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How does ‘spacing’ and ‘interleaving’ improve learning?

In this step we look more closely at the benefits of spaced learning and interleaving.
Monthly diary sheet with one training session planned per week.

If training is divided up and spread over a period of time (spaced), it is likely to produce learning of higher quality than if it all takes place on a single occasion (massed).

The beneficial effect of spaced learning has been known for decades, yet it is often ignored in healthcare. One reason may be that it appears counterintuitive. Completing everything in one go, one might think, should focus the mind and produce the best outcome. However, this is often not the case.

Case Study: Teaching microsurgery skills

In 2006 a group of junior doctors undertook training in the repair of tiny blood vessels. The training comprised four sessions. Each session comprised instruction followed by practice. Half the group received all four training sessions in 1 day (massed), and the other half received the same 4 sessions at a rate of one per week, over 4 weeks (spaced). All were assessed for competence one month after their last session.

What impact do you think the spaced timescale had on competence compared with the massed grouping?

Surgeon being trained to perform microsurgery

When tested one month later, the doctors whose training was spread over four weeks performed significantly better. Some of the single-day group made serious errors which did not occur among the group trained over four weeks. Diagram showing 4 sessions in one day Massing training into a single package offers logistical advantages. However, the aim of healthcare training is to achieve optimum competence and patient safety. If one learning method produces a safer outcome than another, trainers should take advantage of it. The benefits of spacing have been found in numerous studies and in many different areas of knowledge and skills. Diagram showing 4 sessions spaced over 4 weeks Imagine for a moment that you are about to undergo clinical procedure which requires skill and dexterity. Which way would you want your healthcare professional to have learned; the approach that was quickest, or the method that produced the best results?


When a training course contains different elements, such as a clinical skills day, the natural approach is to complete each element and then move on to the next. Diagram showing 3 blocks of learning together With interleaving, instead of studying a topic in one go, one chunk is studied, and the learner then moves on to a different topic. This creates a break in learning for each subject. Later, when the learner returns to the first topic, they start by recalling its content. Diagram showing 3 blocks split into three parts each, and interleaved In this way the learning from session 1 is strengthened in a way that wouldn’t have taken place if it had been completed in one go. By practicing recall at the start of each interleaved section, the learner strengthens the mental connection.

Interleaving offers an alternative to spaced learning. Unlike spacing, interleaving can be used within a tighter timescale. Moving to a different chunk has the effect of emptying working memory because it engages with the new information. Upon return to the original topic, retrieval of its content is required.

Learners may not always appreciate the benefits spacing and interleaving. If trainers use this approach, it is likely to help if they first explain why this approach has been chosen. If learners understand the reason for a spaced or interleaved design, they are more likely to engage fully.

How can trainers take advantage of these effects?

Trainers can use spacing and interleaving in a variety of ways. For example, a one-day course can be adapted to run over two half-days one week apart, or four shorter sessions over four weeks.

Blended learning presents an ideal opportunity for spacing. The online section can be spaced, and a further space allowed before a practical section.

Interleaving can be employed on a study day in which topics are revisited in assessments later in the day, thus encouraging retrieval practice.

Not every training provider models best practice…

Despite the evidence that spacing improves the efficacy of learning, some organisations offer Train the Trainer courses in a concentrated form of successive days. Participants may be attracted by the opportunity to ‘get it done’ in one go, even though they will almost certainly retain less than if they attended the same course spaced over a period of weeks.

Talking point

Consider sharing your answers to the following questions in Comments:

  • Are you involved with any training that is massed, but which could be spaced in some way? How might you do this?

  • Are there any training programmes you deliver in which learners could benefit from interleaving? How could this be achieved?

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