“What is interleaving?”
Answering this question is rather
like answering the question, “what is healthy eating?” It’s complicated.
Eat Your Greens
Answering that eating vegetables is likely to be healthy
would be correct in the eyes of most. Propelling the cabbage soup diet?
Probably not. The core and important ‘vegetables are healthy’ message can
become warped when taken to an extreme. The best answers to the question
involve balance and sense, but there is no single answer and interpretations
vary.
And so it is when understanding interleaving. The core
‘mixing up topics is useful’ message of interleaving can unfortunately become
seriously contorted beyond recognition and bereft of value when applied without
careful thought. Only precise understanding and delicate application appear to
deliver the benefits of this interesting, research-based and valuable strategy
and thus these are what I encourage you to pursue.
So, let me take you on a journey. Let’s explore this concept
of ‘mixing up topics’ and I will share with you what I have discovered so far.
Take a Leaf from my Book
OK, so, good luck with this next section. I’m about to try
and use a book metaphor to help explain how to teach, yet teaching is a process
which often literally involves using books. I don’t really have a choice
though, as you will see, because interleaving is actually a book-related
term!
The verb ‘interleave’ refers to putting layers between
layers, “to combine different things so that parts of
one thing are put between parts of
another thing” (Cambridge). Examples in dictionaries refer to interspersing
things between the pages of books (such as thin sheets of tracing paper which
may protect illustrations or maps). When you think about the use of the word
‘leaf’ in relation to thin paper, pages and books, you begin to understand the
word ‘interleave’ more deeply and one definition given of interleaving is “to
put an interleaf or interleaves in” (Collins).
So, think about this as you consider interleaving in
education. Put different ‘leaves’ in between the pages of your teaching and
learning ‘book’. Typical ‘books’ that teachers deliver do not contain such
‘leaves’, for example when teaching a topic and setting numerous ‘pages’ of
questions on that topic, teaching another topic and setting numerous ‘pages’ of
questions of that topic etc. If you were to interleave your ‘book’ though, you
would add additional ‘leaves’ so that after teaching a few topics, you might
set a ‘page’ of questions on one topic, a ‘page’ on another, a ’page’ on
another. You are interspersing different ‘pages’ in between your usual ‘pages’
of teaching and practice.
Oddly, in a very literal sense, actual textbooks are very
typically blocked page by page with content and then questions on that content,
followed by more content and questions on that content, etc. Interleaving will
require you to think differently about how you design your approach as you will
need to put in your own extra ‘pages’ and change your mode from a standard,
traditional textbook-type approach that you may currently be using.
Digesting Spacing & Interleaving
Consider this as you sit down to enjoy your favourite winter
comfort food: chewing and swallowing are not the same. They’re likely to go
together of course. Undoubtedly, after chewing your beautifully cooked
delicacy, you will indeed want to swallow it. But there are occasions when one
of this pair is not suitably combined with the other and you can (as maybe
you’ve unfortunately choked to discover) do one without the other.
Context and correct application of chewing and swallowing
are key. Despite your frustration at the drooling toddler who’s just chewed but
then spat your homemade casserole, it’s pretty obvious that ‘always do both’ is
not always going to be the right advice and no doubt you’ve been told, “don’t
swallow your gum!" and “don’t chew your meds!” These very subtle but important
chew/swallow distinctions have likely never previously caught your attention.
Yet we are all largely, if unconsciously, aware of their importance! Avoiding
nasty, messy and unintended consequences in your digestive life requires
understanding that chewing and swallowing are different, knowledge that they
usually (and helpfully, please toddlers) go together and correct application of
the right action at the right time!
This is how it is with spacing and interleaving.
Interleaving and spacing are not the same. People can accidentally use the
terms interchangeably (often done as they are closely related) but they have a
different meaning and are separate ideas. Spacing refers to leaving time gaps
between covering content, practice and repeated practice. Interleaving refers
to putting different things in between and mixing up topics. And, exactly as
with chewing and swallowing, it’s useful to develop awareness of their distinct
features, appropriate use and importance.
Understand that interleaving and spacing are different.
Understand they usually go together. Take care in referring to and applying the
correct one at any given time. Hopefully then, if you stick with these tips,
you will avoid the educational equivalents of indigestion, sickness or
mal-absorption in your practice!
The Shape of It
So, you can space, you can interleave, you can do both:
-
You can space practice by teaching a topic (e.g.
area of triangles) and then setting a practice task on it two weeks later, a
further task two months later and a further next year, for example. But if you
always provide tasks on only that topic at each occasion (e.g. multiple
worksheets of ‘area of triangles’ questions) then you are spacing, but not
interleaving.
-
You can interleave practice by teaching about a
number of topics (e.g. area of triangles, rectangles, circles and squares) and
then providing practice tasks that mix up work on these topics (e.g. one question
about area of a triangle, followed by one on area of a circle, then one on area
of a square, then one on area of a triangle again etc.). If you only did this once
though, and never returned to it, then you would be interleaving, but not
spacing. (OK, OK, maybe there’s a bit of spacing because there’s going to be a
gap between your triangle lesson and your triangle question, work with me here
though!).
-
You can offer spaced and interleaved practice by
combining the two strategies. It is likely, of course, that you might see the
benefit of setting mixed topic tasks at multiple occasions over time (e.g. a
set of mixed ‘area of shapes’ questions next week, another mixed set next
month, another mixed set next year) and thus combining spacing and interleaving
is likely to work quite naturally.
Discrimination (The Good Kind)
Exams, and life, require us to choose the most appropriate
content that we have available to apply to a task or a problem. Encouraging
interleaved practice seems wise therefore as it demands that the learner practises
this recognising and choosing skill, in addition to merely practising solving
the problem or completing the task in itself. This is developing in students
the skill of ‘discrimination’, the ability to recognise the nature of the task
and identify what content and strategies are needed to address it, in addition
to actually being able to complete or solve it. Any type of shape could provide
the context for an area calculation mathematics exam question, so students need
to be able to choose the correct approach, not just to use an
approach when directed to do so. And, of course, you want to be ready in life if
you’re ever called upon to work out the area of that corner-shaped IKEA shelving
cabinet you’re considering just to make sure the games consoles all fit on!
Un-interleaved (massed and blocked) practice would be
inferior as students get into the habit of solving a problem and then just
automatically follow the same routine repeatedly with diminishing thought. If
you give a page of ‘calculate the area of these triangles’ questions then after
a while the student will operate on auto-pilot. This is probably necessary and
desirable in the early stages of practice of course. Students need to get the
hang of how to solve this particular problem and how to do this type of task (understanding
and encoding are needed initially before you can apply and retrieve). But doing
this alone would seem to reduce the likelihood of success when students
eventually find themselves in a mixed topic exam. Or indeed in life, when they
are suddenly presented with a novel or unexpected problem or task that they
need to address!
Safe, Sensible and Similar
In cautious times, where you might be wary to adopt research
findings having been burned by myths of years gone by, I would like to reassure
you but also to inspire you. In application of interleaved practice as
described above, there seems little risk. You’re probably already mixing your
practice to some degree or another anyway. It’s hard to see that this could
cause harm. But actually I hope you’d move forwards now too and be inspired to
look for that extra little bit of benefit. Weinstein, Sumeracki and Caviglioli
recommend a choice of topics that are “somewhat related but not too similar” to
identify where you may usefully apply and reap the benefits of interleaving.
Focus your thinking on the benefits of discrimination and also on the benefits
of seeing linkages between topics. A case study related to economics teaching
is offered in my linked blog post to illustrate this. I am enjoying using these
ideas to make some very subtle changes to my teaching which I believe will help
me to be more effective.
It gets silly when you take interleaving to the extreme
though. A child sent home to study alone with this advice of ‘mixing up topics’
may do one maths question, then one science question, then a French one etc.
and are likely to cause themselves more problems due to multitasking
inefficiencies than one who does an hour on a subject, then an hour on another.
Expecting younger students in particular to apply interleaving of their practice
accurately is possibly too much and we should offer students support in the
work we set so they are provided with interleaved practice tasks, rather than
putting the onus on them.
Discussion of the reason why we have provided them
with these interleaved tasks clearly has potential to reap metacognitive
benefit, but we need to be careful to scaffold the teaching of student study
habits in the same way as we scaffold the teaching of content. Interleaving
sits at the top end of the independent study scale in my mind and I would only
expect a student to be able to effectively engage with this this once they have
successfully adopted the more foundational concepts of retrieval practice and
spaced practice.
Practice vs. Delivery
Once you understand the core ‘mixing’ concept of
interleaving, one of the things you need to ask yourself is whether you should
be interleaving the delivery, or just interleaving the practice. My reading
thus far indicates far more support (and rather more logic, as shown above) for
interleaving the practice.
Interleaving delivery strikes me as more controversial and there
is definitely greater potential for this to go wrong at the scheme of work
design level. Mixing for mixing’s sake is probably just going to cause
confusion and I am worried by a move to teach topics in a randomly mixed up way
because of a belief that this alone is going to make students learn better. I
don’t think placing faith in ‘interleaving magic’ like that is going to work.
Any benefit that comes from randomly mixed delivery is likely to be related to
the spacing and retrieval elements required in having to remember what was
being learned previously, but the potential inefficiency of switching may well
override this. I look forward to learning more from research currently in
progress (follow the work of Jonathan Firth and colleagues as listed below for
example). But in the absence of a complete and clear evidence picture for the
time being, I would advise cautious application of common sense and logic.
I have made subtle changes to my own delivery, based on
trying to maximise the benefits to be gained from improving discrimination
skills and from building up layers of understanding with linked topics
gradually over time. I also hope to capture some likely tag on spacing and
retrieval benefits that come from delays between covering some topics and setting
practice on them and between the coverage of one part of a topic and the later
coverage of the remainder of it. But none of this has been done randomly.
Move forward cautiously with thinking based on what research
thus far suggests will be effective. Avoid bandwagons and radical or
time-consuming changes that trace back to magical beliefs or
misconceptions.
False Peak
This is only the start of the journey though I feel and,
rather like the first instalment in Lord of the Rings trilogy, I am going to
have to pause here when really we’re only just getting started. I am currently thinking through further and
more nuanced practical tips for successful implementation as well as a
framework for evaluating the use of ‘mixing topics’ at task, lesson, unit,
subject and school level. This extends somewhat beyond the remit of
‘interleaved practice’ of course, but the wider questions the ‘mixing’ idea
throws up (even if this has happened via misunderstandings around the current
state of interleaving research) do deserve answers.
So, I shall leave you for now and you will have to
interleave your CPD reading with other blog reads in the time you have
available before my next post!
There’s a lot we still don’t know about interleaving, so for
now, be sensitive to your students and what is happening. Examine your subject
for similar topics, consider mixing up the practice you provide on these.
Exercise caution with regards to anything else. If students seem to be
struggling applying content to mixed problem sets, take them back to single
problem practice. If they’re bored to tears and operating like a robot, then
try mixing in some more complex and varied questions. Be wise and reflective in
structuring your teaching and practice.
Patience and reflection are required in addressing
interleaving as reading around this subject quickly reveals that definitions of
the concept vary. I have had to resolve to coming to my own conclusions after
being unable to reconcile a single message from a wide range of sources. I remain
very open to learning more though and would love to hear about your thoughts,
experiences and research in this domain.
I will return with a further instalment when I have more
ready to share. In the meantime, I’ll continue to match the values I use in my
adoption of interleaving to my dietary choices; balance and sense are front and
centre.
So no crash diets for me my friends. Kindly do pass the
broccoli though please…
References, Sources
and Further Reading
Cambridge Dictionary - https://dictionary.cambridge.org/dictionary/english/interleave
Collins Dictionary - https://www.collinsdictionary.com/dictionary/english/interleave
Weinstein, Y., Sumeraki, M.,
& Caviglioli, O. (2019). Understanding How We Learn: A Visual Guide.
Jonathan Firth
Blog Post: Firth, J. (2019).
Interleaving: Using it in the Classroom. https://www.jonathanfirth.co.uk/blog/interleaving-using-it-in-the-classroom
Research Protocol: Firth, J.,
Rivers, I., & Boyle, J. (2019). A Systematic Review of Interleaving as a
Concept Learning Strategy: A Study Protocol. Social Science Protocols 2019 Vol
2. http://journals.ed.ac.uk/social-science-protocols/article/view/3011
Article: Firth, J. (2018). The
Application of Spacing and Interleaving Approaches in the Classroom. Impact:
Journal of the Chartered College of Teaching. https://impact.chartered.college/article/firth-spacing-interleaving-classroom/
Twitter: @JW_Firth
The Learning Scientists
Website: https://www.learningscientists.org/
Twitter: @AceThatTest
Powerful Teaching
Website:
https://www.powerfulteaching.org/
Twitter:
@RetrieveLearn
Book: Agarwal, P.K., &
Bain, P.M. (2019). Powerful Teaching: Unleash the Science of Learning.
Other Sources & Useful
Reading
Brown, P.C., Roediger, H.L.,
& McDaniel, M.A. (2014). Make it Stick: The Science of Successful Learning.
Didau, D. (2015). What if
everything you knew about education was wrong?
Dunlosky, J. (2013).
Strengthening the Student Toobox. American Educator. Fall 2013. https://www.aft.org/sites/default/files/periodicals/dunlosky.pdf
Hattie, J., & Yates, G.
(2014). Visible Learning and the Science of How we Learn.
Jones, K. (2018). Love to
Teach.
Sherrington, T. (2019).
Rosenshine’s Principles in Action.
Rosenshine, B. (2012). Principles of Instruction:
Research-based strategies that all teachers should know. American Educator.
Spring 2012. https://www.aft.org/sites/default/files/periodicals/Rosenshine.pdf
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