Training was adaptive according to a pre-specified algorithmwith three levels of difficulty; as subjects became more proficient,task difficulty increased. Subjects were scanned using fMRI beforeand after training. During fMRI assessment, the letter-memory cri-terion task and two transfer tasks were administered: a numericaln-back task and a Stroop task. A number of other transfer tasks weregiven outside the scanner pre and post training, tapping episodicmemory, speed, verbal fluency, and reasoning (Dahlin et al., 2008a).Fig. 1A depicts gains in letter memory performance during scanningin younger and older adults, expressed as effect sizes. Fig. 1B por-trays gain trajectories for the two age groups across the five-weektraining period for the same letter-memory task assessed outsidethe scanner. As can be seen, both groups improved greatly fromthe intervention, although performance of the old at the end of thetraining thetraining period did not surpass that of the young in the early phasesof training. Further, Fig. 1A shows a clear performance incrementon an untrained 3-back task (that also requires updating) in theyoung, but not in the old. By contrast, there was no transfer to theStroop task, which taxes inhibition rather than updating (Miyakeet al., 2000). In addition, with the exception of n-back, no transferwas observed to the tasks assessed outside the scanner. This pat-tern indicates that the intervention effect was process-specific; thetraining did not affect executive functions or cognition in general,but specifically influenced WM updating.