Inhibition of irrelevant category-response mappings.

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.