First forgetting curve

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First forgetting curve is the forgetting curve for the first repetition in SuperMemo. As all items receive the same default difficulty on entry, they all use one and the same first forgetting curve. The curve shows the level of recall after intervals ranging from 1 day to 7 years. As the curve is made of twenty data points, all intervals of 7 years and more are averaged. Those long intervals are used only if a collection is left in limbo, or in cases of heavy learning overload where low priority items never compete their way to the top of the outstanding queue.

This glossary entry is used to explain SuperMemo, a pioneer of spaced repetition software since 1987

Forgetting curve collected with SuperMemo 17

Figure: The first forgetting curve for newly learned knowledge collected with SuperMemo. Power approximation is used in this case due to the heterogeneity of the learning material freshly introduced in the learning process. Lack of separation by memory complexity results in superposition of exponential forgetting with different decay constants. On a semi-log graph, the power regression curve is logarithmic (in yellow), and appearing almost straight. The curve shows that in the presented case recall drops merely to 58% in four years, which can be explained by a high reuse of memorized knowledge in real life. The first optimum interval for review at retrievability of 90% is 3.96 days. The forgetting curve can be described with the formula R=0.9906*power(interval,-0.07), where 0.9906 is the recall after one day, while -0.07 is the decay constant. In this is case, the formula yields 90% recall after 4 days. 80,399 repetition cases were used to plot the presented graph. Steeper drop in recall will occur if the material contains a higher proportion of difficult knowledge (esp. poorly formulated knowledge), or in new students with lesser mnemonic skills. Curve irregularity at intervals 15-20 comes from a smaller sample of repetitions (later interval categories on a log scale encompass a wider range of intervals)