Spacing Effect

In psychology, the spacing effect is the phenomenon whereby animals (including humans) more easily remember or learn items when they are studied a few times spaced over a long time span ("spaced presentation") rather than repeatedly studied in a short span of time ("massed presentation"). Practically, this effect suggests that "cramming" (intense, last-minute studying) the night before an exam is not likely to be as effective as studying at intervals in a longer time frame. Important to note, however, is that the benefit of spaced presentations does not appear at short retention intervals, in which massed presentations tend to lead to better memory performance.

The phenomenon was first identified by Hermann Ebbinghaus, and his detailed study of it was published in the 1885 book Über das Gedächtnis. Untersuchungen zur experimentellen Psychologie (Memory: A Contribution to Experimental Psychology). This robust finding has been supported by studies of many explicit memory tasks such as free recall, recognition, cued-recall, and frequency estimation (for reviews see Crowder 1976; Greene, 1989).

Researchers have offered several possible explanations of the spacing effect. According to the deficient processing view, massed repetitions lead to deficient processing of the second presentation—that we simply do not pay much attention to the later presentations (Hintzman et al., 1973). According to the encoding variability view, spaced repetition typically entails some variability in presentation contexts, resulting in a greater number of retrieval cues. Contrastingly, massed repetitions have limited presentations and therefore limited retrieval cues. In spite of these findings, the robustness of this phenomenon and its resistance to experimental manipulation have made empirical testing of its parameters difficult.