Students engaging in blocked practice focus their efforts on a particular topic and then move on to the next topic in sequence, resulting in a perception of content mastery. Interleaved practice provides an alternative approach in which students engage in learning activities that require them to determine which concepts are relevant in a given application. In this episode, Josh Samani and Steven Pan join us to discuss their study comparing the effects of blocked and interleaved practice on student learning.
Josh is an Assistant Teaching Professor of Physics at the University of California, Los Angeles. He is also an instructional consultant for the Center of Education Innovation and Learning in the Sciences and Director of the UCLA-APS Physics Bridge Program. Steven is an Assistant Professor of Psychology at National University of Singapore whose research focuses on evidence-based teaching approaches.
Shownotes
- Samani, J., & Pan, S. C. (2021). Interleaved practice enhances memory and problem-solving ability in undergraduate physics. NPJ science of learning, 6(1), 1-11.
- Pan, S. C., Tajran, J., Lovelett, J., Osuna, J., & Rickard, T. C. (2019). Does interleaved practice enhance foreign language learning? The effects of training schedule on Spanish verb conjugation skills. Journal of Educational Psychology, 111(7), 1172.
- Pan, S. C., Lovelett, J. T., Phun, V., & Rickard, T. C. (2019). The synergistic benefits of systematic and random interleaving for second language grammar learning. Journal of Applied Research in Memory and Cognition, 8(4), 450-462.
- Pan, S. C., Lovelett, J., Phun, V., & Rickard, T. (2019). Pan, Lovelett, Phun, and Rickard (2019) Systematic and random interleaving for second language learning (preprint).
- Agarwal, P. K., & Agostinelli, A. (2020). Interleaving in Math: A Research-Based Strategy to Boost Learning. American Educator, 44(1), 24.
- Dweck, C. S. (2008). Mindset: The new psychology of success. Random House Digital, Inc.
Transcript
John: Students engaging in blocked practice focus their efforts on a particular topic and then move on to the next topic in sequence, resulting in a perception of content mastery. Interleaved practice provides an alternative approach in which students engage in learning activities that require them to determine which concepts are relevant in a given application. In this episode, we discuss a study comparing the effects of blocked and interleaved practice on student learning.
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John: Thanks for joining us for Tea for Teaching, an informal discussion of innovative and effective practices in teaching and learning.
Rebecca: This podcast series is hosted by John Kane, an economist…
John: …and Rebecca Mushtare, a graphic designer…
Rebecca: …and features guests doing important research and advocacy work to make higher education more inclusive and supportive of all learners..
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John: Our guests today are Josh Samani and Steven Pan. Josh is an Assistant Teaching Professor of Physics at the University of California, Los Angeles. He is also an instructional consultant for the Center of Education Innovation and Learning in the Sciences and Director of the UCLA-APS Physics Bridge Program. Steven is an Assistant Professor of Psychology at National University of Singapore whose research focuses on evidence-based teaching approaches. Welcome, Josh and Steven.
Josh: Thank you.
Steven: Thank you.
Rebecca: Today’s teas are… Josh, are you drinking tea?
Josh: I’m drinking the purest kind of tea which is no tea at all. Water.
Rebecca: It’s important to tea to have water, so this is good. This is good. How about you, Steven?
Steven: I’m having some very nice chamomile tea in honor of the podcast.
Rebecca: Awesome, even though it’s midnight.
Steven: Yeah. well, non caffeinated
John: …and I’m drinking Irish Breakfast tea today.
Rebecca: I have a classic English breakfast today as well.
John: We’ve invited you here today to discuss your research project on interleaved practice in physics classes that was published in Nature Science of Learning in November 2021. Before we discuss that study, though, could you describe to our listeners what interleaved practice is and how it differs from blocked practice?
Steven: Interleaved practice is a way of arranging learning activities in which you switch between different topics or skills as you try to learn them. So for example, say in the domain of mathematics, you’re learning to solve volume problems, graphing problems, factoring problems. With interleaving, in a single session, you would switch back and forth between those different skills. So maybe you will attempt a volume problem, then switch to a graphing problem, then a factoring problem. You’re constantly switching back and forth, mixing it up, or interleaving, between those different skills or topics. Now in contrast, a more common practice is known as blocking or blocked practice. And that’s where you focus on one skill or topic at a time, sort of exclusively. So for instance, in an initial session, you’ll focus only on, say, volume problems. And then it’s not until the next session, you will only focus on graphing problems. And then the next session after that maybe only factoring problems. So blocking and interleaving are in a way sort of diametrically opposed. In one case, you’re constantly switching back and forth. In the other case, you’re focusing on one at a time. And currently blocking is much more common in everyday practice in classrooms, it seems to be better organized, more intuitive to people, whereas blocking, firstly, most people don’t know about it. But if they hear about it, they may think “Oh, that seems disorganized, haphazard. Why would I even want to do that?” And so interleaving and blocking… very different ways to schedule your learning.
Josh: And I think also, from the point of view of gaining mastery, there’s this intuition that if you want to master something, you kind of need to block your practice on each sub skill, and hammer away at that for a long time until you master that sub skill then move on. We think this is maybe another reason why, in general, people intuitively are drawn to blocking as an initial study strategy.
Steven: Right. And just this idea of practice makes perfect, it kind of sometimes seems to imply that you should focus and target a particular skill or topic and just become really good at it by practicing it over and over. And that’s the essence of blocking.
Rebecca: Can you talk a little bit about some of the prior lab experiments, and what they suggest about interleaved versus blocked practice before we jump into your current study.
Steven: So, the first studies of interleaving were conducted in the domain of motor skills, and this is work dating back to the 1980s. And the chief finding is that… and it was surprising at the time, and still seems somewhat counterintuitive today… that if you interleave as you’re practicing a set of motor skills in a given domain, that results in better overall proficiency than blocking. For instance, in the domain of badminton, learning to serve different types of badminton serves, the finding has been that if you interleave as you practice, and you practice one type of serve, then you switch to another… then another… then another… that results in better serving ability than practicing only one kind of serve at a time before switching to the next. And that finding that interleaving benefits motor skills has been shown in a variety of motor skill domains, including baseball, basketball, and so on. So the earliest work was in motor skills. Moving on to the early 2000s, there was a move into non-motor skill tasks. And this is primarily involving perceptual category learning, where you’re shown, essentially, pictures that exemplify different categories, for instance, bird families, different artists, painting styles, and the finding there has been that if you interleave as you’re viewing these examples, you view one example from a given category, then you view another example from yet another category, you keep switching… that results in better ability to recognize those categories than if you block where you’re just seeing one category over and over at a time, and that finding has been especially the case for categories that are sort of confusable, similar to one another. And it seems that interleaving is a great way to learn to tell them apart. And now, even more recently, there’s been a move to really highly educationally relevant tasks. For instance, I myself have published a couple of studies investigating interleaving with learning grammar rules in a foreign language. And it seems that interleaving is a great way to learn different sets of grammatical rules. Perhaps the most sort of impressive set of recent studies has been worked by some researchers at University of South Florida, in which they interleave math homework in seventh grade classrooms. So early, I mentioned learning to calculate volumes and graphing and so on. That’s literally the kinds of problems that they interleaved in homework in seventh grade classrooms and that results in greatly improved learning over the traditional blocked approach. And so, overall, the literature on interleaving is small but growing, but there have been a variety of promising results across very different domains. But, really, the literature has just scratched the surface and it’s not yet clear whether the benefits of interleaving are universally applicable. But again, it’s showing considerable promise.
John: Your specific study took this out of the laboratory and into the classroom. Could you describe the experiment that you did?
Josh: Yeah. So in the winter quarter of 2020 at UCLA, I was teaching two sections of Physics 5C, which is a large-enrollment Physics for Life Sciences course. This is the course that pre-meds take mainly, but also some other students from the life sciences. And each course had an enrollment of about 180 students. So these were pretty large classes, so we can get some good statistics for our study. And the topics are things like electricity, magnetism, quantum mechanics, all of these things are taught at somewhat of an introductory level. These are not like physics major, really in-depth courses, but nonetheless quite challenging. And most students in this series find these topics quite challenging. And what we did was, we gave the students three homework assignments per week that were spaced out basically as evenly as we could, given the course schedule, and in one section of the course… so there were these two 180-person sections. In one section of the course,for the first month, all of their homework practice on all of these assignments were blocked practice. Whereas in the other section of the course, all the homework assignments were interleaved practice. So what that meant in our study design is that on a given homework assignment, students in the blocked practice condition, for every given topic, they would receive three problems that were what we call isomorphic problems. So isomorphic problems are problems where the surface features are quite different, but the deeper underlying structure is quite similar. In the blocked group, students saw these isomorphic problems all blocked together. Whereas in the interleaved group, students saw these different isomorphic problems for a given topic arranged so that they spanned multiple homework sessions. So instead of seeing all those problems in a single homework session all in succession, they saw them in three different homework sessions that were distributed across a week. At the end of this month, all students were given a surprise test to see if their learning had been retained and if they could transfer their learning to somewhat more challenging problems, in some cases for some of the problems on the test, and then basically, we measure the difference in performance between the blocked group and the interleaved group on this assessment. And then for the second month of the class, we did exactly the same thing with the new topics, but the section that was previously interleaved was now blocked, and vice versa. The idea being that, this way, every student in these two sections received both of the conditions. And we could make sure that regardless of which students are getting what type of problem set, we see the same result. So basically, like an internal replication almost. So that’s basically the design of the study.
Rebecca: So the intervention was the homework. Were the things that you were doing during class time blocked practice, or were those also interleaved practice?
Josh: Yeah, that’s a great question. So actually, maybe I should also clarify that the only thing that was different about these courses was the homework. Everything else was identical to the extent possible. I was teaching the course, so the lectures were back to back and I attempted to make the lectures as identical as possible. And lectures were somewhat traditional in the sense that there was a lot of me talking about generalized concept and abstract principles, but also doing some worked examples, and a bit of audience interaction. Students also had lab sections that they attended each week. They had discussion sections where they worked on problems. But all of those things are exactly the same. The only thing that was different, literally, was the arrangement of the problems. And in particular, the entire group of problems, the blocked group and interleaved got were exactly the same. So it was literally just the ordering of problems and their distribution and nothing else.
John: So why did you use surprise tests rather than embedded assessment?
Josh: Yeah. So in an authentic educational context like this, where you’re trying to measure the effect of some intervention, it’s pretty well known to anyone who’s taught a class in any context whatsoever that students tend to cram they’re studying. And the problem with that is that you could imagine,we do this intervention in the homeworks and we change the ordering, and students do all this stuff that’s different. And all of a sudden, if they know a test is coming, they can study 10 or 20 hours. And we have no idea what they’re doing during that studying, maybe everyone will interleave their practice during that studying. And it’s really quite a large amount of studying. So maybe it’ll just wash out any effects that we would have seen otherwise. So we use surprise tests, basically, to eliminate the contamination of cramming, which we know is ubiquitous. This way, we can measure, with much more precision, the effect of the thing that we did, as opposed to it being contaminated by cramming. And, by the way, it’s also pretty well known in the science of learning literature that cramming does actually work. So when students cram for 20 hours, we expect them all to do pretty well, as opposed to when they don’t, we can kind of see what the homework actually did for them.
Steven: …with the caveat that cramming is effective, but short lived in terms of its benefits. And just to add on to what Josh said, we thought of the surprise test as sort of the purest measure of the effects of our intervention. It was uncontaminated by the cramming and other various things that students may have done in the run up to the announced high-stakes exams.
John: That was something I’ve really liked about this, because it’s a methodology that I think perhaps could be used a bit more in measurements of teaching interventions. I haven’t seen it used very often in the past.
Steven: It’s not as frequently used as perhaps it should be, but there are some studies in which surprise exams are implemented just for the very reason that we did, sort of to have an uncontaminated assessment of whatever was being done in that particular study. One thing I also would add, that I think Josh mentioned… that students were genuinely shocked when they came into the lecture hall and rather than a review session, as we had suggested they were going to experience, he started handing out the surprise exam forms
John: It’s a form of retrieval practice, which is a form of review.
Josh: Oh, yeah, I think, in fact, I’ve actually used that as a form of review in the past, interestingly enough, even before we did this. Another thing I want to add is that using high-stakes, for example, midterm exams to measure the effectiveness of these sorts of things, is also problematic in the sense that, presumably in education, what we’re trying to measure is long-term retention, to a large extent, and students cram on these tests. And so given what Steven said, since cramming is effective only in the short term, what we’re really measuring is just what students know in a very short period of time. And I think it’s more broadly important to move away from that protocol. We should be measuring things at larger time intervals in general.
John: So, what did you find? How large were the effects?
STEVEN So in both stages, first of all, students who had received interleaved practice did significantly better. So, both from the perspective of it being a statistically significant finding, but also in the size of the effect. In stage one, the effect size was 0.4, which for those who maybe haven’t used such measures before, that would be considered like a medium-effect size, a moderate size of an effect. But in an authentic educational context, like in the wild where we’re doing this experiment, it actually might be considered a kind of a large one, because in general effect sizes, not in the lab, for studies that are done in a setting like a classroom, effects tend to be somewhat smaller, because it’s like all the different things that are going on. But in stage two, the effect size was 0.9, which means this is a very large effect, especially by the standard of educational interventions in classrooms. And just for those who, like I said before, effect size is not something their familiar with, in stage one, tthe average performance for blocked students in stage one was 0.43, which means that they answered 43% of the rubric items correctly, whereas in the interleaved class, it was 0.54, so they answered 54% correctly. And in stage two, the blocked students answered 27% of the rubric items correctly and 47% in the interleaved group. So it was a larger difference.
Rebecca: I’m curious about the second stage in that, if they’ve already been surprised one time, were they then primed to get a surprise a second time and maybe motivated more effort and time on homeworks?
Josh: So interestingly, one thing we did in the study, which is part of the published data, is we asked students to report how much study time they devoted before the surprise test. We also asked them to report how surprised they were that there was a surprise test during the review session. And interestingly enough, the surprisal remained very high the second time, and the amount of studying students did before the surprise test beyond the homework was still quite low. So at least from the self-reported measure, we can be pretty confident that things were pretty similar in both of the stages in that respect.
Steven: Perhaps though, if we did this a third time, maybe that would no longer be the case, but it worked both times.
John: Some of our listeners might be wondering how you counted the surprise test? How did you include this in the computation of their grade.
Josh: So in the end, actually, this had no effect on the computation of their grade. When the surprise test was administered, I did offer 1% extra credit to students based on their performance, but it didn’t actually affect the core grading rubric. So we wanted to make sure that if there were, in fact, big differences in performance, it wouldn’t adversely affect anyone in the long term in terms of their grade.
Rebecca: After having this intervention twice in the classes, sid you talk with students about this practice and its impact on them?
Josh: You mean students in those particular classes?
Rebecca: Yeah, after the fact.
Josh: I actually have not. That’s an interesting question. Actually, I haven’t even really seen very many of them to be honest. I teach so many students that it’s very rare for me to interact with anyone from previous classes, because everyone’s so busy. There were one or two instances of this, and they were very surprised and interested, actually, to see the results, but nothing particularly large scale.
Steven: One thing we did do, though, was for the homework assignments, have students rate after they completed those assignments, how well they thought they had learned and so on. And in those ratings, they didn’t seem to show any evidence that one particular homework type, namely interleaving, would actually be better than the other type.
John: Why might interleaved practice have this sort of positive effect on longer-term recall.
STEVEN So there are a variety of viable sort of explanations for the benefits we observed here. And I like to sort of categorize them… actually, Josh and I like to categorize them… sort of into two main categories, first, being interleaving, sort of engaging long-term memory processes, and that enhancing learning, and then the second being interleaving actually promoting specific kinds of learning that are unique, that you don’t get when you engage in blocking. So, with the first, it’s based on the idea that, with interleaving, when you encounter a given problem type, you don’t revisit it again until some time has passed, there has been some spacing or distributed practice. And in the learning sciences literature, distributed practice (or revisiting information after a delay) is actually a very potent enhancer of long-term memory. So again, with interleaving, you see one problem type, and you’re practicing other problem types, you don’t return to that original problem type until sometime later. And so, because of that spacing, the next time you encounter something, the students are going to have to recall from long-term memory, what they remember about that particular problem type in order to solve it, and so that long-term memory that’s constantly being engaged by interleaving, may be enhancing learning. So that’s sort of the first explanation. And the second set of explanations really involves interleaving because you’re switching back and forth between these problem types. This may afford you the opportunity to sort of compare and contrast one problem type with the next. And that can yield a host of possible benefits. You may become better, for example, at going beyond surface features, but actually recognizing what really distinguishes one problem type from the next. So on the surprise exam, you actually can tell this problem type from the next. You can also perhaps get better practice at choosing the right strategy to solve a given problem versus another. And also, our surprise tests had some problems in which students had to combine strategies from multiple problem types in order to come up with a solution. And so it’s possible that with interleaving, because students were switching between problem types, that might have given them the opportunity to think about what relates one problem type to the next, and that could have enabled them to be better able to combine strategies to solve these surprise test problems. None of those kinds of learning are possible with blocking, because you’re focused on one problem type at a time, there’s no switching, no ability to compare and contrast, and so none of those learning opportunities occur. So those are all possible explanations for how interleaving is enhancing learning in this particular study. And it’s also possible that multiple mechanisms are at play here, resulting in this powerful benefit.
John: In some of the lab experiments involving interleaved practice, generally, when students were exposed to interleaved practice, they felt they were not learning as much. When they were exposed to blocked practice, they thought they were learning more, yet the longer-term testing results in most of those experiments suggests that the opposite was true. Why is it that we so often see this sort of metacognitive illusion, where students perceive things that are beneficial as being less helpful, while the types of strategies they most typically use as being more useful?
Josh:: Maybe I can first of all say one thing just about what we actually measured in terms of judgments of learning very specifically, I think Steven did touch on this a bit earlier, but it might be interesting for the listeners to hear that we’ve actually measured two things. So we measured perceived difficulty of the homework. So right after students worked on an assignment, they rated the perceived difficulty, and we also measured judgments of how much they learned during that homework assignment, on that particular set of concepts. And in those two cases, interestingly, students tend to view blocking as being easier, which maybe actually is pretty intuitive because when you kind of are doing the same thing over and over again, you get this fluidity with it and you get into the state where you kind of know what you’re doing and you don’t have to think too hard about it. And I think that probably is what contributes to some degree to what you’re saying… why students don’t maybe respond so well to interleaving. Because you don’t get that fluid feeling of, “Okay, I’m kind of rolling, I’m doing these problems, and I know how to do them all.” So they perceive them as being easier. And they also felt like they learned more… possibly also, because they’re conflating this sense that they’re really fluid with how much they’re actually learning, which it turns out may not actually be the case, and probably isn’t the case. And in fact, that’s what we found here, is that. in both stages, this is what we found in terms of the perceptions. But in both stages, students did better on the surprise test. But also, interestingly enough, students in the blocked group did do better on their homework in general than students in the interleaved group. So it was easier for them. So in some sense, they were accurate about how hard the homework was for them. But they were inaccurate about what that meant in terms of their learning. And maybe I’ll let Steven go beyond what I said about why this may happen. But that’s one idea.
Steven: Yeah, I agree with that interpretation, I would add that one of the sources of metacognitive illusions relating to effective learning strategies involves students, learners, sort of conflating performance with learning. So how well you were actually doing in the moment with how much you’re actually learning sort of underneath everything. And, with blocking, and a variety of learning techniques that are actually less effective of the long term, they can give you high levels of performance as you’re using them, sometimes because they make the learning task much easier. And in our case, with blocking, because your practicing the same type of problem over and over, perhaps after the first problem, you no longer really have to work all that hard, you just repeat the same procedure… performance level is high. So students may infer that oh, well, I’m doing really well, I must be learning quite effectively. But actually, the underlying learning is quite low, whereas with interleaving, the performance level is not as high because they’re switching, it’s more difficult, they may then infer that, “Oh, my performance is low, I’m not doing so well, I’m not necessarily learning as well.” But actually, that struggle is very beneficial for learning over the long term. But this sort of inability to differentiate between learning versus performance, because performance is not always a direct indicator of the underlying learning, may be the source of this sort of disparity.
Rebecca: I love that you’re bringing this up, Steven, because I think a lot of times students or even folks that are new and in a professional position too, that are just starting out as an emerging whatever, whatever field they’re in, feel like they need to perform. And there’s this pressure or grades are often assigned based on performance, rather than the idea that learning and growing requires some struggle. And we don’t always think about that or encourage that.
STEVEN Oh, absolutely, yes.
Josh: Yeah, I think this has some implications for student mindset in general. We talk very often these days about growth mindset, and students having growth mindset being beneficial. I think students internalizing these sorts of results, although it’s very hard to get students to do that, may go some way in convincing them or helping them generate a mindset for themselves of growth, as opposed to a fixed mindset. So, understanding that things that actually are effective for learning oftentimes feel very difficult and lead to lower performance.
Steven: And I would just add on that, some of the more difficult but more effective in the long term learning techniques, they result in more mistakes and more errors. And certainly with interleaving, we saw a greater rate of problems being solved incorrectly than in the blocked condition, so students were making more mistakes. But the act of making those mistakes was not necessarily detrimental for learning in the long term.
Rebecca: Now, we can just get our assessments and things like this to match with that idea…
Josh: Yeah,
Rebecca: …we’d be all set. [LAUGHTER]
Steven: That would solve all our problems.
John: A lot of it, I think, is just the difficulty of convincing students of these issues, that there is benefit from making mistakes, and there’s some substantial learning gains from that. And it’s something I’ve been trying to do in my classes for a long time, without as much success as I’d like. Students like to feel good about their learning, and they like to be successful immediately. But that’s not consistent with long-term recall, or transfer ability.
Josh: Before I forget, along these lines, in terms of student perception, and judgments of learning, there’s kind of a couple of funny anecdotes along the following lines. So, when I was giving the surprise tests, students are shocked. And you can kind of hear this audible thing in the room with like, “Oh my god, we’re doing the surprise test…” and increasing anxiety and all these things. And something that I noticed, and you have to be, of course, very careful about these sorts of anecdotes, but I think it’s possibly indicative of something deeper. What I noticed was, in the blocked conditions, when they were taking the surprise test, there actually were a number of students who immediately decided to give up and turn in their tests. And basically unsolicited said to me, “I haven’t done any studying, how could I possibly answer any of these questions?” And so there’s this interesting thing where students somehow perceive the practice that they were doing as being completely useless. There were a few students in the blocked condition, in particular, who felt this way. And they only felt that after having crammed for an exam, would they be prepared. So there’s this kind of interesting, just also cultural, sort of perception around practice where somehow this spaced practice that they were doing this entire time, was not really doing anything for them and they had to cram to do well on the test. So I think it just speaks again to these kind of conceptions student have about learning, and oftentimes these illusions about learning that are really detrimental.
Rebecca: Yeah, I was just reflecting on what you were saying, Josh, and that I’ve definitely had the same experience with students. I teach web design. So I teach something very different. But we might work on a new project or a new assignment, and so we’re revisiting stuff from the past over and over again, because to start a new project, you have to know the things that we did before. And students will say, “Oh, I can’t do this. We haven’t done this in a while.” So just remembering many of these same instances [LAUGHTER] reflect the same idea. A lot of our textbooks and even adaptive learning platforms are primarily set up to encourage blocked practice, and many of our courses too, and what are some ways that faculty can build interleaved practice into our course design? …maybe beyond there’s the homeworks, as you mentioned, but are there other ways that we can start thinking about it in our practice?
Josh: Yeah, so firstly, one thing that any instructor can do that might promote kind of like an organic form of interleaved practice is to make sure their course is cumulative to a large extent. So if you tell students from the outset that you’re going to have a one midterm on so and so material that’s right before the midterm and this other midterm on so and so material, they’re basically going to focus on that material. And they’re not necessarily going to mix what they learned in that section with what they learned in sections for other tests. So if your course and your exams are cumulative, meaning that you are, for example, testing on a variety of topics, as opposed to just a single topic at a time, it’s a natural incentive for students to interleave their practice, because they need to do that for the exam. And in those cases, it’s probably a good idea to encourage students and say, “Well, you know, the structure of the test is going to be that it’s going to have mixed problems. And so it makes sense for you to mix your practice…” and you don’t even necessarily need to explain what interleaving is for someone to kind of feel like, it’s probably a good idea for me to mix my practice if the test is going to be mixed. Also, I know you said beyond the homework, but it actually can be logistically challenging to do interleaving If you haven’t thought about the sort of schedule you would need to use. I think the schedule we have in our paper actually is a good model for this because we had to think for some time about how you could actually do this effectively in a real classroom. And the main constraint to think about is that, with interleaving, if you’re mixing topics, you can only mix topics together you’ve already had before in the course, like something that students have learned something about. And so you just need to think sort of intentionally about: well, given the schedule of my class, and given the topics that we’ve covered, how spread out can I make the topics over the time that the students have to do the practice. So I’d recommend if people are looking for a concrete version of this, to see how you could arrange the schedule to make this happen. We have a diagram in our paper where you can see how they’ve been shuffled together, and it might be kind of helpful.
Steven: Yeah. And to add on to what Josh said, a lot of the work with interleaving is in the setup, sort of designing the interleave schedule. And probably one of the reasons why blocking is so popular is it’s frankly, much easier, you just: this week, I’m going to focus on this topic and once it’s done, I’m just going to move on. You don’t have to think about it again. With interleaving, the instructor beforehand, probably should sit down and think about: Okay, how am I going to make things cumulative? And then in the service of that, how am I going to perhaps arrange various learning activities where I’m going to require students to revisit other material? I’m going to perhaps mix things, randomize things in a way that is less predictable, less nicely, discreetly organized as a blocked schedule would be. And doing that would be a way to set up interleaving in advance and then just follow that schedule. I think it’s probably very difficult, possibly impossible, literally, to have interleaving sort of introduced midway through. You should plan it in advance and then execute it, and then all the difficult work is done up front.
Josh: And you mentioned also adaptive learning technologies. And at UCLA, for example, we use online homework systems that do automatic grading of assignments and problem banks and things like that. One really easy thing you could do if you use such a tool is just to try to shuffle the problems together from different topics. So we use something called Mastering Physics and on that platform, you can pick and choose the problems very easily, and you don’t want to think too hard about it. You could just make sure that you have problems from different sections mixed in as opposed to when you give a given homework only problems from this one section in the book.
Steven: Also explaining to students from the outset, sending out the expectation that interleaving of the materials will happen and it’s by design, because you could even say potentially that the exam isn’t necessarily going to be nicely organized, where you’re going to be told this problem is on Chapter one, this next problem is gonna be on Chapter Two, it’s probably going to be mixed together, so why not practice in a way that is similar to the actual exam. And moreover, in real life, everyday circumstance, usually, the next situation you encounter is not necessarily predictable and a repeat of what you just saw. Things are often interleaved in the real world. So in a way, engaging in interleaving is kind of a better proxy for what you actually have to do when you apply skills.
Josh: But I would say one last thing, just in terms of implementation, as with many of these sorts of things, you have to know ahead of time that there might be some student resistance. Because the homework is going to feel a little bit more difficult, you have to be prepared that some students are going to say, “Well, this is totally different than what I’m used to” …and maybe feel like it’s just the wrong way to do things. And so you just have to be prepared as an instructor, as an educator. We know this as educators, that we encounter resistance, but it’s a good thing to know ahead of time.
Rebecca: I think one of the key things when we’re introducing techniques that feel like a struggle, where we might fail is that there’s room to fail and not have long-term consequences in terms of grades and things and to think about making sure that we’re setting these things up in a way that promotes learning and promotes engagement with the method rather than just resisting it or just being really upset about how it might negatively impact a grade. Because also when we have emotions running high that are negative, like that’s not going to help our learning either. [LAUGHTER]
Steven: Right and making, I think, some of these activities low stakes, and not being highly detrimental to one’s grade if one bombs an assignments that’s interleaved, probably would be very palatable to students, but would lower that anxiety,
John: One of the things I’ve been doing for about a decade or so now is using progressively cumulative exams in my large class where I have weekly quizzes that a growing share of them are drawn randomly from earlier portions of the course and student resistance to that is pretty high, I do talk to them about the benefits of interleaved practice. But when they’re trying to work through the exam, and they’re trying to remember things from a month or so before, they don’t find that quite as pleasant. But reminding them that the more effort they put into this, the more they’re going to remember in the future, and that the goal of the class isn’t to get them the highest grades on their exams, it’s to give them a preparation in the discipline that’s going to let them be more successful when they take upper-level classes that build on this foundation. That’s what I tell them, and some students do accept that. But I wouldn’t say it’s a universal acceptance of this.
Rebecca: It’s so hard, John.
Josh: Yeah, who would have thought that the purpose of education is for you to remember things a month in the future?
Steven: It’s always a conundrum that perhaps the most effective instructors are not necessarily the most popular instructors. [LAUGHTER]
John: What does the evidence suggest about interleaving, across disciplines and across different types of concepts? Does it seem to work as well in all disciplines?
Steven: There seems to be a promotion of interleaved practice, particularly, I think, in the popular media that latched on to this technique and think, oh, wow, it’s really amazing and counterintuitive and cool. I’m going to recommend it broadly. And I think one of the concerns with that is then you have suggestions to interleave just anything under the sun and in any way. And although the effect of interleaving in controlled studies, in many cases, has been very, very promising, that isn’t necessarily a license to just interleave anything. And in particular, one of the sort of potential moderating factors is maybe the degree to which the materials that you’re interleaving are confusable, or similar with one another. And that may be really critical. So you can’t just interleave my say physics homework with history homework, and things like that. But the problem is then, when some people read these articles online, that say interleave, they don’t get that nuance. I think that’s a bit of a concern. And further, beyond that, there does seem to be different benefits, depending on the type of material. So, about two years ago, some researchers in Germany conducted a meta analysis. And for those listeners who may not be familiar, that’s sort of a statistical analysis of multiple studies in a given literature. And they did this meta analysis on interleaving studies, a good portion of them. And they found that the interleaving benefits were especially strong for perceptual categories like bird families and things like that, learning to recognize pictures. And whereas for text-based materials, like expository texts and short kind of non-visual materials, there was no substantial interleaving benefits. So I think that sort of raises a cautionary note that we don’t know the extent to which interleaving enhances learning across the wide space of possible things that you could use it for. And actually, that was one of the motivations for our current study, because we were thinking, would it actually work in the domain of physics? That hadn’t been investigated before. And actually, very few studies have been conducted in undergraduate classrooms. And so there was lots of unanswered questions that had not actually been empirically tested that we examined in this particular case. And again, yet other circumstances warrant further investigation before interleaving, I think, could be confidently used.
Rebecca: So we always wrap up by asking: what’s next?
Josh: For us, in the sense of research on interleaving, what’s next is getting at this question of generalizability. How broadly across different types of learning, different contexts, do our results generalize. And we think of tackling this in a couple of ways. The first is, you could tackle this from a theoretical and mechanistic standpoint, meaning if you could understand why interleaving works, and be pretty confident about the factors that lead to why it works, then you can look at it in a given scenario and ask yourself, “Well, do those factors exist in this scenario, and therefore, can we be confident that it’s going to generalize to this scenario?” …so, sort of mechanistic theoretical line to understand its generalizability. And the other option is just to scale. So you could, for example, scale our experiment to something that goes across many disciplines simultaneously. We think both of those are really important and promising directions for future research. So, for us, we think, in the broader scope of interleaving research, that’s kind of a nice thing to investigate next. But also, I just want to say that in terms of just interleaving versus blocking, an interesting questions about interleaving versus blocking, there’s still a question that is largely unanswered, what about some sort of a hybrid schedule? Sometimes we think to ourselves, and I think we actually personally have this intuition, that some degree of blocking at the beginning of a very novice learner’s learning might actually be very beneficial. So, for example, imagine you’re learning to play piano, and your instructor teaches you three different scales, and you’ve never played the scales before, and then asks you to play the scales interleaved. So, play this one scale, then play the next scale, play the next scale. You may just be so non-fluid with playing these scales that perhaps your practice won’t actually be very beneficial, even if it’s interleaved. Maybe you need to play one of the scales two or three times over and then start the interleaving. The same may be true for mathematics learning or for problem solving in physics. So there’s still very much open questions about things like that, like, what exactly is an optimal schedule, and under what conditions do these optimal schedules need to be applied.
Steven: And to add on that, sort of the robustness of the interleaving effect across extended durations, perhaps longer than the four weeks that we sort of implemented interleaving assignments, and then had the surprise exam and different, maybe more advanced, materials, rather than an introductory course, maybe a more advanced level course where the students are already coming in with more pre existing knowledge that’s relevant, and so on. There are lots of possibilities to explore as to the extent to which this sort of interleaving effect generalizes to a variety of different educational circumstances.
Josh: I think talking about scale and understanding how this works across disciplines. I also want to say as sort of a tangential note that I’m a physicist by training, Steven is a cognitive psychologist. We connected in a little bit of a sort of random way at UCLA. But it’s been an incredible thing, having an interdisciplinary collaboration. And I think in our view, such collaborations are just really powerful and useful in the science of learning, in particular, that is becoming this very multidisciplinary field. So on a broader note, I hope what’s next for the science of learning is more of this sort of collaboration across disciplines.
Steven: Yes, and both of us brought unique perspectives and skill sets to this particular project. And it ended up working just marvelously. And hopefully there’ll be more of that in the future.
John: Well, thank you. We really enjoyed reading your study, and I think it’s a really nice contribution to the science of learning.
Josh: Thank you for having us.
Steven: Thank you.
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John: If you’ve enjoyed this podcast, please subscribe and leave a review on iTunes or your favorite podcast service. To continue the conversation, join us on our Tea for Teaching Facebook page.
Rebecca: You can find show notes, transcripts and other materials on teaforteaching.com. Music by Michael Gary Brewer.
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