H16 Information Just In Time **

Not to strain short-term memory with complex instructions to be remembered is one of the most established user interface guidelines (see, e.g., [Shneiderman, 1998, p. 75]). Graphical user interfaces address this issue with the concept of "see and choose instead of remember and type in" [Shneiderman, 1998, p. 75]). However, with interactive exhibits, the situation is again more drastic. They often need to explain an unusual form of interaction, but at the same time there is a lack of long learning time or frequent use. Moreover, users may not even have seen instructions on a previous screen - Easy Handover.

WorldBeat only gives minimal information at the beginning, explaining very briefly what the system is about, and how to point the batons at the screen and select an on-screen start button. This is all users need to know to start using the system, and it is also all they wish to read at this moment. If someone takes over the system being used by a predecessor, they will have collected this information from watching the other user. Each instruction - for example how to play drums using the batons (see opening picture) - is only shown when the system is ready to let the user begin using the respective feature.

We noticed users usually only stopping to read when they actually did not know how to continue, and were actively looking for help. We also frequently observed that WorldBeat users did not read longer texts explaining what to do, until those texts were redesigned to be even more succinct, clear, and constructive, as shown in the opening picture.