Have you ever crammed right before a test, only to forget almost all the data soon thereafter? The spacing effect is the phenomenon whereby we learn more when our study session are spread out over time instead of us doing all the studying in the same session – even if the amount of time spent and material studied is exactly the same in both scenarios.

In scientific experiments, the spacing effects has been noticed for many different memory tasks, including recognition, cued recall, free recall and frequency estimation.

N.B! The benefit of spaced study sessions does not appear at short retention intervals.

One of the first researchers to study the spacing effect was Herman Ebbinghaus, who wrote about it in his book Über das Gedächtnis. Untersuchungen zur experimentellen Psychologie (Memory: A Contribution to Experimental Psychology), published in 1885.

Spacing effect and advertising

The spacing effect is a well-known phenomenon among marketers, who use their knowledge about the spacing effect when putting together marketing campaigns. This is one of the reasons why you rarely see the same commercial repeated back-to-back on TV. Also, since encoding variability is an important aspect of the spacing effect, skilled marketers tend to present us with a distributed presentation of somewhat different versions of the same commercial.

Suggested reading

Sara L. Appleton‐Knapp, Robert A. Bjork and Thomas D. Wickens “Examining the Spacing Effect in Advertising: Encoding Variability, Retrieval Processes, and Their Interaction” The Journal of Consumer Research Vol. 32, No. 2 (September 2005), pp. 266-276. The University of Chicago Press.

How to use the spacing effect to your advantage

Utilizing the spacing effect to our advantage makes it easier for us to learn and retain information. By tailoring our study and practice sessions properly, we can become more efficient and proficient learners.

In 2006, a study1 was conducted where students were taught how to solve mathematical problems. A week later, they were tested. In this study, spaced practice yielded significantly better results than mass practice.

An ambitious multi-year study2 of the long-term effects of spacing when learning a foreign language was carried out by Bahrick et al and published in 1993. The researchers examined the retention of newly learned foreign language words over a 9-year period. They found that both the amount of relearning sessions (the repetition effect) and the number of days in between each session (the spacing effect) had a significant impact on retention. The 56-day interval yielded a better recall than the 28-day interval and the 14-day interval. Bahrick and his team also found that 13 sessions spaced 56 days apart yielded roughly the same result as 26 sessions spaced 14 days apart.

So, if you have limited time to spend on study sessions where you repeat previously learned material, getting the optimal spacing is important.

The lag effect

The term lag is sometimes used to denote the time interval between repetitions of learning. The lag effect is thus a branch of the spacing effect. The lag effect is why recall after long lags between repetition is better than when the lag has been short.

Suggested reading:

Kahana, Michael (2005). “Spacing and lag effects in free recall of pure lists” (PDF). Psychonomic Bulletin & Review.

Verkoeijen, Peter P. J. L.; Bouwmeester, Samantha (2014-01-01). “Is spacing really the “friend of induction”?” Frontiers in Psychology. 5: 259