The retention interval model (Izawa, 1981b) was tested via 342 data points based on 60,084 observations from 338 subjects in 6 experiments, by using highly restrictive parameter estimation modes. First, all parameters controlling the retention interval effects were estimated solely from spaced practice data, and those controlling retrieval effects for each intercycle interval variation, under the study-test method only. In spite of this severe restriction of parameter estimations, the model satisfactorily predicted data not only under the study-test method, but also under the anticipation method. The same processes of quantitative investigation were repeated, next, using parameters estimated solely from data under the anticipation method. The model's performances were also satisfactory for both data for its own and for the study-test method. It is indeed remarkable that 335 data points could be accounted for by using only 66 parameters estimated exclusively from data under either method, whichever was selected. Results suggest that anticipation and study-test methods seem to differ little in terms of acquisition (S) and retrieval (T) processes, but merely in terms of retention processes, inherently resulting in more intervening-study-events (tS) and-test-events (tT) intervals under the former than under the latter.