Jonathan Firth (@psychohut) is a high school teacher of psychology in Scotland with a background in psychology and applied linguistics. He has written some school textbooks on psychology that cover a range of topics, but his main areas of interest/research are long-term memory and metacognition. Jonathan has been working on a few small-scale collaborations and classroom-based research projects, and is now just beginning a PhD in education with a focus on how the spacing and testing effects can be applied to classroom activities/timing and course design.

Like many teachers, I have become intrigued by the idea that simply by changing the gap between two or more learning activities such as explanations or revision, I can help my students do better - the so-called ‘spacing effect’. What wonderful thing is this for the stressed and busy teacher - learning can be much more effective simply by changing the timing? It sounds like a gift to our overworked and stressed profession!

Many of us probably already believe that learning works better when spread over a longer period than with last-minute ‘cramming’. What they might not realize is that this is based on one of the oldest research studies in the history of psychology. In the 1880s, German researcher Hermann Ebbinghaus (1) published a series of findings on memory using the curious method of testing himself on lists of nonsense syllables. Among his findings was the ‘forgetting curve’ - the idea that forgetting happens rapidly at first then slows down. He was also among the first to empirically demonstrate the benefits of spacing. Although his experiments didn’t use classroom-type materials, the same phenomena have since been demonstrated hundreds of times with more realistic tasks.

When you stop to think about it, though, this phenomenon is not actually that obvious - how can a larger gap be beneficial to learning, when it is likely to lead to more forgetting in the short-term? The answer may be that introducing long gaps between study opportunities makes the review/retrieval attempts more difficult - and this difficulty appears to be a critical ingredient in establishing a more lasting memory (2, 3).

For the teacher

Anything that can help a learner use their memory more effectively is of potential interest and use to teachers. Despite its potential, though, spacing is not standard practice in the classroom. Most teachers cover a topic from beginning to end in a matter of days or weeks, and set follow-up homework in the same week. Overall, spacing has been described by Dempster as ‘a case study in the failure to apply the results of psychological research’ (4), and more recent reviews (5) still talk of spacing in terms of its potential.

How then, can we begin to apply spacing in the classroom? One avenue could be to re-design the order of lessons, or of activities within those lessons. A great appeal of introducing more spacing is that it simply involves a change in timing, and not necessarily in materials, techniques or lesson content. The benefits of spacing can therefore be obtained without any extra work (although it can be very productively combined with other beneficial techniques too, such as active learning or low-stakes quizzes).

Spacing links to another important and beneficial concept: interleaving, i.e., mixing up tasks rather than doing them in blocks of the same type of task. When we introduce a time delay between studying and re-studying, other material will be covered during any class time in-between. This interleaving can have additional benefits, perhaps by helping learners to more clearly see the links and the differences between different topics or sub-topics. In math, for example, interleaving can help learners to choose the correct strategy to solve a problem (6), and the researchers who study these effects therefore advise against giving students exercises that feature several consecutive examples of the same kind of problem.

In other disciplines, could it be advantageous to break up a topic into smaller parts rather than teaching it all consecutively? What about breaking an explanation into parts, or leaving a video incomplete one day and coming back to it a week later? Or setting homework for a given topic two months after it was studied, instead of in the same week? These would seem like promising ideas based on the existing theories or spacing and interleaving - but have yet to be fully tested out in classroom situations.