The Role of Task-Related Learned Representations in Explaining Asymmetries in Task Switching

Ayla Barutchu,Robert Hester,Neil L Levy,Olivia Carter,Stefanie I Becker,Markus Lappe

doi:10.1371/journal.pone.0061729

Abstract

Task switch costs often show an asymmetry, with switch costs being larger when switching from a difficult task to an easier task. This asymmetry has been explained by difficult tasks being represented more strongly and consequently requiring more inhibition prior to switching to the easier task. The present study shows that switch cost asymmetries observed in arithmetic tasks (addition vs. subtraction) do not depend on task difficulty: Switch costs of similar magnitudes were obtained when participants were presented with unsolvable pseudo-equations that did not differ in task difficulty. Further experiments showed that neither task switch costs nor switch cost asymmetries were due to perceptual factors (e.g., perceptual priming effects). These findings suggest that asymmetrical switch costs can be brought about by the association of some tasks with greater difficulty than others. Moreover, the finding that asymmetrical switch costs were observed (1) in the absence of a task switch proper and (2) without differences in task difficulty, suggests that present theories of task switch costs and switch cost asymmetries are in important ways incomplete and need to be modified.

Highlights

The ability to switch between tasks rapidly and efficiently affords much flexibility, and facilitates adaptation to environmental or situational needs
To examine whether switch costs occurring with unsolvable pseudo-equation differ significantly from the switch costs observed with the symbols in Experiment 1, a repeatedmeasures Analyses of Variance (ANOVA) was computed over the data from the symbol identification task from Experiment 1 and the results of the equivalent condition with unsolvable pseudo-equations of Experiment 2
The observed switch asymmetries when solving addition and subtraction problems was evident when participants switched between the ‘+’ and ‘2’ arithmetic symbols in unsolvable pseudo equations of equal difficulty

Summary

Introduction

The ability to switch between tasks rapidly and efficiently affords much flexibility, and facilitates adaptation to environmental or situational needs (e.g., while shopping for groceries switching to attend to an unexpected business call or your child’s needs). People are significantly better and faster at performing tasks under repeat conditions than when switching between tasks even when tasks are well practiced and people are given sufficient time to prepare for the switch (reviewed in [1]). It is well known that task switching costs are not symmetrical when switching between tasks of unequal difficulty: Somewhat perplexingly, switch costs are generally greater when switching from a difficult to an easy task than vice-versa. Bilinguals have been shown to be slower at switching to their dominant first language than to their secondary language [2,3], and despite people being faster at reading than naming the colour of incongruently coloured words in a Stroop task, they tend to show greater costs when switching to reading than colour naming [4,5,6]. Similar asymmetries in switching costs have been observed across a range of tasks [7,8,9,10,11,12]

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