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It is frequently assumed that presenting the same material in written and spoken form benefits learning and understanding. The present work provides a theoretical justification based on cognitive load theory, and empirical evidence based on controlled experiments, that this assumption can be incorrect. From a theoretical perspective, it is suggested that if learners are required to coordinate and simultaneously process redundant material such as written and spoken text, an excessive working memory load is generated. Three experiments involving a group of 25 technical apprentices compared the effects of simultaneously presenting the same written and auditory textual information as opposed to either temporally separating the two modes or eliminating one of the modes. The first two experiments demonstrated that nonconcurrent presentation of auditory and visual explanations of a diagram proved superior, in terms of ratings of mental load and test scores, to a concurrent presentation of the same explanations when instruction time was constrained. The 3rd experiment demonstrated that a concurrent presentation of identical auditory and visual technical text (without the presence of diagrams) was significantly less efficient in comparison with an auditory-only text. Actual or potential applications of this research include the design and evaluation of multimedia instructional systems and audiovisual displays.
INTRODUCTION
Delivering text simultaneously in written and spoken form is common in multimedia presentations. Conference presenters or educators reading their overheads aloud, text on a TV screen with a voice reading the same text, and instructional multimedia including spoken narration with the same written text presented simultaneously on the computer screen are all familiar. Nevertheless, the assumption that simultaneous presentation of written and auditory text is beneficial may be erroneous. In a number of recent studies evaluating the benefits of multimedia instruction (e.g., Beccue, Vila, & Whitley, 2001; Hegarty, Quilici, Narayanan, Holmquist, & Moreno, 1999; Najjar, 1996;Tergan, 1997), redundant information presentations in different modalities (i.e., presenting the same information in written and spoken form) did not bring about the expected positive effects on learning. Establishing relations between different sources of information may be difficult for learners dealing with multiple representations (Van Someren, Reimann, Boshuizen, & de Jong, 1998). We know, from previous work, that some forms of redundancy can interfere with learning (see Mayer, 2001; Sweller, 1999; and Sweller, Van Merrienboer, &...