Making Sense with Dual Coding

We learn better with words and images than with words alone says Richard E Mayer reviewing four decades of research. Why is that and is it true for everybody?

What is dual coding?

We take in information with all our senses but the two main ones are verbal and visual. Words and images enter our brains through two separate channels. These two routes work separately but can also do so at the same time. On some occasions, they can form some sort of connection. So when learning a new language, for instance, a new word can combine with its image to form a paired bundle of meaning.

Being connected in this way, the meaning is encoded (psychologists’ term for learning) twice — once verbally and once visually. Thus the term ‘dual coding’. Leading cognitive psychologist, Paul Kirschner, calls this ‘double-barrelled’ learning, leaving as it does, a double memory trace, and, as a consequence, doubling the potential retrieval strength. You’re more likely to remember your new vocabulary learning as its retrieval can be triggered by either, or both, visual and verbal memory traces.

Dual coding’s two stories

When Allan Paivio invented his dual coding theory in the early 1970s and tested it out over four decades — it is one of the most rigorously tested theories in education — he only worked on cognitively simple content. There was no teaching or testing of understanding of concepts. It was simple recall of simple content. This I have termed dual coding, story number one. On its own, it is very useful for teachers to know but, we have to recognise, somewhat limited in terms of educational practice.

Story number two is far more interesting and useful to teachers. Paivio wrote about but did not research, the structural differences between verbal and visual information. But others did and what they found forms the basis of story number two. While verbal information is quite obviously linear in nature (think of sentences), visual is non-linear. In 1987 Larkin and Simon published a paper that investigated the significance of this difference in terms of understanding new and complex content.

Two groups of students were presented with identical content and tested on their understanding. One group was presented the material in words alone; the other was given diagrams to support the text. The second group significantly out-performed the first. How was this explained by the researchers? Diagrams made the understanding new concepts easier and more rapid than text on its own — ‘computational advantage’ was the term used.

Story number one is about the combination of words plus the visual. But story number two is the different combination of word plus the visuospatial. By arranging words in a diagram or graphic organiser in a non-linear, spatial, manner, students by-pass the complexities of grammar, or syntax. It’s as if they gain a direct route to the meaning of the new material.

More effective explanations

When teachers use diagrams and other similar visual organisers in their explanations, they tap into this ‘computational advantage’. They make their concepts more accessible and understandable to their

students, as well as more memorable for later retrieval. Which teacher wouldn’t want that?

In following this strategy, there are a few pitfalls to avoid. Beware of presenting an overly complex diagram to your students who would be liable to be cognitively overloaded when encountering new, unfamiliar content. Also, when ensure you make it very obvious which part of the diagram you are referring to when explaining it. Failure to signal the visual to verbal connection will leave many students left behind, forever playing catch-up. As with all new material, cognitive engagement by students is crucial for learning to happen. So take heed of the advice of Clark and Lyons (2004) who write that “visuals ignored, don’t teach”. Ensure you teach how to ‘read’ a diagram and create activities around it that demand students thinking hard about it.

The benefits

Clark and Lyons go on to list the benefits of teaching in this way. Visuals:

• direct attention
• trigger prior knowledge
• minimize cognitive load
• build schema
• transfer to working memory
• motivate

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