Buyer beware: SLA and the spacing effect

Second language acquisition (SLA) often borrows ideas from other disciplines, along with the advantages this brings (e.g. the positive benefits of spaced repetition software for vocabulary learning) potential dangers need to be assessed. This post summarises the case of the spacing effect from cognitive psychology as discussed by John Rogers (2017).


You may remember when at school being told not to cram for an exam, this advice is based on robust studies from cognitive psychology which show positive benefits of spreading out or distributing the times when studying (distributed practice) compared to learning something in one go (massed practice). This is known as the spacing effect. Rogers (2017) points out four differences between how cognitive psychology and SLA has explored this effect – 1. operationalization of massed/distributed training; 2. relationship between session times and testing times; 3. complexity of stimuli; and 4. conceptualisation of “practice”.

Differences in use

  1. SLA has often used what is referred to as the “lag” effect and not actually to the “spacing” effect. The lag effect is due to the differences between two distributed learning conditions whereas the spacing effect refers to comparing massed practice to distributed practice. In contrast to spacing effects being well established in cognitive psychology, lag effects are not as well established.
  2. Spreading out your study time may not have a simple relationship with the spacing effect i.e. longer gaps between study sessions or what is called inter-session intervals (ISI) may not result in better performance when you are tested (retention interval, RI). There is thought to be an optimum ISI:RI ratio for different aspects of learning a language which may differ from ratios suggested in the cognitive psychology literature. Conversely finding positive benefits of massed practice may not negate benefits of distributed practice.
  3. Cognitive psychology suggests that complexity of stimuli could be a moderating variable in optimum ISI:RI ratios. In SLA this could mean that simple vocabulary learning may benefit from large spacing effects but more complex speaking proficiency may not. However, even in the psychology literature the issue of stimuli complexity as a moderator for the spacing effect is questioned.
  4. Finally massed practice is conceptualized in cognitive science studies as only two training sessions, back to back, where participants reach a level of “mastery” or pre-determined learning point in the sessions. In the second training session mastered material is reviewed and re-consolidated. Thus such studies are not looking at multiple training sessions vs one training session. Further saying what is mastery in language learning is problematic, though maybe less so in learning vocabulary than in other language learning areas.

So what?

Although the specifics of the spacing effect case may not interest you, I hope you consider the general point that the pitfalls of borrowed ideas is important when assessing SLA studies. Currently, in the wider educational field, secondary school teacher advocacy of cognitive science findings to the classroom is becoming widespread. However, as can be seen here for the spacing effect, one needs to carefully weigh up how to interpret such work. One thing to look out for then are the differences in use when borrowing constructs from other disciplines.


Rogers, J. (2017). The Spacing Effect and its Relevance to Second Language Acquisition. Applied Linguistics, amw052.


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Mura Nava
Interested in most things language wise. Member of TaWSIG, Teachers as Workers Special Interest Group which promotes discussion and action on working conditions in language teaching. Check us out at

4 thoughts on “Buyer beware: SLA and the spacing effect”

    1. Hi Jenny
      Are you referring to this research-bite article or the reference article?

      as far as I know both are in English : ) Did you mean something else?

  1. Very good point, Mura: beware rushing to simplistic conclusions about an unproven, very general line of investigation. You sum up the article, which is pretty thin soup really, well. .

    1. hi Geoff
      I guess u could say this is a summary of a summary : )
      I was not aware of the issues in the spacing effect and I read this article at the same time as some critical commentary of some applications of cognitive science in school teaching;
      though it is remarkable that the spacing effect is “large” enough to be relevant in language learning (e.g. spaced repetition of vocab learning) and not worry too much about the pitfalls : )

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