Date: May 28 2020
Summary: A summary of the spacing effect
Keywords: ##zettel #spacing #effect #archive
The spacing effect accounts for the fact that learning is improved when studying is spread out over time. It was first discovered and described by Hermann Ebbinghaus during 1880 - 1885.  His findings were later accurately reproduced and documented by Murre & Dros.  (Click for results of that study here)
The spacing effect has not been very well utilized in US-based education institutes despite its multitudinous benefits.  Cepeda et al. determined that in a memory based challenge, spaced based learning outperformed massed learning ~96% of the time.  This coincides with the deficient processing view posited by Hintzman that stated how massed repetition leads to a lack of attention in later reviews. 
According to Pyc and Rawson, labored but correct recall while practicing improves memory. Spacing items of recall produce greater effort during retrieval and enables thorough conversion of the item to memory.   Semantic processing of information during repetitions assists in making that information more anti-fragile, to borrow from Nassim Taleb, during reviews. This causes performance in later memory testing to be unaffected by changes in such things like the type of font used when presented information.  
However, a confounding factor in the idea of the spacing effect is the encoding variability theory. This theory states that one's performance on a memory test is related to overlaps amongst current contextualized material both during testing and while encoding. According to this view, spaced repetition typically entails some variability in presentation contexts. Yet, this results in a positive outcome being that there are then more retrieval cues associated with that material. 
However, there are concerns about the spacing effect that have impeded its overall adoption into educational formats. Dempster made a case examining potential rationales for the lack of adoption in a review of the current state of the spacing effect (though the study is old over 30 years old, it still remains that education systems do not incorporate the spacing effect).  His biggest point of concern was the lack of studies that showed effective classroom utilization of the method.
Despite such misgivings, it is still a phenomenon that have given rise to many benefits and potential applications for at least personal education. Principle of which is in the form ofspaced repetition systems. These systems have determined the best spacing algorithms for a learner to use the spacing effect to assist in learning diverse educational material.
Lag: the length of time between learning repetitions. 
 This is known as the retrieval effort hypothesis.
 Short-term perceptual priming is the mechanism that supports the spacing effects in cued-memory tasks when unfamiliar stimuli are used as targets.
Zelko, Jacob. Spacing Effect. https://jacobzelko.com/05282020163507-spacing-effect. May 28 2020.
 H. Ebbinghaus, “Ueber das gedächtnis,” 1885.
 J. M. J. Murre and J. Dros, “Replication and Analysis of Ebbinghaus’ Forgetting Curve,” PLoS ONE, vol. 10, no. 7, p. e0120644, Jul. 2015, doi: 10.1371/journal.pone.0120644.
 F. N. Dempster, “A Case Study in the Failure to Apply the Results of Psychological Research,” Am. Psychol., p. 8, 1988.
 N. J. Cepeda, H. Pashler, E. Vul, J. T. Wixted, and D. Rohrer, “Distributed practice in verbal recall tasks: A review and quantitative synthesis.” Psychol. Bull., vol. 132, no. 3, p. 354, 2006.
 D. L. Hintzman, “Theoretical implications of the spacing effect.” 1974.
 M. A. Pyc and K. A. Rawson, “Testing the retrieval effort hypothesis: Does greater difficulty correctly recalling information lead to higher levels of memory?” J. Mem. Lang., vol. 60, no. 4, pp. 437–447, 2009.
 N. Mammarella, R. Russo, and S. Avons, “Spacing effects in cued-memory tasks for unfamiliar faces and nonwords,” Mem. Cognit., vol. 30, no. 8, pp. 1238–1251, 2002.
 S. M. Cormier, Basic processes of learning, cognition, and motivation. Psychology Press, 2014.
 M. J. Kahana and M. W. Howard, “Spacing and lag effects in free recall of pure lists,” Psychon. Bull. Rev., vol. 12, no. 1, pp. 159–164, 2005.