Here is another helpful summary, relevant to those making and using on-line instructional videos or lectures. There are several underlining principles of using multimedia resources, based on theories of how the human brain processes a combination of verbal and visual information: 1)It is better to provide explanations in two forms of information rather than one e.g. a film with corresponding verbal explanation is better than just a visual aid; 2) Multimedia explanations should include words in verbal rather than written form e.g. try watching a subtitled film; 3) Coherent summary highlighting key words/visuals is better than detailed explanations.
All common sense really, but neatly put together.
Mayer, R. And Moreno, R. A Cognitive Theory of Multimedia Learning – pls contact me for a full reference.