Students received a personalized or nonpersonalized version of a narrated animation explaining how the human respiratory system works. The narration for the nonpersonalized version was in formal style, whereas the narration for the personalized version was in conversational style in which “the” was changed to “your” in 12 places. In 3 experiments, students who received the personalized version scored significantly higher on transfer tests but not on retention tests than did students who received the nonpersonalized version. The results are consistent with a cognitive theory of multimedia learning in which personalization causes students to actively process the incoming material. Suppose you are sitting at your computer, exploring a Web site on health information. You click on a link about how the human respiratory system works, and you see a short presentation on the screen. The presentation consists of an animation depicting the processes of inhaling air into the lungs, exchanging oxygen from the lungs into the bloodstream and carbon dioxide from the bloodstream into the lungs, and exhaling air out of the body. The presentation also consists of a corresponding narration spoken in a human voice describing the processes being shown in the animation. Figure 1 shows frames from the animation along with the corresponding narration. This is an example of a multimedia learning situation because the instructional message consists of words—in the form of narration—and pictures—in the form of animation (Mayer, 2001). During the past decade, researchers increasingly have been exploring ways of fostering meaningful learning in computer-based multimedia learning environments (Mayer, 2001; Rouet, Levonen, & Biardeau, 2001; Sweller, 1999). The two most important paths toward fostering meaningful learning are (a) to design multimedia instructional messages in ways that reduce cognitive load (Mayer & Moreno, 2003; Paas, Renkl, & Sweller, 2003; Van Merrienboer, Kirschner, & Kester, 2003), thus making more capacity available for deep cognitive processing during learning, and (b) to increase the learner’s interest (Harp & Mayer, 1998; Mayer, Sobko, & Mautone, 2003; Moreno & Mayer, 2000; Renninger, Hidi, & Krapp, 1992), thus causing the learner to use the available capacity for deep processing during learning. Examples of techniques to reduce cognitive load in computerbased multimedia presentations include eliminating extraneous words, sounds, and pictures (coherence principle), presenting words as narration rather than as on-screen text (modality principle), placing on-screen text near rather than far from corresponding pictures (spatial contiguity principle), and presenting narrative simultaneously with corresponding animation rather than successively (temporal contiguity principle). Overall, design principles aimed at reducing cognitive load succeed when they free up limited cognitive capacity that was being used for extraneous processing and make it available for deep cognitive processing during learning. Design principles that reduce cognitive load in multimedia learning are based on a large and growing research base. Examples of techniques to increase learner interest in computerbased multimedia presentations include using a human voice rather than a machine voice (voice principle) and using words in a conversational style rather than a formal style (personalization principle). Overall, design principles based on increasing interest succeed when they encourage learners to use their available cognitive capacity for active cognitive processing during learning— that is, to organize the presented material into coherent representations and integrate the pictorial and verbal representations with each other and with prior knowledge. In contrast to research on cognitive load, there is not yet a large research base concerning design principles that increase the learner’s interest in multimedia learning.