Basically, a hot medium excludes and a cool medium includes; hot media are low in participation, or completion, by the audience and cool media are high in participation. A hot medium is one that extends a single sense with high definition. High definition means a complete filling in of data by the medium without intense audience participation. A photograph, for example, is high definition or hot; whereas a cartoon is low definition or cool, because the rough outline drawing provides very little visual data and requires the viewer to fill in or complete the image himself. The telephone, which gives the ear relatively little data, is thus cool, as is speech; both demand considerable filling in by the listener. On the other hand, radio is a hot medium because it sharply and intensely provides great amounts of high-definition auditory information that leaves little or nothing to be filled in by the audience. A lecture, by the same token, is hot, but a seminar is cool; a book is hot, but a conversation or bull session is cool.