Inhibition of irrelevant category–response mappings

Abstract

When switching tasks, performance tends to be worse for n – 2 repetitions than with n – 2 switches. This n – 2 repetition cost has been hypothesized to reflect task-set inhibition: specifically, inhibition of irrelevant category–response mappings involved in response selection. This hypothesis leads to divergent predictions for situations in which all tasks involve the same stimulus categories: An n – 2 repetition cost is predicted when response sets differ across tasks, but not when the response set stays the same. The authors tested these predictions by having subjects perform relative judgements with different reference points. In Experiment 1, the stimulus categories were the same across reference points, but the response set either differed or stayed the same (the multiple- and single-mapping conditions, respectively). An n – 2 repetition cost was found in the multiple-mapping condition but not in the single-mapping condition. Experiment 2 provided evidence against the possibility that these divergent effects reflected differences in memory load. These findings confirm predictions that link n – 2 repetition costs to inhibition of irrelevant category–response mappings.

Keywords:

• Task switching
• Inhibition
• Response selection
• Reference points

Acknowledgments

This research was supported by National Institute of Mental Health Grant R01-MH073879–01 to Gordon Logan, whom we thank for use of his laboratory facilities. We also thank Katherine Arbuthnott, Gordon Logan, Ulrich Mayr, Nachshon Meiran, and two anonymous reviewers for their comments on this work.

Notes

¹ A significant n – 2 repetition benefit of 17 ms, F(1, 19) = 8.88, MSE = 331.23, p < .01, η _p ² = .32, was present in the single-mapping condition even when trial sequences involving the stimuli 1 and 9 (for which stimulus–response mappings stay the same across reference points) were excluded, indicating that the benefit is not due to retrieval of stimulus–response mappings that bypasses the category level.

² However, we note that there was no explicit requirement to maintain the category–response mappings in memory in the multiple-mapping condition, as reminders of the mappings were displayed in the bottom corners of the screen for the duration of the experiment.

³ Although we refer to semantic categories, it is possible that the mapping involves spatial categories (e.g., left and right) that are associated with semantic categories (e.g., smaller and larger).

⁴ Additional RT analyses of our data revealed patterns of distance effects (shorter RTs with increasing distance between reference point and stimulus) that are more consistent with performance of relative judgements (Dehaene, 1989; Schneider & Logan, 2007) than with distance-independent categorization of stimuli that might arise from alternative labelling of stimulus categories across reference points.

⁵ We thank Gordon Logan for suggesting this explanation.

⁶ The reverse situation—a benefit masking a cost—was suggested by Mayr and Kliegl (2003, Exp. 3) as an explanation of their finding of an n – 2 repetition benefit when task cues repeated from trial n – 2 to trial n. On the basis of correlational analyses of their data, they argued that task-set inhibition still occurred, but that the cost of inhibition was masked by a benefit from positive priming of cues. We thank Ulrich Mayr for drawing our attention to this interpretation.

Additional information

Notes on contributors

Frederick Verbruggen

Frederick Verbruggen is a Postdoctoral Fellow of the Research Foundation–Flanders (FWO–Vlaanderen).