Another concern about the current corpus of WM training
studies is that there is almost no standardization and little
convergence of findings. To begin, each research group
has a different, favored approach to training (see Fig. 1
for examples), and there are very few cross-laboratory
replications of a given WM training protocol. Moreover, to
date there is not a single published comparative efficacy
study. Thus, we are unable to determine whether a given
approach to training provides a more effective tool for
cognitive enhancement, or whether different training
regimes may be used to differentially target particular
cognitive skills.