Is an illustration always worth ten thousand words? Effects of prior knowledge, learning style and multimedia illustrations on text comprehension

Comprehension of relatively novel technical material was examined in four groups of undergraduates (IN=81) under "text only", "multimedia" and two "diagram" conditions of text supplementation. Multimedia supplementation resulted in superior text comprehension, while standard diagrams did not improve comprehension over "text only" condition. Students with low prior knowledge showed significantly higher comprehension when using multimedia illustration than when studying text alone, whereas for students with high prior knowledge multimedia made no significant difference. Surface learners underperformed overall, but showed remarkably higher comprehension with multimedia than with text alone and nearly equalled comprehension of students with deep, achieving or mixed approaches to learning in the multimedia condition. The results indicate that effects of text supplementation are mediated by prior knowledge and learning style: multimedia appears more beneficial to surface learners with little prior knowledge and makes little or no difference for knowledgable achievers or deep learners