There was a meta-analysis of Memory Training in Normal elderly done back in 1992 which covered about 31 papers and found that 1) retesting alone enhances memory performance on standardized tests. This isn’t that fact surprising. If you look at test/retest literature on psychological tasks this is one of their big concerns; that people do remember a long time just giving them a test last week and giving it to them two weeks from now even though it is the same person, it involves them better because they have learned something about the test itself. They found that memory training does improve performance on follow-up tests. The training gains though were specific to the training and there was very poor generalizability.