Further investigating effects of task repetition proportion onn-2 repetition costs: Task shielding as a potential modulating factor?

Previous research has shown thatn - 2 repetition costs are reduced when the experimental procedure allows for task repetitions. The present study aimed to further elucidate possible mechanisms underlying this effect. To this end, three experiments were conducted in which the possibility of task repetitions was tied to individual tasks. In Experiment I, the specific repetition proportions varied between participants. The reduction ofn - 2 repetition costs was stronger when the relative amount of task repetitions associated with a particular task was high, suggesting that inhibition is reduced when the presence of repetitions tied to a specific task can easily be detected. In Experiment II, task preparation time varied between blocks to investigate whether cue-based preparation underlies this reduction ofn - 2 repetition costs. While the duration of the preparation interval had no effect in this respect, additional combined analyses of both experiments revealed an influence of stimulus congruency:n - 2 repetition costs were highest when repetitions were precluded and the task stimulus was incongruent, whereas no effect of stimulus congruence onn - 2 repetition costs was observed with tasks that possibly repeated. This data pattern was replicated in Experiment III. This result is interpreted in terms of task shielding which is reduced for tasks without repetitions, making these tasks more vulnerable to crosstalk from competing tasks when they are still in an inhibited state.