Editing Forgetting curve (section)

== History ==
[[File:Ebbinghaus curve.png|thumb|295x295px|The forgetting curve, with original data from Ebbinghaus]]
From 1880 to 1885, [[Hermann Ebbinghaus]] ran a limited, incomplete study on himself and published his hypothesis in 1885 as ''{{lang|de|Über das Gedächtnis}}'' (later translated into English as ''Memory: A Contribution to Experimental Psychology'').<ref name="Ruger1913">{{cite book|last=Ebbinghaus|first=Hermann|translator-last=Ruger|translator-first=Henry|translator-last2=Bussenius|translator-first2=Clara|url=https://archive.org/details/memorycontributi00ebbiuoft/page/n5/mode/2up|title=Memory: A Contribution to Experimental Psychology|year=1913|publisher=New York city, Teachers college, Columbia university}}</ref> Ebbinghaus studied the memorisation of nonsense syllables, such as "WID" and "ZOF" (CVCs or Consonant–Vowel–Consonant) by repeatedly testing himself after various time periods and recording the results. He plotted these results on a graph creating what is now known as the "forgetting curve".<ref name="Ruger1913" /> Ebbinghaus investigated the rate of forgetting, but not the effect of [[spaced repetition]] on the increase in retrievability of memories.<ref>{{cite web|last=Wozniak|first=Piotr|title=Did Ebbinghaus invent spaced repetition?|url=https://www.supermemo.com/en/blog/post/did-ebbinghaus-invent-spaced-repetition|access-date=2020-07-11|website=www.supermemo.com|date=22 November 2017 }}</ref>

Ebbinghaus's publication also included an equation to approximate his forgetting curve:<ref name="Ruger1913-77">Ebbinghaus (1913), p. 77</ref>

<math display="block">b = \frac{100k}{(\log(t))^c +k}</math>

Here, <math>b</math> represents 'Savings' expressed as a percentage, and <math>t</math> represents time in minutes, counting from one minute before end of learning.  The constants c and k are 1.25 and 1.84 respectively. Savings is defined as the relative amount of time saved on the second learning trial as a result of having had the first. A savings of 100% would indicate that all items were still known from the first trial. A 75% savings would mean that relearning missed items required 25% as long as the original learning session (to learn all items). 'Savings' is thus, analogous to retention rate.

In 2015, an attempt to replicate the forgetting curve with one study subject has shown the experimental results similar to Ebbinghaus' original data.<ref name="Murre2015">{{cite journal |last1=Murre |first1=Jaap M. J. |last2=Dros |first2=Joeri |title=Replication and Analysis of Ebbinghaus' Forgetting Curve |journal=[[PLOS ONE]] |date=2015 |volume=10 |issue=7 |page=e0120644 |doi=10.1371/journal.pone.0120644|pmid=26148023 |pmc=4492928 |bibcode=2015PLoSO..1020644M |doi-access=free}}</ref>

Ebbinghaus' experiment has significantly contributed to [[experimental psychology]]. He was the first to carry out a series of well-designed experiments on the subject of forgetting, and he was one of the first to choose artificial stimuli in the research of experimental psychology. Since his introduction of nonsense syllables, a large number of experiments in experimental psychology has been based on highly controlled artificial stimuli.<ref name="Murre2015" />