Editing Spacing effect (section)

== Practical applications and long-term retention ==

===Advertising===
The spacing effect and its underlying mechanisms  have important applications to the world of advertising. For instance, the spacing effect dictates that it is not an effective advertising strategy to present the same commercial back-to-back (massed repetition). Spaced ads were remembered better than ads that had been repeated back to back.<ref name=":1">{{Cite book|title=The Psychology of Advertising|last1=Fennis|first1=Bob|last2=Stroebe|first2=Wolfgang|publisher=Psychology Press|year=2010|isbn=978-0203853238|location=Hove|pages=104}}</ref> Layout variations presented in short spacing intervals also resulted in improved recall compared to ads presented in exact repetition.<ref name=":1" /> The same effect was also achieved in a study involving website advertisements. It was revealed that sales diminish progressively as the customer visited the site and was exposed to the ad several times. However, if the elapsed time between the visits was longer, the advertisement had a bigger effect on sales.<ref>{{Cite book|title=Handbook of Marketing Decision Models, Second Edition|last1=Wierenga|first1=Berend|last2=Lans|first2=Ralf van der|publisher=Springer|year=2017|isbn=9783319569390|location=Cham|pages=193}}</ref> If encoding variability  is an important mechanism of the spacing effect, then a good advertising strategy might include a distributed presentation of different versions of the same ad.

Appleton-Knapp, Bjork and Wickens (2005)<ref>{{cite journal | doi = 10.1086/432236 | volume=32 | title=Examining the Spacing Effect in Advertising: Encoding Variability, Retrieval Processes, and Their Interaction | year=2005 | journal=Journal of Consumer Research | pages=266–276 | last1 = Appleton-Knapp | first1 = Sara L.| issue=2 }}</ref> examined the effects of spacing on advertising. They found that spaced repetitions of advertisements are more affected by study-phase retrieval processes than encoding variability. They also found that at long intervals, varying the presentation of a given ad is not effective in producing higher recall rates among subjects (as predicted by variable encoding). Despite this finding, recognition is not affected by variations in an ad at long intervals.

===Application in education===
Studies have shown that long-term spacing effects are prevalent in learning and produce significant learning gains, particularly when the spacing gaps are on the order of days or weeks.<ref>{{Cite book|title=Learning and Memory: A Comprehensive Reference|last=Byrne|first=John|publisher=Academic Press|year=2017|isbn=9780128051597|location=Boston, MA|pages=481}}</ref> Although it is accepted that spacing is beneficial in learning a subject well and previous units should be revisited and practiced, textbooks are written in discrete chapters that do not support these findings. Rohrer conducted a two-part study in 2006 where students were taught how to solve math problems.<ref>{{Cite journal|last1=Rohrer|first1=Doug|last2=Taylor|first2=Kelli|date=April 19, 2007|title=The shuffling of mathematics problems improves learning|url=https://www.researchgate.net/publication/227181272|journal= Instructional Science|doi=10.1007/s11251-007-9015-8|access-date=April 23, 2016|volume=35|issue=6|pages=481–498|s2cid=55686289}}</ref> In part 1, students either used mass or spaced practice, and spaced practice showed significant improvement over mass practice when tested one week later. In the second part of the experiment, practice problems were either grouped by type or mixed randomly. The desirable difficulties encountered by the randomly mixed problems were effective, and the performance by students who solved the randomly mixed problems was vastly superior to the students who solved the problems grouped by type. The reasoning behind this increased performance was that students know the formula for solving equations, but do not always know when to apply the formula. By shuffling problems around and dispersing them across multiple chapters, students also learn to identify when it is appropriate to use which formula. There is conclusive evidence that cumulative final exams promote long-term retention by forcing spaced learning to occur.

===Learning and pedagogy===
The long-term effects of spacing have also been assessed in the context of learning a foreign language. Bahrick et al. (1993)<ref>{{Cite journal |last=Bahrick |first=Harry P. |last2=Bahrick |first2=Lorraine E. |last3=Bahrick |first3=Audrey S. |last4=Bahrick |first4=Phyllis E. |date=1993 |title=Maintenance of Foreign Language Vocabulary and the Spacing Effect |url=https://www.jstor.org/stable/40063054 |journal=Psychological Science |volume=4 |issue=5 |pages=316–321 |issn=0956-7976}}</ref> examined the retention of newly learned foreign vocabulary words as a function of relearning sessions and intersession spacing over a nine-year period.

Both the amount of relearning sessions and the number of days in between each session have a major impact on retention (the repetition effect and the spacing effect), yet the two variables do not interact with each other.

For all three difficulty rankings of the foreign words, recall was highest for the 56-day interval as opposed to a 28-day or a 14-day interval. Additionally, 13 sessions spaced 56 days apart yielded comparable retention to 26 sessions with a 14-day interval.

These findings have implications for educational practices. Current school and university curricula rarely provide students with opportunities for periodic retrieval of previously acquired knowledge.<ref>[http://www.huffingtonpost.co.uk/james-gupta/the-death-of-the-universi_b_8173492.html "The death of the university lecture"], Huffington Post, retrieved 2016-25-04</ref> Without spaced repetitions, students are more likely to forget foreign language vocabulary.

=== Lag effect ===
While the spacing effect refers to improved recall for spaced versus successive (mass) repetition, the term 'lag' can be interpreted as the time interval between repetitions of learning. The ''lag effect'' is simply an idea branching off the spacing effect that states recall after long lags between learning is better versus short lags.<ref>{{Cite journal|last=Kahana|first=Michael|date=2005|title=Spacing and lag effects in free recall of pure lists|url=https://memory.psych.upenn.edu/files/pubs/KahaHowa05.pdf|journal=Psychonomic Bulletin & Review|volume=12|issue=1|pages=159–164|doi=10.3758/bf03196362|pmid=15948289|s2cid=18549788|access-date=April 22, 2016|doi-access=free}}</ref> Michael Kahana's study showed strong evidence that the lag effect is present when recalling word lists. In 2008, Kornell and Bjork published a study<ref>{{Cite journal|last=Kornell, Bjork|first=Nate, Robert|date=2008|title=Is Spacing the "Enemy of Induction"?|url=http://psych.colorado.edu/~ketels/psych4145/Kornell.Bjork.2008a.pdf|journal=Psychological Science|volume=19|issue=6|pages=585–592|doi=10.1111/j.1467-9280.2008.02127.x|pmid=18578849|s2cid=18139036|access-date=April 23, 2016}}</ref> that suggested inductive learning is more effective when spaced than massed. Inductive learning is learning through observation of exemplars, so the participants did not actively take notes or solve problems. These results were replicated and backed up by a second independent study.<ref>{{Cite journal|last1=Verkoeijen|first1=Peter P. J. L.|last2=Bouwmeester|first2=Samantha|date=January 1, 2014|title=Is spacing really the "friend of induction"?|journal=Frontiers in Psychology|volume=5|pages=259|doi=10.3389/fpsyg.2014.00259|issn=1664-1078|pmc=3978334|pmid=24744742|doi-access=free }}</ref>