The Effect of Repetition on Retention

It is a common experience that repetition impacts memory. The more a passage is repeated on day 1 of practice, the better condition it is in when the next day’s work begins. But how much practice does it require to maintain “X” amount of material? How much retention is gain for each repetition? At what point does the diminishing returns outweigh the value of the additional retention?

Ebbinghaus did a series of double tests to find the answer to these questions. He learned 6 series of 16 syllable lists, repeating each list either 8, 16, 24, 32, 42, 53, or 64 times. The next day he repeated the tests, the results were remarkably consistent across all levels of study. Through the course of his study he found that it took an average of 31 repetitions to learn a list of 16 syllables. So the lists learned 8, 16, and 24 times were not learned to his standard of error free reproduction. However the 42, 53, and 64 repetition lists were significantly over studied for his standard.

The next day he relearned the lists and recorded the amount of repetitions and time it took to learn each list to his standard. The results across all lists was an average savings of 12.7 seconds with each test set of 6 lists falling within the narrow range of 12 and 13.7 seconds saved. The average savings per list (out of the 6) was 2.1 seconds and the average time it took to read a list was 6.6 – 6.8 seconds. On average, across the entire exercise he experienced a savings of one repetition for every three repetitions done the preceding day.

And as for the question of diminishing returns, the greatest savings occurred at the 42 repetition level. Some of this he attributed to: “An increase of the readings used for the first learning beyond 64 repetitions proved impracticable, at least for six series of this length. For with this number each test requires about 3/4 of an hour, and toward the end of this time exhaustion, headache, and other symptoms were often felt which would have complicated the complicated(sic) (I think the translation should have said “results”) of the test if the number of repetitions had been increased.”

So when your students asks “Do I really need to play it again????” You can say quite confidently: “Yes, Dr. Ebbinhaus says do it 42 times!” It is indeed true that repetition is the mother of all learning. In coming articles we will look at the effect of thoughtful repetition.

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