What is Dual-Coding?

During the 1960s, Canadian psychologist Allan Paivio made an interesting yet seemingly simple observation; he discovered that people found it easier to remember concrete nouns that can be imagined compared to abstract nouns where images were harder to come by. 

For example, if I were to present to you a list containing only words like truth, justice, liberty, ambiguity you would find it more difficult to recall these later. But if I gave you a list with words like tree, car, river or house you would be more able to recall them. Indeed, if you were presented with a list of words containing both concrete and abstract nouns, you should be able to recall more of the concrete nouns. 

This makes intuitive sense and explains the effectiveness of certain mnemonic strategies often employed by contestants at the World Memory Championships (yes, there is such a thing). In addition, studies using mental chronometry (the measure of the amount of time it takes to carry out various cognitive tasks) find that the ability to mentally rotate objects in the mind hastens the ability to compare shapes for similarity. If, for example, I were to show you a set of three-dimensional shapes (two of which were the same, viewed from a different angle) success on the task would correlate with your ability to hold the representation of the shape in your mind and rotate it until it matched one of the other shapes. 

Later studies using brain scanning technology found that when such tasks are performed, the occipital cortex (the area of the brain associated with sight) is activated, implying that we are ‘seeing’ the objects.

These findings led Paivio to propose that the human cognitive system codes information in two ways, reflecting the unique ability of our cognitive architecture to deal simultaneously with both language and nonverbal objects and events, a theory that became known as dual coding (See below)

The Dual Coding Model

Paivio went on to propose that the language system can deal directly with linguistic input and output, that is, speech and writing, while at the same time serving a symbolic function with respect to nonverbal objects, events and behaviours. This means that there are two cognitive subsystems; one specialised to deal with the representation and processing of nonverbal objects and events (in other words, images) and one specialised to deal with language.

It’s easy to see the implications this model might have for learning and how verbal and nonverbal inputs and recollections can aid imagination in order to consolidate information. It also hints at the possibility that visual imagery might help to solve complex problems.

The notion that our cognitive architecture consists of verbal and non-verbal elements is also important to the model of working memory first proposed by Alan Baddeley and Graham Hitch in the early 1970s (see here for a breakdown of memory models)  

The images in our heads, therefore, might help us to learn things and apply what we have learned to new problems. To be creative or imaginative relies on the information we have successfully stored as part of our long-term memory, it also relies on our ability to hold such information in mind while it’s manipulated (that is, in our working memory). I can create simple shapes in my mind’s eye and then add to them to create more complex structures, utilising the information in my long-term memory, visualising the content and then putting them all together in my working memory

But I can accomplish even more sophisticated feats than this. In my mind’s eye I can stand at my front door, open it and peer into my hallway; I can do this because not only can I visualise objects, places and events, I can also recall what my front door and hallway look like. Of course, I can do much more inside my head – I can create vast complex narratives, imagine people I have never met and project myself into the future (a topic for another time perhaps).

Implications for learning

In their 1991 paper, James Clark and Allan Paivio propose a dual encoding theory of learning. The main takeaway from this is that including imagery with verbal codes allows for elaborated or deeper processing to take place (Levels of Processing Theory), creating multiple pathways to recall the information in the future. It also follows that if an image is attached to an abstract word or concept the chances of being able to manipulate that information in working memory is enhanced. 

This can be accomplished in a number of ways, including:

  • Pairing written/verbal and visual stimuli
  • Encouraging students to add visual images to their notes, in the form of hand-drawn pictures that are relevant to the written or verbally presented concept (the quality of the drawn image doesn’t appear to impair recall) – see this paper from an in-depth analysis
  • Ask students to recall information using words, images or a combination of both. This allows for  a strengthening of the association between the written concept and its attached image
  • If students are unable to recall a concept, encourage them to visualise the associated image – this should help trigger the verbal memory
  • Consider other mnemonic strategies such as the method of loci

Individual differences

Note, of course, that there are individual differences in the ability to use imagery and some are more skilful at manipulating images in the mind’s eye, indeed, aphantasia is the inability to form images in the mind, a condition that has only recently been identified, while hyperphantasia refers to extremely vivid internal imagery.     

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