Research School Network: Dual Coding: More than just adding a picture Exploring the nuances of this strategy

Knowledge about cognitive science has grown over the last few years. As terms like ​‘retrieval practice’, ​‘dual coding’ and ​‘interleaving’ become more widely used, there are also instances where some opportunities are missed by a limited understanding. This is the third in our series of posts and we have previously looked at retrieval practice and interleaving. Today we focus on Dual Coding.

Dual coding acknowledges that there are two cognitive processes which work in tandem: the nonverbal and the verbal. Simply put, one subsystem deals with images and one with linguistics. Alan Paivio (1991) proposed that information processed in both of these channels would be acquired and retained better in long term memory.

Rather than a thumbs up for learning styles or a simple instruction to add pictures to words, this is a useful way of considering how to use words and images together, and to consider where some of our uses of the verbal are redundant.

Images: the good and bad
There are many reasons why images are powerful and useful, even before we consider the benefits of dual coding. Visuals can direct attention, they can help us to build on prior knowledge, they can help to make the abstract concrete. The ​‘picture superiority effect’ is the idea that images can convey much more information than text – an image paints a thousand words.

This power of images can mean that we can complement written text or our explanations and lead to better learning. Anyone who has tried to build an IKEA wardrobe can appreciate how a clearly designed image supports the instructions.

Here is an example, taken from the NASA climate website:
Plants take up water from the ground through their roots. Then, they store the water in their stems and leaves. The water eventually travels to small holes on the underside of leaves. There, the liquid water turns into water vapor and is released into the air. This process is called transpiration. It acts as nature’s air conditioner.

If this text was shared with pupils, or the teacher explained it, it might become easily forgotten or hard to conceptualise. The accompanying image adds clarity and concreteness.

But images can also cause problems when they distract. For example, if an image is there to simply add colour or make a presentation more ​‘interesting’ then it may well distract from the information. And even some images designed to complement the verbal may well have lots of additional distractions. Also, some combinations of text and images are better than others. The split attention effect occurs when images and text are not integrated, for example in using a key for a diagram instead of merely labelling the image.

The concept of the separate channels allows us to consider where we might have redundancy. As a general rule, we should avoid presenting the same information verbally in two ways at the same time. For example, we should avoid narrating text heavy slides. Or we should avoid paraphrasing the text on our slides. These cause the verbal channel to be over-stimulated. We can instead ask the slides to be read or use images to reduce some need for text. Reduce the strain on the verbal channel, allow the image channel to support. Another implication of this is the impact of listening to music when studying or completing other tasks. If the music has lyrics, then those will complete with the verbal side of the equation and material will be harder to study, so instrumental music may well be more useful.

The most important thing for a teacher to do is to be aware of this concept and consider it when preparing slides, when designing resources, when planning explanations, when discussing study and revision. Here are some ideas:

When designing slideshow presentations, use only images that complement the verbal. Ideally, if you are talking then you remove most if not all text from the image. Choose images which do not distract – sometimes vector diagrams or outlines are more effective than photographs. Avoid the temptation of adding gifs or ​‘fun’ images to liven up your presentation. You might even eschew slideshows altogether, drawing images on the board as you explain. For example, you draw a timeline as you explain.

For revision, encourage opportunities to encode information in multiple ways. So if learning quotations, they could draw an image which captures the essence of the quotation. For larger pieces of text or elaborate processes or definitions, the text could be composed into a diagram or a series of images. Take away the text and then use the image to recreate the text. Compare afterwards. When we have created these images these can also be cues for retrieval practice. Graphic organisers can help with rearranging lists of information to explore relational concepts too.

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