• 1885 - Forgetting curve: German psychologist Hermann Ebbinghaus, the pioneer of experimental study of memory, publishes his Contribution to Experimental Psychology. He used himself as his sole experimental subject. His work might be considered the first step to SuperMemo (formulated exactly 100 years later). Ebbinghaus' work was very influential (English translation 1913), yet for years it was not followed by similar research of major significance! His negatively exponential forgetting curve makes an important part of SuperMemo as of 1991. A myth that can be tracked down to this History of SuperMemo account says that Ebbinghaus invented spaced repetition!
• 1901 - Spaced review: American psychologist William James suggests that review of the learning material should be spaced in time. Similar conclusions were drawn by Ebbinghaus and Jost. Expanding rehearsal is the idea that gave birth to SuperMemo in 1985.
• 1913 - Spacing effect: W. H. Pyle confirms the superiority of spaced review experimentally in a classroom setting
• 1932 - Psychology of study: C. A. Mace hints on the efficient learning methods in his book "The psychology of study". He mentions "active rehearsal" and "repetitive revisions" that should be spaced in gradually increasing intervals, roughly "intervals of one day, two days, four days, eight days, and so on". This proposition is later taken on by other authors (including Tony Buzan), but does not permeate into the practice of study. Only a computer implementation of the idea, SuperMemo 1.0, half a century later, opened a way for a wider public to benefit from spaced repetition
• 1969 - Strength Paradox:

Robert Bjork notices a reverse relationship between the probability of recall and the memory effect of a review. This will lead to Bjork's theory of disuse (1992) that will distinguish between the storage strength and the retrieval strength. The existence of those two memory variables has been first proven in 1988 on the basis of the properties of memory underlying the concept of SuperMemo (published in 1995), and the precise relationship between the two variables was computed with the help of data obtained from SuperMemo in 2005.

1972 - Expanding rehearsal: Sebastian Leitner publishes "So lernt man lernen" in which he describes his Leitner cardbox. The Leitner cardfile technique can be considered a precursor of spaced repetition. Although the timing of repetition in Leitner box is only loosely related to retention levels and is highly affected by the intensity of learning, the technique points to the benefits of expanding rehearsal in which successive repetitions occur in increasing intervals. The Leitner system appears ineffective in cases when it produces intervals substantially different than those that result in the desired level of knowledge retention; however, it appeared very popular in dozens of flashcard programs. 

1982 - Active recall: Piotr Wozniak, a student of molecular biology at the Adam Mickiewicz University of Poznan, Poland, becomes frustrated with his learning progress. He embarks on a self-study course which will ultimately lead to the development of SuperMemo. He begins with an obvious conclusion that active recall serves memory far better than passive review. As a result, Wozniak starts writing down all his mission-critical knowledge on paper in the flashcard form.

1984 - Minimum information: Wozniak concludes that learning is much faster if knowledge is split into a number of simple questions and answers reviewed independently. This conclusion was later formulated as the minimum information principle, which is now considered part of the definition of the SuperMemo method.

1985 - Spaced repetition: Unaware of the previous work in the field, yet using experimental methods first applied by Ebbinghaus a century before, Wozniak runs two simple experiments on his own memory and finds out how review intervals affect the recall. He formulates his first repetition spacing algorithm that will later be known as SuperMemo. His learning with the new method begins on August 25, 1985.  This day marks the birth of computational spaced repetition, i.e. the technique in which knowledge is reviewed in optimum intervals that are determined by a computer with the goal of reaching a desired level of knowledge retention. For a detailed description of the first algorithm see: Using SuperMemo without a computer

1987 - Spaced repetition software: Piotr Wozniak, now a student of computer science at the University of Technology in Poznan, writes his first computer program employing spaced repetition. In 16 evenings, he writes a very simple SuperMemo 1.0 for MS DOS in Borland's Turbo Pascal 3. The first computer algorithm introduced the concept of E-factor (i.e. the number that makes it possible to differentiate between items of different difficulty). Wozniak begins repetitions with SuperMemo 1.0 using his human biology learning material on December 13, 1987. See picture

1988 - SuperMemo gradually gains popularity at the Adam Mickiewicz University of Poznan, and the University of Technology in Poznan, Poland

• SuperMemo 2.0 is written during summer vacation (Turbo Pascal 4.0)
• Tomasz Kuehn from University of Technology in Poznan writes SuperMemo for Atari ST (Pascal)
• Przemyslaw Glowacki from University of Technology in Poznan writes SuperMemo for Atari XL (Basic)
• SuperMemo 3.0 is completed by October 1988. It uses an up-to-date interface with pull-down menus
• in an article that will make part of his Master's Thesis, Piotr Wozniak demonstrates the existence of the two components of long-term memory
  

1989 - first attempts are made to make SuperMemo available commercially

• Tomasz Kuehn makes the first attempt to commercially sell SuperMemo. His advertisement in Polish computer journal Komputer (currently PC World Komputer) sold 10 copies of SuperMemo 2.0.
• SuperMemo 4.0 is completed in February with the learning algorithm based on computing the matrix of optimum intervals
• SuperMemo 5.0 in October makes another step ahead in improving the learning method. It uses an algorithm based on computing the matrix of optimal factors

1990 - Under the supervision of Prof. Kierzkowski, the Head of the Computer Science Department, Piotr Wozniak writes his Master's Thesis: Optimization of learning. A new approach and computer application. This 200-pages dissertation was entirely devoted to the theoretical aspects of SuperMemo, described the evolution of the learning algorithm, included the model of intermittent learning and presented the author's optimistic vision of future applications

1991 - SuperMemo enters the commercial arena:

• July 5, a commercial company, SuperMemo World, is formed by Piotr Wozniak and his fellow graduate Krzysztof Biedalak. The real capital: one 286 personal computer
• SuperMemo 2 is released as freeware
• SuperMemo 6.0 is completed with the learning algorithm based on the approximation of forgetting curves
• September, Dr Janusz Murakowski joins SuperMemo World
• November, SuperMemo 6 unexpectedly becomes a finalist of the Software for Europe 1992 Award Competition

1992

• January, Marczello Georgiew and Tomasz Kuehn join SuperMemo World
• February, Andrzej Horodenski from Computer World initiates commercial sales of SuperMemo 6 by writing the first ever article about the SuperMemo method and software
• March, SuperMemo World displays its products at CeBIT '92
• September, SuperMemo 6 receives the first degree award at Softarg '92, Katowice, Poland
• September, SuperMemo 6 receives a special award of the Polish Computer Science Society
• December, SuperMemo World turns its first quarterly profit
• December, SuperMemo 6 is awarded in the Product of the Year 1992 competition organized by PC Kurier, Poland

1993

• January, after months of programming effort, SuperMemo 7.0 is released, one of few Windows software products in Poland at that time
• March, SuperMemo 5 is released as freeware

• March, German Chancellor Helmut Kohl comes to the stand of SuperMemo World during CeBIT '93

In the picture: Krzysztof Biedalak explains the principles of SuperMemo to Chancellor Kohl

• May, SuperMemo 7.2 AudioVisual for Windows is released. This is the first SuperMemo able to display graphics and play sounds
• August, SuperMemo 1.0 for Amiga is released
• September, SuperMemo tops the chart of best Polish software applications for Amiga (Amiga Magazine)
• September, SuperMemo 7 is awarded at Softarg, Katowice, Poland
• December, SuperMemo becomes the first Polish software ever reviewed in Byte International
• December, SuperMemo 7 is awarded in Product of the Year 1993, PC Kurier, Poland

1994

• January, SuperMemo is voted 4-th most popular Polish software by readers of Polish PC World (behind anti-virus and word- processing products)
• March, SuperMemo for Amiga is voted the Product of the Year 1993 among Polish software for Amiga by readers of Amiga Magazine
• March, SuperMemo World displays SuperMemo 7.3 at CeBIT '94
• March, SuperMemo is awarded for the best value/price ratio by the CENA/VYKON journal, Czech Republic
• May, SuperMemo 7 is awarded a prestigious Gold Medal at Infosystem Computer Fair in Poznan
• July, 10,000-th copy of SuperMemo has been sold
• August, SuperMemo USA, Inc. publishes SuperMemo 7.4 on CD-ROM, including the audio release of Advanced English best-seller. This title becomes the first Polish Windows software title on CD-ROM ever
• September, SuperMemo World is granted the special award of the fair's president at Softarg and receives a free display at Softarg 1995
• September, SuperMemo World signs its first OEM bundling deal with JTT, second largest computer-maker in Poland
• October, SuperMemo World publishes the European release of SuperMemo on CD-ROM
• October, SuperMemo 7.2 tops the ranking of best-selling software sold on illegal software market, ahead of Microsoft Word 6.0 and Microsoft Works 3.0 (PC World Komputer, Vol. 11, 1994)
• December, SuperMemo for Windows receives the Reader's Choice distinction from PC World Komputer (Vol. 12, 1994) by being voted second most popular Polish software in Poland and the most popular Polish Windows software in Poland
• December, Wozniak completes his Economics of learning. This doctoral dissertation was entirely devoted to the SuperMemo method and outlined the theoretical basis for the future versions of SuperMemo for Windows. The concept of Knowledge Machine was an inspiration for future Incremental Learning

1995

• January, SuperMemo 6 is released as freeware
• February, SuperMemo receives a positive review in the most prestigious European computer journal: German Chip
• March, releasing SuperMemo 1.0 for Macintosh (this version was later discontinued due to poor profitability)
• March, SuperMemo Worlds displays its Multilingual SuperMemo 7.5 CD-ROM at CeBIT'95
• April, Polish Prime Minister Waldemar Pawlak buys a copy of SuperMemo for personal use (he refused a free gift)
• April, SuperMemo User Survey reveals that users of SuperMemo consider the program their single most important application!
• April, SuperMemo World signs a comprehensive OEM deal with Optimus, the greatest computer-maker in Poland
• May, 30,000-th copy of SuperMemo has been sold
• September, five hundred beta-testers get their hands on a Pre-Release CD-ROM with the first hypermedia SuperMemo codenamed Genius - precursor of SuperMemo 8.0.
• November, SuperMemo World is the first Polish company ever to display its products at Comdex in Las Vegas (in the picture: Marczello Georgiew)

• 1996
  • January, SuperMemo is voted the best Polish application by readers of PC World, Komputer
  • January, first SuperMemo hypermedia CD-ROM title is released: Video English (with Genius 1.0, early precursor of SuperMemo 8)
  • June, SuperMemo Corporation is incorporated in the US with a goal of making it the first company of Polish origin on NASDAQ. The company came close to securing substantial venture capital but ultimately ... closed
  • September, Cross Country hypermedia best-seller CD-ROM is released (with Genius 2.0, precursor of SuperMemo 8)
  • September, precursor of SuperMemo 8, Genius 2.0, receives its first award as the hypermedia authoring tool at Softarg, Poland
  • October, 60,000 readers of Chip in Poland receive a CD-ROM with the full version of the hypermedia authoring SuperMemo (Genius 2.0). Free!
  • November, first Polish multimedia encyclopedia CD-ROM is released together with SuperMemo as an integrated tool for learning selected encyclopedic material
• 1997
  • January, SuperMemo World, Polish veteran of CeBIT and the first Polish company present at Comdex makes a strategic conversion towards the Internet away from major software fairs. SuperMemo Website at www.supermemo.com will become SuperMemo World's best marketing tool ever
  • January, Polish PWN Encyclopedia with SuperMemo is voted the best Polish software product by readers of PC Kurier
  • February, The Internet welcomes SuperMemo. This website becomes operational
  • February, SuperMemo 8 enters beta-testing. For the first time, beta-testing is run exclusively over the Internet with a dramatic impact on bug-spotting and reliability
  • May, over 100 international over-Internet beta-testers submit their final reports. This SuperMemo 8 beta-testing program alone brought more valuable data than all programs before
  • May 12, SuperMemo World releases Deine Chancen in Deutsch with SuperMemo 8 (first commercial CD-ROM with hypermedia SuperMemo)
  • June 12, for the first time ever SuperMemo can be downloaded from the web
  • Oct 22, 80,000 readers of Chip in Poland receive a CD-ROM with SuperMemo 8.0 (Free!) and a demo of Advanced English 97
  • November 6, SuperMemo Research is formed with the purpose of investigating Internet applications of SuperMemo and fostering international scientific, business, and educational contacts
  • November 10, Advanced English 97 with SuperMemo 8 is released
• 1998
  • January 14, SuperMemo 8 is chosen the Product of the Year 1997 by journalists of a respected Polish journal PC Kurier (ahead of MS Internet Explorer 4.0PL)

  

  • January 31, SuperMemo 8.4 ends the 16-bit line of SuperMemo for Windows (available for download from this website)
  • March 20, SuperMemo Library hosted by Michal Hejwosz and Piotr Maksimczyk is inaugurated at this website
  • May 25, SuperMemo World signs a licensing and distribution contract with Vulcan Media. By September 1998, the two companies will jointly develop the largest network of sales representatives in Poland covering virtually all software resellers in the country. Additionally, SuperMemo technology will become integrated with all new educational titles released by Vulcan Media (including the Multimedia Encyclopedia best-seller)
  • August 1, SuperMemo World as the first company in Eastern Europe opens an e-commerce store at Yahoo Stores
  • September 28 - SuperMemo 98 is released
  • November 27 - SuperMemo 98 is featured among most successful Delphi application at Inprise Corp. website
  • December 1 - SuperMemo appears on DVD as part of the best-selling Polish Multimedia Encyclopedia (PWN, 1999 Edition). This title has sold 45,000 copies in two years
• 1999
  • April 26, 300,000 copies of Easy English #1 CD-ROM have been released in Poland. This is the largest run of SuperMemo ever
  • May 10, SuperMemo MegaMix 99 is released with 319 SuperMemo collections written by users of SuperMemo (this collection took four years to compile!)
  • July 5, on the eighth anniversary of SuperMemo World, 1,000,000th CD-ROM with SuperMemo has been released
  • September, SuperMemo for Windows CE is released
  • October 4, SuperMemo 99 introduces a new concept: the reading list. Reading lists extend the application of SuperMemo to the area of knowledge acquisition, selection, prioritization, and formulation. SuperMemo 99 helps the user to read articles imported from the web and should further increase the gap between electronic and printed matter
  • November 23, in its probably greatest success ever, SuperMemo has been nominated to the title of the Product of the Decade by PC Kurier, Poland (among three other contenders)

  

• 2000
  • January, SuperMemo for Windows CE receives Real Mobility Award
  • March, SuperMemo for Palm Pilot is released
  • July, SuperMemo World s.c. and Internet Investment Fund, Poland, sign an agreement on the development of a system for Mobile learning with SuperMemo
  • November, SuperMemo 2000 introduces the concept of incremental reading that makes it possible to read hundreds of articles at the same time. This is probably the single most important development in the history of SuperMemo since the implementation of spaced repetition
  • December, Polish Orthography SuperMemo CD-ROM is listed among recommended educational tools by the Polish Ministry of Education
• 2001
  • April, SuperMemo goes Internet
• 2002
  • May, SuperMemo 2002 adopts HTML as the default data format in incremental reading
• 2004
  • May, SuperMemo for Pocket PC becomes the first SuperMemo to adopt the new XML data exchange format
  • September, SuperMemo 2004 adopts the XML data exchange format
• 2005
  • March, SuperMemo for Windows originally developed in Delphi 1.0 is 10 years old (it succeeded SuperMemo for Windows developed in Borland Pascal in the years 1992-1995)
  • March, First SuperMemo DVD: Extreme English DVD combines the most popular learning material (Advanced English) with the most widely distributed SuperMemo (Multimedia SuperMemo) 
  • May, SuperMemo 98 for Windows is released as freeware 
  • August, SuperMemo method is 20 years old
• 2006
  • SuperMemo 2006 for Windows in conjunction with SleepChart will now collect all data needed to study circadian correlates of learning. This will open new vistas to study the impact of sleep on learning (and vice versa)
• 2007
  • March, SuperMemo 2006 for Windows pioneers tools for tackling the overload of the learning material: priority queue, auto-sort and auto-postpone. This makes it possible to increase the volume of incremental reading without a detriment to the retention of the top priority material
  • Dec 13, SuperMemo software is 20 years old
• 2008
  • April, Wired Magazine publishes a 7 page article on the history of SuperMemo
  • December, a contract with the Polish Ministry of Education brings SuperMemo to 144,000 computers in Polish schools
• 2009
  • March, SuperMemo 2008 pioneers the optimization of learning based on the optimization of the timing of sleep. SuperMemo thus enters a long road towards the future in which sleep can be optimized for the sake of learning, while learning can be optimized with the view to the timing of sleep. The bridge between the two worlds initiates a process in which truckloads of data are being generated for investigating the relationship between sleep and memory. See: impact of sleep on learning
  • September, SuperMemo 2008 introduces the concept of incremental video, which is an extension of incremental reading into the world of video. It also makes further inroads in the area of visual learning
  • December, iPhone has its own SuperMemo too
• 2012

  • SuperMemo World opens SuperMemo Language Center in Poznan, Poland

• 2013
  • After 14 years of slow progress, the concept of Incremental Learning is largely complete with SuperMemo 16 for Windows

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See also:

• History of SuperMemo software development
• Wired Magazine: History of SuperMemo
• Interview with the author of SuperMemo (1994)
• Decade of SuperMemo
• The Decade interview (2001)
• Awards granted to SuperMemo
• (if you know Polish) Algorytm wkuwania: A few notes on the first steps of SuperMemo at University of Technology in Poznan in 1987 collected by Andrzej P. Urbanski - teacher of computer science of Piotr Wozniak, Krzysztof Biedalak and Tomasz Kuehn who all set up SuperMemo World in 1991