ABSTRACT
The cross-sectional investigations we discussed in the previous chapter all confirm that long term maintenance of knowledge depends upon extended periods of exposure to the target content. Semi-permastore access was only achieved after many months of exposure to names and faces of high school classmates, to Spanish language, and to the content of high school algebra. Extended training in these investigations confounds two variables that have long been known to affect retention: when training continues over several years, both the amount of training and the temporal distribution of training increase, and their respective effects on retention cannot be sorted out. Of course, one can vary amount and distribution of practice independently, but naturalistic investigations are not likely to provide that opportunity. We therefore performed several quasi-experimental follow-up investigations for the purpose of assessing the independent contributions of the amount and the distribution of training on the long term maintenance of knowledge.
