The retention interval, or RI, refers to the amount of time following the last spaced study session before a final test (aka: test delay).

Spacing variables: Retention Interval (RI)

The spacing interval refers to the interval of time separating different study sessions (aka: lag).

Spacing variables: Spacing Interval

The two main variables influencing the spacing effect are the spacing interval (lag) and the retention interval (test delay).

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Long-term recall is improved when studying is broken up into many short sessions rather than long concentrated ones (memory consolidation is improved). 

Spacing effect

Carvalho, P.F., Sana, F. & Yan, V.X. (2020). Self-regulated spacing in a massive open online course is related to better learning. npj Sci. Learn. 5(2), 1-7.

Self-regulated spacing in a massive open online course is related to better learning

- Origins of the spacing effect (early literature)
- Displays of spacing effect in different domains
- Spacing v. Massing

Types of references on the spacing effect

The spacing effect has been shown to improve long-term recall in a variety of domains such as: 
- Conditioning (even in non-human animals)
- Verbal learning
- Motor learning
- Learning educational material

Scope of the spacing effect (different domains)

Spacing has shown to improve long-term recall more than massing by many studies. Some people however (such as E.Z. Rothkopf during in September of 1977), have posited that massing is better mode of studying when dealing with problems of induction. Kornell, N., & Bjork (2008) presented compelling evidence against this claim (spacing is also better for induction).

Effects of Spacing compared to Massing

Spacing effect variables

A memory strategy where one associates multiple items with each other by using imagery, sentence generation, or other strategies (e.g. dog and spoon).

Mediators

Spacing out study sessions over time rather than cramming in one night has been found to be highly effective, especially in long-term retention of information.

Rated as high utility. It has wide generalization, is easy to implement and has been found to effectively boost academic performance.


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