Pictures make a presentation worse. That’s both counterintuitive and intended to be challenging. Pictures added to a slide full of text add significantly to the cognitive load. A single, focused, well-composed image can change the impact of the whole presentation. Use pictures correctly to improve the value of a presentation.
Pictures can give clarity to a complex topic by means of visual explanation. Adding random clip art is, of course, heinous. Adding pictures to a “standard” slide already containing bulletpoints is likely to significantly increase extraneous cognitive load. Effectively, the image is something else the audience has to process while reading and listening. The image will consume slide real estate. This will add to the complexity of the whole visual image of the slide and further consume cognitive load. The more complex the slide becomes, the less can be understood. The standard apology acknowledges this, yet still comits the sin. Pictures can decrease the value of a presentation.
A single image, bled to the edge of the slide, appropriate composed will have a positive benefit to the overall value of the presentation by making complex ideas approachable, memorable and allow for processing whilst listening. This is the multimedia principle. An image will last in the memory longer than text and allow an audience to rebuild components of the presentation and further process beyond the actual time of the presentation. Everyone know which film a glass slipper is in. Remember also that displaying an image for an extended period of time will subconsciously encourage the audience to further interogate the image and become distracted. Pictures can increase the value of a presentation.
The use of pictures in a presentation must be considered as more than simply decoration, function dictates form. Effective choice and composition will greatly improve a presentation adding cognitive value. Pictures simply added to a text filled slide will further distract the audience. If you can remember Cinderella simply from an image, how might you improve your next presentation?