Photo source: Edudemic
Visual aids can be a great asset to any presentation: according to the U.S. Department of Labor, "three days after an event, people retain 10% of what they heard from an oral presentation, 35% from a visual presentation, and 65% from a visual and oral presentation." However, visual aids must be used correctly in order to be effective.
One study from the University of California showed a coherence effect demonstrating how irrelevant visual aids had negative effects on learning. In the study, two groups were given information on a problem, and were asked to come up with a solution. The “embellished presentation group” was given a few additional sentences and/or illustrations with irrelevant information. The group that was given only the essential information generated a median of 90% more creative solutions than the embellished presentation group. According to the study, adding extraneous words or pictures interfere with our cognitive processes by “encouraging learners to pay attention to words or images that are not relevant, by disrupting how learners organize words or pictures into a causal chain, and by priming inappropriate schemas to be used to assimilate the incoming words and pictures.”
Visual aids have the potential to be effective and beneficial to presentations only when they fit in with how our brains work. Written text (especially bullets) on a slide takes more time for our brains to process, especially when we are simultaneously listening to someone speak. However, according to an article from Dr. Stephen Kosslyn from Harvard University and Robert Lane, a presentation consultant, “showing people meaningful, content-based visuals, as opposed to text, lessens their cognitive exertion and improves overall experience”. The key is using visuals which are “meaningful” and “content-based”. Speech, text, and pictures compete for our perceptual and cognitive resources when they don’t complement each other. It should be very apparent to your audience how all aspects of your presentation relate to your main theme and to one another. That way, instead of reading bullets or deciphering an unrelated image, the brain can concentrate on you and your coherent message.