Mix up your teaching to get better results

A US psychology professor is proposing a rethink on how we teach to improve retention of learning - but the reaction has been muted. Simon Creasey reports

The common reaction of a teacher to a student haphazardly flitting between tasks and topic areas is to tell that child to focus on the job at hand, or they'll get a sanction or two to help maintain their concentration.

This may be the wrong move, according to Robert Bjork, distinguished research professor in the department of psychology, University of California, Los Angeles (UCLA), in the US. For, rather than being deliberately wayward or lacking in attention span, the student may simply be adopting a learning style that Bjork believes could soon be used in a more structured way throughout education.

Although conventional wisdom dictates that the best way to teach students a subject is by "blocking" - focusing on one particular topic for a sustained time - Bjork argues that teachers could enhance learning and levels of retention if they instead embraced a technique known as "interleaving".

Interleaving basically means mixing up lesson topics. For example, say you wanted to teach children about the Tudor monarchs of England. The conventional method would dictate that you taught all the information on Henry VII, then all the information on Henry VIII and so on through each of the monarchs in turn, to give an overall knowledge of the subject. Bjork argues, however, that children would retain the information better if the heads of state were interleaved.

"People don't think they should introduce a topic, cover some of it and then come back to it and pick it up in the context of something else. But research suggests that this should be the approach taken," Bjork reveals.

To date, the bulk of the research into interleaving has focused on how it relates to motor skills - Bjork is involved in a trial with an amateur golfer, where he is interleaving coaching methods to help the player significantly reduce his handicap - but more recent research has gone further.

Bjork cites the example of a trial undertaken by Professor Doug Rohrer and his colleague Kelli Taylor in 2007, in which participants were given the task of learning formulae for calculating the volumes of different solids. Those taught using interleaving enjoyed retention levels of 63 per cent when tested a week later compared with a 20 per cent retention rate in those taught by blocking.

In another of Bjork's studies - about which he co-authored an article for Psychological Science titled "Learning concepts and categories: is spacing the 'enemy of induction'?" - participants were asked to learn the style of 12 famous artists based on six paintings by each. The study found that interleaving the artists' paintings, rather than presenting six by one artist and then moving on, increased participants' ability to identify an individual's work later. Overall, 78 per cent of participants performed better with interleaved learning than with blocked learning.

Bjork says the key finding of the research is that interleaving may mean a slower rate of learning but it gives a better long-term effect. "Conditions of learning that make performance improve rapidly (such as blocking) often fail to support long-term retention and transfer (of knowledge), whereas conditions that create challenges and slow the rate of learning often optimise long-term retention and transfer," he explains.

No strict rules currently exist about how teachers might apply interleaving most effectively in a classroom environment, according to Bjork, but he says that the best results have been achieved when the intertwined subjects are related - as in the artist or Tudor monarch examples above.

As for what age groups would respond best to interleaving and how much time should be spent on each topic during the process, Bjork says that good results have been achieved with children of all ages, while optimum time per topic tends to depend on the subject matter. He concedes, however, that more research needs to be done to provide definitive results.

Testing process

One of the ways to fast-track this research - and research into interleaving in general - would be for more teachers to test Bjork's interleaving theory in a classroom environment and measure long-term retention versus results achieved by blocking. For that to occur, Bjork's theory will need some high-profile support.

Alistair Smith, one of the UK's leading trainers in modern learning methods, thinks that in some circumstances interleaving as a mechanism for delivering content may be necessary and so, tentatively, would offer such support. He adds, however, that application would not be easy, particularly in the UK.

"Typically, schools do not create the right circumstances for this method because they block subjects, teach them discretely and do so in narrow chunks of time," Smith says. "In a 45-minute lesson I would revisit and test but I wouldn't try to interleave. Over two hours I may well do so but I would try to stay within the discipline."

Guy Claxton, professor of the learning sciences at the University of Winchester, England, is more wary of interleaving, arguing that determining the best method of learning is dependent on what you are learning in the first place.

"It would be utter nonsense to suggest that someone prepare for their piano exam by interleaving bars from Chopin, Ravel and Scott Joplin. Or that you got to be a Nobel laureate in physics by mixing your experiments up with bits of chemistry and biology," he says.

Claxton adds that interleaving would work only if schools were judged as a success based on the "most trivial kinds of learning", involving the "retrieval of relatively isolated or disconnected gobbets of 'fact'".

Bjork concedes that interleaving faces challenges, not least in convincing the likes of Claxton of its merits. He explains that another barrier to wider adoption is that no one currently knows with any certainty why the approach works.

"One theory suggests that having to resolve the interference among the different things under study forces learners to notice similarities and differences among them, resulting in the encoding of higher order representations, which then foster both retention and transfer," Bjork says. "Another explanation suggests that interleaving forces learners to reload memories (and) such repeated reloadings are presumed to foster learning and transfer."

Bjork says that a more definitive answer to this and the other queries and criticisms posed about interleaving will emerge over the next decade after more research. He believes that at the end of this period he will also be able to clarify how curricula should be structured to accommodate interleaving. One thing that is clear is that Bjork's work has some potentially dramatic implications for teaching.

"A lot of these things still need to be tested because there have been relatively few controlled experiments in classrooms to date, but more testing is going on all the time and I think that potentially the body of research that's accumulated over the past 20 years provides the foundation for some pretty dramatic changes," Bjork says.

"The possibilities are exciting but there's still a lot more work that needs to be done."


Research suggests that interleaving - mixing up learning - increases levels of retention compared with traditional blocking methods.

While this can be a slower learning process, advocates say that it works better in the long term than conventional methods.

More research needs to be done to clarify particulars such as at what age students will respond best to interleaving and how it should actually work in practice.

Some argue that applying interleaving is impractical for many subjects and has been shown to be successful only with trivial kinds of learning.

But advocates argue that with more research they can prove its effectiveness.


- Rohrer, D. and Taylor, K. (2007) "The shuffling of mathematics practice problems improves learning", Instructional Science, 635: 481-498.

- Kornell, N. and Bjork, R.A. (2008) "Learning concepts and categories: is spacing the 'enemy of induction'?", Psychological Science, 619: 585-592.

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