The effect of spaced practice on explicit and implicit memory

The spaced‐practice effect refers to the strong and pervasive positive influence on long‐term explicit memory which results from interposing at least one other item between the repetitions of any to‐be‐remembered item in a list‐learning paradigm. Limited prior empirical evidence suggests that spaced practice could also have a similar positive effect on implicit memory performances, as revealed through a tachistoscopic identification task. Four experiments involving another implicit memory task, namely a perceptual clarification procedure, were conducted to test for the effect of spaced practice with greater methodological control than previously used. Low‐frequency words were displayed to subjects under a variety of conditions including incidental (Expts 1 and 2) and intentional (Expts 3 and 4) learning instructions. Although spacing regulated to a large extent the performances in subsequent free recall (Expt 2) or recognition (Expts 1, 3, 4) control tasks, the advantage of spaced over massed items in the perceptual clarification procedure was always small in magnitude, and only reached significance in the last experiment. Overall analysis of the data shows with a reasonably high degree of certitude that spaced practice exerts a real but probably slight and fluctuating effect upon implicit memory performance.