The creation of a shared understanding of the project vision of all relevant stakeholders is vital to the requirements engineering process. One way to create such a shared understanding is through the use of vision videos that visualize the project vision at an early project stage. However, not all functional aspects can be presented. For example, the fact that an access code is valid for only a single use can be hard to visualize. One low-effort solution could be the insertion of short texts or short audio clips. In this work, our question is twofold: What effects do short pieces of additional information have in vision videos? What are suitable ways to add this information to vision videos? To answer these research questions, we investigated three different methods of inserting additional information to vision videos in an eye tracking study. We inserted short texts either below the scene or as overlays and also investigated the addition of short audio clips. These methods were evaluated in terms of participants’ video comprehension, visual effort, cognitive load and subjective preference. The results of our study show that the pieces of additional information improve vision comprehension, thereby supporting the creation of a shared understanding. All investigated methods lead to only marginal increases of the viewers’ cognitive load. Based on our results, we derive recommendations on how to insert additional information in vision videos.