Redundancy Effect: Simultaneous presentations of similar (redundant) content must be avoided. Avoid words as narrations and identical text with graphics. When the same information is presented more than once the multiple processing is negative for comprehension since it increases external cognitive load. If novices can benefit from partially redundant information (integrated text and picture for example), expert's performances can be impaired. These six first effects try to minimize extraneous cognitive load (to reduce the number of cognitive processes involved that are unnecessary for learning).
The redundancy effect refers to the phenomenon in instruction where learning is hindered when additional information is presented to learners compared to the presentation of less information. It can take one of two forms. First, when identical information is given in two or more forms such as pictures and words or text in both written and audio form. If one of these forms is redundant, then eliminating it may enhance learning. Second, when additional information is given in order to enhance or elaborate information, for example, a full text and a summarized text. If the elaborations in the full text are redundant, then the elimination of the additional information may result in enhanced learning. Mayer (2001) uses the term "coherence effect' in reference to this situation.