The appropriate uses for special effects in presentations are:
To focus and increase audience attention: Special effects can be used to highlight key points and emphasize important information, which can help to keep the audience engaged and focused on the presentation.
To provide visual cues: Special effects can be used to visually demonstrate concepts and ideas, which can help to clarify complex information and make it easier for the audience to understand.
To improve their effectiveness: Special effects can be used to enhance the overall effectiveness of a presentation, by making it more engaging, informative, and memorable.
Using special effects solely to add excitement to dull presentations or to show off the presenter's abilities is not an appropriate use, as it can distract from the content of the presentation and detract from its overall effectiveness.