Our understanding of media differences sheds light on another set of confounding factors: the interaction between the type of skill or knowledge being measured and the medium in which it is being assessed. For example, consider what the members of the Chicago Cubs could demonstrate about their knowledge of physics if they were given a practical "test" in the ballpark. Their ability to intercept a baseball at the precise place where it falls to earth would clearly demonstrate that they understand things like velocity and trajectory. But were we to give the ballplayers a paper-and-pencil test on the principles of physics (and no formal instruction), they probably would not score as well. The written test does a good job of measuring explicit knowledge—the ability to describe physics concepts—but to assess the Cubs' hands-on knowledge, the field test would be a much fairer and more accurate measure of their understanding.
This rather far-fetched example illustrates a point with strong implications for the classroom. Just as students have varying capacities for using different media, media have different capacities for representing different kinds of ideas. For example, skill with the music of language, drama, or poetry is difficult to demonstrate through text but can be easily demonstrated through speech. An aspiring actor might do this by acting the part and the aspiring writer, by reading a poem aloud. Likewise, understanding of a particular narrative might be communicated best through recorded speech or the creation of a video or a drama, using a tool like Grolier Interactive's Hollywood. The format of a text-based outline is helpful for demonstrating the relationships between concepts, but in some cases, a visual map (generated through a tool like Inspiration) might be a more effective way to show these relationships.
The demonstration of some kinds of skill and knowledge fall obviously into certain media categories, such as architectural knowledge and drawing, advertising knowledge and animation, and music knowledge and sound. However, we can gain a richer understanding of what people know by crossing media lines and assessing content with media not usually associated with assessment. This is rare in traditional assessments, which usually consist of a single medium (overwhelmingly printed text) chosen primarily on the basis of availability and with little thought to its appropriateness. This reliance on singular media prevents teachers from fully evaluating different kinds of knowing.