Verbal redundancy in multimedia learning environments: A meta-analysis.

Verbal redundancy arises from the concurrent presentation of text and verbatim speech. To inform theories of multimedia learning that guide the design of educational materials, a meta-analysis was conducted to investigate the effects of spoken-only, written-only, and spoken--written presentations on learning retention and transfer. After an extensive search for experimental studies meeting specified inclusion criteria, data from 57 independent studies were extracted. Most of the research participants were postsecondary students. Overall, this meta-analysis revealed that outcomes comparing spoken--written and written-only presentations did not differ, but students who learned from spoken--written presentations outperformed those who learned from spoken-only presentations. This effect was dependent on learners' prior knowledge, pacing of presentation, and inclusion of animation or diagrams. Specifically, the advantages of spoken--written presentations over spoken-only presentations were found for low prior knowledge learners, system-paced learning materials, and picture-free materials. In comparison with verbatim, spoken--written presentations, presentations displaying key terms extracted from spoken narrations were associated with better learning outcomes and accounted for much of the advantage of spoken--written over spoken-only presentations. These findings have significant implications for the design of multimedia materials.