Cognitive constraints on multimedia learning: When presenting more material results in less understanding

In 4 experiments, college students viewed an animation and listened to conc urrent narration explaining the formation of lightning. When students also received concurrent on-screen text that summarized (Experiment 1) or duplic ated (Experiment 2) the narration, they performed worse on tests of retenti on and transfer than did students who received no on-screen text. This redu ndancy effect is consistent with a dual-channel theory of multimedia lean-L ing in which adding on-screen text can overload the visual information-proc essing channel, causing learners to split their visual attention between 2 sources. Lower transfer performance also occurred when the authors added in teresting but irrelevant details to the narration (Experiment 1) or inserte d interesting but conceptually irrelevant video clips within (Experiment 3) or before the presentation (Experiment 4). This coherence effect is consis tent with a seductive details hypothesis in which the inserted video and na rration prime the activation of inappropriate prior knowledge as the organi zing schema for the lesson.