N - 2 repetition costs depend on preparation in trials n - 1 and n - 2.

In task switching, a common result supporting the notion of inhibitory processes as a determinant of switch costs is the occurrence of n - 2 repetition costs. Evidence suggests that this effect is not affected by preparation. However, the role of preparation on preceding trials has been neglected so far. In this study, evidence for an influence of preparatory processes on n - 2 repetition costs is provided by focusing on the cue-target interval on trials n - 1 and n - 2. N - 2 repetition costs were affected by an interaction of both n - 1 and n - 2 preparation time, being more pronounced when both preparatory intervals were long. The results provide support for the notion of active preparation processes involved in backward inhibition.