High quality visual evidence on presentation slides may offset the negative effects of redundant text and phrase headings

This paper compares students' learning from a presentation that relies on the topicsubtopic slide structure versus students' learning from a presentation that follows an assertionevidence slide structure. In our experiment, two audiences heard the same recorded presentation, but one audience (48 participants) viewed topic-subtopic slides and another (52 participants) viewed assertion-evidence slides. The presentation, which took about 10 minutes to view, presented background information about cancer and then explained the process of how magnetic resonance imaging can detect cancerous tumors. Students were tested immediately after the presentation and then again several days later. One conclusion drawn from this experiment is that although not statistically significant, a positive trend occurred for the assertion-evidence slides leading to better comprehension of complex concepts. However, in comparison with results from participants viewing topic-subtopic slides in an earlier experiment, the participants viewing the topic-subtopic slides in the experiment of this paper fared much better. Two possibilities explain this result. One possible reason that the comprehension and retention of complex concepts in the topic-subtopic approach of this experiment fared better is that these slides included much more animation of text and images than in the previous experiment. Another possible reason for the increased scores by the topic-subtopic participants has to do with the visual evidence used for the topic-subtopic slides. For all eight slides presenting the complex concept of how magnetic resonance imaging works, the visual evidence had the same design as in the assertion-evidence slides. While the size of that evidence was typically smaller, the auditorium in which the experiment occurred had a relatively larger projected image than exists in most rooms. If the visual evidence of the topic-subtopic slides significantly affected the results, then the design of visual evidence appears to play a larger role in the comprehension of complex concepts than previously assumed.