You might think that the teaching technique known as spaced repetition, which has gained more and more traction over the past few years with language learning apps and our very own solution here at Wranx, was developed quite recently. However, it can trace its routes back over a century thanks to the work of Hermann Ebbinghaus who developed the idea of the Ebbinghaus Forgetting Curve.
This German psychologist, who pioneered the experimental study of memory, first identified the spacing effect phenomenon in his 1885 book Über das Gedächtnis. Untersuchungen zur experimentellen Psychologie (Memory: A Contribution to Experimental Psychology).
Along with his research into spaced repetition, Ebbinghaus also discovered the forgetting curve, a hypothesis that looked at the decline of memory retention over time. But what do you need to know about Ebbinghaus and the forgetting curve?
As opposed to the popular held thought at the time, Ebbinghaus wanted to show that higher mental processes could be studied through experimentation. He wanted to use simple acoustic encoding and maintenance rehearsal to control potentially confounding variables.
However, Ebbinghaus needed a list of words that could be easily memorised but which had no prior cognitive associations, as this would affect his results. Therefore, he used items that would later be called “nonsense syllables,” which are consonant-vowel-consonant combinations (also known as the CVC trigram) where the consonant does not repeat and the syllable does not have prior meaning.
After eliminating those with meaning, Ebbinghaus had 2,300 syllables to choose from and memorise. He would pull random syllables out of a box, write them down in a notebook, read out the syllables, and attempt to recall them at the end of the procedure to the sound of a metronome and with the same voice inflection.
Although there are several limitations to his work, primarily because he was the only subject to be tested, Ebbinghaus’ research about memory was groundbreaking, with findings that are still relevant and supported to this day. Arguably his most famous finding was the forgetting curve.
The forgetting curve shows how information or knowledge stored within the brain is lost over time if the individual makes no attempt to retain it. A related concept is the strength of memory, which refers to the durability that memory traces in the brain; the stronger the memory, the longer a person call recall it for.
With newly acquired information or knowledge, the curve shows that humans tend to halve their memory in a matter of days or weeks unless they consciously review the learned material. The speed of forgetting depends on a number of factors too, such as the difficulty of learned material, how meaningful it is, its representation, and physiological factors like stress and sleep.
Even though Ebbinghaus tried to eliminate meaning with his experiments, it was later determined that humans impose meaning even on nonsense syllables. For instance, the nonsense syllable PED (the first three letters of several common words) is actually less nonsensical than a syllable such as KOJ and others that differ in association value.
Having said that, the basal forgetting rate doesn’t differ much between individuals, whereas performance rates can be explained by mnemonic representation skills.
In addition to the forgetting curve, Ebbinghaus was the first person to describe the learning curve. Although he never used the term ‘learning curve,’ he presented diagrams of learning against trial number and noted that the store can decrease or even oscillate.
As you can probably guess, the learning curve refers to how fast an individual learns new information or knowledge. The sharpest increase occurs after the first piece of trying or teaching, but then gradually evens out. This means that less and less new information or knowledge is retained after each repetition. Just like the forgetting curve, the learning curve is exponential over time.
As a result of his discovery of the forgetting curve, Ebbinghaus also came up with the effects of “overlearning”. In general terms, this means that if an individual learns something more than is usually necessary to memorise it, they would effectively achieve overlearning. This can also mean that information or knowledge is more impervious to being lost or forgotten, making the forgetting curve much shallower.
The forgetting curve supports transience too, one of the seven kinds of memory failures that alludes to the process of forgetting over a period of time.
While some aspects that contribute to the speed of forgetting cannot be changed, Ebbinghaus said basic training in mnemonic techniques could help overcome differences in performance. He asserted that the best methods for increasing memory strength were:
Better memory representation (e.g. mnemonic techniques) – Coming up with a song is perhaps the most commonly used mnemonic technique. An example of which is how children remember their ABCs. However, other types include names, expressions, models, odes, note organisation, images, connections, and spellings.
Repetition based on active recall (especially spaced repetition) – When reviewing learned information, spacing out sessions over time makes items easier to remember. This is achieved through spaced presentation rather than repeat studying in a short span of time, also known as massed presentation.
Ebbinghaus believed that each repetition in learning increases the optimum interval before the next repetition is needed and for near-perfect retention, initial repetitions may need to be made within days. However, later research suggested that higher original learning could also produce slower forgetting.
What’s more, some memories remain free from the effects of interference and don’t always follow the typical forgetting curve. For this reason, there is debate among supporters of Ebbinghaus about the shape of the curve for events and facts significant to the subject.
Memories of shocking events like the Kennedy Assassination or 9/11 are vividly imprinted in memory according to the flashbulb theory, while considerable variations in written recollections are possible when memory incorporates after-acquired information.
But when it comes to purposefully learning information or acquiring new knowledge, Ebbinghaus and his forgetting curve theory promote positive outcomes through better memory representation and repetition based on active recall.