Brunken and colleagues (2002) investigated multi-media learning and the processes that make it work. In two experiments they showed that the multimedia format facilitates learning through the processes of the dual coding effect and the modality effect.
The dual coding effect refers to the effect by which learning is improved when related pictures are presented at the same as text-based information, and the modality effect shows that learning is enhanced when information is presented through the visual and auditory modalities simultaneously.
The idea behind both of these effects is that there are separate processing systems for visual and auditory information, both of which are limited in capacity. Presenting information in both modalities allows for the combined resources of both systems to process information, using more cognitive resources and increasing knowledge acquisition.
The experiments showed that reaction times on tasks were faster when two pieces of information were presented through both modalities (visually and auditorially), compared to when they were presented through one modality only (both visually). Knowledge acquisition was also higher in the first condition.
We have consistently found in our research that people who are better at dividing their processing resources in dual or competing task situations, such as multimedia environments, are likely to be better at their jobs and better at managing other people.