Exam preparation: Retrieval practice and interleaving

Written by: John Dabell | Published:
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Research shows that two of the most effective revision and study techniques are those of retrieval practice and interleaving. John Dabell looks at what the various academic studies can tell us

Many students do not know how to study effectively and often rely on time-consuming techniques or approaches that do not promote longer term learning and retention.

As Taylor (2017) points out, when left their own devices, students are over-reliant on “bamboo revision strategies”, those techniques that have “pitifully low neurological value” – such as re-reading their notes, highlighting key details and summarising (see also Cohen, 2013). They also avoid a “practice, practice, practice” regime.

There is no one-size-fits-all approach when learning how to effectively study, but there are some techniques that have been proven to work better than others. It is these evidence-based methods based on decades of learning science research that we need to tap into.

Professor John Dunlosky of Kent State University reviewed 1,000 scientific studies looking at 10 of the most popular revision strategies and found the two most effective methods are retrieval practice/practice testing and spaced practice/distributed practice (Dunlosky et al, 2013).

He says they can help students of any age and “they can enhance learning and comprehension of a large range of materials, and, most important, they can boost student achievement” (Dunlosky, 2013).

Retrieval practice

Reconstructing knowledge by recall improves meaningful learning. The Dunlosky et al research says testing can enhance retention by triggering elaborative retrieval processes and the more difficult and effortful the retrieval practice, the better it is for long-term learning (Karpicke, 2016).

Retrieval is the active process we engage in to boost learning and this might be as simple as engaging in recall-based self-testing using the copy-cover-check method.

There are many ways to practise retrieving information and promoting retrieval practice in the classroom and typically this involves giving students frequent tests (multiple-choice, short-answer, and fill-in-the-blank tests), quizzes, “do it now” tasks and challenge grids. Students can make their own practice questions or find questions from online sources, and teachers can use the exit tickets approach (for more on exit tickets, see Dabell, 2018).

Another great way to recall information is via the humble flashcard. These can be hand-made on index cards (questions on one side, answers on the reverse). Students can also make flashcards on a computer and print them out or use flashcard software.

Dunlosky et al (2013) note that practice testing with feedback consistently outperforms practice testing alone and Karpicke (2016) adds that when practising retrieval, students need to retrieve more than once and space their retrievals as this will bolster long-term learning.

Although students might think that rereading information works best, Roediger and Karpicke (2006) found that students who used mainly retrieval practice remembered more than 50 per cent more than those who had just read and reread material.

Retrieval practice does more than improve memorisation skills, it also increases understanding by improving complex thinking and application skills, organisation of knowledge and transfer of knowledge to new concepts (Pan & Rickard, 2018).

Furthermore, it has been shown that the act of taking practice tests has positive wellbeing effects. Smith et al (2016) found that retrieval practice is particularly effective at combatting the negative effect of stress on memory.

A final word of warning though: marking in red apparently pen hinders retrieval practice (for more on this, see Gnambs et al, 2015).

Distributed practice

The second effective revision strategy is spaced practice, where learning occurs over multiple sessions at different points in time. This strategy has been demonstrated in more than 200 research studies. When making memories, time really matters (Kelley et al, 2018).

Lots of students will cram right before an exam, but a more effective strategy is to distribute preparation over multiple sessions – committing something to memory takes time and repetition. The message then is space, not race.

Research suggests that there is an “optimal gap” between revision sessions in order to better retain the information. By spacing their learning activities out over time, e.g. one to two hours every other day, or at least once per week, students will be able to learn more information and retain it more effectively than after a marathon of cramming.

The gap between revision sessions should be between 10 and 20 per cent of the total time students want to retain the information. If a test is in a month, students should review their information around once a week. If the test is in a week, they need to create time once a day (Cepeda et al, 2008).

Having lots of spaced sessions allows students to “divide and conquer” by focusing on sections, portions and subsets of information rather than trying to cover everything. This allows students to spend more time processing and integrating important concepts and details and each study session gives them an opportunity to revisit and review what they have previously learned.

Distributing their efforts allows students to more effectively encode information into long-term memory, fill in any knowledge gaps and be better equipped to use that information.

Rohrer and Taylor (2007) found that students who spaced out their revision sessions did considerably better than those who crammed. Those who distributed their practice got an average of 74 per cent compared to crammers who got 49 per cent. Clearly then information needs to be covered and then recovered.

The Learning Scientists website tells us that spacing is effective because it allows time for topics to be forgotten and relearnt, it cements information into long-term memory and we can learn more information over time than in one longer session.

Spacing as a technique has been described by Bjork and Bjork (2011) as “one of the most robust across the entire history of experimental research on learning and memory” and Dunlosky’s research (2013) has found using spacing instead of cramming has resulted in a 10 to 30 per cent difference in final test results.

Spacing of practice improves long-term retention because students are using maintenance rehearsal to revisit material over time and thus strengthen the memory trace (Kelley & Watson, 2013).

What else works?

Related to spacing is interleaving. Brown et al (2014) in their book Make It Stick say: “Research shows unequivocally that mastery and long-term retention are much better if you interleave practice than if you mass it.”

Interleaving , shuffling and mixing practice by switching between different kinds of problems, questions and subjects is also effective and the research found that it had “relatively dramatic effects on students’ learning and retention of mathematical skills” (Dunlosky et al, 2013) and also supports other kinds of cognitive skills.

The key to interleaving is basically to “jumble” things up (Smith et al, 2017) and as Pan (2015) says, “mixing it up boosts learning” compared to more traditional methods of block learning where students master one topic before moving on to the next in preparation for exams.

Researchers think that interleaving improves the brain’s ability to tell apart, or differentiate, between concepts and this strengthens memory associations (Rohrer, 2012). As the brain has to continuously focus on searching for different solutions it is more taxing than studying just one topic for a long time, and this difficulty means the brain has to work harder, which means it remembers more. Interleaving allows better discrimination.

Other strategies for effective learning that cognitive psychologists have found include, Elaboration, Concrete Examples and Dual Coding (see The Learning Scientists’ website for more details).

  • John Dabell is a teacher, teacher trainer and writer. He has been teaching for 25 years and is the author of 10 books. He also trained as an Ofsted inspector. Visit www.johndabell.com and read his previous best practice articles for SecEd via http://bit.ly/2gBiaXv

Further information & research

  • Bjork & Bjork: Making things hard on yourself, but in a good way: Creating desirable difficulties to enhance learning, (in Psychology and the Real World, Gernsbacher et al (ed), Worth Publishers, 2011: http://bit.ly/2Z1Ye86
  • Bjork: Spacing improves long-term retention, GoCognitive YouTube video with Robert Bjork (2012): http://bit.ly/2Tobizx
  • Bjork: The benefits of interleaving practice, GoCognitive YouTube video with Robert Bjork (2012): http://bit.ly/2MXCGDm
  • Brown et al: Make it Stick: The science of successful learning, May 2014.
  • Cepeda et al: Spacing effects in learning: A temporal ridgeline of optimal retention, Psychological Science, 2008: http://bit.ly/2Tsv9xt
  • Cohen: Revision techniques - the good, the OK and the useless, BBC, May 2013: https://bbc.in/33vlafe
  • Dabell: Slippy learning, January 2018: https://johndabell.com/2018/01/27/slippy-learning/
  • Dunlosky: Strengthening the student toolbox: Study strategies to boost learning American Educator, 2013: http://bit.ly/2Trdjee
  • Dunlosky et al: Improving students’ learning with effective learning techniques: Promising directions from cognitive and educational psychology, Psychological Science in the Public Interest, January 2013: http://bit.ly/2KJrKGJ
  • Gnambs et al: The effect of the color red on encoding and retrieval of declarative knowledge, Learning and Individual Differences, August 2015: http://bit.ly/31xZvkO
  • Karpicke: A powerful way to improve learning and memory, Psychological Science Agenda, June 2016: http://bit.ly/2YFvaE5
  • Kelley et al: Making memories: Why time matters, Frontiers in Human Neuroscience, October 2018: http://bit.ly/3074Vms
  • Kelley & Watson: Making long-term memories in minutes: A spaced learning pattern from memory research in education, Frontiers in Human Neuroscience, September 2013: http://bit.ly/2H1nK33
  • Learning Scientists: Spaced Practice, Learning Scientists website: www.learningscientists.org/spaced-practice
  • Learning Scientists: Elaboration, Learning Scientists website: www.learningscientists.org/elaboration
  • Learning Scientists: Concrete Examples, Learning Scientists: www.learningscientists.org/concrete-examples
  • Learning Scientists: Dual Coding, Learning Scientists: www.learningscientists.org/dual-coding
  • Pan: The interleaving effect: Mixing it up boosts learning, Scientific American, 2015: http://bit.ly/2ySqWtB
  • Pan & Rickard: Transfer of test-enhanced learning: Meta-analytic review and synthesis, University of California, 2018: http://bit.ly/2YEjeCB
  • Roediger & Karpicke: Test-enhanced learning: Taking memory tests improves long-term retention, Washington University, 2006: http://bit.ly/2ySqiMv
  • Rohrer: Interleaving helps students distinguish among similar concepts, Educational Psychology Review, July September 2012: http://bit.ly/2Tr93LW
  • Rohrer & Taylor: The shuffling of mathematics problems improves learning, 2007: http://bit.ly/2H1cyDH
  • Smith et al: Retrieval practice protects memory against acute stress, Science, November 2016: http://bit.ly/2ZWDWKr
  • Smith et al: The key to interleaving: Jumble it up! The Learning Scientists, July 2017: http://bit.ly/2KJrwiA
  • Taylor: Retain. Revise. Recall. Repeat, Core Teaching, January 2017: http://bit.ly/2Z0QQG6


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