Evidence for a multiple-process account of the generation effect

Model-based measurement procedures are described that result in measures for the probability of sufficient storage and the probability of successful retrieval. These procedures were applied in a study of the underlying memory changes that occur as a function of generative encoding and the degree of congruity of the response to the provided stem. Consistent with previous findings, free recall data resulted in a congruous generation effect, and a larger, incongruous generation effect. Newly developed process measures showed that the two generation conditions (congruous and incongruous) both had higher rates for the probability of sufficient storage than the two corresponding read conditions. The additional improvement in free recall for the incongruous generation condition was strictly due to a gain in the probability of retrieval. Evidence is thus provided that there is an important role for both storage and retrieval processes in explaining the full range of generation effects.