Any recovery from interruptions involves a switch in task (albeit not necessarily from a competing task) and on the basis of the current results alone we cannot rule out that this switch is somehow responsible for the cost asymmetry. However, in Bryck and Mayr (2008) we did find a cost asymmetry even after 5 s unfilled delays between trials and in the absence of any switches in tasks. As we would argue, such delays increase the probability of loosing the current task set, which then triggers working

memory updating. The LTM-interference/updating account can explain both the clearly LTM-induced cost asymmetry studied here and the traditional switch cost asymmetry (see also, Mayr, 2008, 2009; Waszak et al., 2003). Therefore, according to Occam’s razor any inferences about an additional process (such as carry-over) should be based on strong evidence that the trial-to-trial switching situation is in

some way unique BMS-754807 mw and cannot be handled by the LTM-interference/updating Smad inhibitor account alone. One result that at first sight seems to support the carry-over model comes from Yeung, Nystrom, Aronson, and Cohen (2006). Participants switched between tasks that required subjects to attend either to word or to face stimuli. After task switches there was greater activity in neural areas associated with the currently irrelevant task than after non-switch trials. Also, the degree of this irrelevant-task activity predicted RT switch costs. These results are consistent with the carry-over account, but not necessarily inconsistent with the LTM interference account. With only two tasks it is impossible to tell to what degree there would have been also heightened activity on no-switch trials––only to a lesser degree than on switch trials. It is not at all incompatible Adenosine with an LTM model when interference is greater for a more recently used alternate task (e.g., on switch trials) than for a less recently used task (e.g., on no-switch trials; for

related findings see Bryck & Mayr, 2008). In fact, Wylie, Javitt, and Foxe (2004) looked for activation in neural areas associated with task dimensions that had been performed in a previous block of trials, but were not relevant on the current single-task block. Consistent with the LTM model, they found increased task-irrelevant activity (compared to a control situation in which the irrelevant task had not yet been experienced), even though no immediate switching between tasks was involved. We are aware of one set of studies that proposed a specific version of a carry-over model, and also made an explicit effort of ruling out an LTM account of the cost asymmetry. Yeung and Monsell (2003a) had presented a connectionist model that explains different patterns of cost asymmetry as resulting from the combination of carry-over of task activation and the relative amounts of control activation required when tasks either do or do not directly compete with each other.