DUAL CODING THEORY SUPPORTS THE LEARNING EFFICACY OF ILLUSTRATED TEXT. As we read illustrated text we simultaneously process visual and verbal information with separate cognitive processes. In short, the learning and recall of verbal information are strengthened with images.

Dual Coding Theory is built on the use of imagery in associative learning. Verbal learning is effective when accompanied by visual learning. Since there are two cognitive processes, one does not need to take the place of the other; in contrast, they support one another.

Images and illustrations enhance learning in several ways. Three common types of illustrations are 

•realistic/representational 
•analogical: image is a different topic but implies a similarity to the topic being learned 
•logical: this demonstrates a conceptual or logical relationship of the illustration's components to each other

Images and illustrations promote learning by motivating the learner and facilitating recall and understanding.


For example, Levie & Lentz proved that illustrated text learning was 36% higher than text alone. (Jonnassen, 1996) Images provided with the text are more effective than those generated by the learner's imagination.

Although pictures facilitate learning, an author must take caution not to use illustrations in a deprecating way. Don't embellish the text with pictures for their own sake; this retracts from learning. Also, providing a caption focuses the reader while illustrations with no captions could lose the learner.

One of the most effective uses of illustrations is to substitute words, we all know that "a picture is worth a thousand words." Illustrations offer valuable information that language can not communicate efficiently

1920s Cartoon by Lauren Stout

The illustration above exemplifies several uses for images. It is from a website on the culture of the 1920s and encompasses a comic for motivation, communicates extralinguistic information and demonstrates the use of a caption to guide the reader.

For further information regarding Dual Coding see Pavio, 1991

Kimberly Hall
Graduate Student
Department of Educational Technology
San Diego State University