In situations where a source of textual instruction, or a source of graphical instruction alone provides full intelligibility then only one source of instruction should be used (either the textual or the graphical), and the other source, which is redundant, should be removed completely from the instructional materials. In these contexts a single source of instruction returns higher levels of learning than either an integrated format (text integrated into the graphic), or a dual format (both text and graphic presented in parallel).