• Emily Rose Seeber

4 strategies for interleaving practice without destroying students' self-confidence


During recent weeks I have been focusing my wider reading on the cognitive science behind learning and I have read a 'trilogy' of books written by practicing scientists for teachers and learners to improve their learning strategies. One of the strategies for improving retention of new learning which all three books refer to throughout as the gold standard for consolidation of new learning is interleaving.

This is when practice is mixed up so that learners are not focusing on a single skill at a time (massed practice), but switching between different kinds of skill (interleaving). This aids the learner as they now need to focus on how they select the correct strategy as well as how to use the strategy to answer the question. It gives students the mental cues they need to retrieve the strategy from their long-term memory, makes memory retrieval sufficiently challenging to embed it into the long term memory rather than short term memory, and allows for the remodelling of the memory with each retrieval to situate the learning within the context of new ideas which have been accumulated in the interim period. Memory retrieval has been shown to interrupt the process of forgetting, so interleaving practice ensures that students are recalling different skills and strategies throughout the task, preventing them from forgetting their prior learning.

One of the challenges in interleaving vs. massed practice, is that learners feel less secure after a session in which they have moved between different kinds of practice rather than focusing on mastering a specific skill. This can also cause them to lose confidence in their teacher: this is certainly something I don't want in my classroom. Although this mastery gained through massed practice is satisfying for the student, it is less likely to lead to long-term memory as the retrieval of this memory became easier and easier throughout the session so the brain can use the short-term memory as a shortcut and avoid embedding the learning in the long-term memory. Practice is more effective for learning if it is harder, and this makes it feel less like learning to students; even when they can later see the evidence under research conditions!

1. The spiral curriculum

If you are a subject lead, then one way to out the lessons from cognitive science into practice is to redesign the curriculum to form a spiral. This means that topics are taught year-on-year with new material covered with each spiral. For example when teaching the concept of the atom:

  • Year 7: Particle Theory - this introduced the students to the notion of individuals particles and their behaviour.

  • Year 8: Elements, Mixtures and Compounds - in particular that atoms of a particular element are all identical and that atoms and bulk matter have different properties.

  • Year 9: The Structure of the Atom - this takes the student inside the atom and extends their understanding of the idea that all carbon atoms are the same, to all carbon atoms have 6 protons.

  • Year 10: Bonding - this relies on pre-existing knowledge of the structure of the atom to draw dot-and-cross diagrams

  • Year 11: Moles Calculations - these require students to understand relative atomic mass and relative formula mass accurately

This contrasts with the idea that topics which relate to each other should all be taught together in order to help students see the links between the concepts. The science behind interleaving suggests that although students may find it harder to spot the links when each topic is visited rarely, they will embed those links more firmly into their long-term memories.

This spiral could also be focused specifically on calculations; the part of the curriculum which we usually default to a lot of massed practice in lessons. For example the scheme below allows for a lot of interleaved practice and could be spaced over Year 9-11 with one of these taught each term. With each new stage the previous stages can be effectively interleaved into problem sets.

Year 9:

  • Relative Atomic Mass calculations

  • Determining the percentage of each element within a known compound and Relative Formula Mass calculations

  • Determining Moles of a Substance

Year 10:

  • Empirical Formula calculations

  • Reacting Mass calculations

  • Water of Crystallisation calculations

Year 11:

  • Solution calculations and Making Standard Solution calculations

  • Volumes of Gases calculations

2. Sorting Problems into Categories

One of the aspects that students find challenging about interleaving is the aspect of selecting the right problem solving strategy. In order to scaffold this part of the learning, this could be done as a separate practice first before asking the students to go through and solve some of the problems.

an 'interleaving' card sort

For example, when teaching moles calculations different kinds of moles calculations can be printed on different cards and the students then sort these into categories:

  • Relative atomic mass calculation

  • Empirical formula calculation

  • mol = mass / Mr calculation

  • mol = conc x vol / 1000 calculation

  • mol = vol / 24000 calculation

  • Water of crystallisation calculation

Once the students have sorted the cards (and they have been checked by their teacher) their retrieval cues for each problem-solving strategy will be strengthened. The students should then note down some of the strategies they used to sort the cards. Then the students should shuffle the cards and solve the the problems as they come out of the deck, interleaving their practice, but having scaffolded the learning to strengthen their ability to identify the kind of problem they are working through first.

3. Using concept cartoons

One of the great benefits of concept cartoons is that they encourage students to evaluate lots of different ideas about the same phenomenon and compare them critically against each other. If the concept cartoon is chosen carefully, the ideas the students are discussing can draw on a variety of different areas the students have encountered before.

For example, over the last couple of weeks, my Year 10 class have been studying the Periodic Table: Group 1 and Group 7 elements. As part of a lesson focused on explaining the order of reactivity of the Group 1 metals, I used a concept cartoon to encourage the students to evaluate ideas about what the order of reactivity might be, and the possible explanations for this order.

During the activity students were practising their knowledge and understanding of atomic structure from earlier in the year, and interleaving this with their understanding of how the Periodic Table if organised (into groups with similar properties), and their understanding of electrostatic forces (what influences the strength of the force between the nucleus and the electron). Not only were the students using these pieces of knowledge as they evaluated each statement, at the end they needed to determine which effects were the most important in order to make a judgement about what they were going to observe when sodium was added to lithium (they had already seen the lithium reaction). I have since got the students evaluating statements about Group 7 elements, and they demonstrated significant improvement in evaluating and correcting the statements where appropriate. The Group 1 concept cartoon is available here, and the Group 7 evaluation exercise is available here.

4. Interleave the surface structure first

Students find learning abstract concepts difficult as they tend to focus on the surface structure rather than the deep structure when problem solving, which means that they find it difficult to see the links between related problems in different contexts. Interleaving requires students to mix up different problems altogether. This makes it really difficult for students to distinguish different types of problems if the surface structure is the same in each case, as they are needing to access the deep structure which differs.

One way to tackle this problem is to organise a problem set in four stages:

  1. Start with problems with the same surface structure (which should be minimal if possible) and the target deep structure. For example, three problems on determining empirical formula where students are given the mass of each element in the compound. This gives the student confidence in their ability to use the problem-solving strategy.

  2. Then move in to problems with different surface structure but retaining the same target deep structure. For example, student can be given examples in which they are given percentages instead of masses, given experimental data, or even calculating the percentages of each element in a known compound. This aids students' ability to transfer their knowledge and deepens their understanding of the abstract concept being targeted.

  3. Next problems should have different surface and deep structures. Other calculations can be mixed in, but the surface structures must be sufficiently different that the students cannot be distracted by similarities in the surface structure. For example, if an empirical formula calculation involves determining the formula of magnesium oxide from an experiment burning magnesium in oxygen, there should not be a moles calculation question which refers to burning magnesium, such as 'What is the mass of magnesium oxide formed by burning magnesium in excess oxygen?' as these similarities can interfere with students identifying the deep structure at this stage.

  4. Finally problems can have the same surface structure but different deep structures. This really tests students ability to identify the deep structure of a problem. A range of moles calculation examples which refer to a particular compound could be used such as magnesium oxide as in the example above.

Designing a problem set according to this structure takes time and effort. And the moment I have made one, I will attach it here! But this strategy takes account of the recommendations of the cognitive scientists, while still scaffolding the difficulty for the students, allowing them to access the learning and giving them confidence in their ability before ramping up the 'desirable difficulty'. Throwing students straight into stages 3 and 4 would, for my classes at least, be considered 'undesirable difficulty': they would be unable to solve the problems and would just switch off. This staggering of the interleaving aims to ensure that students are in their zone of proximal development throughout the task so that they can engage fully with the learning, getting the full benefit from the interleaving in stages 3 and 4.

Although interleaving practice is what the cognition experts recommend, it still goes against what students and teachers feel helps effective learning. Hopefully some of the strategies I have suggested can help you use the edu-research in a way that does not damage your students' self-confidence in their learning, and will lead to real benefits in their long-term retention of ideas and their ability to select the right technique for the job. Essentially making them more likely to remember and select the correct problem-solving strategy in an exam, and, thus, raising levels of attainment: which is something we are all hoping to achieve!

#cognitivescience #pedagogy #chemistry #PCK

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© 2017 by Emily Rose Seeber.