When dealing with instructional information, working memory can be divided into auditory and visual processors. The capacity limits of each processor are a major impediment when students are required to learn new material. Nevertheless, there is one strategy that can effectively expand working memory capacity by using the partially independent status of the auditory and visual processors. Under specific and well-defined conditions, presenting some information in visual mode and other information in auditory mode can increase effective working memory capacity and so reduce the effects of cognitive overload. This effect is called the instructional modality effect or modality principle. It is an instructional principle that can substantially increase learning. This chapter discusses the theory and data that underpin the principle and the instructional implications that flow from the principle.

When a multimedia lesson containing complicated material is presented at a fast pace, the result can be a form of cognitive overload called essential overload. Three multimedia design methods intended to minimize essential overload are the segmenting, pre-training, and modality principles. The segmenting principle is that people learn more deeply when a multimedia message is presented in learner-paced segments rather than as a continuous unit. The pre-training principle is that people learn more deeply from a multimedia message when they know the names and characteristics of the main concepts. The modality principle is that people learn more deeply from a multimedia message when the words are spoken rather than printed.