3.3.1 Target Acquisition
Task For the target acquisition task, the prototype was implemented in accordance to the multi-directional pointing task described in ISO 9241-9 [7]. If the user successfully selected a target, visual (target color changed from black to orange) and tactile feedback (the mobile vibrated) was provided, as literature suggests that a combination of different feedbacks can improve the response times [4].
3.3.2 Reading Task
For the prototype for the reading task we used the Lightweight User Interface Toolkit (LWUIT) for Java ME because it allows an easy way to switch between different text sizes and offers built-in text scrolling support.
For the passages of text, eight standardized reading comprehension texts of about 200 words each were used. These passages of text and reading comprehension questions were taken out of [10], which is a reading skills training book. Each participant was asked to answer two multiple-choice questions on a sheet of paper about the passage they just read. The passages of text were displayed to the participants in a randomized order.
3.4 Test Track
In order to realistically test reading and target selection while walking, we designed two different track layouts (see Figure 4) of 35m and 29.5m length for the two phases of the user study. The idea of conducting the test in a real world setting (e.g. inner city centre) was rejected as our pre-studies had shown the likeness of participants walking against lamp posts, columns and pedestrians. The area covered by the two track layouts measured about 9 m x 7.2 m.