# What was Ebbinghaus contribution to SuperMemo?

## Contents

# Question

You place Ebbinghaus in history of SuperMemo and then you say he did not have any actual contribution to spaced repetition. This is confusing. Why is he listed in SuperMemo history? Do you say he had no idea how to space repetitions? What is the Ebbinghaus myth?

# Answer

## The Ebbinghaus myths

### Spaced repetition

**The Ebbinghaus myth** is that Ebbinghaus knew how to compute optimum intervals in learning. In fact, he was a **pure science** researcher interested in how memory works. SuperMemo was born out of the **practical need** to memorize massive amounts of information. For purity, Ebbinghaus used nonsense syllables and short spans of time. SuperMemo started with English-Polish word pairs and long spans of time.

Ebbinghaus did not have any impact on the development of SuperMemo because SuperMemo (on paper) was created in ignorance of his work on memory.

### Forgetting curve

Each time you google for forgetting curves and Ebbinghaus, you will find the formula R=exp(-kt/S). This is an example of how a single mixup in a single source (Wikipedia) can result in widespread amplification and propagation of false information. Here are the facts:

- Ebbinghaus studied the costs of re-learning (his equivalent of forgetting in sketching the forgetting curve)
- Ebbinghaus discovered that forgetting is best described by a power function, not an exponential function (k=b(log(t))^c/(100-b))
- power function shows in forgetting when there is a superposition of exponential forgetting curves (i.e. where material is of heterogeneous difficulty)
- the formula attributed to Ebbinghaus (R=exp(-kt/S)) was actually first published by Wozniak, Murakowski and Gorzelanczyk in 1995
- SuperMemo measures homogeneous forgetting of memorized items, and its forgetting curves are exponential (except the first interval where items are heterogeneous with undetermined difficulty)

## Ebbinghaus contribution

Here is why Ebbinghaus should be listed in history of SuperMemo:

- Ebbinghaus pioneered research in the field of memory
- Ebbinghaus figured out the shape of the forgetting curve. SuperMemo plots its own forgetting curves as of 1991
- Ebbinghaus was the prime example of self-experimentation on one's own memory. Similar self-experimentation lead to SuperMemo
- Ebbinghaus was aware that spaced presentation is better than massed presentation

# Further reading

To better understand the role of Ebbinghaus in the history of psychology:

- http://psy.ed.asu.edu/~classics/Ebbinghaus/memory7.htm (1885, forgetting curve)
- http://psy.ed.asu.edu/~classics/Ebbinghaus/memory8.htm (1885, spaced repetition)

More on SuperMemo:

- http://super-memory.com/english/ol/beginning.htm (1990)(first steps 1982-1987)
- http://www.super-memory.com/english/2vm.htm (1995)(forgetting as R=exp(-kt/S))(original PDF)
- http://help.supermemo.org/wiki/SuperMemo_Algorithm (2016)(the algorithm that uses exponential forgetting curves for homogeneous and power forgetting curves for heterogeneous material)

Dr Jaap Murre's replication of the negative power forgetting curve:

See also: Who invented spaced repetition?

# Example

This beautifully researched page perpetuates Ebbinghaus myth:

http://www.gwern.net/Spaced%20repetition

Quote (Nov 2014): *We can thank Ebbinghaus for investigating in such tedious detail than we can, in fact, program a computer to calculate both the forgetting curve and optimal set of reviews*