Dempster, F. N.
The Spacing Effect: A Case Study in the Failure to Apply the Results of Psychological Research
For a given amount of study time, spaced presentations yield significantly better learning results than massed presentations—a dependable and replicable phenomenon—robust: two spaced presentations are about twice as effective as two massed presentations.
American classrooms and textbooks do not include spaced reviews.
Why is it that research findings that appear to have significant implications are not used by teachers or curriculum developers?
1) Phenomenon has not been known long enough
Ebbinhaus published in 1885 (memory)
2) Phenomenon has not received recent documentation
It has appeared in the literature continually for 100 years
3) Cannot be linked to current concerns of educators
Spacing effect has immediate and obvious implications
4) Has not been demonstrated satisfactorily in school activities
Repeated short drill in math facts, text element recall, remembering content, vocabulary learning have all been studied
5) Discontinuities in the literature
This may be due to applied vs. scientific lines of research, variations in terminology creating confusion
6) Too many studies using school-like activities have failed to show the spacing effect
Effect is subject to certain unknown boundary conditions, age differences (emerges later)
7) Phenomenon has not been demonstrated satisfactorily in classroom
8) Too little is known about actual classroom practice to justify widespread application of the spacing effect
-nothing published on the amount of time teachers typically devote to review—and to what extent reviews are spaced rather than massed. To what extent are reviews verbatim or paraphrased? Several studies have failed to show spacing effects in text processing when paraphrased
9) Phenomenon is not sufficiently understood. Levels of attention, interest, practice, rehearsal, interpretation are important
Massed presentations may not allow for sufficient rehearsal
Anything that increases the likelihood that a repetition will receive full attention should improve learning
Spacing effect is counterintuitive

Ebinghaus Link