The effects of spaced repetition on explicit and implicit memory

Undergraduate students studied stimulus words (nouns) which were presented successively under three conditions; (1) spaced repetition, (2) massed repetition, and (3) single presentation. Immediately after the study task, they were given either an explicit memory test (free recall) or an implicit memory test. In Experiment 1, 5 male and 57 female students were given a word-fragment completion task as an implicit memory test. The results showed significant spacing effects on implicit memory as well as on explicit memory. In Experiment 2, 38 female students were given a lexical decision task as an implicit memory test. The results showed significant spacing effects on explicit memory but not on implicit memory. These results were interpreted as an evidence that spacing effects on implicit memory tests reflect conceptually-driven processing.