The principle of dual coding, as first put forth by Allan Paivio in 1971, states that our brains can process information from two channels at the same time.

We can take in things that we hear and read on one channel (the written word is processed like sound by our brain), and things that we see on another (for more on this, see the 29 March issue of Tes, and an interview with Professor Uta Noppeney).

Dual coding has some important implications for the classroom.

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A teacher’s job involves a great deal of explanation. We have things that we know, understand and can do that we are trying to pass on to people who don’t know or understand them or can’t do them.

Barak Rosenshine’s seminal study on methods of instruction suggests that the most effective teachers talk for a greater proportion of the lesson than less effective ones. The problem is that our words are ephemeral; they only last as long as our pupils’ working memories can hold on to them.

Oliver Caviglioli, author of the forthcoming book Dual Coding with Teachers, explains: “Cognitive load theory tells us that when teachers make a verbal explanation, their students can suffer what is called the ‘transient information effect’. The words disappear and so the student has to try to keep them all in mind.”

That’s where dual coding - at its simplest, presenting images alongside text or speech -  can help.

Research by Mayer and Anderson (1991) found that when verbal information was presented alongside relevant images, it became much more memorable. And these images can be kept in place to aid pupils in subsequent tasks.

I may explain the formation of waterfalls while drawing a diagram of the processes, for example, and then leave the diagram in place when students come on to write their own explanation.

“Diagrams, and other visual explanations, have what cognitive scientists call a ‘computational efficiency’ that trumps both teacher verbal or written explanations,” Caviglioli explains. “This means that visuals are more easily and rapidly understood, leaving untapped cognitive resources available for deeper analysis.”

Dual coding don’ts

Dual coding can also show us what to avoid in the classroom.

Because we take in spoken and written information on the same channel, we want to avoid speaking over what pupils are reading or we risk overloading them. This is most often done when a PowerPoint slide contains a block of text that we read to the class or if one pupil is reading out loud from a book as others follow along.

Although the latter is sometimes held up as good practice in terms of developing literacy, we should be aware that it is likely to make the text harder to follow. Think about what it is like to watch a film with subtitles up in your own language; they quickly become a distraction.

This principle also suggests that we don’t want to overload the channel dealing with images, avoiding those that don’t support the text or spoken explanation explicitly. We also want to ensure that any images are well placed and have a logical order to them. A haphazard scattering of images is unlikely to create computational efficiency.

As with so many elements of education, dual coding is something that is done naturally by expert teachers. However, as with all these simple things, it is often worth exploring them in more detail to see how we can finesse our approach and ensure that it provides the most benefit for our pupils.

Mark Enser is head of geography and research lead at Heathfield Community College in East Sussex. His first book, Making Every Geography Lesson Count, is out now. He tweets @EnserMark