

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

“…Competition between task-sets is manifest at two levels. Competition at the S-R level is indicated by a response congruence effect: responses are slower and less accurate to incongruent than to congruent stimuli (Brown, Reynolds, & Braver, 2007;Goschke, 2000;Meiran, 2000;Rogers & Monsell, 1995;Wendt & Kiesel, 2008). …”

“…Competition at the task-set level is indicated by longer RTs to congruent stimuli -for which mere S-R activation via the irrelevant task-set should facilitate response selection, than to univalent stimuli -which should activate neither the irrelevant task-set nor its responses (Aron, Monsell, Sahakian, & Robbins, 2004;Rogers & Monsell, 1995;Steinhauser & Hübner, 2007), and by other evidence (Elchlepp, Lavric, Mizon, & Monsell, 2012;Monsell, Taylor, & Murphy, 2001). …”

“…(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.…”

“…They labeled this persistence of a previous task-set "task-set inertia", and proposed that the resulting conflict with the now-appropriate task-set results in "additional time for the system to settle to a unique response decision (or response retrieval) after the next imperative stimulus has arrived" (p.437). When it was found (Meiran, 1996;Rogers & Monsell, 1995) that the (mean) switch cost seemed to have two components -one eliminable by active preparation, one not -the idea of passive "inertia" seemed appropriate to account for the latter Task-set inertia could incorporate either persisting activation of the previous task-set or persisting inhibition of the now-appropriate task, or both (Allport et al, 1994; Masson, Bub, Woodward, & Chan, 2003;Yeung & Monsell, 2003; see Vandierendonck et al, 2010, for review). Hence, the core idea of task-set inertia is that persisting activation of task-set activation and/or inhibition from the most recent trial, or last few trials, is a major source of conflict and the (residual) switch cost (Altmann & Gray, 2008;Gilbert & Shallice, 2002;Mayr & Keele, 2000;Meiran, Chorev, & Sapir, 2000;Yeung & Monsell, 2003).…”

“…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.…”