the psychology of learning and motivation - Percepts and Concepts ...

92 Richard E. Mayersituation could lead to extraneous overload in which the learner spends somuch cognitive capacity on processing the extraneous material that notenough capacity is left for essential and generative processing. A possiblesolution to this problem is to direct the learner’s attention to the essentialmaterial by inserting appropriate highlighting, which can be called signaling.When essential material is highlighted, learners can use theirlimited cognitive capacity for essential and generative processing.The signaling principle is that people learn better from multimedialessons when cues are added that highlight the organization of the essentialmaterial. Signaling cues include outlines, headings keyed to the outlines,and pointer words such as ‘‘first, second, third,’’ as well as typographicalhighlighting of printed text such as using bolding, italics, or underlining.In five out of six experimental comparisons, students who learned with asignaled lesson performed better on a transfer test than did students wholearned with a nonsignaled lesson, yielding a median effect size of d =0.52. For example, in a computer-based narrated animation on howairplanes achieve lift, students learned better when the narrator includedan outline, headings, and vocal emphasis on key words (Mautone &Mayer, 2001, Experiments 3a and 3b) and in a paper-based lesson onlightning formation, students learned better when the text included anoutline and headings (Harp & Mayer, 1998, Experiment 3a). Similarly,students learned better from a paper-based biology lesson that includedgraphic organizers that highlighted the organization of the material (Stull& Mayer, 2007, Experiments 1–3). There is some preliminary evidencethat the signaling principle is most applicable to situations in whichhighlighting is used sparingly (Stull & Mayer, 2007), the learners lackreading skill (Meyer, Brandt, & Bluth, 1980), and when the material iscomplex (Jeung, Chandler, & Sweller, 1997).4.2.3. Redundancy PrincipleLet’s again consider a narrated animation that explains how lightningstorms develop. You might be tempted to add concurrent on-screencaptions that contain the same sentences as in the narration, perhaps tobetter accommodate people’s preferences for printed or spoken text. Thiswell-meaning modification, however, can create an extraneous overloadsituation because the learner has to scan back and forth between theprinted words and graphics and because the learner may try to reconcilethe printed and spoken text. By adding on-screen text, you may havecaused learners to engage in so much extraneous processing that they donot have enough remaining cognitive capacity for essential and generativeprocessing, as shown in the top portion of Figure 2.The redundancy principle is that people learn better from animationand narration than from animation, narration, and on-screen text. In fiveout of five experimental comparisons conducted in our lab, learners