How retrieval practice works part 1

You’re right to be interested in retrieval practice.

Retrieval practice is the use of low-stakes testing (written/verbal questions) to benefit pupils’ long-term memories (McDaniel at al., 2007). It’s more effective than non-testing methods like re-reading.

Used in conjunction with other effective teaching methods, retrieval practice has the potential to be a powerful tool for teachers.

The value of retrieval has been known for over a century (Myers, 1914).

Positive evidence can be seen –

  • In educational settings (Yang et al., 2021).
  • With college and university-aged pupils (Foss & Pirozzolo, 2017; Thomas et al., 2020).
  • With school-aged pupils (Marsh et al., 2012; McDaniel et al, 2011; Rowley & McCrudden, 2020).
  • With pre-school children (Fritz et al., 2007).
  • Using various materials (Carpenter, 2009; Roediger & Karpicke, 2006; Carpenter & Pashler, 2007).
  • Using various test types (Yang et al, 2021).


Retrieval practice research with real teachers in classroom settings doesn’t consistently find positive/strong positive benefits (Churches et al., 2020; Perry et al., 2021).

Something gets lost in translation.

Two things may help:

  1. More high-quality classroom studies (Churches et al., 2020).
  2. A better understanding of the mechanisms driving the benefits of retrieval (Carpenter, 2009).

In this blog we uncover two mechanisms that help explain why retrieval practice works and we’ll see how they might guide teachers. In part 2, we discover two more mechanisms.

Remember, neuroscience can’t tell teachers what to do. Neuroscience is one source of valuable evidence to help teachers make better decisions.

First, let’s be clear what we want for pupils’ memories…

Storage and retrieval strength

Memory has two dimensions (Bjork & Bjork, 1992):

Storage strength – how deep-rooted/interconnected memories are.

Retrieval strength – how accessible memories are.

Teachers want pupils to have lasting and accessible knowledge. This means building storage and retrieval strengths.

Imagine asking a pupil to retrieve what ‘conduction’ is. To answer well, the pupil needs:

(1) Stored knowledge.

(2) Clear paths to the knowledge, i.e., the knowledge doesn’t get confused with related knowledge about ‘convection’.

In this blog I’ll use neuroscientific evidence to show that retrieval practice improves storage strength by speeding up memory storage and improves retrieval strength by clearing paths to the target memory.

Mechanism 1: reactivation speeds up storage

Storing memories means building on what we know (Shing & Brod, 2016).

Storing memories = learning

The process for storing memories in the brain is called consolidation (Dudai, 2012). Fragile memory traces are transformed into stable knowledge in networks called schemas.

The driving force for consolidation is memory reactivation. Memories are reactivated and replayed (neural replay) to relevant schemas (Deuker et al., 2013). Parts of the memories are extracted and stored.

Figure 1.

Parts of the memory (red dots), through neural replay (reactivation), consolidate into the schema (red dot network).

The thing is, neural replay (reactivation) happens during rest and sleep. Rest and sleep tend to happen at a delay after we encounter the information.

But what if we didn’t have to wait for rest and sleep? We could speed up memory consolidation (storage).

Retrieving information from memory is another form of reactivation that may act similarly to neural replay (Antony et al., 2017).

Except this reactivation happens when we retrieve information. There’s no delay.

Retrieving information from memory therefore –

  • Reactivates the memory mimicking neural replay.
  • Triggers consolidation (storage) quickly (Anthony et al., 2017; Ferreira et al., 2018; Wing et al., 2013; Ye et al., 2020).*
  • Slows forgetting.

Retrieval practice therefore improves storage strength by stabilising memories quickly.

But why does the brain do this when we retrieve a memory?

By forcing ourselves to retrieve information rather than look it up, we’re telling our brains –

“This information is important and unavailable in our environment… learn it.”

The brain invests resources in storing the information because storing it means less effort accessing it next time!

Now you know why “memory is the residue of thought” (Willingham, 2009):

‘thought’ = ‘reactivation’ and reactivation is a mechanism for learning.

What might this mean for teachers?

(1) Invest in retrieval

Retrieval may speed up memory storage i.e., learning. This makes it (potentially) a very powerful strategy.

But sometimes the obvious gets overlooked: retrieval is just a strategy.

What we ask pupils to retrieve is of fundamental importance.

There isn’t time in lessons for pupils to practise retrieving everything you teach. But it’s a promising enough strategy to warrant investing energy deciding what the important knowledge/skills are that pupils should retrieve and practise.

Zoom out to plan retrieval at curriculum level whilst allowing flexibility to be responsive at lesson level.

(2) Prioritise feedback

Retrieval practice could be a double-edged sword…

If pupils retrieve the wrong answer, they may store the error (Bridge & Paller, 2012).

How do we protect against this?

We prioritise time for feedback (Agarwal et al., 2020).

Imagine we set a retrieval practice task at the end of the lesson – a quick ‘exit ticket’ (Lemov, 2021, pp.228-233). We scan pupils’ answers and plan time to give feedback that pupils engage with next lesson.

We could also factor in another retrieval attempt in next lesson’s exit ticket for questions many pupils got wrong.**

Mechanism 2: coactivation clears paths

Our brains adapt so they can –

  1. best represent our environment and
  2. preserve future energy/resources.

One thing that violates both goals is memory interference.

Interference is when your brain can’t distinguish between related/competing memories (Anderson & Neely, 1996).

Think of the pupil who cannot decide if something is an example of ‘conduction’ or ‘convection’. The memories of each concept aren’t properly distinguished: they interfere. This leads to confusion and energy expenditure.

A remedy?


When retrieving an answer, we tend to imprecisely search our memories. It’s messy, like rummaging through a cupboard to reach the ketchup, other stuff gets disturbed.

Whilst searching for the target, we coactivate related memories. For example, when trying to retrieve what a simile is, I coactivate knowledge of metaphors.

Coactivating memories reduces interference by changing the strength of the connections between the memories.

Think of solving the interference problem like resolving a fight between kids: you either get them to make up (integrate) or you separate them (distinction) (Paller et al., 2020). The brain uses integration and distinction too (Ritvo et al., 2019).

During retrieval:

  • Strong coactivation of memories strengthens their connections which integrates the knowledge; they can be recalled together next time, reducing interference.
  • Moderate coactivation of memories weakens their connections which separates the knowledge; each can be recalled in isolation next time, reducing interference.***

Figure 2

Connections to the target memory (green dot) are either strengthened (thick black lines) or weakened (dashed lines) after retrieval. This reduces interference.

Next time we retrieve the memory, the path is clearer. Retrieval strength has improved.

Changing connections between memories changes the relationships between our knowledge. It changes the very way we think.

Now consider ‘re-reading’ information.

When we re-read, we reactivate the same memory trace. There’s much less coactivation, much less path-clearing and much less benefit to memory.

What might this mean for teachers?

(1) Vary retrieval practice questions

Retrieval (through coactivation) changes the strength of connections between memories. It changes the relationships between pupils’ knowledge.

It can be tempting to use the same set of retrieval questions across lessons. The problem is, asking retrieval questions in the same way creates only one set of relationships, only one path to that knowledge.

We want multiple paths. This increases retrieval strength.

To do this, we vary retrieval questions that target the same knowledge.

Figure 3

(2) Minimise cues

By minimising cues, we force pupils to effortfully search their memory to retrieve information.

My hunch: more searching -> more coactivation -> greater benefit to memory.

How do you minimise cues?

  • Rephrase questions to provide fewer/vaguer cues as pupils’ knowledge grows.

For example:

[Specific cue] “Which of these is an example of alliteration?”

[Vaguer cue] “Which language device is used in each of these examples?”

  • Give fewer cues/hints to pupils. Practise being comfortable with silence whilst they think.

This links to the finding that optimal retrieval conditions balance effort with success (Endres & Renkl, 2015): pupils should work as hard as possible to successfully retrieve the answer.

To do this, try providing just-in-time verbal or written hints if you think pupils will be unsuccessful without them.

In the next blog, we discover two more mechanisms that provide insights into how we might use retrieval practice better.

*Retrieved memories are not ‘fully’ consolidated (if there is such thing (Dudai, 2012)) and interact with the brains usual consolidation processes during rest/sleep although it is not yet clear exactly how (Ferreira et al., 2018).

**It’s difficult to know if pupils have ‘retrieved’ an error rather than just guessed e.g. when using multiple-choice questions, pupils might ‘recognise’ rather than ‘retrieve’ the wrong answer. Either way though, providing another opportunity for retrieval (after feedback) is unlikely to be harmful.

*** This can happen simultaneously in different brain areas creating multiple co-existing memory traces for the same information, some integrated and some distinct (Schlichting et al., 2015). This may allow us to understand relationships between knowledge whilst preserving individual pieces of knowledge.


Agarwal, P. K. (2020). Retrieval Practice: A Power Tool for Lasting Learning. Educational Leadership, 77(8), 76-81.

Anderson, M. C., & Neely, J. H. (1996). Interference and inhibition in memory retrieval. In Bjork, E. L., & Bjork, R. A. (Eds.), Memory Handbook of perception and cognition (pp. 237-313). Academic Press.

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Carpenter, S. K. (2009). Cue strength as a moderator of the testing effect: The benefits of elaborative retrieval. Journal of Experimental Psychology: Learning, Memory, & Cognition, 35, 1563e1569.

Carpenter, S. K., & Pashler, H. (2007). Testing beyond words: Using tests to enhance visuospatial map learning. Psychonomic Bulletin & Review, 14(3), 474-478.

Churches, R., Dommett, E. J., Devonshire, I. M., Hall, R., Higgins, S., & Korin, A. (2020). Translating Laboratory Evidence into Classroom Practice with Teacher‐Led Randomized Controlled Trials—A Perspective and Meta‐Analysis. Mind, Brain, and Education14(3), 292-302.

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Ferreira, C. S., Charest, I., & Wimber, M. (2018). Retrieval aids the creation of a generalised memory trace and strengthens episode-unique information. NeuroImage, 201, 115996.

Foss, D. J., and Pirozzolo, J. W. (2017). Four semesters investigating frequency of testing, the testing effect, and transfer of training. Journal of Educational Psychology. 109, 1067–1083.

Fritz, C. O., Morris, P. E., Nolan, D., & Singleton, J. (2007). Expanding retrieval practice: An effective aid to preschool children’s learning. Quarterly Journal of Experimental Psychology, 60(7), 991-1004.

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Rowley, T., & McCrudden, M. T. (2020). Retrieval practice and retention of course content in a middle school science classroom. Applied Cognitive Psychology, 34(6), 1510-1515.

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Thomas, A. K., Smith, A. M., Kamal, K., & Gordon, L. T. (2020). Should you use frequent quizzing in your college course? Giving up 20 minutes of lecture time may pay off. Journal of Applied Research in Memory and Cognition, 9(1), 83-95.

Willingham, D. T. (2009). Why Don’t Students Like School?: A Cognitive Scientist Answers Questions About How the Mind Works and What It Means for the Classroom. Jossey Bass.

Wing, E. A., Marsh, E. J., & Cabeza, R. (2013). Neural correlates of retrieval-based memory enhancement: an fMRI study of the testing effect. Neuropsychologia, 51(12), 2360-2370.

Yang, C., Luo, L., Vadillo, M. A., Yu, R., & Shanks, D. R. (2021). Testing (quizzing) boosts classroom learning: A systematic and meta-analytic review. Psychological Bulletin.

Ye, Z., Shi, L., Li, A., Chen, C., & Xue, G. (2020). Retrieval practice facilitates memory updating by enhancing and differentiating medial prefrontal cortex representations. Elife, 9, e57023.

10 thoughts on “How retrieval practice works part 1

  1. Really enjoyed reading this blog and would like to save it/get a copy along with access to other related material.


    1. Hi Stephen, thanks for reading and for picking up on this. Reference here and I’ll add it in.
      2020): 292-302.
      Churches, R., Dommett, E. J., Devonshire, I. M., Hall, R., Higgins, S., & Korin, A. (2020). Translating Laboratory Evidence into Classroom Practice with Teacher‐Led Randomized Controlled Trials—A Perspective and Meta‐Analysis. Mind, Brain, and Education, 14(3), 292-302


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